HomeMy WebLinkAboutSusista feasibility Vol 1 Section 9 though 19 1983:1
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SUSITNA HYDROELECTRIC PROJECT
FEASIBILITY REPORT
VOLUME 1
ENGINEERING AND
ECONOMIC ASPECTS
SECTIONS 9 -19
FINAL DRAFT
Prepared by:
•ARLIS
. Alaska Resources
LIbrary &Information Services
Anchorage Alaska
l..---__ALASKA POWER AUTHORITY __---I
SUSITNA HYDROELECTRIC PROJECT
FEASIBILITY REPORT
VOLUME 1 -ENGINEERING AND ECONOMIC ASPECTS PAGE
1 -INTRODUCTION ....•....•••....•.•...•..•..••.••.•••••..•..•.••.•1-1
1.1 -Introduction ••.........••.............•.••...••••.....1-1
1.2 -Project Description .••...••••..••••..•••••..••.•..•••.1-2
1.3 -Objectives and Scope of Current Studies •••••.•.•••..••1-3
1.4 - Plan Formulation Selection Process •••••...••••...•••••1-4
1.5 Organization of Report •••...••...••••...•••••..•••..••1-6
1.6 -Principal Project Parameters •••.•••....••••...•••..•••1-9
3 -SCOPE OF WORK •...••••....•.•...•...........•.•.•••.....•....•
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2 -
SUMMAR Y '"III Q ..
2.1 -Scope of Work .
2.2 - Previous Studies ••..•••..••••••••••.••••••.••••••..•••
2.3 -Railbelt Load Forecasts ••••••.••••••••••••.•••••..••••
2.4 -Railbelt System and Future Power Generation Options ••••
2.5 - Susitna Basin •....•....•.•.•••.•..••••..•.••....•..•.•
2.6 -Susitna Basin Development Selection ••••••••••••.••••••
2.7 -Susitna Hydroelectric Development ••••••••••.•••••.••••
2.8 -Watana Development ......•..•.•••.•.••••....•..••••..•.
2.9 - Devil Canyon Development •••.••••...•••••••••••••••••••
2.10 - Transmission Facilities •••••.••.....•••••••••••••••.••
2.11 -Construction Cost Estimates and Schedules ••••••.••••••
2.12 -Environmental Impacts and Mitigation Measures •••.•.•••
2.13 -Project Operation .
2.14 -Economic and Financial Evaluation ••.•••••.••••••••..••
2.15 - Conclusions and Recommendations ••••••••••••••••••..•••
3.1 - Evolution of Plan of Study ..•••••..••••.•..••••••..•••
3.2 -Task 1:Power Studies •...•••.••••••.••••••...•••••.••
3.3 -Task 2:Surveys and Site Facilities ••••••.•••••..•••.
3.4 - Task 3:Hydrology ...•...•....•••..••.••••.••..•••.••.
3.5 -Task 4: Seismic Studies •.••.••....••••••.•••••••..•••
3.6 -Task 5: Geotechnical Exploration .••••••....••••••.•••
3.7 -Task 6:Design Development ...•••..••••.•...•••••..•••
3.8 - Task 7:Environmental Studies •••.•.•••..••••••••.••••
3.9 -Task 8:Transmission •...•••.•..•.••..•••••.•••.•••...
3.10 -Task 9:Construction Cost Estimates and Schedules •.••
3.11 -Task 10:Licensing ••••.••..•••...••.••...••.....••...•
3.12 - Task 11:Marketing and Financing •••••••••••.•••••••.••
3.13 -Task 12: Public Participation Program ••••••.••••••••••
2-1
2-1
2-1
2-1
2-2
2-6
2-15
2-2'2
2-33
2-40
2-46
2-47
2-49
2-58
2-60
2-62
3-1
3-1
3-4
3-4
3-7
3-8
3-9
3-10
3-12
3-13
3-15
3-16
3-17
3-18
Note:Sections 1 to 8 are bound under separate cover.
VOLUME 1 -ENGINEERING AND ECONOMIC ASPECTS (Cont'd)
4 -PREVIOUS STUDIES ••.•....•••.•.•.•..•••••.••.••••••••.•••••..•
4.1 -Early Studies of Hydroelectric Potential •.••••••...••••
4.2 -U.S.Bureau of Reclamation -1953 Study••••••..••••••••
4.3 - U.S.Bureau of Reclamation -1961 Study ••.•..••••..•••
4.4 - Alaska Power Administration -1974 ••..••••••.•••••••..
4.5 - Kaiser Proposal for Development •..•..••••••••••••••.•.•
4.6 -U.S.Army Corps of Engineers-1977 &1979 Studies •••••••
5 -RAILBELT LOAD FORECASTS ••••••••••.•...•••••....•.•••••••.•••••
5.1 -Scope of Studies ......................•..•............•
5.2 -Electricity Demand Profiles ••••••....•••••••.•••••••...
5.3 -Battelle Load Forecasts ••.•••.•.•.•••••...••••....••••
6 -RAILBELT SYSTEM AND FUTURE POWER GENERATION OPTIONS ••..•••••••
6.1 - Basis of Study ••••••.•.•.•.•••••••..•••.•••••..•••.•••
6.2 -Existing System Characteristics •••••••...•..•••••••••:.
6.3 - Fairbanks -Anchorage Intertie ....•••••••••....••••••
6.4 -Hydroelectric Options ••.•....•.•••••••••...••••••••....
6.5 -Thermal Options -Development Selection ••...•.•••••••••
6.6 -Without Susitna Plan ..•.•.•••••.....•••••••...•..•••••
7 -SUSITNA BASIN ...•....•...•..•••.•.•••••.•••....•••••••..••.••
-Socioeconomics .••.•••.•••••.•.••••••••••....•••.••••••
-Recreational Resources •.•.~.•.••••••••••..•••••••••••••
-Aesthetic Resources .
-Cl imato logy 'II •••••••
-Hyd r 0 logy "l:f • lit a a • " ".
-Regional Geology .•••••••••••••••••...•••••••••.•••••••
-Se i sm i city ,..
-Water Use and Quality ..•••.•••••.••.••••••.••.••••.•.•
-Fisheries Resources •.•••••...••••••..•••••••••••••••••
-Wildlife Resources ...•••....•••..•...•.••.•.•••••••...
- Botanical Resources •••••••••..•.•.••••••••.•••..••••••
-Historic and Archaeological Resources ••••••••.••..•••••
7.1
7.2
7.3
7.5
7.6
7.7
7.8
7.9
7.10
7.11.
--"-"--------7-.-1-d---b-a·A·Ei-[J·s-e -.
8 -SUSITNA BASIN DEVELOPMENT SELECTION •••••....•••••••.•••.••••••
8.1 - Plan Formulation and Selection Methodology .•...••••••••
8.2 -Damsite Selection .
8.3 -Site Screening .
8.4 -Engineering Layouts .
8.5 - Capital Cost ~..
8.6 - Formulation of Susitna Basin Development Plans •••...••
8.7 -Evaluation of Basin Development Plans ••••....•••••.•••
8.8 -Preferred Susitna Basin Development Plan •••••••••••••••
VOLUME 1 -ENGINEERING AND ECONOMIC ASPECTS (Cont'd)
PAGE
11 -SELECTION OF ACCESS PLAN ••••.•.•••••....•••.....•••••.•..••••
11.1 -Background ..
11.2 -Objectives ...•....•...•....••••.•.•........•..•.....••
11.3 -Approach ..
11.4 -Corridor Selection and Evaluation ..••••••....•••••.•.••
11.5 -Route Selection and Evaluatiun ••...•••••.•...••••••...
11.6 -Description of Basic Plans ......••••.....••••••.....••
11. 7 -Ad d i t ion alP 1an s ..
11.8 -Evaluation Criteria ...••••.....••••••..•...••••••.•..•
11.9 - Evaluation of Access Plans .••..•••••••.•..•••••••.••••
11.10-Identification of Conflicts ...••••.•..•..••••.•....•••
11.11-Comparison of Access Plans ...•••••••..•.••••••••.•••••
11.12-Recommended Access Plan ••••••.••••..•....•••••••..•••••
10 -SELECTION OF DEVIL CANYON GENERAL ARRANGEMENT ...••••..•••••..•
10.1 -Site Topography ...•••...••••.••••••..·.••••...•••..••••
10.2 -Site Geology ...............•..........................
10.3 - Geotechnical Considerations .••••.••••••....•••••..••••
10.4 - Seismic Considerations ••....•••...••••••...••••...••••
10.5 -Selection of Reservoir Level ..•••••..•••••....•••••..••
10.6 -Selection of Installed Capacity •.••••••••••••••....•••
10.7 -Selection of Spillway Capacity •••...•••.•.•.•••••...•••
10.8 -Main Dam Alternatives •...••••.•.•••••...••••••..••••••
10.9 - Diversion Scheme Alternatives ••••...•••••••.••.••••.•.
10.10 - Spillway Alternatives'•••....•••••...•••••••.•••••••..•
10.11 -Power Facilities Alternatives ••..••••.•...•••••••..•••
10.12 -General Arrangement Selection ••.•.••••••....•••••..•••
10.13 -Preliminary Review ...••.....•••••...••••••...••••••..•
10.14 - Final Review ...••.••........••...•••.....•...•....••••
9 -SELECTION OF WATANA GENERAL ARRANGEMENT •.•••.•..••••..•••••••
9.1 -Site Topography ...•...••..•....•.•...•.•........•••...
9.2 -Site Geology .•.••.....••..•••...•.•...•••...•...•.•.••
9.3 - Geotechnical Design Considerations ...•.•...••.•.••••..
9.4 - Seismic Considerations .••.•..••...••...••••..•••..••••.
9.5 -Selection of Reservoir Levels .••..••.••.••••...••••.••
9.6 -Selection of Installed Capacity ••••..••••...••••....•••
9.7 -Selection of the Spillway Design Flood .••....••••..•••.
9.8 -Main Dam Alternatives .••~••..•.•••.•••.•...••••..•••..
9.9 - Diversion Scheme Alternatives .••.•••....•••...••••.•.••
9.10 - Spillway Facilities Alternatives •.•••••....•••..•••..•
9.11 -Power Facilities Alternative ••••..•••••..••••...••••.•
9.12 -Selection of Watana General Arrangement ••..•••••..••••
9.13 - Preliminary Review ..••••.•••••.••~••.•••••...•••••~.•••
9.14 Intermediate Review •.••..•••••.••••..•••••...••••••••••
9.15 - Final Review .•.....••...••....•.•..........•......••..
9-1
9-1
9-1
9-7
9-10
9-10
9-13
9-16
9-17
9-19
9-23
9-24
9-27
9-30
9-35
9-39
10-1
10-1
10-1
10-6
10-9
10-9
10-10
10-11
10-11
10-14
10-17
10-17
10-19
10-20
10-24
11-1
11-1
11-2
11-3
11-3
11-5
11-7
11-9
11-10
11-19
11-26
11-27
11-30
VOLUME 1 -ENGINEERING AND ECONOMIC ASPECTS (Cont'd)
12 -WATANA DEVELOPMENT .•••••••••...•••••••••..•.•••••••..••••••••
12.1 -General Arrangement ..•..••••••••.•...•••••••••...•••.•
12 a 2 -Site Ac cess ..11III Q .
12.3 -Site Facilities •....•.••...a ••a •••••••••••••••••••••••
12.4 - Diversion •••.•..•••...••.•.••••.•..••...•••.••.....•••
12.5 -Emergency Release Facilities •..•.•••••••••••.••••••••••
12.6 -Comparison with Precedent Structures .••;••••••••••.••••
12.7 -Relict Channel Treatment •••••......•••••••••••..•••••••
12.8 - Outlet Facilities •.•.•a •••••••••••••••••••••••••••••••
12.9 -Main Spillway .
12.10-Emergency Spillway ••••.•••••••••••.•..•.•••••••....•••
12.11-Intake ..a •••••••••••a •••••••••••••••••••••••••••a •••••
12.12-Penstocks _....................•..............a
12.13-Powerhouse a •••••••••••••••••••••••••••••••••••••••••••
12.14-Reservoir __...............•
12.15-Tailrace a •••••••••••••••••••••••••••••••••••••••••••••
12.16-Turbines and Generators ••••...•••••••••••..•.••••••••••
12.17-Miscellaneous Mechanical Equipment •...•••••••••...•••••
12.18-Accessory Electrical Equipment •••••••••.•••••••••••.•
12.19-Switchyard Structures and Equipment •••••••••...••.•••••
12.20-Project Lands .........•.....................•.........
PAGE
12-1
12-1
12-2
12-3
12-7
12-10
12-10
12-30
12-36
12-40
12-43
12-45
12-51
12-52
12-60
12-61
12-63
12-67
12-75
12-91
12-92
13 -DEVIL CANYON DEVELOPMENT .••••••••••••.•..•.•••••••••...••••••13-1
13.1 -General Arrangement....................................13-1
13.2 ~.Site Access 13-2
13.3 -Site Facilities ••••••..••••••••••••••••••••••••••••••••13-3
13.4 -Diversion ............................................•13-7
13.5 -Arch Dam ....................................•..•......13-8
13.6 - Saddle Dam .............................•....•........•13-10
13.7 - Primary Outlet Facilities..............................13-14
13.8 -Main Spillway ...................•.....................13-16
13.9 -Emergency Spillway .•••••••••••••••••••••••••••••••••••13-19
13.10-Devil Canyon Power Facil ities.................•.•..••••13-20
______~.,.,___,~._l3.....~_..1~1~__._J.~._eD~s_t_o_c_k.s_._._._._._._..._...,.....,.•~.~.~._.•~.~.~.._..~._._.~..~.~.._._.~.~'L ....._.~.~.~.~.~.~._._.~._11-._.~._.~_13~_22 __.~..
13.12-Powerhouse and Related Structures •••.••••••.•..••••••••
13.13-Reservoir .............................•..............•
13.14-Tailrace Tunnel .................•.....................
13.15-Turbines and Generators ••••••.••••••••••••••••••••••••
13.16-Miscellaneous Mechanical Equipment .•...••••••••..•••••
13.17-Accessory Electrical Equipment •••••••••••••••••••••••••
13.18-Switchyard Structures and Equipment •••••••••.••••••••••
13.19-Project Lands ..........•..................•......•..•.•.
13-23
13-28
13-29
13-30
13-32
13-34
13-39
13-40
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VOLUME 1 -ENGINEERING AND ECONOMIC ASPECTS (Cont'd)
PAGE
14 -TRANSMISSION FACILITIES .•.•..••••.••....•.••.••.••.••.••.••••14-1
14.1 -Electric System Studies ••••••.••.•••••••.•••••••.•••••14-1
14.2 -Corridor Selection ..••.•.••.••.•••••••.•••••.•••••••..14-8
14.3 -Route Selection ........................•..............14-16
14.4 -Towers,Foundations and Conductors ••••.•••••.•••••.••••14-21
14.5 -Substations 14-24
14.6 - Dispatch Center and Communications ••••••.••••••••.••.••14-28
15 -PROJECT OPERATION •.••••.••..•.•••.•••••••.••.••.••••.••••.••••15-1
15.1 -Plant and System Operation Requirements •..••••••.••.•••15-1
15.2 -General Power Plant and System Railbelt Criteria •••••••15-1
15.3 -Economic Operation of Units •••.••.•••••.••.••.••••.•••15-3
15.4 - Unit Operation Reliability Criteria ••..•••••••••••••••r 15-5
15.5 - Dispatch Control Centers •••••••.•••••••••••••.••••••••15-6
15.6 -Susitna Project Operation ••••••••••••••••••••••.••.••••15-7
15.7 -Performance Monitoring ••••.••.••••••••••••••••••.•••••15-13
15.8 -Plant Operation and Maintenance •••.•••••.••.••••••••••15-14
16 -ESTIMATES OF COST ••.•.•.••.••.•••••••••••••.•.••.•••••••••••.16-1
16.1 -Construction Costs 16-1
16.2 -Mitigation Costs .•..••••••••••.•.•..•.•••••..•••.••••••16-6
16.3 -Operation,Maintenance and Replacement Costs ••••••.••••16-7
16.4 - Engineering and Administration Costs ••••••••••.••.•••••16-7
16.5 -Allowance for Funds Used During Construction ••.••.•••••16-9
16.6 -Escalation ..................•.......................••.16-9
16.7 -Cash Flow and Manpower Loading Requirements............16-9
16.8 - Contingency ..........................•..•.............16-10
17 -DEVELOPMENT SCHEDULES.........................................17-1
17.1 -Preparation of Schedules ••••••.•••••••••••••••••••••..17-1
17.2 -Watana Schedule ......•...•.............................17-1
17.3 - Devil Canyon Schedule••.••.••••.•••••••••••••••••••••••17-4
18 -ECONOMIC,MARKETING AND FINANCIAL EVALUATION..................18-1
18.1 -Economic Evaluation .•.•..•••••.•.••.••.••.••.••••••••.18-1
18.2 -Probability Assessment and Risk Analysis ••••••••.••..••18-15
18.3 -Marketing ...................•.....•...............••..18-28
18.4 -Financial Evaluation ••••.•••••.•••••.•••••••.•••.•••••18-31
18.5 -Financial Risk .0......................................18-37
19 -CONCLUSIONS AND RECOMMENDATIONS ••••••.••••••••.•••••.•••••••••19-1
19.1 - Conclusions .••........................•............•..19-1
19.2 -Recommendations .................•......•..............19-2
VOLUME
2
DESCRIPTION
ENVIRONMENTAL ASPECTS
(Sections 1 through 11)
3
4
5
6
7
Appendix A
Al
A2
A3
A4
A5
Appendix B
Bl
B2
B3
B4
B5
B6
B7
B8
Appendix C
Cl
C2
C3
Append ix D
PLATES
HYDROLOGICAL STUDIES
Water Resources Studies
Probable Maximum Flood Study
Reservoir Hydraulic Studies
Reservoir and River Thermal Studies
Climatic Studies for Transmission Line
DESIGN DEVELOPMENT STUDIES
Dam Selection Studies
Watana General Arrangement Stud ies
Devil Canyon Gener a1 Arrangement Stud ies
Power Facilities Selection Studies
Arch Dam Analysis -Devil Canyon
Watana Dam Analysis
Site Fac il it ies
Watana Plant Simulation Studies
COST ESTIMATES ,
Watana Hydroelectric Development - Estimate of Cost
Devil Canyon Hydroelectric Development - Estimate of
Cost
Construction Manpower Forecasts
COORDINATION AND PUBLIC PARTICIPATION
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I)LIST OF TABLES
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TABLE
1.1
5.1
5.2
5.3
5.4
5.5
5.6
5.7
6.1
6.2
6.3
6.4
6.5
6.6
6.7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
7.14
7.15
7.16
7.17
8.1
8.2
8.3
8.4
TITLE
Principal Project Parameters
Historical Annual Growth Rates of Electric Utility Sales
Annual Growth Rates in Utility Customers and Consumption Per Customer
Utility Sales by Railbelt Regions
Summary of Railbelt Electricity Projections
Forecast Total Generation and Peak Loads -Total Railbelt Region
ISER 1980 Railbelt Region Load and Energy Forecasts Used for Generation
Planning Studies for Development Selection
December 1981 Battelle PNL Railbelt Region Load and Energy Forecasts
Used for Generation Planning Studies
Total Generating Capacity Within the Railbelt System
Generating Units Within the Railbelt -1980
Schedule of Planned Utility Additions (1980-1982)
Operating and Economic Parameters for Selected Hydroelectric Plants
Results of Economic Analyses of Alternative Generation Scenarios
Summary of Thermal Generating Resource Plant Parameters/1982$
Alaskan Fuel Reserves
Typical NOAA Cl imate Data Record
Monthly Summary for Watana Weather Station Data Taken During January
1981
Summary of Cl imatological Data
Recorded Air Temperatures at Talkeetna and Summit in OF
Pan Evaporation Data
Average Annual and Monthly Flow at Gage in the Susitna Basin
Gold Creek Natural Flows .
Watana Estimated Natural Flows
Devil Canyon Estimated Natural Flows
Peak Flows of Record
Estimated Flow Peaks in Susitna River
Maximum Recorded Ice Thickness on the Susitna River
Suspended Sediment Transport in Susitna River
Estimated Sediment Deposition in Reservoirs
Water Appropriations Within One Mile of the Susitna River
Hectares and Percentage of Total Area Covered by Vegetation/Habitat
Types
Summary of Earthquake Sources Considered in Ground Motion Studies
Potential Hydroelectric Development
Dam Crest and Full Supply Levels
Capital Cost Estimate Summaries -Susitna Basin Dam Schemes -Cost in
$Million 1980
Results of Screening Model
LIST OF TABLES (Cont1d)
TABLE
8.5
8.6
8.7
8.8
8.9
8.10
8.11
8.12
8.13
8.14
8.15
8.16
8.17
8.18
8.19
9.1
9.2
9.3
9.4
9.5
10.1
10.2
11.1
---_.•._-----_._-
12.1
12.2
12.3
12.4
12..5
12.6
12.7
12.8
12.9
12.10
TITLE
Information on the Devil Canyon Dam and Tunnel Schemes
Tunnel Schemes Power Output and Average Annual Energy
Capital Cost Estimate Summaries for Scheme 3 Tunnel Alternative
Costs in $Million 1980
Susitna Environmental Development Plans
Results of Economic Analyses of Susitna Plans
Results of Economic Analyses of Susitna Plans -Low and High Load
Forecast
Basic Economic Data for Evaluation of Plans
Economic Evaluation of Devil Canyon Dam and Tunnel Schemes and
Watana/Devil Canyon and High Devil Canyon/Vee Plans
Environmental Evaluation of Devil Canyon Dam and Tunnel Schemes
Social Evaluation of Susitna Basin Development Schemes/Plans
Energy Contribution Evaluation of the Devil Canyon Dam and Tunnel
Schemes
Overall Evaluation of Tunnel Scheme and Deyil Canyon Dam Scheme
Environmental Evaluation of Watana/Devil Canyon and High Devil
Canyon/Vee Development Plans
Energy Contribution Evaluation of the Watana/Devil Canyon and High
Devil Canyon/Vee Plans
Overall Evaluation of the High Devil Canyon/Vee and Watana/Devil Canyon
Dam Plans
Combined Watana and Devil Canyon Operation
Present Worth of Production Costs
Design Data and Design Criteria for Final Review of Layouts
Evaluation Criteria
Summary of Comparative Cost Estimates
Design Data and Design Criteria for Review of Alternative Layouts
Summary of Comparative Cost Estimates
Susitna Access Plans
Identification of Conflicts
Watana Peak Work Force and Camp/Vill age Design Population
Rockfill and Earth Dams in Excess of 500 feet
Summary of Design Data for Large Embankment Dams in Seismically Active
Areas
Dams in Seismic Areas
General ized Surficial Stratigraphic Column Area 110 11 and Rel ict Channel
Ring Follower Gates
Preliminary Unit Data
Assumed Properties for Static Analyses of Watana Dam
Watana Dam - Crest Elevation and Freeboard
Recent High Head Francis Turbines
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LIST OF TABLES (Cont'd)
13.1 Watana Peak Work Force and Camp/Village Design Population
13.2 Arch Dam Experience
13.3 Preliminary Compensation Flow Pump Data
13.4 Preliminary Unit Data
14.1 Power Transfer Requirements (MW)
14.2 Summary of Life Cycle Costs
14.3 Transmission System Characteristics
14.4 Technical,Economic and Environmental Criteria Used in Corridor
Selection
14.5 Technical,Economic and Environmental Criteria Used in Corridor
Screeni ng
14.6 Summary of Screening Results
14.7 EMS Alternatives I and II Comparative Cost Estimates
15.1 Energy Potential of Watana - Devil Canyon Developments for Different
Reservoir Operating Rules
15.2 Minimum Acceptable Flows Below Watana Dam During Reservoir Filling
15.3 Turbine Operating Conditions
TABLE
16.1
16.2
16.3
16.4
18.1
18.2
18.3
18.4
18.5
18.6
18.7
18.8
18.9
18.10
18.11
18.12
18.13
18.14
18.15
18.16
18.17
18.18
TITLE
Summary of Cost Estimate
Estimate Summary -Watan a
Estimate Summary - Devil Canyon
Mitigation Measures -Summary of Costs Incorporated in Construction
Cost Estimates
Real (Inflation Adjusted)Annual Growth in Oil Prices
Domestic.Market Prices and Export Opportunity Values in Natural Gas
Summary of Coal Opportunity Values
Summary of Fuel Prices Used in the OGP5 Probability Tree Analysis
Economic Analysis Susitna Project -Base Plan
Summary of Load Forecasts Used for Sensitivity Analysis
Load Forecast Sensitivity Analysis
Discount Rate Sensitivity Analysis
Capital Cost Sensitivity Analysis
Sensitivity Analysis -Updated Base Plan (January 1982)Coal Prices
Sensitivity Analysis -Real Cost Escalation
Sensitivity Analysis - Non-Susitna Plan with Chakachamna
Sensitivity Analysis -Susitna Project Delay
Summary of Sensitivity Analysis Indexes of Net Economic Benefits
Railbelt Utilities Providing Market Potential
List of Generating Plans Supplying Railbelt Region
Forecast Financial Parameters
100%State Appropriation of Total Capital Costs ($5.1 billion in
1982 0011 ars)
LIST OF TABLES (Cont'd)
TABLE
18.19
18.20
18.21
18.22
18.23
TITLE
$3 Billion (1982 Dollars)State Appropriation Scenario 7%Inflation and
10%Interest
$2.3 Bi 11 ion (1982 Dollars)Minimum State Appropriation Scenario 7%
Inflation and 10%Interest
Financing Requirements -$Billion for $3.0 Billion State Appropriation
Scenario
Financing Requirements -$Billion for $2.3 Billion State Appropriation
Scen ario
Basic Parameters of Risk Generation Model
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LIST OF FIGURES
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Figure
1.1
1.2
1.3
4.1
5.1
5.2
5.3
6.1
6.2
6.3
6.4
6.5
6.6
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.20
Titl e
Loc at i on Map
Plan Formulation and Selection Methodology
Pl anning Approach
Damsites Proposed by Others
Historical Total Railbelt Utility Sales to Final Customers
ISER 1980 Energy Forecasts Used for Development Selection Studies
December 1981 Battelle Load and Energy Forecasts Use for Generation
Pl ann ing St ud ies
Loc at i on Map
Formulation Plans Incorporating Non-Susitna Hydro Generation
Selected Alternative Hydroelectric Sites
Generation Scenario Incorporating Thermal and Alternative Hydropower
Developments -Medium Load Forecast
Formulation of Plans Incorporating All-Thermal Generation
Alternative Generation Scenario -Battelle Medium Load Forecast
Data Collection Stations
Average Annual Flow Distribution Within the Susitna River Basin
Monthly Average Flows in the Susitna River at Gold Creek
Flow Duration Curve Mean Monthly Inflow at Watana Pre-Project
Flow Duration Curve Mean Monthly Inflow at Devil Canyon Pre-Project
Annual Flow Duration Frequency Curves -Susitna River at Gold Creek
1:50 Year Annual Flood Inflow Hydrograph -Susitna River at Watana
Dams ite
1:10,000 Year Flood Inflow Hydrograph -Susitna River at Watana
Damsite
Probable Maximum Flood Inflow Hydrograph -Susitna River at Watana
Dams ite
Suspended Sediment Transport -Susitna River at Selected Station
Regional Geology
Talkeetna Terrain Model and Section
1943 Earthquake Geology Map
Location and Territorial Boundaries of Wolf Packs -1980
Division of Nelchina Caribou Herd Ranges
Relative Densities of Moose -November 1980
Employment,Population and Per Capita Personal Income in the
Matanuska-Susitna Borough and Valdez-Whittier-Chitina Census
Division,1979-1980
Communities in the Vicinity of Susitna Basin
Existing Structures
Land Use Aggregations
LIST OF FIGURES (Cont'd)
10.1 Devil Canyon Geologic Map
10.2 Devil Canyon Diversion -Headwater Elevation Tunnel Diameter
10.3 Devil Canyon Diversion - Total Cost Tunnel Diameter
11.1 Access Plan Selection Methodology
11.2 Pl an 2
11.3 Pl an 4
11.4 Plan 6
11.5 Pl an 8
11.6 Plan 10
11.7 Plan 11
8.1 Susitna Basin Plan Formulation and Selection Process
8.2 Profile Through Alternative Sites
8.3 Mutually Exclusive Development Alternatives
8.4 Schematic Representation of Conceptual Tunnel Schemes
8.5 Generation Scenario with Susitna Plan El.3 -Medium Load Forecast
8.6 Generation Scenario with Susitna Plan E2.3 -Medium Load Forecast
8.7 Generation Scenario with Susitna Plan E3.1 -Medium Load Forecast
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9.1 Watana Geologic Map
9.2 Watana Relict Channel -Top of Bedrock
9.3 Mean Response Spectra at Devil Canyon and Watana Sites for Safety
Ev aluation
9.4 Watana Reservoir -Dam Crest Elevation/Present Worth of Product Costs
9.5 Watan a Diversion -Headwater El evat ion/Tunne 1 Di ameter
9.6 Watana Diversion -Up~tream Cofferdam Costs
9.7 Watana Diversion Tunnel and Cofferdam Cost/Tunnel Diameter
9.8 Watana Diversion - Total Cost/Tunnel Diameter
12.1 Watana Diversion - Total Facility Rating Curve
12.2 Watana Reservoir Filling Sequence
··--1-Z-.-3-···---Watana-ReseY'-vQil"Emel"genc.y ..Dr-awdown--.----------------___.
12.4 Watana Comparison of Grain Size Curves for Various Core Materials
12.5 Watana Required Grain Size Curves Main Dam
12.6 Watana -Composite Grain Size Curve -Borrow Site D
12.7 Earthquake Time History
12.8 Watana - Unit Output
12.9 Watana - Turbine Performance Cat Rated Head)
12.10 Francis Turbines Specific Speed Experience Curve for Recent Units
13.1 Devil Canyon Diversion Rating Curve
13.2 Devil Canyon - Unit Output
13.3 Devi l Canyon - Turbine Performance (at Rated Head)
1 LIST OF FIGURES (Cont'd)
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14.1
14.2
14.3
14.4
14.5
14.6
14.7
14.8
14.9
14.10
14.11
14.12
14.13
14.14
14.15
15.1
15.2
15.3
15.4
15.5
16.1
16.2
16.3
18.1
18.2
18.3
18.4
18.5
18.6
18.7
18.8
18.9
18.10
18.11
18.12
Title
Railbelt 345 kV Transmission System Single Line Diagram
Alternative Transmission Line Corridors Southern Study Area
Alternative Transmission Line Corridors Central Study Area
Al ternat Ive Transmission Line Corridors Northern Study Area
Anchorage to Fairbanks -Proposed Transmission Line Route
X-Frame Guyed Steel Tower
Transmission Tower Foundation Concepts
Willow Switching Station -General Layout
University Substation -General Layout
Ester and Knik Arm Stations -General Layout
Stations Typical Elevation -Low Level Bus Arrangement
Energy Management System,Alternative I,System Configuration
Energy Management System,Alternative II,System Configuration
Willow System Control Center,Functional Layout
Energy Management System,Alternative I,Configuration Block Diagram
Typical Load Variation in Alaska Railbelt System
Frequency Analysis of Average Annual Energy for Susitna Developments
Watana - Unit Efficiency (at Rated Head)
Devil Canyon - Unit Efficiency (at Rated Head)
Watana Plant Simulation -December 2000
Watana Development Cumulative and Annual Cash Flow January 1982
Do 11 ars
Devil Canyon Development Cumulative and Annual Cash Flow January 1982
Do 11 ars
Susitna Hydroelectric Project Cumulative and Annual Cash Flow Entire
Project January 1982 Dollars
Probability Tree -System with Alternatives to Susitna
Probability Tree -System with Susitna
Susitna Multivariate Sensitivity Analysis -Long Term Costs vs
Cumulative Probability
Susitna Multivariate Sensitivity Analysis - Cumulative Probability vs
Net Benefits
Risk Analysis Study Methodology
Elements of the Risk Analysis
Structural Relationship for Handling Risk Activity Combinations,
Damage Scenarios and Criterion Values
Cumulative Probability Distribution for Watana Project Cost
Cumulative Distribution of Devil Canyon Costs
Cumulative Probability Distribution for Susitna Hydroelectric Project
Historical Water Resources Project Cost Performance (40 Projects)
Comparison of Susitna Risk Results with Historical Water Resources
Project Cost Performance (48 Projects)
LIST OF FIGURES (Cont'd)
Figure
18.13
18.14
18.15
18.16
18.17
18.18
18.19
18.20
18.21
18.22
18.23
18.24
18.25
18.26
18.27
18.28
18.29
18.30
18.31
18.32
18.33
Title
Watana Schedule Distribution Exclusive of Regulatory Risks
Watana Schedule Distribution Including the Effect of Regulatory Risks
Cumulative Probability Distribution for Days of Reduced Energy
Delivery to Anchorage
Cumulative Probability Distribution for Days per Year with No Susitna
Susitna Energy Delivery to Fairbanks
Railbelt Region - Generating and Transmission Facilities
Service Areas of Railbelt Utilities
Relative Distribution of Energy Supply Generating Facilities,Net
Generation for Types of Fuel and Relative Mix of Generating
Technology -Railbelt Utilities 1980
Energy Demand and Deliveries from Susitna
Energy Pricing Comparisons -1994
System Costs Avoided by Developing Susitna
Energy Pricing Comparisons -2003
Energy Cost Comparison -100 Percent Debt Financing and 7 Percent
Inflation
Energy Cost Comparison -State Appropriations $3 Billion (1982
dollars)
Energy Cost Comparison - $2.3 Billion (1982 dollars)-Minimum State
Appropr iat ions
Energy Cost Comparison -Pricing Restricted 94/95 and 03/04
Energy Cost Comparison Meeting SB/646 Requirements with
100 Percent Financing
Energy Cost Comparison Meetings SB/646 Requirements With $3.0
Billion Appropriation
Bond Financing Requirements
Debt Service Cover
Watana Unit Costs as Percent of Best Thermal Option in 1996
Cumulative Net Operating Earnings by 2000
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lIST OF PLATES -VOLUME 1
SECTION 8
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
SECTION 9
9.1
9.2
9.3
9.4
9.5
9.6
9.7
9.8
9.9
9.10
9.11
SECTION 10
10.1
10.2
10.3
10.4
10.5
SECTION 11
11.1
11.2
Devil Canyon -Hydro Development -Fill Dam
Watan a -Hydro Development -Fill Dam
Watana - Staged Fill Dam
High Devil Canyon -Hydro Development
Susitna III -Hydro Development
Vee -Hydro Development
Denali and Maclaren -Hydro Development
Preferred Tunnel -Scheme 3 - Plan View
Preferred Tunnel -Scheme 3 -Sections
Watana -Arch Dam Alternatives
Watana -Alternative Dam Axes
Watana -Preliminary Schemes
Watan a -Scheme WP1 - Pl an
Watana -Scheme WP3 -Sections
Watan a -Scheme WP2 and WP3
Watana -Scheme WP2 -Sections
Wat an a -Sc heme WP4 -Pl an
Watana -Scheme WP4 -Sections
Watana -Scheme WP3A
Watana -Scheme WP4A
Devil Canyon -Scheme DC1
Devil Canyon -Scheme DC2
Devil Canyon -Scheme DC3
Devil Canyon -Scheme DC4
Devil Canyon -Selected Scheme
Alternative Access Corridors
Alternative Access Routes
LIST OF PLATES -VOLUME 3
WATANA
Plate No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
---_._._-~_.-
33
34
35
36
37
38
39
DEVIL CANYON
40
41
42
Title
Railbelt Area
Reservoir Pl an
Site Layout
General Arrangement
Hydrological Data - Sheet 1
Hydrological Data - Sheet 2
Simulated Reservoir Operation
Main Dam - Pl an
Main Dam -Sections
Main Dam - Grouting and Drainage
Diversion -General Arrangement
Diversion -Sections
Diversion - Intake Structures
Main Spillway -General Arrangement
Main Spillway - Control Structure
Main Spillway -Chute Sections
Main Spillway - Flip Bucket
Outlet Facilities -General Arrangement
Outlet Facilities -Gate Structure
Emergency Spillway
Emergency Release -Sections
Downstream Portals - Plan and Sections
Power Facilities ~General Arrangement
Power Facilities -Access
Power Facilities - Plan and Sections
Power Intake -Sections
Powerhouse - Plans
Powerhouse - Plans
Transformer Gallery - Plan and Sections
Surge Chamber and Tailrace -Sections
Electrical Legend
p~w~rJ:lQJtS_e =SjngkLtn~Qiagram ___
Switchyard -Single Line Diagram
Block Schematic Computer Aided Control System
Access Plan -Recommended Route
General Layout -Site Facilities
Main Construction Camp Site
Village and Town Site
Watana and Devil Canyon -Construction Camp Details
Reservoir Pl an
Site Layout
General Arrangement
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LIST OF PLATES -VOLUME 3
Pl ate No.
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
CONSTRUCTION SCHEDULES
75
76
Title
Hydrological Data - Sheet 1
Hydrological Data - Sheet 2
Simulated Reservoir Operation
Dams - Plan and Profile
Main Dam -Geometry
Main Dam -Crown Section
Main Dam -Sections
Main Dam - Thrust Blocks
Main Dam - Grouting and Drainage
Main Dam -Outlet Facilities
Saddle Dam -Sections
Diversion -General Arrangement
Diversion -Sections
Main Spillway -General Arrangement
Main Spillway - Control Structure
Main Spillway -Chute Section
Emergency Spillway -General Arrangement
Emergency Spillway -Sections
Power Facilities -General Arrangement
Power Facilities -Access
Power Facilities - Plan and Sections
Power Intake -Sections
Powerhouse Plans
Powerhouse -Sections
Tr an sformer Gall ery - Pl an and Sections
Surge Chamber and Tailrace -Sections
Tailrace Portal - Plan and Sections
Powerhouse -Single Line Diagram
Switchyard -Single Line Diagram
General Layout -Site Facilities
Main Construction Camp Site
Temporary Vi 11 age
Watana Construction Schedule
Devil Canyon Construction Schedule
j
LIST OF REFERENCE REPORTS
The following reports and documents were prepared during the course of the study
program.Specific references in the text of the report are cited and listed
separately by section;they should not be confused with the following list.
I1
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Number
Rl
R2
R3
R4
R5
R6
R7
R8
R9
RIO
Rll
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
R25
R26
R27
R28
R29
R30
R31
R32
R33
R34
R35
R36
R37
Report
Plan of Study
Plan of Study, Revision 1
Pl an of Study, Revision 2
Plan of Study, Revision 3
Forecasting Peak Electrical Demands for
Alaska's Railbelt
Closeout Report,Review of ISER Work
Task 1 Termination Report,September 1980
Field Reconnaissance of Reservoir Area -
Timber Report
Marketability and Disposal Study for
Reservo ir Area
Aerial Photography and Photogrammetric Mapping
Control Network Survey Report
Hydrographic Surveys
Field Data Collection and Processing
Gl ac ier St ud ies
Regional Flood Studies
Hydraulic and Ice Studies
Reservoir Sedimentation
River Morphology
Review of Available Materials
Fie 1d Data Index
Water Quality -Annual Report -1980
Water Quality -Annual Report -1981
Water Quality -Interpretation -1981
Ice Observations -1980
Processed Climatic Data for Six Weather Stations
(6 vol umes)
Interim Report on Seismic Studies
Final Report on Seismic Studies
1980 Geotechnical Report (Superceded by R29)
1980-81 Geotechnical Report
OGP Data
Development Selection Report
Review of Previous Studies and Reports
Closeout Report February 1981
Tunnel Alternative Report July 1981
Evaluation of Arch Dam at Devil Canyon Site
1981 Upper Limit Capital Cost Estimate,July 1981
Scour Hole Development Downstream of High
Head Dams
1980 Summary Environmental Report
Prepared By
Acres
Acres
Acres
Acres
WCC
Acres
Acres
R&M
R&M
R&M
R&M
R&M
R&M
R&M/U.of Al aska
R&M
R&M/Acres
R&M
R&M
Acres
R&M
R&M
R&M
R&M
R&M
R&M
wce
wce
Acres
Acres
Acres
Acres
Acres
Acres
Acres
Acres
Acres
TES
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)
LIST OF REFERENCE REPORTS (Cont'd)J
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Acres
Acres
Acres
Acres
Acres
Acres
Acres
Acres
Prepared By
TES
TES
TES
TES
TES
TES/Acres
Acres
TES
TES
ADF&G
ADF&G
TES
TES
TES
TES
TES
TES
TES
Acres
TES
R&M
Acres
Acres
Acres
Acres/TES
TES
TES
TES
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Report
Environmental Report - Fish Ecology -1980
Environmental Report -Plant Ecology -1980
Environmental Report -Big Game -1980
Environmental Report - Birds and Non Game
Mammals -1980
Environmental Report -Furbearers -1980
Environmental Report -Land Use Analysis -1980
Environmental Report -Socioeconomics -1980
Environmental Report -Cultural Resources -1980
Fish and Wildlife Mitigation Policy - Revised
Instream Flow Study Plan
Draft Fishery Mitigation Plan
Draft Wildlife Mitigation Plan
Phase 1 Report - Fish Ecology
Phase 1 Report -Big Game
Phase 1 Report -Plant Ecology
Phase 1 Report - Bird and Non-Game Mammal s
Phase 1 Report -Furbearers
Phase 1 Report -Land Use
Phase 1 Report -Socioeconomics
Phase 1 Report -Cultural Resources
Phase 1 Report -Recreation
Sociocultural Report
Environmental An alys i s of AlternatiVe Access Pl an
Access Planning Study
Access Route Selection Report
Electric System Studies
Transmission Line Corridor Screening Report
Transmission Line Selected Route
Switching Stations and Substations -Single
Line Diagrams
Agency Consultation Report
----lnit-i-al--Version-Rrelim-in aryLicensing-----------
Documentation,April 1980
Preliminary Licensing Documentation -2nd Version
November 1981
Status of Susitna Basin Water Rights
Project Overview Report,2nd Draft
Economic Marketing and Financial Evaluation
Susitna Risk Analysis
Number
R38
R39
R40
R41
R42
R43
R44
R45
R46
R47
R48
R49
R50
R51
R52
R53
R54
R55
R56
R57
R58
R59
RoO
R61
R62
R63
R64
R65
R66
R67
-------------------R6g----
R69
R70
R71
-R72
R73
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9 -SELECTION OF WATANA GENERAL ARRANGEMENT
This section describes the evolution of the general arrangement of the
Watana project,which,together with the Devil Canyon project,com-
prises.the development plan selected as part of Section 8. This sec-
tion also describes the site topography,geology, and seismicity of the
Watana site relative to the design and arrangement of the various site
facilities.The process by which reservoir operating levels and the
installed generating capacity of the power facilities were established
is presented,together with the means of handling floods expected
during construction and subsequent project operation.
The main components of the Watana development are as follows:
-Main dam;
-Diversion facilities;
- Spillway facilities;
-Outlet facilities;
-Emergency release facilities;and
-Power facilities.
A number of alternatives are available for each of these components and
they can obviously be combined in a number of ways.The following par-
agraphs describe the various components and methodology for the prelim-
inary,intermediate,and final screening and review of alternative gen-
eral arrangement of the components,together with a brief description
of the selected scheme. A detailed description of the various project
components is given in Section 12.
9.1 -Site Topography
The project site is located in a broad U-shaped valley at river mile
184,approximately 2.5 miles upstream of the confl uence of Tsusena
Creek with the Susitna River.The river at the site is relatively
wide,although turbulent.On the right bank,the valley rises at an
approximate slope of 2H:1V from river level at Elevation 1450 for
approximately 600 feet,then gradually flattens to a maximum elevation
of 2350 between the Susitna River and Tsusena Creek.The left bank
ri ses more steeply from the ri ver for about 450 feet at a slope of
1.4H:1V,then flattens to 3H:1V or less to approximate Elevation 2600.
9.2 -Site Geology
A detailed description of the geology and site investigations at the
Watana site is given in the 1980-1981 Geotechnical Report (1).The
following is a brief summary of the findings presented in ·the Geotech-
nical Report.
9-1
(a)Geologic Conditions
A summary of site overburden and bedrock conditions is presented
in the following paragraphs.A geologic map of the damsite area
is shown in Figure 9.1.
(i)Overburden
Overburden thickness in the damsite area ranges from 0 up
to 80 feet in localized areas.On the lower slopes,the
overburden consists primarily of talus.The upper areas of
the abutments near the top of the slope are deposits of
glacial tills,alluvium,and talus.Subsurface investiga-
tions show the contact between the overburden and bedrock
to be relatively unweathered.
The depth of the ri ver all uvi um beneath the proposed dam
averages about 80 feet and consists of sand,silt,coarse
gravels,ard boulders.
(ii)Bedrock Lithology
The damsite is primarily underlain by an intrusive dioritic
body which varies in composition fro~granodiorit~to
quartz di orite to di or tt e.The texture is massi ve and the
rock is hard,competent,and fresh except wi thi n sheared
and altered zones.These rocks have peen intruded by ~afic
lind felsic dikes which are generally 9D1Y a few feet tgick.
The contacts are healed and competent.The rock immedi-
ately downstream from the damsite is an andesite porphyry.
This rock is medium to dark gray to green and contains
quartz diorite inclusions.The contact zone of the ande-
site with the diorite is generally weqthered and fractured
up to 10 to 15 feet above the contact.
(iii)Bedrock Structures
There are two major and two minor joint sets at the site.
Set I,which is the most prominent set,strikes 320 0 and
dips to 80 0 NE to vertical.This set is found throughout
the damsite and parallels the general structural trend in
the regi on.Set I has a subset,whiGh strikes 290 0 to
300 0 with a dip of 75 0 NE.Thfs subset is local ized in
the downstream area near where the diversion tunnel por-
tals are proposed.This subset also parallels the shear
zones in the downstream area of the site.Set II trends
northeast to east and dips vertically.··This set is best
developed in the upstream portion of the damsite area,
but is 1oca11y promi nent in the downs tr earn areas.Sets
III and IV are minor sets but can be locally well
9-2
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j developed. Set III trends N-S with variable dips ranging
from 40°east to 65°west,while Set IV trends 090° with
subhorizontal dips.Set III forms numerous open joints
on the cl iff faces near the "Fi ngerbuster,II and several
shear zones parallel this orientation.Set IV appears to
have developed from stress relief from glacial unloading
and/or valley erosion.
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The average spacing of Joint Sets I
and 6 to 12 inches,respectively.
Sets III and IV is quite variable
few inches to several feet.
- Shears and Fracture Zones
a nd II is 1 to 2 feet
The spacing of Joint
and can range from a
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Several shears,fracture zones,and alteration zones are
present at the site (Figure 9.1).For the most part,
they are small and discontinuous.All zones greater than
10 feet in width have been delineated on the geologic map
(Figure 9.1).
Shears are defined as having breccia,gouge,and/or
slickenslides indicating relative movement.Two forms of
shearing are found at the site.The first type is found
only in the diorite and is characterized by breccia of
sheared rock that has been rehealed into a matrix of very
fine grained andesite/diorite.These shear zones have
hi gh RQDs and the rock is fresh and hard.The second
type is common to all rock types and consists of unhealed
brecca and/or gouge.These shear zones are soft,fri-
ab1e,and often have secondary mi nera 1i zat i on of carbon-
ate and chlorite showing slickenslides.These zones are
generally less than 1 foot wide.
Fracture zones are also common to a11 rock types and
range from 6 inches to 30 feet wide (generally less than
10 feet).These zones are closely spaced joints that are
often iron oxide stained or carbonate coated.Where
exposed,the zones trend to form topographic lows.
Alterati on zones are areas where hydrothermal sol uti on
have caused the chemical breakdown of the feldspars and
mafic minerals.The degree of alteration encountered is
highly variable across the site.These zones are rarely
seen in outcrop as they are easily eroded into gull ies,
but were encountered in all the boreholes.The transi-
tion between fresh and altered rock is gradational.The
zones may range to 20 feet thick although are usually
less than 5 feet.
9-3
(b)Structural Features
The Watana site has several significant geologic features consist-
ing of shears,fractures and alteration zones described previous-
ly (Figure 9.1).
The two most prominent areas have been named the "Fi ns" and the
"Fingerbuster."The "Fins"is located on the north bank of the
river upstream from the diversion tunnel intake.It is an area
approximately 400-feet wide,characterized by three major north-
west trendi ng zones of sheari ng and a lterat i on that have eroded
into steep gu 11 ies .These a lterat ion zones are separated by i n-
tact rock bands (ribs)5 to 50 feet wide.The 20-foot-wide up-
stream zone of the series coincides with the diorite/andesite
porphyry contact.The other two zones,approximately 55 and 30
feet wide,are filled with severely altered rock.This zone
trends 310°with a near vertical dip.The extension of the zone
has been extrapolated to extend northwestward outcroppng in
Tsusena Creek.
The "Fingerbuster"is located downstream from the damsite and is
exposed in a 40-foot-wide deep talus-filled gully along the ande-
site porphyry/diorite contact (Figure 9.1).The rock is severely
weathered with closely spaced joints trending parallel to Set I
(330°)and Set III (0°).Slickensides indicate vertical displace-
ment.The extens ion of thi s zone to the south is based on a
strong north-south topographic lineament.Because of the lack of
exposure,its location and extent have been approximated.
A prominent alteration zone was encountered on the south bank
where a drill hole encountered approximately 200 feet of hydro-
thermally altered rock.Although core recovery in this boring was
good,the quality of rock was relatively poor (Figure 9.1).
(c)Ground Water Conditions
The groundwater regime in the bedrock is confined to movement
alongfracturesand joints.The water table is a subdued replica
....of --the--surface-to·pographY:---Water revels on -t-fie--r i ghr-ilbulmen1:
were deep,ranging from about 110 to 280 feet.Ground water con-
diti ons on the south abutment are compl icated because of the
apparent continuous thick permafrost resulting in a perched water
table near surface and a deep table below the frost.
(d)Permafrost Conditions
Permafrost conditions exist on the north-facing slopes (left bank)
of the damsite area.Measurements indicate that permafrost exists
to a depth of 200 to 300 feet.Temperature measurements show the
permafrost to be "war m"(withi n 1°C of freezi ng).No permafrost
was found on the north abutment but sporadic areas of frost can be
expected.
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(e)Permeability
The rock permeability does not vary s tqnt t icant ly within the site
area;generally ranging between 1 x 10-
4 em/sec to 1 10-
6
em/sec.The permeabil ity is controll ed by a degree of fractures
withi n the rock,with the higher permeabi 1ity occurri ng in the
more sheared and fractured zone.Permeabilities tend to decrease
with depth.
(f)Reservoir Geology
The topography of the Watana Reservoir and adjacent slopes is
characterized by a narrow V-shaped stream-cut valley superimposed
on a broad U-shaped glacial valley.Overburden masks much of the
bedrock especially in the lower and uppermost reaches of the res-
er voi r,
The lower P9rtions of the Watana reservoir are predominantly cov-
ered by a veneer of glacial till with scattered outwash deposits.
On the south si de of the Sus itna Ri ver,the Fog Lakes area is
characterized by a fluted ground moraine surface.Upstream in the
Watana Creek area,a broad flat plain is mantled with glacial till
and semi-consolidated Tertiary sediments.These are predominantly
stratified,poorly graded,fine sands,and silts with some clays.
The river valleys contain significant amounts of alluvial deposits
and reworked outwash. Ice disintegration features such as kames
and eskers have been observed in the river valley.
A non-conformable contact between argillite and the diorite pluton
at the damsite area was mapped approximately three miles upstream
from the dams i te ,Semi -conso 1i dated,Tert iary age sedimentary
rocks and volcanics are present just downstream from the conflu-
ence of metabasalt flows with thin interbeds of metachert,argil-
lite,marble,and metavolcaniclastic rocks.The rocks between Jay
Creek and Oshetna Creek are metamorphic amphi bol ite and mi nor
amounts of greenschist and foliated diorite.
The mai n structura 1 feature of the Watana Reservoir is the Ta 1-
keetna Thrust Fault whi ch trends northeast-southwest.The Ta 1-
keetna Thrust Fault crosses the Susitna River approximately eight
miles upstream from the dams i te.This fault has been studied in
detail as part of the seismic studies,and has been determined to
be inactive (2).
(g)Construction Material Investigations
Extensive investigations have been conducted both prior to and
during the current studies to identify quantities of suitable ma-
terials for the construction of an embankment dam and for concrete
aggregates.Detailed discussion of-these borrow and quarry sites
is presented in the 1980-81 Geotechnical Report (1).
9-5
(i)Rock Fill Material
The source for rockfill material is Quarry A,which com-
prises the rock knob immediately adjacent to the left abut-
ment.The rock in Quarry A is di orite and andesite.The
rock is generally hard,durable and fresh,and is suitable
for use as rockfill in the dam.
(ii)Core Material
Two sources have been identified for the site core material
and are desi gnated as Borrow Site 0 and Borrow Si te H.
Borrow Site 0 is located immediately northwest of the dam-
site on the north bank.The upper few feet of material
comprise tundra,topsoil,and boulders,which is underlain
by thick glacial tills composed of gravelly silty sands
with some clay.An alternative source of core material,
designated Site H,is located approximately 7 miles down-
stream from the damsite on the south bank of the river.
(iii)Filter Material
Borrow Site E has been ident ifi ed as a pr imary source of
material for filter and transition zones of the embankment.
This area is located at the confluence of the Tsusena Creek
and the Susitna Ri ver approximately 2.5 mi les downstream
from the damsite.The area is covered by about 2 feet of
organics and silt underlain by a few feet thick layer of
silty sand to clean sand and a thick layer of sandy and
gravelly material exists.Sufficient quantities are avail-
able in this borrow site to meet the project requirements
for filter materials and will also be a major source of
gravel materials for the shells of the dam.
(iv)Gravels and Cobbles for Shells
To identify additional sources of gravel for the shells,
seismic refraction survey investigations were performed
---~----------------~-------b()1;h-l:Jp str earn anddowns-tream--fr om~-t-he---dams-ite --i n-the
Susitna River valley.These investigations confirmed that
sufficient quantities of granual material are available for
use in the supporting shell zones of the dam to supplement
Borrow Site E.Available data indicates that the grain
size distribution of these materials will be similar to
that from Borrow Site E, with probably a higher percentage
of coarser material.
(v)Concrete Aggregate
The material available from Borrow Sites E, C, F,and the
riverbed alluvium is suitable for use as coarse and fine
aggregate for concrete.Processi ng wi 11 be required to
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produce desired gradations.The coarser particles are
rounded and petrographic analyses have indicated the mate-
rial to be of good quality.Sufficient quant t t i es are
available within the identified sources.
9.3 - Geotechnical Design Lonsiderations
This section deals with the geotechnical aspects of design of the dam
and other major structures at the Watana site.
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(a)
(b)
Main Dam Excavation and Foundation Treatment
As discussed previously,the riverbed alluvium ranges up to ap-
proximately 80 to 100 feet in depth.The character of this mater-
ial has not yet been well defined and its stability during a
strong earthquake event is questionable.The overburden material
on the abutments is relatively thin,except for gullies and pock-
ets.Most of this material is frozen and will become unstable
when thawed and is therefore unsuitable for the dam foundation.
Localized sheared and altered zones beneath the proposed dam will
not adversely affect the dam foundation.Potential seepage
through these zones will be eliminated by a grout curtain cutoff
combined with a downstream drainage system.
Although the two major geologic structures at the site,the "Fins"
on the upstream si de and the "Fi ngerbuster"on the downstream
side,have had an influence on the overall project layout,they do
not directly affect the dam at its proposed location.
Extensi ve permafrost is present on the south bank and sporadic
permafrost may be encountered on the north bank. This permafrost
is within 1°C of freezing.Thawing of the permafrost and grouting
of the foundation will be required.
Cofferdams and Dewatering
Because of the pervious nature of the thick ri verbed deposits,
some form of cutoff will probably be required beneath both the up-
stream and downstream cofferdams to control seepage. A sl urry
trench cement bentonite cutoff constructed from an initial rock-
fill/gravel closure dike is currently proposed.Such a cutoff is
unlikely to be fully effective and continuous dewatering will be
required to handle seepage through the cutoff until the dam con-
struction is above the diversion stage pool level.
Further exploration is necessary in the riverbed to better define
the alluvial materials at the cofferdam sites and provide data for
the final design.
9-7
(c)Underground Structures
The rock conditions at the Watana site are suitable for the con-
structi on of tunnel s and underground caverns.The 1 ocati on and
the orientation of these structures is influenced by the orienta-
tion and location of rock discontinuities.Permafrost conditions
will not have any major adverse impact except where thawing may be
required for grouting.
The RQD values indicate that 85 percent of the rock is of a good
to excellent category.The remaining 15 percent represents poor
qua1 ity rock associ ated with rock di scontt nuit tes.The major
joint sets at the Watana site are oriented at N40W (Set I)and
N45E (Set II).Other four joint sets are minor.The major shear
and fracture zones al so parall el these general trends.The most
favorable orientations for the tunnels and the large underground
caverns are with their long axis perpendicular to the major joint
sets.These factors have been a major consideration in selection
of the alignments of the tunnels and major caverns to achieve max-
imum stability and minimum support requirement.
Although little is known at this time about the insitu stress re-
gime at the site,the general tectonic stress regime within the
region is in a compression mode.Conventional rock bolt support
is generally considered adequate inmost areas with spans less
than 40 feet.For larger spans and in areas of poor quality rock,
the support requirements have been determi ned on a case-by-case
basis.In the case of large span openings,intersection of nearby
Vertical and subhorizontal joints can create unstable blocks in
the crown.Allowances have been made for the use of support mea-
sures such as shotcrete,welded wire fabric,and concrete lining
in areas of potentially poor rock quality and in water carrying
tunnels under high head (such as penstocks).
Although the rock mass is fairly impervious,intersection of rock
discontinuities may cause ground water seepage and high pore pres-
sures during operation.
---+unne-l-exeava-tio n-ean-be-per-formed-u si-ng -either-convent-i-ona-ldri-ll --
and blast techniques or high production mechanical excavating
equipment.Sufficient information is not available at this time
to make this decision,and for feasibil ity assessment purposes,
conventional drill and blast methods have been assumed.
The spaci ng between long tunnels has been set at 2.5 times the
diameter of the largest tunnel.The spacing between the major
caverns has been set such that a pillar thickness of 1.5 times the
span of the larger cavern is maintained.
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(d)Stability of Soil and Rock Slopes
In most areas the excavation slopes will be in rock.The slopes
in the overburden ha ve been determined based on soil properties,
ground water table,and the height of the slope.In general,
slopes in overburden will not be steeper than 2H:IV below the
water table and 1.5H:1V above the water tabl e. A bench of ade-
quate wi dth wi 11 be provt ded at the overburden-rock contact to
accommodate any local slumping or slope failure and to intercept
and dispose of ground/seepage water.Flatter slopes may be
required where frozen ground may become unstable during thawing.
The cut slopes in rock will be controlled by the local joint dips
and orientations.Major joint set dips are near vertical and
where such joints control slopes,they will be cut at IH:IOV,with
fl atter slopes where necessary to ensure stabil i ty ,In genera 1,
slopes will be cut back to the dip of the controlling joint set or
flatter.Locally,rock bolting or similar support techniques and
drainage systems will be provided to stabilize individual blocks,
ensure overall stability of rock slopes and maintain safe working
conditions.
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(e)
(f)
Use of Excavated Rock in Dam Construction
Since most of the rock excavation will be within the diorite and
andesite,the quality of rock will be acceptable for use as rock-
fill.Poor quality or weathered rock will not be acceptable fill.
The use of rockfill in the dam will be limited to the downstream
shell,and in zones or rip-rap material.
Relict Channel
A deep bedrock depress ion exi sts on the north bank of the ri ver
extendi ng from about 2,500 feet west of Deadman Creek northwest
toward Tsusena Creek.The depth to bedrock is as much as 400 feet
below the surface and the reservoir 1eve l.The overburden con-
sists of several sequences of glacial deposits,lake sediments,
and alluvium varying in thickness and character both laterally and
with depth.Some of these granular deposits exhibit high permea-
bil ity,and temperatures below O°C were noted at a depth of
several hundred feet suggesting the possibility of permafrost.
The ground water surface has not been well defined.Perched water
tables are evidenced by the presence of several surface lakes.
Artesian conditions have been encountered in at least one boring.
With the proposed range of reservoir levels,these overburden de-
posits will become saturated.A bedrock contour map of the Relict
Channel area is presented in Figure 9.2.
Additional investigation will be necessary to properly character-
ize the subsurface conditions in the area prior to construction.
Details of the potential design problems to be dealt with in the
Relict Channel and the possible methods of treatment are discussed
further in Section 12.
9-9
9.4 -Seismic Considerations
For earthquake engineering and design considerations,.the project
structures have been cl ass ified as either crit ical structures or non-
critical structures.Critical structures include the dam and similar
major structures whose fail ure may result in sudden and uncontrolled
release of large volumes of water which may endanger property and lives
downstream.The non-critical structures are those structures whose
failure can be assessed as an economic or financial loss to the project
in terms of lost revenue,repair,and/or replacement cost.Critical
structures wi 11 be designed to safely withstand the effect of the
II Safety Ev al uat ion Earthquake"(SEE)for the site.No significant dam-
age to these structures wi 11 be accepted under these cond it ions.The
design of noncritical structures for earthquake conditions is under-
taken on the basis of conventional Uniform Building Code recommenda-
tions.
Two sources will be used for determination of the most severe SeE con-
dition as a basis for design of structures at Watana,a Ben ioff Zone
.max imum earthquake of magn itude 8.5 at a distance of 40 miles' from the
site,and a Terrain maximum earthquake of magnitude 6.25 at a distan~e
of less than 6 miles from the site.
Design of critical concrete structures is generally based on a conser-
vative analysis using an 80th percentile response spectrum for The Ter-
rain SEE,with a 10 percent damping ratio (Figure 9.3),scaled down by
a factor of 80 percent.
Although the Terrain earthquake would result in more severe ground
motions,the duration of these motions is relatively short and the
likelihood of occurrence of such an event is extremely small.A more
likely source of strong ground shaking at the Watana site is the Beni-
off Zone.
The design of the Watana dam has therefore been based on the projected
time history for this event as discussed in Section 12.
9.5 -Selection of Reservoir Levels
The selected elevation of the Watana dam crest is based on considera-
tions of the value of the hydroelectric energy prOduced from the asso-
ciated reservoir,geotechnical constraints on reservoir levels,and
freeboard requ irements.Fi rm energy,average annual energy,construc-
tion costs and operation and maintenance costs were determined for the
Watana development with dam crest elevations of 2240,2190,and 2140
feet.The relative value of energy produced in terms of the present
worth of the long-term production costs (LTPW)for each of these three
dam elevations was determined by means of the OGP generation planning
model described in Section 6.The physical constraints imposed on dam
height and reservoir elevation by geotechnical considerations were re-
viewed and incorporated into the crest elevation selection process.
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fJ Finally,freeboard requirements for the PMF and settlement of the dam
after construction or as a result of seismic activity were taken into
account.
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(a)
(b)
Methodology
Firm and average annual energy produced by the Susitna development
are based on 32 years of hydrological records.The energy pro-
duced was determined by using a multi-reservoir simulation of the
operation of the Watana and Devil Canyon reservoirs.A variety of
reservoir drawdowns were exami ned,and drawdowns produci ng the
maximum firm energy consi stent with engineeri ng feasi bil ity and
cost of the intake structure were selected (see Section 9.11).
Mi nimum fl ow requirements were estab 1ished at both project sites
based on downstream fisheries considerations.
As discussed in Section 9.6,to meet system demand the required
maximum generating capability at Watana in the period 1993 and
2010 ranges from 665 MW to 908 MW.For the reservoir 1eve1 de-
terminations,energy estimates were made on the basis of assumed
average annual capacity requirements of 680 MW at Watana in 1993,
increasing to 1020 MW at Watana in 2007, with an additional 600 MW
at Devil Ca nyon comi ng on 1 ine in the year 2002.The long term
present worth costs of the generation system required to meet the
Railbelt energy demand were then determined for each of the three
crest elevations of the Watana dam using the OGP5 model.
The construction cost estimates used in the OGP5 modeling process
for the Watana and Devil Canyon projects were based on preliminary
conceptual layouts and construction schedules.Further refinement
of these layouts has taken place during the optimization process.
These refi nements have no si gnifi cant impact on the reservoir
level selection.
Economic Optimization
Economic optimization of the Watana reservoir level was based on
an evaluation of three dam crest elevations of 2240, 2190,and
2140 feet.These crest elevations apply to the central portion of
the embankment with appropriate allowances for freeboard and seis-
mic settlement,and correspond to maximum operating levels of the
reservoir of 2215,2165,and 2115 feet,respectively.Average
annual energy calculated for each case using the reservoir simula-
tion model are given in Table 9.1,together with corresponding
project construction costs.
In the determination of LTPW,the Susitna capital costs were ad-
justed to include an allowance for interest during construction
and then used as input to the OGP5 model.Simulated annual energy
yields were distributed on a monthly basis by the reservoir opera-
tion model to match as closely as possible the projected monthly
9-11
- For flood magnitudes up to the 1:10,000-year event,there will
be no danger of overtopping the lowest point in the relict chan-
ne1.
energy demand of the Rai1belt and then input to the OGP5 model.
The LTPW of meeti ng the Rail belt energy demand usi ng the Susitna
development as the primary source of energy,were then determined
for each of the three reservoir levels.
On the ri ght si de of the reservoir created by the Watana dam a
relict channel of considerable depth connects the reservoir to
Tsusena Creek.As the water surface elevation of the reservoir is
increased up to and beyond 2200 feet,a low area in the relict
channel would require costly water retaining structures to be
built and other measures to be taken.In addition to the cost the
techni ca1 feasi bil ity of these measures is not as certai n as
desired on a project of this magnitude.Because of the
considerations relating to seismic stability,seepage problems and
permafrost conditions in the relict channel area,it was concluded
that the relict channel area should not be constantly under water.
By comparing normal reservoir levels plus flood surcharge to
ground surface contours,it was determined that with normal
______l'eseC\tQtI"J~_'v'e 1~of 2185 and a sma1}fr~~l:>oar~_c:ll~~_JtLeJQJJQwi ng
conditions would exist:
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The results of these evaluations are shown in Table 9.2,and plots
showing the variation of the LTPW with dam crest elevation are
shown in Figure 9.4.This figure indicates that on the basis of
the assumptions used,the minimum LTPW occurs at a Watana crest
elevation ranging from approximately 2160 to 2200 feet (reservoir
levels 2140 to 2180).A higher dam crest will still result in a
development which has an overall net economic benefit relative to
thermal energy sources.However,it is also clear that as the
height of the Watana dam is increased,the unit costs of addition-
al energy produced at Watana is somewhat greater than for the dis-
placed thermal energy source.Hence,the LTPW of the overall
system wou1 d increase.Conversely,as the hei ght of the dam is
lowered,and thus Watana produces 1ess energy,the unit cost of
the energy produced by a thermal generation source to replace the
lost Susitna energy,is more expensive than Susitna energy.In
this case also,the LTPW increases.
GeotechnicB1 Considerations(c)
For the PMF a freeboard dike in the low area of up to 10 feet in
height would provide adequate protection.This dike would be
wetted only a few days during a PMF event.
-If seismic settlement or settlement due to permafrost melting
di d occur,the combi nati on of the 10 feet freeboard dike con-
structed on a suitable foundation plus a normal reservoir level
of 2185 would ensure that breakthrough in the relict channel
area would not occur.
9-12
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(d)
With this approach,the Watana project will develop the maximum
energy reasonably available without incurring the need for costly
water retaining structures in the relict channel area.
Conclusions
It is important to establish clearly the overall objective slight-
ly of setting the Watana reservoir level.An objective which is
to minimize the LTPW energy cost will lead to selection of a
slightly lower reservoir level than an objective which is to maxi-
mize the amount of energy which can be obtained from the available
resource,while doing so with a technically sound project.
The three values of LTPW developed by the OGP5 computer runs de-
fined a relationship between LTPW and Watana dam height which is
relatively insensitive to dam height.This is highlighted by the
curve of LTPW versus dam height in Figure 9.4.This figure shows
there is only a slight variation in the LTPW for the range of dam
heights included in the analysis.Thus,from an economic stand-
point,the optimum crest elevation could be considered as varying
over a range of elevations from 2140 to 2220 feet with little
effect on project economics.The governing factors in establish-
ing the upper limit of darn height were consequently the geotechni-
cal considerations discussed in (c) above.
The normal maximum operating level of the reservoir was therefore
set at Elevation 2185, al l owi nq the objective of maximizing the
economic use of the Susitna resource still to be satisfied.
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9.6 -Selection of Installed Capacity
The generating capacity to be installed at both Watana and Devil Canyon
was determined on the basis of generation planning studies described in
Sections 6 and 8,together with appropriate consideration of the fol-
1owi ng:
-Available firm and average energy from Watana and Devil Canyon;
-The forecast energy demand and peak load demand of the system;
-Available firm and average energy from other existing and committed
plant;
-Capital cost and annual operating costs for Watana and Devil Canyon,
-Capital cost and annual operating costs for alternative sources of
energy and capacity;
-Environmental constraints on reservoir operation;and
- Turbine and generator operating characteristics.
(a)Methodology
The following procedure was used to select the installed capacity
Watana:
9-13
-The firm and average energy available at both Watana and Devil
Canyon was determined using the reservoir simulation program
described in Section 9.5 (see Plate 8.6).
- A determinat ion was then made of the generating capacity re-
quired to utilize the available energy from the Susitna Project
in the hydrological years of record,based on the following
assumptions:
• In a wet year,energy developed at either Watana or Devil Can-
yon,displaces excess thermal energy (from coal,gas turbine,
combined cycle,or diesel plants).
• In an average year,where thermal energy is required to meet
system energy demand,hydro energy is used either to satisfy
peak demand with thermal energy supplying base load (Option
I);or hydro energy is used to supply base load requirements
with thermal energy at peak demand (Option 2).The actual
choice is based on dispatching the most economic energy
first.
Devil Canyon energy is used predominantly as base load ener:-gy
because of environmental constraints on downstream flow varia-
tions.
•The maximum installed capacity WqS determined on the basis of
the estab 1ished peak generat i ng capacity required plus any
hydro standby or spinning reserve equipment.
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Watana Installed Capacity
The required total capacity at Watana in a wet year,excluding
standby and spinning reserve capacity,is summar lzed below.The
capacities are based on the Battelle medium load forecast.
Capacity {MW
Opt i on 1 Option 2
Devil Devil
----------_•.._~------
j{at_CLOlL .Jhermal.._C_a~oYQIL _~W~a.t_ao_a_.Ihermal__C_a_oy_o_~
Demand Year Peak Base Base Base Peak Base
1993 801 0 0 801 0 0
1995 839 0 0 839 0 0
2000 874 66 0 742 198 0
2002 (Including
Devi 1 Canyon)660 0 354 660 0 354
2005 (Including
Devi 1 Canyon)750 0 376 750 0 376
2010 (Including
Devi 1 Canyon)900 0 493 900 0 493
(b)
~~I(~~1-···_·····_······_._.
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On the basis of this evaluation,the ultimate power generation
capability at Watana was selected as 1020 MW for design purposes,
to allow a margin for hydro spinning reserve and standby for
forced outage.This installation also provides a small margin in
the event that the load growth exceeds the Battelle medium load
forecast.
Unit Capacity
Selection of the unit size for a given total capacity is a compro-
mise between the initial least cost solution,generally involving
a scheme with a smaller number of large capacity units,and the
improved plant efficiency and security of operation provided by a
1arger number of smaller capacity units.Other factors incl ude
the size of each unit as a proportion of the total system load and
the mini~um anticipated load on the station.Any requirement for
a minimiJm downstream flow would also affect the selection.Growth
of th~~ctual load demand is also a significant factor,since the
installation of units may be phased to match the actual load
growth.The number of units and their individual ratings were
determi ned by the need to del iver the required peak capacity in
the peak demand month of December,at the minimum December reser-
voir level,with the turbine wicket gates fully open.
An examination was made of the economic impact on power plant pro-
ducti On.costs of vari ous combi nati ons of a number of units and
rated capacity,which would provide the selected total capacity of
1020 MW.For any given installed capacity,plant efficiency in-
creases as the number of units increases.The assumed capitalized
value used in this evaluation was $1.00 per kWh,based on the eco-
nomic analysis completed for the thermal generation system. Vari-
ations in,the number of units and capacity will affect the cost of
the power intakes,penstocks,powerhouse,and tailrace.The dif-
ferences in these capital costs were estimated and included in the
evaluation.The results of this analysis are presented below.
Capitalized
Rated Val ue of
Capacity Additional Additional
Number of Unit Energy Capital Cost Net Benefit
of Units (MW)($Millions)($Millions)($Millions)
4 250 0 0 0
6 170 40 31 9
8 125 50 58 -8
It is apparent from this analysis that a six-unit scheme with a
net benefit of approximately $9 million is the most economic al-
ternative.This scheme also offers a higher degree of flexibility
and secur t ty of operation compared to the four-unit alternative,
9-15
as well as advantages if unit installation is phased to match
actual load growth.The net economic benefit of the six unit
scheme is $17 million greater than that of the eight-unit scheme,
while at the same time,no significant operational or scheduling
advantages are associated with the eight-unit scheme.
A scheme incorporating six units each with a rated capacity of 170
MW,for a total of 1020 MW,has been adopted for all Watana al-
ternat ives .
9.7 -Selection of the Spillway Design Flood
Norma 1 design practice for projects of thi s magnitude,together with
applicable design regulations,require that the project be capable of
passing the PMF routed through the reservoir without endangering the
dam.
In addition to this requirement,the project should have sufficient
spillway capacity to safely pass a major flood of lesser magnitude than
the PMF without damaging the mai n dam or anci 11 ary structures.The
frequency of occurrence of thi s flood,known as the spi 11 way des ign
flood or Standard Project Flood (SPF),is generally selected on the
basis of an evaluation of the risks to the project if the spillway de-
sign flood is exceeded,compared to the costs of the structures re-
quired to safely discharge the flood.For this study,a spillway de-
sign flood with a return frequency of 1:10,000 years was selected for
Watana. A list of spillway design flood frequencies and magnitudes for
several major projects is presented below.
Spi 11 way
Spillway Desi gn Flood Basin Capacity
Peak PMF After Routi ng
Project Frequency Inflow (cfs)(cfs )(cfs)*
Mica,Canada PMF 250,000 250,000 150,000
Chuychjl1 FClll~_,
~.-.._.__._--~_.."-----.-----------"-------
Canada 1:10,000 600,000 1,000,000 230,000
New Bullards,USA PMF 226,000 226,000
170,000
Oroville,USA 1:10,000 440,500 711,400
440,500
Guri,Venezuela
(final stage)PMF 1,000,000 1,000,000 1,000,000
Itaipu,Brazi 1 PMF 2,195,000 2,195,000 2,105,000
Sayano,USSR 1:10,000 480,000 N/A 680,000
All spillways except Sayano have capacity to pass PMF with surcharge.
9;;;16
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The flood frequency analysis (see Section 7.2)produced the following
values:
9.8 -Main Dam Alternatives
This section describes the alternative types of dam considered at the
Watana site and the basis for the selected alternative.
Additional capacity required to pass the PMF will be provided by an
emergency spillway consisting of a fuse plug and rock channel on the
ri ght bank.
Inflow Peak
326,000 cfs
156,000 cfs1:10,000 years
FrequencyFlood
Probable Maximum
Spillway Design
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(a)Comparison of Embankment and Concrete Type Dams
The selection between an embankment type or a concrete type dam is
usually based on the configuration of the valley,the condition of
the foundation rock,depth of the overburden,and the relative
availability of construction materials.Previous studies by the
COE envisaged an embankment dam at Watana.Init ia1 studi es com-
pleted this as part of this current evaluation included comparison
of an earthfill dam with a concrete arch dam at the Watana site.
An arrangement for a concrete arch dam alternative at Watana is
presented in Plate 9.1.The results of this analysis indicated
that the cost of the embankment dam was somewhat lower than the
arch dam,even though the concrete costs used significantly lower
than comparable costs used for Devil Canyon.This preliminary
evaluation did not indicate any significant advantages to be
gained by constructing the concrete arch relative to the arrange-
ment of other structures,or the construction schedule~
IJ
Based on the overall cost differences descri bed above, and the
likelihood that the cost of the arch dam would increase relative
to that of the embankment dam,the arch dam alternative was elim-
inated from further consideration.
(b)Selection of Dam Type
!..1\
The development of the design of the main dam,together with a
description of the various features of the dam,is given in Sec-
tion 12.The dam is,of course,the central and most costly com-
ponent of the project,and a brief discussion of the development
of the finally selected design,together with some of the factors
which influenced development of the general arrangement is pre-
sented in this section.
Selection of the configuration of the embankment dam cross-section
was undertaken within the context of the following basic consider-
ations:
9-17
-The availability of suitable construction materials within eco-
nomic haul distance,particularly core material;
-The relatively limited construction season available for place-
ment of compacted fill materials.
-The requirement that the dam be capable of withstanding the ef-
fects of a significant earthquake shock as well as the static
loads imposed by the reservoir and its own weight;
- A vertical core located centrally within the dam;and
-An inclined core with both faces sloping upstream.
The advantages and disadvantages of these two a lternat ives are
discussed in Section 12. A central vertical core was chosen for
the embankment based on a revi ew of precedent desi gn and the
nature of the available impervious material.
The mai n dam wi 11 consi st of a compacted core protected by fi ne
and coarse filter zones on both the upstream and downstream slopes
of the core.The upstream and downstream outer supporti ng fi 11
zones will contain relatively free draining compacted gravel or
rockfill,providing stability to the overall embankment structure.
The location and inclination of the core is fundamental to the de-
sign of the embankment.Two basic alternatives exist in this re-
gard:
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The exploration program undertaken during 1980-81 indicated that I
adequate quantities of materials suitable for dam construction
were located within reasonable haul distance from the site.The 1
potential borrow materials for the dam are discussed in Section ,.
9.2.The well graded silty sand materal from Borrow Site Dis
considered the most promising source of impervious fill.Compac-\
tion tests indicate a natural moisture content slightly on the wet
side of optimum moisture content,so that control of moisture con-
tent will be critical in achieving a dense core with high shear
strength.j
...-'~~-p ot ential~soar-c es-fbr th-e~up-s-tr-e-a-rn--a-n-d~d-own-s-tre-am~s-h-e-l-"s~i-nc-lude--------
either river gravel from borrow areas along the Susitna River,or _/
compacted rockfill from quarries or excavations for spillways.
During the intermediate review process,the upstream slope of the
darn was flattened from 2.5H:1V used during the initial review to
2.75H:1V.This slope was based on a conservative estimate of the
effect ive shear strengh parameters of the avail able construction
materials,as well as a conservative allowance in the design for
the effects of earthquake loadings on the darn.
During the final review stage,the exterior upstream slope of the
darn was steepened from 2.75H:1V to 2.4H:1V,reflecting the results
of the preliminary static and dynamic design analyses being under-
taken at the same time as the general arrangement studi es.As
!
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A section with a 2.4H:1V upstream slope and a 2.H:1V downstream
slope located on alternative axis number 3,was used for the final
review of altnerative shcemes.Further refinements to the design
were subsequently incorporated in the final design presented in
Secti on 12.
part of the final review,the volume of the dam with an upstream
slope of 2.4H:1V was computed for four alternative dam axes.The
location of these alternative axes are shown on Plate 9.2.The
dam volume associated with each of the four alternative axes is
listed below:
(]
I)
)
Alternative
Axi s Number
1
2
3
4
Total Volume
(mi 11 i on yd31
69.2
71. 7
69.3
71. 9
9.9 -Diversion Scheme Alternatives
The topography of the site generally dictates that diversion of the
river during construction be accomplished using diversion tunnels with
upstream and downstream cofferdams protecting the main construction
area.
The configuration of the river in the vicinity of the site favors loca-
tion of the diversion tunnels on the right bank,since the tunnel
length for a tunnel on the left bank would be approximately 2,000 feet
greater.In addition,rock conditions on the right bank are more
favorable for tunneling and excavation of intake and outlet portals.
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(a)Design Flood for Diversion
The recurrence interval of the design flood for diversion is gen-
erally established based on the characteristics of the flow regime
of the river,the length of the construction period for which di-
version is required and the probable consequences of overtopping
of the cofferdams.For this feasibility analysis,design criteria
and experi ence from other projects simi 1ar in scope and nature
have been used in selecting the diversion design flood.
At Watana,damage to the partially completed dam could be signifi-
cant,or more importantly,would probably result in at least one-
year delay in the completion schedule.A preliminary evaluation
of the construction schedule indicates that the diversion scheme
would be required for 4 or 5 years until the dam is of sufficient
height to permit initial filling of the reservoir.A design flood
with a return frequency of 1:50 years was selected based on exper-
ience and practice with other major hydroelectric projects.This
approximates a 90 percent probability that the cofferdam will not
9-19
(d)Emergency Release Facilities
________~the__foLlowing-a]-ter:--n at-i-ve---Uned--tun nel--schemes--wer:__e-exami-ned --as
part of this analysis:
The emergency release facilities influenced the number,type,and
arrangement of the diversion tunnels selected for the final
scheme.
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7,940 cfs
23,100 cfs (June)
890 cfs (March)
81,100 cfs
-Pressure tunnel with a free outlet;
-Pressure tunnel with a submerged outlet;and
- Free flow tunnel.
A basic consideration in evaluation of any diversion tunnel scheme
is an examination of the advantages and disadvantages of concrete-
lined tunnels compared to unlined tunnels.Preliminary hydraulic
studies indicated that the design flood routed through the diver-
sion scheme would result in a design discharge of approximately
80,500 cfs.For concrete-lined tunnels,design velocities of the
order of 50 feet per second have been used in several projects.
For unlined tunnels,maximum design velocities rang from 10 ftjs
in good quality rock to 4 ftjs in less competent material are typ-
ical.Thus, the volume of material to be excavated using an un-
lined tunnel would be at least 5 times that for lined tunnel.The
reliability of an unlined tunnel is more dependent on rock condi-
tions than is a lined tunnel,particularly given the extended per-
iod during which the diversion scheme is required to operate.
These considerations,together with the considerable higher cost
and the somewhat questionable feasibility of four unlined tunnels
with diameters approaching 50 feet in this type of rock,are con-
sidered sufficient to eliminate consideration of unlined tunnels
for the diversion scheme.
be overtopped during the 5-year construction period.The diver-
si on desi gn flood together with average flow characteri s ti cs of
the river significant to diversion are presented below:
Average annual flow
Maximum average monthly flow
Minimum average monthly flow
Design flood inflow (1:50 years)
(b)Cofferdams
For the purposes of establ ishi ng the overall general arrangement
of the project and for subsequent diversion optimization studies,
the upstream cofferdam section adopted comprises an initial clo-
sure dam structure approximately 30 feet high placed in the wet.
(c)Diversion Tunnels
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(e)
At an early stage of the study,it was established that some form
of low level release facility was required to permit lowering of
the reser voir in the event of an extreme emer gency, a nd to meet
instream flow requirements during fill ing of the reservoir.The
most economical alternative available would involve converting one
of the diversion tunnels to permanent use as a low level outlet
facility.Since it would be necessary to maintain the diversion
scheme in service during construction of the low level outlet
works,two or more diversion tunnels would be required.The use
of two diversion tunnels also provides an additional measure of
security to the diversion scheme in case of the loss of service of
one tunnel.
The low 1evel rel ease facil it ies wi 11 be operated approximately
three years during filling of the reservoir.Discharge at high
heads usually requires some form of energy dissipati on pri or to
returning the flow to the river.Given the space restrictions im-
posed by the size of the diversion tunnel,it was decided to util-
ize a double expansion system constructed within the upper
tunnel.
Optimization of Diversion Scheme
Given the considerations described above relative to design flows,
cofferdam configuration and alternative types of tunnels,an eco-
nomic study was undertaken to determine the optimum combination of
upstream cofferdam height and tunnel diameter.
Capital costs were developed for three heights of upstream coffer-
dam embankment with a 30-foot-wi de crest and exteri or slopes of
2H:IV.A freeboard allowance of 5 feet for settlement and wave
runup and 10 feet for the effects of downstream ice jammi ng on
tailwater elevations was adopted.
Capital costs for the 4,700 foot long tunnel alternatives included
allowances for excavation,concrete liner,rock bolts,and steel
supports.Costs were also developed for the upstream and
downstream portals,including excavation and support.The cost of
intake gate structures and associated gates was determined not to
vary significantly with tunnel diameter and was excluded from the
analysis.
Curves of headwater elevation versus tunnel diameter for the vari-
ous tunnel alternatives with submerged and free outlets are pre-
sented in Figure 9.5.The relationship between capital cost and
crest elevation for the upstream cofferdam is shown in Figure
9.6.The capital cost for various tunnel diameters with free and
submerged outlets is given in Figure 9.7.
The results of the optimization study are presented in Figure
9.8,and indicate the following optimum solutions for each alter-
native.
9-21
9-22
(f)Selected Diversion Scheme
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110
Upstream Cofferdam
1595
1555
Diameter Cofferdam Crest
Type of Tunnel (feet)Elevation (ft)Total Cost ($)
Two pressure tunnels 30 1595 66,000,000
Two free flow tunnels 32.5 1580 68,000,000
Two free flow tunnels 35 1555 69,000,000
The cost studies indicate that a relatively small cost differen-
tial (4 to 5 percent)separates the various alternatives for tun-
nel diameter from 30 to 35 feet.
An important consideration at this point is ease of cofferdam clo-
sure.For the pressure tunnel scheme,the invert of the tunnel
entrance is below riverbed elevation,and once the tunnel is com-
plete diversion can be accomplished with a closure dam sect ion
approximately 10 feet high.The free flow tunnel scheme however
requires a tunnel invert approximately 30 feet above the riverbed
level,and diversion will involve an end-dumped closure section 50
feet high.Two basic problems are associated with closure embank-
ments of 50 feet high -velocities during final closure would be
quite high,thus requiring large size stone,and subsequent seal-
ing of the closure embankment in the wet must be done at signifi-
cant depth,with re 1at i ve ly no control compared to the lower
essentially dry embankment.
Based on the preceeding considerations,a combination of one pres-
sure tunnel and one free flow tunnel (or pressure tunnel with free
outlet)was adopted. This will permit initial diversion to be
made using the lower pressure tunnel,thereby simplifying the cri-
tical closure operation and avoiding potentially serious delays in
the schedule.Two alternatives were re-evaluated as follows:
More detail ed 1ayout studi es i ndi cated that the higher cofferdam
associated with the 30 foot diameter tunnel alternative would re-
quire 1ocati ng the inlet portal further upstream into "The Fi nsII
shear zone. Since good rock conditions for portal construction
are essential,and the 35 foot diameter tunnel alternative would
permit a portal location downstream of liThe Fins",this latter al-
ternati ve was adopted.As noted in (e),the overall cost differ-
ence was not significant in the range of tunnel diameters consid-
ered,and the scheme i ncorporati ng two 35 foot diameter tunnel s
with an upstream cofferdam crest Elevation 1555 was incorporated
as part of the selected general arrangement.
Tunnel Diameter
-------··---~---~tf eet-)---
30
35
The various components of the selected diversion scheme are des-
cribed in Section 12.
Consideration was also given to combinations of these alternatives with
or without supplemental facilities such as valved tunnels and an emer-
gency spillway fuse plug for handling the PMF discharge.
9.10 -Spillway Facilities Alternatives
As discussed in Section 9.7,the project has been designed to safely
pass floods with the following return frequencies:
Total Spillway
Di scharge (cfs)
145,000
310,000
Frequency
1:10,000 years
All spillway alternatives were assumed to incorporate a concrete
ogee type control section controlled by fixed roller vertical lift
gates.Chute spillway sections were assumed to be concrete lined,
with ample provision for air entrainment in the chute to prevent
cavitation,and with pressure relief drains,and rock anchors in
the foundation.A detailed description of the selected spillway
alternative is given in Section 12.
Flood
Spillway Design
Probable Maximum
Discharge of the spillway design flood will require a gated service
spillway on either the left or right bank. Three basic alternative
spillway types were examined:
- Chute spillway with flip bucket;
- Chute spillway with stilling basin;and
- Cascade spillway.
(b) Environmental Mitigation
During development of the general arrangements for both the Watana
and Devil Canyon dams,a restriction was imposed on the amount of
excess dissolved nitrogen permitted in-the spillway discharges.
Clearly,the selected spillway alternatives will greatly influence and
be influenced by the project general arrangement.
(a) Energy Dissipation
The two chute spillway alternatives considered achieved effective
energy dissipation either by means of a flip bucket which directs
the spillway discharge in the form of a free-fall jet into a
plunge pool well downstream from the dam or a stilling basin at
the end of the chute which dissipates energy in a hydraulic jump.
The cascade type spillway limits the free fall height of the dis-
charge by utilizing a series of 20 to 50 feet steps down to river
level,with energy dissipation at each step.
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9-23
Supersaturation occurs when aerated flows are subjected to pres-
sures greater than 30 to 40 feet of head which forces excess nit-
rogen into solution.This occurs when water is subjected to the
high pressures that occur in deep plunge pools or at large hydrau-
lic jumps.The excess nitrogen would not be dissipated within the
downstream Devil Canyon reservoir and a bUildup of nitrogen con-
centrat i on could occur throughout the body of water.It woul d
eventually be discharged downstream from Devil Canyon with harmful
effects on the fish population.On the basis of an evaluation of
the related impacts,and discussions with interested federal and
state agencies,spillway facilities were designed to limit dis-
charges of water from either Watana or Devi 1 Canyon that may
become supersaturated with nitrogen to a recurrence period of not
less than 1:50 years.
9.11 -Power Facilities Alternative
Selection of the optimum power plant development involved consideration
of the following:
-Location,type and size of the power plant;
- Geotechnical considerations;
-Number,type,size and setting of generating units;
-Arrangement of intake and water passages;and
-Environmental constraints.
The selection of the installed capacity of 1020 MW at Watana is des-
cribed in Section 9.6.The detailed comparison of power facilities al-
ternatives is described in Appendix B.A summary of the general con-
clusions is described below.
(a)Comparison of Surface and Underground Powerhouse
Studies were carri ed out to compare the construction costs of a
surface powerhouse and of an underground powerhouse at Watana.
These studies were undertaken on the basis of preliminary concep-
tual layouts assuming six units and a total installed capacity of
840 MW.The comparative cost estimates for powerhouse civil works
and .al.ect~tcaland-mechan-ical-eq u-i-pment-{-exGlud-i-Ag---Gemmen-items)
indicated an advantage in favor of the underground powerhouse of
$16,300,000.The additional cost for the surface powerhouse
arrangement is primarily associated with the longer penstocks and
the steel linings required.Although construction cost estimates
for a 1020 MW plant would be somewhat higher,the overall conclu-
sion favoring the underground location would not change.
The underground powerhouse arrangement is also better suited to
the severe winter conditions in Alaska,is less affected by river
flood flows in summer,and is aesthetically less obtrusive.This
arrangement has therefore been adopted for further development.
9-24 .
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(b)Comparison of Alternative Locations
Preliminary studies were undertaken during the development of con-
ceptua 1 project 1ayouts at Watana to i nvesti gate both ri ght and
left bank locations for power facilities.The configuration of
the site is such that left bank locations generally required
longer penstock and/or tailrace tunnel s and were therefore more
expensive.
The location of the left bank was further rejected because of in-
dications that the underground facilities would be located in rel-
atively poor quality rock.The underground powerhouse was there-
fore located on the ri ght bank such that the major openi ngs 1ay
between the two major shear features ("The Fi ns" and the "Fi nqer-
buster").
(c)Underground Openings
Because no construction adits or extensive drilling in the power-
house and tunnel locations have been completed it has been assumed
that full concrete-l i ni ng of the penstocks and tai lrace tunnel s
will be required.This assumption is conservative and is for pre-
liminary design only;in practice,a large proportion of the tail-
race tunnels will probably be unlined,depending on the actual
rock quality encountered.
The mi nimum center-to-center spaci ng of rock tunnels and caverns
has been assumed for layout studies to be 2.5 times the width or
diameter of the larger excavation.
(d)Selection of Turbines
The selection of turbine type is governed by the available head
and flow.For the des i gn head and specifi c speed,Franci s type
turbi nes have been selected.Franci s turbi nes have a reasonably
fl at 1oad-effi ci ency curve over a range from about 50 percent to
115 percent of rated output with peak efficiency of about 92 per-
cent.
The number and rating of individual units is discussed in detail
in Section 9.6.The final selected arrangement comprised six
units producing 170 MW each,rated at minimum reservoir level
(from reservoir simulation studies)in the peak demand month
(December)at full gate.The unit output at best efficiency and a
rated head of 680 feet is 181 MW.
(e)Transformers
The selection of transformer type,size,location and step-up rat-
ing is described in Section 12.18 and summarized below:
-Single phase transformers are required because of transport lim-
itations on Alaskan roads and railways;
9-25
Di rect transformation from 15 kV to 345 kVis preferred for
overall system transient stability;
An underground transformer gallery has been selected for minimum
total cost of transformers,cables,bus,and transformer losses,
and
The preliminary design of the power facilities involves two tail-
race tunnels leading from a common surge chamber.An alternative
arrangement with a single tailrace tunnel was also considered,but
no significant cost saving was apparent.
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-3.0
+3.0
+4.0
+6.0
- 2.0
Base Caseo
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Cost Difference ($x 10
6)
6 Penstocks 3 PenstocksItem
Total
Intake
Penstocks
Bi furcati ons
Valves
Powerhouse
Capitalized Value of Extra Head Loss
Power Intake and Water Passages
The power intake and approach channel are significant items in the
cost of the overall power facilities arrangement.The size of the
intake is controlled by the number and minimum spacing between the
penstocks,which in turn is dictated by geotechnical considera-
tions (Sections 9.2 and 9.3).
- A grouped arrangement of three sets of three single-phase trans-
formers for each set of two units has been selected (a total of
nine transformers)to reduce the physical size of the transfor-
mer gallery and to provide a transformer spacing comparable with
the unit spacing.
Despite a marginal saving of $2 million (or less than 2 percent in
a total estimated cost of $120 million)in favor of three pen-
stocks,the arrangement of six individual penstocks has been
retained.This arrangement provides improved flexibility and
security of operation.
The preferred penstock arrangement comprises six individual pen-
stocks,one for each turbine.With this arrangement,no inlet
valve is required in the powerhouse since penstock dewatering can
be performed by using the control gate at the intake.An alterna-
tive arrangement with three penstocks was considered in detail to
assess any possible advantages.This scheme would require a bi-
furcation and two inlet valves on each penstock and extra space in
the powerhouse to accommodate the inlet valves.Estimates of rel-
ative cost differences are summarized below:
(f)
Optimization studies on all water passages were carried out to
determine the minimum total cost of initial construction plus the
capitalized value of anticipated energy losses caused by conduit
friction,bends and changes of section.For the penstock optimi-
zation,the construction costs of the intake and approach channel
were included,as a function of the penstock diameter and spacing.
Similarly,in the optimization studies for the tailrace tunnels,
the costs of the surge chamber were included,as a function of
tailrace tunnel diameter.
(g) Environmental Constraints
Apart from the potential nitrogen supersaturation problem discus-
sed in Section 9.10,the major environmental constraints on the
design of the power facilities are:
- Control of downstream river temperatures;and
- Control of downstream flows.
The intake design has been modified to enable power plant flows to
be drawn from the reservoir at four different levels throughout
the anticipated range of reservoir drawdown for energy production
in order to control the downstream river temperatures within ac-
ceptable limits.
Minimum flows at Gold Creek during the critical summer months have
been studied to mitigate the project impacts on salmon spawning
downstream of Devil Canyon.These minimum flows represent a con-
straint on the reservoir operation,and influence the computation
of average and firm energy produced by the Susitna development.
These studies are discussed in detail in Section 15.
The Watana development will be operated as a daily peaking plant
for load following.The actual extent of daily peaking will be
dictated by unit availabil ity,unit size,system demand,system
stability,generating costs,etc.,(as described in Section 15).
9.12 -Selection of Watana General Arrangement
Preliminary alternative arrangements of the Watana Project were devel-
oped and subjected to a series of review and screening processes.The
layouts selected from each screening process were developed in greater
detail prior to the next review,and where necessary,additional lay-
outs were prepared combining the features of two or more of the altern-
atives.Assumptions and criteria were evaluated at each stage and add-
itional data incorporated as necessary.The selection process followed
the general selection methodology established for the Susitna project,
and is outlined below.
9-27
(a)Selection Methodology
The determination of the project general arrangement at Watana was
undertaken in three distinct review stages:preliminary,inter-
mediate,and final.
(i)Preliminary Review (completed early in 1981)
This comprised four steps:
- Step 1:Assemble available data;
Determine design criteria;and
Establish evaluation criteria.
- Step 2:Develop pre 1 iminary 1ayouts and desi gn cr iteri a
based on the above data including all plausible
alternatives for the constituent facilities and
structures.
- Step 3:Review all layouts on the basis of technical
feasibil ity,readily apparent cost differences,
safety,and environmental impact.
-Step 4:Select those layouts that can be identified as
most favorable,based on the evaluation criteria
established in Step 1,taking into account the
preliminary nature of the work at this stage.
(ii)Intermediate Review (completed by mid-1981)
This involved a series of 5 steps:
- Step 1:Review all data,incorporating additional data
from other work tasks.
Review and expand design criteria to a greater
level of detail.
Review evaluation criteria and modify,if neces-
sary.
- Step 2: Revise selected layouts on basis of the revised
criteria and additional data.Prepare plans and
principal sections of layouts.
- Step 3:Prepare quantity estimates for major structures
based on drawings prepared under Step 2.
Develop a preliminary construction schedule to
evaluate whether or not the selected layout will
allow completion of the project within the re-
qUired time frame.
9-28
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Prepare a preliminary contractor's type estimate
to determine the overall cost of each scheme.
- Step 4:Review all layouts on the basis of technical
feasibility,cost impact of possible unknown
conditions and uncertainty of assumptions,safe-
ty,and environmental impact.
- Step 5:Select the two most favorable layouts based on
the evaluation criteria determined under Step 1.
(iii)Final Review (completed early in 1982)
- Step 1:Assemble and review any additional data from
other work tasks.
Revise design criteria in accordance with addi-
tional available data.
Finalize overall evaluation criteria.
- Step 2: Revise or further develop the two layouts on the
basis of input from Step 1 and determine overall
dimensions of structures,water passages,gates,
and other key items.
- Step 3:Prepare quantity take-offs for all major struc-
tures.
Review cost components within a preliminary con-
tractor's type estimate usi ng the most recent
data and criteria,and develop a construction
schedul e.
Determine overall direct cost of schemes.
- Step 4:Review all layouts on the basis of practicabil-
ity,technical feasibility,cost,impact of pos-
sible unknown conditions,safety,and environ-
mental impact.
- Step 5:Select the final layout on the basis of the
evaluation criteria developed under Step 1.
(b) Design Data and Criteria
As discussed above,the review process included assembling rele-
vant design data,establishing preliminary design criteria,and
expandi ng and refi ni ng these data duri ng the intermedi ate and
final reviews of the project arrangement.The design data and
design criteria which evolved through the final review is pre-
sented in Table 9.3.Data and criteria developed during the pre-
liminary and intermediate review stages are given in Appendix B
for reference.
9-29
(c)Evaluation Criteria
The various layouts were evaluated at each stage of the review
process on the basis of the criteria summarized in Table 9.4.The
criteria listed in Table 9.4 illustrate the progressively more de-
tail ed eval uat i on process 1 eading to the fi nal sel ected arrange-
ment.
9.13 -Preliminary Review
The development selection studies described in Section 8 involved com-
parisons of hydroelectric schemes at a number of sites on the Susitna
River.As part of these comparisons a preliminary conceptual design
was developed for Watana incorporating a double stilling basin type
spillway (Plate 8.2).
Ei ght further 1ayouts were subsequently prepared and exami ned for the
Watana project during this preliminary review process,in addition to
the scheme shown on Plate 8.2.These eight layouts are shown in sche-
matic form on Plate 9.3.A1ternat i ve 1 of these 1ayout s was the
scheme recommended for further study in the Development Sel ect i on-
Report (3).
This section describes the preliminary review undertaken of alternative
Watana layouts.
(a)Basis of Comparison of Alternatives
Although it was recogni zed that provi si on would have to be made
for downstream releases of water during filling of the reservoir
and for emergency reservoir drawdown,these features were not in-
corporated in these preliminary layouts.These facilities would
either be inter-connected with the diversion tunnels or be pro-
vided for separately.Since the system selected would be similar
for all layouts with minimal cost differences and little impact on
other structures,it was decided to exclude these facilities from
overgl1 assessment at this early
Ongoi nggeofechni Cc:ir---ex-proralion-s-ljaa-raentTfl ea--fne f\ira major
shear zones crossi ng the Susitna Ri ver and runni ng roughly par-
allel in the northwest direction.These zones enclose a stretch
of watercourse approximately 4500 feet in 1ength (see Section
9.2).Preliminary evaluation of the existing geological data in-
dicated highly fractured and altered materials within the actual
shear zones,which would pose serious problems for conventional
tunneling methods and would be unsuitable for founding of massive
concrete structures.The originally proposed dam axis was located
between these shear zones,and as no apparent major advantage
appeared to be gained from large changes in the dam location,lay-
outs generally were kept withi n the confi nes of these boundi ng
zones.
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(b)
An earth and rockfill dam as described in Section 9.8 was used as
the basis for all layouts.The downstream slope of the dam was
assumed as 2H:1V in all alternatives,upstream slopes varying
between 2.5H:1V and 2.25H:1V were examined in order to determine
the influence of variance in the dam slope on the congestion of
the layout.In all these preliminary arrangements,except that
shown on Plate 8.2,cofferdams were incorporated within the body
of the main dam.
Floods greater than the routed 1:10,000 year spillway design flood
and up to the probable maximum flood were assumed to be passed by
surcharging the spillways except in cases where an unlined cascade
or stilling basin type spillway served as the sole discharge fa-
cility.In such instances,under large surcharges,these spill-
ways would not act as efficient energy dissipators but would be
drowned out,acting as steep open channels with the possibility of
their total destruction.In order to avoid such an occurrence the
design flood for these latter spillways was considered as the
routed probable maximum flood.
On the basis of information existing at the time of the prelim-
inary review,it appeared that an underground powerhouse could be
located on either side of the river.A surface powerhouse on the
right bank appeared feasible but was precluded from the left bank
by the close proximity of the downstream toe of the dam and the
adjacent broad shear zone.Locating the powerhouse further down-
stream would require tunneling across the shear zone, which would
be expensive,and excavating a talus slope.Furthermore,it was
found that a left bank surface powerhouse would either interfere
with a left bank spillway or would be directly impacted by dis-
charges from a right bank spillway.
Description of Alternative
(i)Double Stilling Basin Scheme
The Scheme as shown on Plate 8.2 has a dam axis location
similar to that originally proposed by the COE,and a right
bank double stilling basin spillway.The spillway follows
the shortest line to the river avoiding interference with
the dam and discharging downstream,almost parallel to the
flow,into the center of the river.A substantial amount
of excavation is required for the chute and stilling
basins,although most of this material could probably be
used in the dam.A large volume of concrete is also
required for this type of spillway,resulting in a spillway
system that would be very costly.The maximum head dis-
sipated within each stilling basin is approximately 450
feet.Within world experience,cavitation and erosion of
the chute and basins should not be a problem if the struc-
t ures are proper ly designed. Extensive eros i on down stream
would not be expected.
9-31
The diversion follows the shortest route,cutting the bend
of the river on the right bank,and has inlet portals as
far upstream as poss i b1e without havi ng to tunnel through
liThe Fins ll
•It is possible that the underground powerhouse
is in the area of "The Ff nqer-bus t er ",but the powerhouse
could be located upstream almost as far as the system of
drain holes and galleries just downstream of the main dam
grout curtain.
(ii)Alternative 1
This alternative is that recommended for further study in
the Development Selection Report (3)and is similar to the
layout described in (i)above,except that the right side
of the dam has been rotated clockwise,the axis relocated
upstream and the spi llway changed to a chute and fl i P
bucket.The revised dam alignment resulted in a slight
reduction in total dam volume compared to the above alter-
native.A localized downstream curve was introduced in the
dam close to the ri ght abutment in order to reduce the
length of the spillway.The alignment of the spillway is
almost parallel to the downstream section of the river and
it discharges into a pre-excavated plunge pool in the river
approximately 800 feet downstream from the fl i P bucket.
This type of spillway should be considerably less costly
than one incorporating a stilling basin,provided that ex-
cessive pre-excavation of bedrock within the plunge pool
area is not required.Careful design of the bucket will be
required however,to prevent excessive erosion downstream
causing undermining of the valley sides and/or build up of
material downstream which could cause elevation of the
tailwater levels.
(iii)Alternatives 2 through 20
Alternative 2 consists of a left bank cascade spillway with
the main dam axis curving downstream at the abutments.The
cascade sp t l lway would require an extremely 1argevol ume of
-....rock-excavation~but"it-i-sproba ble-th-at--mos-t--of-th-i-s-mate-
rial,with careful scheduling,could be used in the dam.
The excavation would cross liThe Fingerbuster ll and extensive
dental concrete would be required in that area.In the up-
stream portion of the spillway,velocities would be rela-
tively high because of the narrow configuration of the
channel and erosion could take place in this area in prox-
imi ty to the dam. The di scharge from the spillway enters
the river perpendicular to the general flow but velocities
would be relatively low and should not cause substantial
erosion problems.The powerhouse is in the most suitable
location for a surface alternative where the bedrock is
close to the surface and the overall rock slope is approxi-
mately 2H:IV.
9-32
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Alternative 2A is similar to Alternative 2 except that the
upper end of the channel is divided and separate control
structures are provided.This division would allow the use
of one structure or upstream channel whi 1e mai ntenance or
remedial work is being performed on the other.
Alternative 2B is similar to Alternative 2 except that the
cascade spillway is replaced by a double stilling basin
type structure.This spillway is somewhat longer than the
similar type of structure on the right bank in the alterna-
tive described in (i)above.However,the slope of the
ground is less than the rather steep right bank and thus,
it may be easier to construct,a factor which may partly
miti gate the cost of the longer structure.The di scharge
is at a sharp angle to the river and being more concen-
trated than the cascade could cause erosion of the opposite
bank.
Alternative 2C is a derivative of 2B with a similar ar-
rangement,except that the double stilling basin spillway
is reduced in size and augmented by an additional emergency
spillway in the form of an inclined,unlined rock channel.
Under thi s arrangement the concrete spi llway acts as the
main spillway,passing the 1:10,000 year design flood with
greater flows passed down the unlined channel which is
closed at its upstream end by an erodable fuse plug.The
problems of erosion of the opposite bank still remain,al-
though these could be overcome by excavati on and/or slope
protection.Erosion of the chute would be extreme for sig-
nificant flows,although it is highly unlikely that this
emergency spillway would ever be used.
Alternative 20 replaces the cascade of Alternative 2 with a
lined chute and flip bucket.The comments relative to the
fl iP bucket are the same as for Alternat ive 1 except that
the left bank location in this instance requires a longer
chute,partly offset by lower construction costs because of
the fl atter slope.The fl iP bucket di scharges into the
river at an angle which may cause erosion of the opposite
bank.The underground powerhouse is located on the ri ght
bank, an arrangement which provides an overall reduction of
the length of the water passages.
(iv)Alternative 3
This arrangement has a dam axis location slightly upstream
from Alternative 2, but retains the downstream curve at the
abutments.The main spillway is an unlined rock cascade on
the left bank which passes the design flood.Discharges
beyond the 1:10,000 year flood would be discharged through
the auxiliary concrete-lined chute and flip bucket spillway
on the right bank. A gated control structure is provided
for this auxiliary spillway which gives it the flexibility
9-33
(v)Alternative 4
to be used as a backup if maintenance should be required on
the main spillway.Erosion of the cascade may be a pro-
blem,as mentioned previously,but erosion downstream
should be a less important consideration because of the low
unit discharge and the infrequent operation of the spill-
way.The diversion tunnels are situated in the right abut-
ment, as with previous arrangements,and are of similar
cost for all these alternatives.
This alternative involves rotating the axis of the main dam
so that the left abutment is relocated approximately 1000
feet downstream from its Alternative 2 location.The relo-
cation results in a reduction in the overall dam quantities
but would require siting the impervious core of the dam
directly over the "Fi ngerbuster"shear zone at maximum dam
height.The left bank spillway,consisting of chute and
fl iP bucket,is reduced in 1ength compared to other 1eft
bank 1ocat ions,as are the power faci 1ity water passages.
The diversion tunnels are situated on the left bank;there
is no advantage to a right bank location,since the tunn~ls
are of similar length owing to the overall downstream relo-
cation of the dam.Spillways and power facilities would
also be lengthened by a right bank location with this dam
configuration.
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(c)Selection of Schemes for Further Study
A basic consideration during design development was that the main
dam core should not cross the major shear zones because of the ob-
vious problems with treatment of the foundation.Accordingly,
there is very little scope for realigning the main dam apart from
a slight rotation to place it more at right angles to the river.
Locati on of the spi 11 way on the right bank results ina shorter
distance to the river and allows discharges almost parallel to the
genera 1 direction of ri ver flow.The double sti 11 i ng bas n ar-
······-----range-menfwoura--6e-extremeTYeXpensi ve,particuTarlyrrTE must-Be
designed to pass the probable maximum flood.An alternative such
as 2C would reduce the magnitude of design flood to be passed by
the spillway but would only be acceptable if an emergency spillway
with a high degree of operational predictability could be con-
structed.A fl iP bucket spi 11 way on the ri ght bank, di schargi ng
directly down the river,would appear to be an economic arrange-
ment, although some scour might occur in the plunge pool area.A
cascade spillway on the left bank could be an acceptable solution
providing most of the excavated material could be used in the dam,
and adequate rock conditions exist.
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The length of diversion tunnels can be decreased if they are
located on the right bank. In addition,the tunnels would be
accessible by a preliminary access road from the north,which is
the most likely route.This location would also avoid the area of
"The Fingerbuster"and the steep cliffs which would be encountered
on the left side close to the downstream dam toe.
The underground configuration assumed for the powerhouse in these
preliminary studies allows for location on either side of the
river with a minimum of interference with the surface structures.
Four of the precedi ng 1ayouts,or vari at ions of them, were sel-
ected for further study:
(i)A variation of the double stilling basin scheme, but with a
single stilling basin main spillway on the right bank, a
rock channel and fuse plug emergency spillway,a left bank
underground powerhouse and a right bank diversion scheme;
(ii)Alternative 1 with a right bank flip bucket spillway,an
underground powerhouse on the left bank, and right bank di-
version;
(iii)A variation of Alternative 2 with a reduced capacity main
spillway and a right bank rock channel with a fuse plug
serving as an emergency spillway;and
(iv)Alternative 4 with a left bank rock cascade spillway,a
right bank underground powerhouse,and a right bank diver-
si on.
9.14 -Intermediate Review
For the intermediate review process,the four schemes selected as a re-
sult of the preliminary review were examined in more detail and modi-
fied.A description of each of the schemes is given below and shown on
Plates 9.4 through 9.9.The general locations of the upstream and
downstream shear zones shown on these plates are approximate,and have
been refined on the basis of subsequent field investigations for the
design studies described in Section 12.
(a)Description of Alternative Schemes
The four schemes are shown on Plates 9.4 through 9.9:
(i)Scheme WP1 (Plate 9.4)
This scheme is a refinement of Alternative 1. The upstream
slope of the dam is flattened from 2.5:1 to 2.75:1.This
conservative approach was adopted to provide an assessment
of the possible impacts on project layout of conceivable
measures which prove necessary in dealing with severe
earthquake design conditions.Uncertainty with regard to
9-35
the nature of river alluvium also led to the location of
the cofferdams outside the limits of the main dam embank-
ment.As a result Of these conditions,the intake portals
of the divers i on tunnel s on the ri ght bank are al so moved
upstream from "The Fi ns",A chute spillway with a fl iP
bucket is located on the ri ght bank.The underground
powerhouse is located on the left bank.
(ii)Scheme WP2 (Plates 9.6 and 9.7)
This scheme is derived from the double stilling basin lay-
out.The main dam and diversion facilities are similar to
Scheme WPI except that the downstream cofferdam is relocat-
ed further downstream from the spillway outlet,and the
di versi on tunnel s are correspondi ngly extended.The mai n
spillway is located on the right bank, but the two stilling
basins of the preliminary DSR scheme are combined into a
single stilling basin at the river level.An emergency
spillway is also located on the right bank, and consists of
a channel excavated in rock,discharging downstream from
the area of the relict channel.The channel is closed at
its upstream end by a compacted earthfill fuse plug and is
capable of discharging the flow differential between the
probable maximum flood and the l:lO,OOO-year design flood
of the main spillway.The underground powerhouse is
located on the left bank.
(iii)Scheme WP3 (Plates 9.5 and 9.6)
This scheme is similar to Scheme WPI in all respects,ex-
cept that an emergency spillway is added, cons ist i ng of
right bank rock channel and fuse plug.
(iv)Scheme WP4 (Plates 9.8 and 9.9)
The dam location and geometry for Scheme WP4 are similar to
that for the other schemes.The diversion is on the right
bank and discharges downstream from the powerhouse tailrace
outlet ~A-rock··cascadespi-l-lwayi-s--loeated--on--the--left
bank and is served by two separate control structures with
downstream stilling basins.The underground powerhouse is
located on the right bank.
(b)Comparison of Schemes
The main dam is in the same location and has the same configura-
tion for each of the four layouts considered.The cofferdams have
been located outside the limits of the main dam in order to allow
more extensive excavation of the alluvial material and to ensure a
sound rock foundation beneath the complete area of the dam.The
overall design of the dam is conservative,and it was recognized
during the evaluation that savings in both fill and excavation
costs can probably be made after more detailed study.
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The diversion tunnels are located on the right bank.The upstream
flattening of the dam slope necessitates the location of the
diversion inlets upstream from "The Fins"shear zone which will
require extensive excavation and support where the tunnels pass
through this extremely poor rock zone and could cause delays in
the construction schedule.
A low-lying area exists on the right bank in the area of the rel-
ict channel and requires an approximately 50-foot high saddle dam
for closure,given the reservoir operating level assumed for the
comparison study.As discussed in Section 9.5,however,the
finally selected reservoir operating level wi 11 require only a
nominal freeboard structure at this location.
A summary of capital cost estimates for the four alternati ve
schemes is given in Table 9.5.
The results of this intermediate analysis indicate that the chute
spillway with flip bucket (Scheme WPl)is the least costly spill-
way alternative.
The scheme has the additional advantage of relatively simple oper-
ating characteristics.The control structure has provision for
surcharging to pass the design flood.The probable maximum flood
can be passed by additional surcharging up to the crest level of
the dam.In Scheme WI?3 a similar spillway is provided,except
that the control structure is reduced in size and discharges above
the routed design flood are passed through the rock channel emer-
gency spillway.The arrangement in Scheme WPI does not provide a
backup facility to the main spillway,so that if repairs caused by
excessive pl unge pool erosion or damage to the structure itself
require removal of the spillway from service for ·any length of
time,no alternative discharge facility would be available.The
additional spillway of Scheme WP3 would permit emergency discharge
if it were required under extreme circumstances.
The stilling basin spillway (Scheme WP2)would reduce the poten-
tial for extensive erosion downstream,but high velocities in the
lower part of the chute could cause cavitation even with the pro-
vision for aeration of the discharge.This type of spillway would
be very costly,as can be seen from Table 9.5.
The feasibility of the rock cascade spillway is entirely dependent
on the quality of the rock,which dictates the amount of treatment
required for the rock surface and also the proportion of the exca-
vated material which can be used in the dam.For determining the
capital cost of Scheme WP4,conservative assumptions were made re-
garding surface treatment and the portion of material that would
have to be wasted.
9-37
The diversion tunnels are located on the right bank for all alter-
natives examined in the intermediate review.For Scheme WP2,the
downstream portals must be located downstream from the stilling
basin,resulting in an increase of approximately 800 feet in the
1ength of the tunnels.The 1eft bank 1ocat i on of the powerhouse
requires its placement close to a suspected shear zone, with the
tailrace tunnels passing through this shear zone to reach the
river.A longer access tunnel is also reqUired,together with an
additional 1,000 feet in the length of the tailrace.The left-
side location is remote from the main access road,which will pro-
bably be on the north side of the river,as will the transmission
corridor.
(c)Selection of Schemes for Further Study
Examination of the technical and economic aspects of Scheme WP1
through WP4 indicates there is little scope for adjustment of the
dam axis owi ng to the confi nement imposed by the upstream and
downstream shear zones.In addition,passage of the diversion
tunnels through the upstream shear zone could result in signifi-
cant delays in construction and additional cost.
From a comparison of costs in Table 9.5,it can be seen that the
flip bucket type spillway is the most economical, but because of
the potential for erosion under extensive operation it is undesir-
able to use it as the only discharge facility.A mid-Jevel re-
1ease wi 11 be requtr ed for emergency drawdown of the reservoir,
and use of this release as the first-stage service spillway with
the flip bucket asa backup facility would combine flexibility and
safety of operation with reasonable cost.The emergency rock
channel spillway would be retained for discharge of flows above
the routed 1:10,000-year flood.
The stilling basin spillway is very costly and the operating head
of 800 feet is beyond precedent experience.Erosi on downstream
should not be a problem but cavitation of the chute could occur.
Scheme WP2 was therefore eliminated from further consideration.
The cascade spiTlway was ····a-rso·not---favoreCi-for t-echni-c·a-'·andeco-,;;
nomic reasons.However,this arrangement does have an advantage
in that it prOVides a means of preventing nitrogen supersaturation
in the downstream discharges from the project which could be harm-
ful to the fish population,as discussed in Section 9.10.A cas-
cade configuration would reduce the dissolved nitrogen content,
and hence,this alternative was retained for further evaluation.
The capacity of the cascade was reduced and the emergency rock
channel spillway was included to take the extreme floods.
The results of the intermediate review indicated that the follow-
ing components should be incorporated into any scheme carried for-
ward for final review:
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-Two diversion tunnels located on the right bank of the river;
-An underground powerhouse also located on the right bank;
-An emergency spillway,comprising a rock channel excavated on
the ri ght bank and di schargi ng well downstream from the ri ght
abutment.The channel is sealed by an erodible fuse plug of im-
pervi ous materi al desi gned to fail if overtopped by the reser-
voir;and
- A compacted earthfill and rockfill dam situated between the two
major shear zones which traverse the project site.
As discussed above,two specific alternative methods exist with
respect to routing of the spillway design flood and minimizing the
adverse effects of nitrogen supersaturation on the downstream fish
population.These alternatives are:
- A chute spillway with flip bucket on the right bank to pass the
spillway design flood,with a mid-level release system designed
to operate for floods wi th a frequency of up to about 1:50
years;or
-A cascade spillway on the left bank.
Accordingly,two schemes were developed for further evaluation as
part of the final review process.These schemes are described
separately in the paragraphs below.
9.15 -Final Review
The two schemes considered in the final review process were essentially
deviations of Schemes WP3 and WP4.
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(a)Scheme WP3A (Plate 9.10)
This scheme is a modified version of Scheme WP3 described in
Section 9.14.Because of scheduling and cost considerations,it
is extremely important to maintain the diversion tunnels down-
stream from liThe Fins.1I It is also important to keep the dam axis
as far upstream as possible to avoid congestion of the downstream
structures.For these reasons,the inlet portals to the diversion
tunnels were located in the sound bedrock forming the downstream
boundary of "The Fins,II The upstream cofferdam and mai n dam are
maintained in the upstream locations as shown on Plate 9.10.As
mentioned previously,additional criteria have necessitated modi-
fications in the spillway configuration,and low-level and emer-
gency drawdown outlets have been introduced.
The main modifications to the scheme are as follows:
9-39
(i)Mai n Dam
Continuing preliminary design studies and review of world
practice suggest that an upstream slope of 2.4H:IV would be
acceptable for the rock shell.Adoption of this slope re-
sults not only in a reduction in dam fill volume but also
in a reduction in the base width of the dam which permits
the main project components to be located between the major
shear zones.
The downstream slope of the dam is retained as 2H:IV.The
cofferdams remain outside the limits of the dam in order to
allow complete excavation of the riverbed alluvium.
(ii ) Diversion
In the intermediate review arrangements,diversion tunnels
passed through the broad structure of 'The Fins,II an i n-
tensely sheared area of breccia,gouge, and infills.Tun-
neling of this material would be difficult,and might even
require excavation in open cut from'the surface.High cost
would be involved,but more importantly would be the time
taken for construction in this area and the possibility of
unexpected delays.For this reason,the inlet portals have
been relocated downstream from this zone with the tunnels
located closer to the river and crossing the main system of
jointing at approximately 45°. This arrangement allows for
shorter tunnels with a more favorable orientation of the
inlet and outlet portals with respect to the river flow
directions.
A separate low-level inlet and concrete-lined tunnel is
provided,leading from the reservoir at approximate Eleva-
tion 1550 feet to downstream of the diversion plug where it
merges with the diversion tunnel closest to the river.
This low-level tunnel is designed to pass flows up to 6000
cfs during reservoir filling.It will also pass up to
30,000 cfs under 500-foot head to allow emergency draining
-..------~-----------of-th-e-Teservoir-as .discnssed-i-n-Sect-i-on-9.9.----_..
Initial closure is made by lowering the gates to the tunnel
located closest to the river and constructing a concrete
closure plug in the tunnel at the location of the grout
curtain underlying the core of the main dam.On completion
of the plug,the low-level release is opened and controlled
discharges are passed downstream.The closure gates within
the second diversion tunnel portal are then closed and a
concrete closure plug constructed in 1 ine with the grout
curtain.After closure of the gates,filling of the reser-
voir would commence.
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(iii)
(i v)
Outlet Facilities
As a provision for drawing down the reservoir in case of
emergency, a mid-level release is provided.The intake to
these facilities is located at depth adjacent to the power
facilities intake structures.Flows will then be passed
downstream through a concrete-lined tunnel,discharging be-
neath the downstream end of the main spillway flip bucket.
In order to overcome potential nitrogen supersaturation
problems,Scheme WP3A also incorporates a system of fixed
cone valves at the downstream end of the outlet facilities.
The valves were sized to discharge in conjunction with the
powerhouse operating at 7000 cfs capacity,flows up to the
equi va 1ent routed 50-year flood.Si x cone va 1ves are
required,located on branches off a steel manifold and pro-
tected by individual upstream closure gates.The valves
are partly incorporated into the mass concrete block form-
ing the flip bucket of the main spillway.The rock down-
stream is protected from erosion by a concrete facing slab
anchored back to the sound bedrock.
Spi 11 ways
As discussed in Section 9.10 above,the designed operation
of the main spillway facilities was arranged to limit dis-
charges of potentially ni trogen-supersaturated water from
Watana to flows having an equivalent return period greater
than 1:50 years.
The main chute spillway and flip bucket discharge into an
excavated plunge pool in the downstream river bed.Re-
1eases are controlled by a three-gated ogee structure lo-
cated adjacent to the outlet facilities and power intake
structure just upstream from the darn centerl t'ne ,The de-
sign discharge is approximately 114,000 cfs corresponding
to the routed l:lO,OOO-year flood (145,000 cfs)reduced by
the 31,000 cfs flows attributable to outlet and power fa-
cilities discharges.The plunge pool is formed by excavat-
ing the alluvial river deposits to bedrock.Since the exca-
vated plunge pool approaches the limits of the calculated
maximum scour hole,it is not anticipated that,given the
infrequent discharges,significant downstream erosion will
occur.
The emergency spillway is provided by means of a channel
excavated in rock on the right bank,discharging well down-
stream from the right abutment in the direction of Tsusena
Creek.The channel is sealed by an erodible fuse plug of
impervious material designed to fail if overtopped by the
reservoir,although some preliminary excavation may be
necessary.The crest level of the plug will be set at Ele-
vation 2230, well below that of the main dam.The channel
will be capable of passing the excess discharge of floods
9-41
greater than the 1:10,000-year flood up to the probable
maximum flood of 310,000 cfs.
(v)Power Facilities
The power intake is set slightly upstream from the dam axis
deep within sound bedr-ock at the downstream end of the
approach channel.The intake consists of six units with
provision in each unit for drawing flows from a variety of
depths covering the complete drawdown range of the reser-
voir.This facility also provides for drawing water from
the different temperature strata withi n the upper part of
the reservoir and thus regulating the temperature of the
downstream discharges close to the natural temperatures of
the river.For this preliminary conceptual arrangement,
flow withdrawals from different levels are achieved by a
series of upstream vertical shutters moving in a single set
of guides and operated to form openi ngs at the required
level.Downstream from these shutters each unit has a pair
of wheel-mounted closure gates which will isolate the indi-
vidual penstocks.
The six penstocks are 18-foot-diameter,concrete-lined
tunnels inclined at 55° immediately downstream from the in-
take to a nearly horizontal portion leading to the power-
house. This horizontal portion is steel-lined for 150 feet
upstream from the turbine units to extend the seepage path
to the powerhouse and reduce the flow within the fractured
rock area caused by blasting in the adjacent powerhouse
cavern.
The six 170 MW turbine/generator units are housed within
the major powerhouse cavern and are serviced by an overhead
crane which runs the length of the powerhouse and into the
service area adjacent to the units.Switchgear,mai nten-
ance room and offices are located within the main cavern,
with the transformers situated downstream ina separate
gallery excavated above the tailrace tunnels"Six inclined
-~-tunne-l-s--Gal"-I"-y--the--Go nne Gt-i-n g..-0u5--du G-ts-fl"-om--the-mai-npowel"-
hall to the transformer gallery.A vertical elevator and
vent shaft run from the power cavern to the main office
building and control room located at the surface.Vertical
cable shafts,one for each pair of transformers,connect
the transformer gallery to the switchyard di rect ly over-
head.Downstream from the transformer gallery,the under-
lying draft tube tunnels merge into two surge chambers, one
chamber for three draft tubes,which also house the draft
tube gates for isolating the units from the tailrace.The
gates are operated by an overhead traveling gantry located
in the upper part of each of the surge chambers.Emerging
from the ends of the chambers,two concrete-l i ned, low-
pressure tailrace tunnels carry the discharges to the
river.Because of space restrictions at the river,one of
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these tunnels has been merged with the downstream end of
the diversion tunnel.The other tunnel emerges in a separ-
ate portal with provision for the installation of bulkhead
gates.
The ori entati on of water passages and underground caverns
is such as to avoid,as far as possible,a1ignrnent of the
main excavations with the major joint sets as described in
Section 9.3.
fl
I)
(vi)Access
Access is assumed to be from the north (right)side of the
river.Permanent access to structures close to the river
is by a road along the right downstream river bank and then
via a tunnel passing through the concrete forming the flip
bucket.A tunnel from this point to the power cavern pro-
vides for vehicular access.A secondary access road across
the crest of the dam passes down the left bank of the val-
ley and across the lower part of the dam.
(b)Scheme WP4A (Plate 9.11)
This scheme is similar in most respects to Scheme WP3A previously
discussed,except for the spillway arrangements.
(i)Ma in Dam
The main dam axis is similar to that of Scheme WP3A,except
for a sl ight downstream rotation at the 1eft abutment at
the spillway control structures.
(ii)Diversion
The diversion and low level releases are the same for the
two schemes.
(iii)Outlet Facilities
The outlet facil Hies used for emergency drawdown are sep-
arate from the main spillway for this scheme.The outlet
facilities consists of a low-level gated inlet structure
discharging up to 30,000 cfs into the river through a con-
crete-lined,free-flow tunnel with a ski jump flip bucket.
This facility may also be operated as an auxiliary outlet
to augment the main left bank spillway.
(iv) Spill way s
The main left bank spillway is capable of passing a
flow equivalent to the 1:10,000-year flood through a
of 50-foot drops into shallow pre-excavated p1 unge
The emergency spillway is designed to operate during
of greater magnitude up to and including the PMF.
9-43
design
ser ies
pools.
floods
(c)
Main spillway discharges are controlled by a broad multi-
gated control structure discharging into a shallow stilling
basin.The feasibility of this arrangement is governed by
the qual ity of the rock in the area,requiri ng both dura-
bility to withstand erosion caused by spillway flows,and a
high percentage of sound rockfill material that can be used
from the excavation directly in the main dam.
On the basis of the site information developed concurrently
with the general arrangement studi es ,it became apparent
that the major shear zone known to exist in the left bank
area extended further downstream than initial studies have
indi cated.The cascade spi 11 way channel was therefore
lengthened to avoid the shear area at the lower end of the
cascade.The arrangement shown on Pl ate 9.11 for Scheme
WP4A does not reflect this relocation,which would increase
the overall cost of the scheme.
The emergency spillway consisting of rock channel and fuse
plug is similar to that of the right bank spillway scheme.
(v)Power Facilities
The power facilities are similar to those in Scheme WP3A.
Evaluation of Final Alternative Schemes
An evaluation of the dissimilar features for each arrangement (the
mai n spi llways and the discharge. arrangements at the downstream
end of the outl ets)i ndi cates a savi ng in capital cost of
$197,000,000,excluding contingencies and indirect cost,in favor
of Scheme WP3A.If this difference is adjusted for the savings
associated with using an appropriate proportion of excavated
material from the cascade spillway as rockfill in the main dam,
this represents a net overall cost difference of approximately
$110,000,000 including contingencies,engineering,and administra-
tion costs.
the qual ity of the rock in the downstream area on the 1eft bank,
it is known that a major shear zone runs through and is adjacent
to the area presently allocated to the spillway in Scheme WP4.
This would require relocating the left bank cascade spillway
several hundred feet farther downstream into an area where the
rock quality is unknown and the topography less suited to the
gentle overall slope of the cascade.The cost of the excavation
would substantially increase compared to previous assumptions,
irrespective of the rock quality.In addition,the resistance of
the rock to eros i on and the suitabi 1ity for use as excavated
material in the main dam would become less certain.The economic
feasibility of this scheme is .largely predicated on this last
factor,since the ability to use the material as a source of rock-
fill for the main dam represents a major cost saving.
9-44 .
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In conjunction with the main chute spillway,the problem of the
occurrence of nitrogen supersaturation can be overcome by the use
of a regularly operated dispersion type valve outlet facility in
conjunction with the main chute spillway.As this scheme presents
a more economic solution with fewer potential problems concerning
the geotechnical aspects of its design,the right bank chute
arrangement (Scheme WP3A)has been adopted as the final selected
scheme.
9-45
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LIST OF REFERENCES
1.Acres American Incorporated,Susitna Hydroelectric Project,1980-
81 Geotechnical Report, prepared for the Alaska Power Author-
ity,February 1982.
2.Woodward-Clyde Consultants,Final Report on Seismic Studies for
Susitna Hydroelectric Project,prepared for Acres American
Incorporated,February 1982.
3.Acres American Incorporated,Susitna Hydroelectric Project,
Development Selection Report, prepared for the Alaska Power
Authority,December 1981.
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TABLE 9.1:COMBINED WATANA AND DEVIL CANYON OPERATION
Watana Dam Watana*Dev il Canyon*Total Average
Crest Elevat ion Cost Cost Cost Annual Energy
(f't MSL)($x 106 )($x 10
6)($x 10 6 )(GWh)
2240 (2215
reservoir elevation)4,076 1,711 5,787 6,809
2190 (2165
reservoir elevation)3,785 1,711 5,496 6,586
2140 (2115
reservoir elevation)3,516 1,711 5,227 6,264
Watana Project alone (prior to year 2002)
Crest Elevat ion
(f't MSL)
2240
2190
2140
Average Annual
Energy (GWh)
3,542
3,322
3,071
*Estimated costs in January 1982 dollars,based on preliminary conceptual
designs,including relict channel drainage blanket and 20 percent
cant ingenc ies.
TABLE 9.2:PRESENT WORTH OF PRODUCTION COSTS
I 1IIf
Watana Dam
Crest Elevat ion
(ft MSL)
2240 (reservoir
elevat ion 2215)
2190 (reservoir
elevation 2165)
2140 (reservoir
elevat ion 2115)
*LTPW in January 1982 dollars.
Present Worth
of Productign Costs
($x 10
7,123
7,052
7,084
River Flows
TABLE 9.3:DESIGN DATA AND DESIGN CRITERIA FOR FINAL REVIEW OF LAYOUTS
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Average flow (over 30 years of record):
Probable maximum flood (routed):
Maximum inflow with return period of 1:10,000 years:
Maximum 1:10,000-year routed discharge:
Maximum flood with return period of 1:500 years:
Maximum flood with return period of 1:50 years:
Reservoir normal maximum operating level:
Reservoir minimum operating level:
Dam
Type:
Crest elevat ion at point of maximum super elevat ion:
Height:
Cutoff and foundation treatment:
Upstream slope:
Downstream slope:
Crest width:
Diversion
Cofferdam type:
Cutoff and foundation:
Upstream cofferdam ~rest elevation:
Downstream cofferdam crest elevat ion:
Maximum pool level during construction:
Tunnels
Final closure:
Releases during impounding:
Spillway
Design floods:
Main spillway -Capacity:
-Control structure:
Emergency spillway -Capacity:
- Type:
Power Intake
Type:
Number of intakes:
Draw-off requirements:
Drawdown:
7,860 cfs
326,000 cfs
156,000 cfs
115,000 cfs
116,000 cfs
87,000 cfs
2215 ft
2030 ft
Rockfill
2240 ft
890 ft above foundat ion
Core founded on rock;grout curt ain and
downstream drains
2.4H:1V
2H:1V
50 ft
Rock fill
Slurry trench to bedrock
1585 ft
1475 ft
1580 ft
Concrete lined,
Mass concrete plugs
6,000 Gf~maximum via bypass to outlet
structure
Passes PMF,preserving integrity of dam
with no loss of life
Passes routed 1:10,000-year flood with no
damage to structures
Routed 1:10,000-year flood
with 5 ft surcharge
Gated ogee crests
PMF minus 1:10,000 year
Fuse plug
Reinforced concrete
6
Multi-level corresponding to temperature
strat a
185 feet
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TABLE 9.3:(Cont'd)
Penstocks
Type:
Number of penstocks:
Powerhouse
Type:
Transformer area:
Control room and administration:
Access -Vehicle:
-Personnel:
Power Plant
Type of turbines:
Number and rating:
Rated net head:
Design flow:
Normal maximum gross head:
Type of generator:
Rated output:
Power factor:
Frequency:
Transformers:
Tailrace
Water passages:
Surge:
Average tailwater elevation (full generation):
Concrete-lined tunnels with downstream
steel liners
6
Underground
Separate gallery
Surface
Rock tunnel
Elevator from surface
Francis
6 x 170 MW
690 ft
3,500 cfs per unit
745 ft
Vertical synchronous
190 MVA
0.9
60 HZ
13.8-345 kV,3-phase
2 concrete-lined tunnels
Separate surge chambers
1458 ft
PRELIMINARY REVIEW
Technical feasibility
Compatibility of layout
with known geological
and topographical site
features
Ease of construction
Physical dimensions
of component structures
in certain locations
Obvious cost differences
of comparable structures
Environmental accept-
ability
Operating characteristics
TABLE 9.4:EVALUATION CRITIERA
INTERMEDIATE REVIEW
Technical feasibility
Com pat ibility of layout
with known geological and
topographical site features
Ease of construct ion
Overall cost
Env ironment al accept-
ability
Operating characteristics
Impact on construction
schedule
FINAL REVIEW
Technical feasibility
Compat ibility of layout
with known geological and
topographical site features
Ease of construction
Overall cost
Environmental impact
Mode of operation of spill-
ways
Impact on construct ion
schedule
Design and operat ing .lJm.i.t a-
tions for key structures
:\
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TABLE 9.5:SUMMARY OF COMPARATIVE COST ESTIMATES
INTERMEDIATE REVIEW OF ALTERNATI~E ARRANGEMENTS
(January 1982 $x 10 )
WP1 WP2 WP3 WP4
,Diversion 101.4 112.6 101.4 103.1
I
:I Service Spillway 128.2 208.3 122.4 267.2
Emergency Spillway 46.9 46.9
Tailrace Tunnel 13.1 13.1 13.1 8.0
Credit for Use of Rock in Dam -i.!.hl)~)~)(72.4)
Total Non-Common Items 231.0 349.7 265.0 305.9
Common Items 1643.0 1643.0 1643.0 1643.0------
Subtotal 1874.0 1992.7 1908.0 1948.9
Camp &Support Costs (169~)299.8 318.8 305.3 311.8
Subtotal 2173.8 2311.5 2213.3 2260.7
Cant ingency (2m~)434.8 462.3 442.7 452.1---------
Subtotal 2608.6 1773.8 2656.0 2712.8
Engineering and
Administ rat ion (12.590 326.1 346.7 332.0 339.1
TOTAL 2934.7 3120.5 2988.0 3051.9
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FIGURE 9.1
SHEAR, WIDTH GREATER THAN 10FEET,
VERTICAL UNLESS DIP SHOWN
SHEAR, WIDTH LESS THAN 10 FEET,
INCLINED,VERTICAL,EXTENT WHERE
KNOWN
FRACTURE ZONE, WIDTH GREATER THAN
10 FEET,VERTICAL UNLESS DIP SHOWN
FRACTURE ZONE, WIDTH LESS THAN
10 FEET, INCLINED, VERTICAL EXTENT
WHERE KNOWN
JOINTS: INCLINED, OPEN INCLINED,
VERTICAL (SETS I AND II ONLY,
EXCEPT FOR OPEN JOINTS)
ALTERATION ZONE, WIDTH AS SHOWN
DIORITE TO QUARTZ DIORITE,INCLUDES
MINOR GRANODIORITE
ANDESITE PORPHYRY,INCLUDES
MINOR DACITE AND LATITE
DIORITE PORPHYRY
OTHER:
CONTACTS:
J45 LITHOLOGIC, DASHED WHERE INFERRED,
- DIP WHERE KNOWN .
STRUCTURE:
LEGEND
LITHOLOGY:
NOTES
I.ADDITIONAL GEOLOGIC DATA FROM COE,I978,
GEOLOGIC FIELD 800KS I THRU 28.
2.TOPOGRAPHY FROM COE,I978,1"=200'.
3.EXTENT OF SHEARS,FRACTURE ZONES,AND
ALTERATION ZONES ARE INFERRED 8ASED
ON GEOLOGIC MAPPING AND SUBSURFACE
EXPLORATIONS, AND ARE SUBJECT TO
VERIFICATION THROUGH FUTURE DETAILED
INVESTIGATIONS.
4. DETAILS OF GEOLOGIC FEATURES PRESENTED
IN 1980-81 GEOTECHNICAL REPORT.
WATANA
GEOLOGIC MAP
,I
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0s0
0q
q,.:lD
'"~v v....llJ llJII
+
REFERENCE:BASE MAP FROM COE,I978 -1"=200'WATANA TOPOGRAPHY,SHEET 8 a 13 OF 26,
COORDINATESIN FEET,ALASKA STATE PLANE (ZONE4)
Ii 3,225,000 -
4o
SCALE Ei~~~iiiiiiii;;;;;;dT MILES
DETAILED DISCPRESENTEDINU~~I~~9~::~EG~~~ICT CHANNELECHNICALREPORT.
FIGURE 9.2
SCALE
2200~
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LEGEND
~__~_20~-___-_~OP OF BEDROCKoFOOTCONTOURCSONTOUR INTER¥.
\90
0---
DASHED. AL 50 FEET
,,,0 """"""'."~.
/:::::;:;::;;;;;;;;;=::::::-../~..=",.,..•••~•••""~-...._n"0"',,~~~ioo reer..=-,~~"OO~W...Wi',"'"a,_W""
US/TNA'--::::'••.~~t .t PROALERIVER'~OR CROSS-SECTION LO
CATION
OR BEDROCKRELICT
w
DM-A a B
,-.
N 3,234,000
N 3,232.QOO
N 3.230000
143,225.000
N3,225.QOO
N 3224.000
I
M=61/4
DAMPING =0.10
SO!!!PERCENTILE
/V ...........r-,
//MEAN \
V ................\
/V/'<,,\
ap=0.71 //V V
"ii"P'=0.55
I"\.
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~~
~t::::::::
o
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zo
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w
a,
C/)
2
o
0.02 0.03 0.05 0.1 0.2 0.3
PER 100 (SEC)
0.5 2 5 10
MEAN RESPONSE SPECTRA AT DEVIL CANYON AND WATANA.
SITES FOR TERRAIN SAFETY EVALUATION EARTHQUAKE
FIGURE 9.3
7300
i ]
72.00
I II
7100
I 1 --I 1 CDO
x
fJ
..,..
lJ)7000I-
lJ)
0u
z
0
i=o
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0
0
ll::6900a..
LL.
0
]]::I:
l-
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0
~
\1 I-6800zw
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ll::a..
6700IIJ
../~
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IJ
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6600
6500
2.140 2.160 2180 2200
DAM CREST ELEVATION
2220
( FE ET )
22.40 2.260
WATANA RESERVOIR
DAM CREST ELEVATION / PRESENT WORTH OF PRODUCTION COSTS
FIGURE 9.4 •
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TYPICAL
TUNNEL
SECTION
1450 L-.-..L--'---L --JL ---'
25 30 35 40 45
TUNNEL DIAMETER (FT.)
NOTE
FOR 80,000 CFS
WATANA DIVERSION
HEADWATER ELEVATION /TUNNEL DIAMETER
FIGURE 9.5
11I.
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zo
f-
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W
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W
1650
1600
1550
1500
VAT '720COST
50XI06
I
--
I
,
lOX 10
6 20X 10
6 30XI06 40XI06
CAPITAL COST $
WATANA DIVERSION
UPSTREAM COFFERDAM COSTS
FIGURE 9.6
""¢
,Lv
~r_~Q O~~/
~~<c,'v~~~~A
""
~~~~
~'v
~~~
;V
"
0
TYPICAL
TUNNEL
SECTION
70
TUNNEL DIAMETER (FT.)
45403530252015
80
60
(J
II .-50
CD
0
x
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I-
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l]
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a.«o 3-0
[J
20
iJ
10
!J
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I '\J
WATANA DIVERSION
TUNNEL COST /TUNNEL DIAM ETER
FIGURE 9.7
[i
[]
11
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u
u
U
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100 .........-------,-----.,.-----,-------,-------,
40
WATANA DIVERSION
TOTAL COST /TUNNEL DIAMETER
FIGURE 9.8
-'--l-J L--'-~'
---I
---.J -------.i ,---'
zzoo.-/
PLATE
9.1
,ta°O
1600
\60 0
.'1-00
'1-\00
000n:
...___'700 I
200
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
WATANA
ARCH DAM ALTERNATIVE
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)/PREPARED FOR COMPARISON OF ALTERNATIVEg'SITE DEVELOPMENTS ONLY.
~
2400
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ALASKA POWER AUTHORITY
'SUSITNA HYDROELECTRIC PROJECT
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SCALE 0 200 400 FEET
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PLATE
9.2
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SUSITNA HYDROELECTRIC PROJECT
ALTERNATIVE 3 ALTERNATIVE 4
WATANA
PRELIMINARY SCHEMES
WATANA
PRELIMINARY SCHEMES
-~-ACRES AMERICAN INCORPORATED
PLATE
9.3
L-L-L.-J ,
,~--'~--'
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-2ZS0
~2300
PLATE
9.4
2\00
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WATANA
SCHEME WPI
PLAN
SUSITNA HYDROELECTRIC PROJECT
200
ALASKA POWER AUTHORITY
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SCALEO~~s_;;;iij
2100
2150
2200
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2250
NOTE
THIS DRAWING ILLUSTRATES A
PRELIMINARY CONCEPTUAL PROJECT LAYOUT
PREPARED FOR COMPARISON OF
ALTERNATIVE SITE ,DEVELOPMENTS ONLY
_______1750 ------
1700 _
16!SO~
1600 --""-
1!S50----f\...
...-r--.'"OO~~,-2~~--
_~RiVeR BED ALLUVIUM
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WHEEL GATES
PLATE
9.5
WATANA
SCHEME WP3
SECTIONS
50
ALASKA POWER AUTHORITY
SUSITNAHYDROELECTRIC PROJECT
-.......:.._._.
-------SOUND ROCK--..........
RIGHT SIDE -....-
~------------
SCALE B0 5 10 FEET
SCALE AO~~~i;;;;;;;;;;;:ii
4'
...........Ii~"""~-'"'"I2'n
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SECTION C-C
SCALE A
TYPICAL CHUTE WALL SECTION
SCALE B
..!iQill
l THIS ORAWING IUUSTRATES A PRELIMINARY CONCEPTUAL
PROJECT LAYOUT PREPARED FOR COMPARISON OF
ALTERNATIVE SITE DEVELOPMENTS ONLY
2.SECTIONS FOR SCHEME WPI ARE SIMILAR EXCEPT THAT
GATE STRUCTURE IS ISO' WIDE WITH CREST EL 2150 AND
3-40'WlDEx53'HIGH GATES
....2200
~
z
5 2150
!i~
w2100
SECTION E-E
SCALE A
..--~-~--~---..-..-----.--"0--..-.....--....------:::--------
SECTION B-B
SCALE A
------...........--..--
~C
SPILLWAY PROFILE I-~""---""---
SCALE A ~--
...C
2250
2150
2100
2200
SECTION 0-0
SCALE A
-------
EXCAVATE ALLUVIUM<,-__................_/IN RIYERBED
»->:
ORIGINAL GR~~_~-
»>/'/
»>.>
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ORIGINAL GROUND
SURFACE*RIGHT SlOE
..-..---
-<ft'2000 i ~2
1950
1900
"---\<~''''-.~~
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EL.2225
..-.;:-------:....._-------=:.::::::::--
~-----
SOUND ROCK-
RIGHTSlOE
PRESSURE RELIEF
DRAINS
ORIGINAL GROUNO~.--~---
*--~-~
SECTION A-A
SCALE A
"'A__-----+Al---r--
I GROUT
~---------------------------------------.
R
IGINALGROUNG GE "__-=:::____~
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2250
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z
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~2150
iil
2100
1 _L_
PLATE
9.6
SUSITNA HYDROaECTRlC PROJECT
WATANA
SCHEME WP2 a WP3
PLAN a SECTIONS
ALASKA POWER AUTHORITY
~--ACRES AMERICAN INCORPOftATEO
SECTION A-A
SCALE"":8
~,I
3'RIP-RAP,I ~
EL.2222 j
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IS I
ROCK FILL ~11'6'"<,1 ROCKFILL
FILTER
..._-_.__..-_...
50
200
I;;If!2250
z
zo
~2200
~
NOTE
THIS DRAWING ILLUSTRATES A
PRELIMINARY CONCEPTUAL PROJECT LAYOUT
PREPARED FOR COMPARISON OF
ALTERNATIVE SITE DEVELOPMENTS ONLY
SCALEA '1!0!!!!!!!!'!!!ii;;iiiiiiiiii
SCALE B ~0!!!!!!!!!!!!5iiiiiiii~
CP~~~
/-
2175~
~2150~~
CJ
GENERAL ARRANGEMENT
SCALE: A
2225
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.REUEF DRAINS
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GROUTJ'i,
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SPILLWAY PROFILE
~Ol 7)'
...
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"!1500
1400
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.4""1'
SECTION A-A SECTION B-B
PLATE
9.7
WATANA
SCHEME WP2
SECTIONS
:SU:)II NA NTUI10RECTRIC PROJECT
ALASKA POWER AUTHORITY_.._......._-~
~
~o FEET
THIS DRAWING ILLUSTRATES A
F'REUM1NARY CONCEPTUAL PROJECT LAYOUT
PREPARED FOR COMPARISON OF
AlJ'ERNATlVE SITE DEVELOPMENTS ONLY
0.!iQ.I!i;
SCALE
L __
PLATE
9.8
WATANA
SCHEME WP4
PLAN
200~OFEET
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
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2150_
2200-
In,!700 !
:::=::::::::::
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?ELI7.0 l
.?QOO
2250
"c1",'"
NOTE
THIS DRAWING ILLUSTRATES A
PRELIMINARY CONCEPTUAL PROJECT LAYOUT
PREPARED FOR COMPARISON OF
ALTERNATIVE SITE DEVELOPMENTS ONLY
~
fEuDeD!
CASCADE
SPILLWAY
0°-"'"~<,'"~-,
,,0",'"I
-------...---....
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1
...._-----L __---j-----.r FEDROCK SURFACELEFTSIDE
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~--"1 <,••~~R~~rs~~R§ii,~E L-,...............--:----./
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-.........n ........
1500
1400
1600
2400
230
200'
220'
2100
zo
~1900
>a ISDO
1700
STATIONING ,IN :FEET
'SPILLWAY'PROFILE
SCALE:A
~
114'
=r::::-':~:..T:S:...__
\
~EL.2IB5
11
~--._~:~-.~..-._-
,(N~--.------...
EL 2120Iei. ano
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------,",,"I -----------------rEL2t6S
-~
NORMAL MAX.W.L
EL 2200
2200 '""¥'"
i3
i=~21!50 i=EL 2140~A\la'ilfi:j\\i€'AIKw.
2100
GROUTCURTAIN---;~PRESSURE RELIEF O'hAINS
I
-'A -'8 SECTION B-B
SCALE: B
SPILLWAY CONTROL STRUCTURE
SCALE:B·
PLATE
9.9
WATANA
SCHEME WP4
SECTIONS
SUSITNA HYDROELECTRIC PROJECT
ALASKA POWER AUTHORITY
~
~
THIS DRAWING ILlUSTRATESA
PRELIMINARY l:OftCEPTUAL PROJECT LAYOUT
PREPARED FOR COMPARISON OF
ALTERNATIVE SITE DEVELOPMENTS ONLY
SCALE 9
o 200 400 FEET
SCAlE A I I
o 50 100 FEET
i
SECTION C-C
SCALE:B
30'Wx43'H FIXED
WHEEL GATES
c ..
SECTION A-A
SCALE: 8
,'C --.._r . .~
L-...:...--"'---...r.:I I
.__I .50',~~~r=I:-[il:M~\~...~
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I I
I'2100
2250
)-
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==2200
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200 400 FEET
PLATE
9.10
7".O~O~
.><>">:
,,00 /
,.~o/
,.00
~oo;-
1750----
____1700 _
WATANA
SCHEME WPM
ALASKA POWER AUTHORITY
SUSITNAHYDROELECTRIC PROJECT
->'i>~O
'/.'/.<i'/",'"'"
~~
N ALTERNATIVE SITEDEVELOPMENTS ONLY I ACRES AMERICA;-mc'Ofi;CIRATEo
~
~
----22"0
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---2300
»<./r:rr':J (_/(// )\'::Y'"''J 'v ~-"--J ~-IiliAD -----,~-THIS DRAWING ILLUSTRATES A---/'./II /I )ltV 0 :_'........:..x,PRELIMINARY CONCEPTUAL PROJECTLAYOUT
.E PREPARED FOR COMPARISON OF
L_-'----~
THIS DRAWINGILLUSTRATES A
PREUMINARY CONCEPTUAL PROJECT LAYOUT
PREPARED FORCOMPARISON OF
ALTERNATIVE SITE DEVELOPMENTS ONLY
PLATE
9.11
.>",ooor:
,,0 ~
,q /'
00 /,q /•
\'Of:;O
»>:
210 0;---
WATANA
SCHEME WP4A
200 400 FEET
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
~
.'l.\f:J0
~~------------ACRES AMERICAN INCORPORATED
2100/
~/SO
2200 ....
2200,,0,,,'"
/~~TAIL.RACE TUNNEL
//30' CIA.
8I:J
1
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~
------2>00
---2230
.e,
I]
[J
10 -SELECTION OF DEVIL CANYON GENERAL ARRANGEMENT
This section describes the development of the general arrangement of
the Devil Canyon project.The site topography,geology,and seismicity
of the Devil Canyon site are described relative to the design and ar-
rangement of the various site facilities,in a manner similar to that
presented in Section 9 for the Watana site.The method of handling
floods during construction and subsequent project operation is also
outlined in this section.
The reservoir level fluctuations and inflow for Devil Canyon will es-
s ent l al ly be controlled by operation of the upstream Watana project.
This aspect is also briefly discussed in this section.A detailed des-
cription of the various project components is given in Section 13.
10.1 -Site Topography
The Devil Canyon site is located at river mile 152 of the Susitna
River,approximately 32 miles downstream from the Watana site,near the
entrance to a 2-mile long,steep-walled canyon. The valley wall on the
left side of the river rises very steeply from-Elevations 900 to 1300
on the left bank at a slope of approximately 0.4H:1V to a relatively
gently sloping plateau area which reaches Elevation 1600.within the
general project area.On the right side,the valley is less pro-
nounced,rising at about 1.1H:1V to Elevation 1500,then much more
gradually to approximate Elevation 1900. The steep left bank contains
overhanging cliffs and detached blocks of rock.
10.2 -Site Geology
A detailed description of the site investigations and the geologic and
geotechnical conclusions at the Devil Canyon site is provided in the
1980-81 Geotechnical Report (1).The following is a brief summary and
interpretation of the findings presented in the Geotechnical Report.
(a)Geologic Conditions
The overburden and bedrock conditions at the Devil Canyon site are
summarized in the following paragraph.A geologic map of the dam-
I)site area is shown in Figure 10.1 in this section.
IJ
IJ
I 1iJ
I
J
( i )Overburden
The valley walls at the Devil Canyon site are very steep
and are generally covered by a thi n veneer of overburden
consisting pr imer il y of talus at the base.The flatter up-
1and areas are covered by 5 to .35 feet of overburden of
glacial origin.A topographic depression along the elon-
gated 1akes on the south bank has an overburden cover in
10-1
excess of B5 feet of glacial materials.The overburden on
the alluvial fan or point bar deposit at the Cheechako
Creek con fl uence th i ckens from 100 feet to more th an 300
feet over a distance of less than 400 feet.
The river channel alluvium appears to be composed of cob-
bles,boulders,and detached blocks of rock and is inferred
to be up to'30 feet thick.
(ii)Hedrock Lithology
The bedrock at the Devil Canyon site is a low-grade meta-
morphosed sedimentary rock consisting predominantly of
argill ite with interbeds of graywacke.A geologic map of
the site is shown in Figure 10.1.The argillite is a
fresh,med i um-to-dark gray,th in ly bedded,fine grained
argillaceous rock with moderately well-developed foliation
parallel to the bedding.The graywacke is a fresh,light
gray,mainly fine grained sandstone within an argillaceous
matrix.The graywacke is well indurated and exhibits
poorly developed to non-existent foliation.The graywacke
is interbedded with the argill ite in beds generally less
than 6 inches thick.Contacts between beds are tight and
both rock types are fresh and hard.Minor quartz veins and
stringers are commonly found in the argill ite.These are
generally less than 1 foot wide and unfractured with tight
contacts.Sulphide mineral izat ion is common with pyrite
occurring in as much as 5 percent of the rock.
The area has also been intruded by numerous felsic and
mafic dikes ranging from 1 inch to 60 feet wide (averaging
20 feet).The dikes have northwest to north orientation
(Figure 10.1)with steep dips.When closely fractured they
are easily eroded and tend to form steep talus-filled gul-
lies,some of which exhibit shearing with the host rock.
The felsic dikes are light gray and include aplite and
rhyol ite~The mafic dikes are fine grained --and appear to
·--be-ofd+or+~e~odiabas·eeompos+t-ion-.--_.._~---_.._---~.__._._.-----_.
(iii)Bedrock Structures
Bedding
The argillite/graywacke has been completely deformed as
evidenced by refolded folds and the development of mul-
tiple foliations.The primary foliation parallels the
bedding at 035°to 090°,subparallel to the river,and
dips 45°to BOoSE (Figure 10.1).Where exposed,the
foliation planes appear slaty and phyllitic.The north
canyon wall at the dams ite appears to be controlled by
the bedding planes.
1
I
)
I
1
\
1
1
1
l
1
l
I
I
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and dips 45°to 80
0SE.Where exposed, the foliation
planes appear slaty and phyll it i c.Th e north canyon
wall at the damsite appears to be controlled by the
bedding planes.
Joints
Four joint sets have been delineated at Devil Canyon.
Set I (stri ke 320°to 355°and dips 60°to 70
0NE)and
Set II (strike 040°to 065°and dips 40°to 60
0S)are
the most significant.Set I joints are the most
prominent with spacing of 15 feet to 2 feet,and on the
upper canyon walls of the south bank these joints are
open as much as 6 inches.Set III is subparallel to the
bedding/foliation and,when it intersects with Set I,
can cause the formation of loose blocks.Set III joints
(strikes 005°to 030°and dip 85°NW to 85°SE)are also
often open on the south bank and where they dip towards
the river they may create potential slip planes.This
set has variable spacing and sporadic distribution.The
fourth set is a minor set with low dip angles'and
variable strike orientation.
Joint spacings measured from the borehole cores range
from less than 1 foot to more than 10 feet.The spacing
and tightness of the joints increase with depth.
Shears and Fracture Zones
Shears and fracture zones were encountered in localized
areas of the site in both outcrops and boreholes (Figure
10.1).Shears are defined as areas containing breccia,
gouge, and/or sl i ckenslides indicating relative move-
ment. These zones are soft and friable and are charac-
terized by high permeability and core loss during drill-
ing.Fracture zones,often encountered in conjunction
with the shears,are zones of very closely spaced
joints.With depth,these zones become tighter and more
widely spaced.Where exposed,they are eroded into deep
gullies.
The most common trend of these features is northwest,
parallel to Joint Set 1.These zones have vertical to
steep northeast dips and are generally less than 1 foot
wide.Northwest trending shears are also associated
with the contacts between the argillite and mafic dikes
and are up to 1 foot wide.
A second series of shears trend northeasterly,subpara1-
1e1ing the bedding/foliation and Joint Set II,with high
10-3
Several structural features at the Devil Canyon site were investi-
gated during the 1980-81 program.
In summary,these included the east-west trending sheared and
fractured zone beneath the proposed saddle dam area;a bedrock
drop-off beneath ~orrow Site G;and bedrock conditions beneath the
Susitna River.
Seismic refraction and drilling data confirm the existence of a
highly sheared and fractured zone on the 1eft bank beneath the
proposed saddle dam that generally trends parallel to the river.
The dip on this feature is inferred to be parallel or subparallel
to the bedding/foliation at approximately 65°to the south.The
linear extent of the feature has not been determined but may be up
to 2,50U feet.No evidence was found during the 1980-81 program
to suggest movement along this feature.This conclusion was con-
firmed during the seismic investigations (3).Further investiga-
tion of this feature will be required to define its extent and to
determine the type of foundation treatment that will be required
beneath the saddl edam.
These average less than 6anglesoutheasterlydips.
inches in width.
Structural Features
Upstream from the damsite,a several-hundred-foot drop-off in the
bedrock surface under the alluvial fan was detected by seismic re-
fraction surveys.Land access restrictions imposed during the
study prohibited any further investigation of this area.Possible
explanation for this apparent anamalous drop-off could be attrib-
uted to misinterpretation of the seismic data or else the lower
velocity material could be either a highly fractured rock in lieu
of soil or an offset of the rock surface caused by faulting.The
latter interpretation is unlikely in that work performed (3) in
this area concluded that there was no compelling evidence for a
fault.Future work remains to be done in this area to more
clearly define this feature.
(b)
Detailed examination of rock core and mapping in the river valley
bottom showed no evidence for through going faulting in the river-
bed.
(c)Ground Water Conditions
Ground water migration within the rock is restricted to joints and
fractures.It is inferred that the ground water level is a sub-
dued replica of the surface topography with the flow towards the
river and lakes.Measured water levels in the boreholes varied
from ground surface to 120 feet.
I \
I I
I J
(d)Permafrost
No permafrost was found in either the bedrock or surficial materi-
al at or around the damsite.
(e)Permeability
kock perme ab i l ity ranges from approximately 1 x 1u-4 ern/sec to
1 x 10-6 cm/sec with lower permeabilities generally at depth.
Higher permeabi 1 ity occur in the more weathered fractured rock
zones.
lj
II
( 1
IJ
(f)
(g)
Devil Canyon Reservoir Geology
The Devil Canyon reservoir will be confined to a narrow canyon
where the topography is controlled by bedrock.The overburden is
thin to nonexistent,except in the upper reaches of the reservoir
where alluvial deposits cover the valley floor.A large intrusive
plutonic body composed predominantly of biotite granodiorite with
local areas of quartz diorite and diorite,underlies most of the
reservoir and adjacent slopes.This rock 'is light gray to pink,
medium grained,hard,massive,and competent.The other rock
types in the reservoir is the argillite and graywacke which are
exposed at-the damsite.The rock has been isoclinically folded
into steeply dipping structures striking generally northeast-
southwest.The argi 11 ite has been intruded by mass ive granod io-
rite,and as a result,large isolated roof pendants of the argill-
ite and graywacke are found locally throughout the entire reser-
voir and surrounding areas.The joint measurements at selected
areas indicate structural trends simil ar to those at the damsites.
Construction Material Investigations
A major source of construction materials for the Devil Canyon
Project is the alluvial fan deposit,Borrow Site G,which lies
near the Cheechako Creek confl uence approximate ly 1,000 feet up-
stream from the damsite.The area contains large quantities of
sands and gravels with inclusions of boulders and cobbles above
the river level.
(i)Shell Materials for the Saddle Oam
Clean gravel and cobble fill will be obtained from the
alluvial fan Site G.This material will be supplemented by
rockfill obtained from the excavations of other structures
where suitable and economic.Potential sources of rockfill
are likely to be the emergency spillway located adjacent to
the saddle dam and Quarry Site K (1).
10-5
(ii)Core Material for the Saddle Dam
No suitable source for the core material for the saddle dam
has been identified at this time near the site.It is,
therefore,proposed that the core material ~e transported
from Borrow Site D near the Watana site,wher~sufficient
quantities of suitable material have been identified.Ad-
d it ional invest igat ions should be performed in an attempt
to locate a suitable source nearer the Devil Canyon site
prior to final design.
(iii)Filter Material for the Saddle Dam
Filter materials will be obtained by processing deposits in
the alluvial fan Borrow Site G,discussed above.
(iv)Concrete Aggregate
The coarse and fine aggregate for the concrete structures
will also be obtained from the Borrow Site G. The results
of the laboratory testing indicate that the material from
this source is of adequate qua}ity.The gravel particles
are generally rounded with accompanying sub anqul ar sands.
Petrographic analyses indicate that the material includes
quartz diorites,granites,andesites,diorites,dacites,
metavolcanics,rocks,aplites,breccias,schists,phill-
ites,arqill ites,and amphibol ites.Generally,the mater-
i al has 1ess than 2 percent del eter ious const ituents such
as chert,muscovite,and argillite.
10.3 -Geotechnical Considerations
The geotechnical investigations to date have been primarily directed
toward the important geological features which may have significant im-
pact on the feasibility of the project.More detaileq investigations,
including exploratory adits,will be required prior to the detailed
es gn.
(a)Arch Uam Foundation and Abutments
The geologic and topographic conditions are favorable for an arch
dam at the Devil Canyon site.The rock is principally hard,com-
petent,and fresh with weathering limited to joints and shear
zones.Intrusive mafic and felsic dikes,where present,are hard,
and the contact with the parent rock is tight.The orientation of
the dikes is generally northwest to north.They will have no im-
portant adverse effect on the stability of the abutments.The un-
confined compress ive strength of the intact rock ranges between
16,000 psi and 32,000 psi.The stresses imposed by the arch dam
are about 1,000 psi or less under normal conditions.Even under
10-6
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extreme loading conditions,the stresses will be well within the
acceptable limits for bearing considerations.On the right abut-
ment,the arch dam thrust block will be seated in good sound rock.
On the left side,the bedrock surface is below the crest elevation
and a concrete thrust block will be required to transfer the loads
to competent rock. This thrust block will form an abutment to the
saddle dam.
No large-scale,continuous oriented rock discontinuities,which
might affect abutment stabi lity,have been found.Open fractures
and joints have been noted to extend up to 80-100 feet back from
the valley walls on the south abutment. This area will,there-
fore,require extensive dental work and foundation treatment.The
stability of the right abutment (north bank)is controlled by the
bedding planes and foliations that strike roughly parallel to
subparallel to the canyon walls and dip steeply into the canyon.
The bedding planes generally are tight with undulating surfaces.
Preliminary analyses indicate no stability problems in this area.
Additional rock investigations and in situ testing will be
required to provide data for final design.
The dam foundation and the thrust blocks will be founded on sound
rock,requiring removal of all the overburden and weathered rock.
Extensive dental excavation will be required in some areas to form
an acceptable foundation.The entire dam foundation area will be
consolicjation grouted to fill all the openings and cavities in
rock at shallow depth.
A double row grout curtain will be provided under the entire dam
including the abutments and an appropriate distance beyond the dam
into the abutments. A system of drai n ho les and drai nage gal-
leries will be included to control uplift pressures and to safely
release seepage water.
Underground Structures
The rock conditions at the site are suitable for the construction
of tunnels and underground caverns.For the most part,the under-
ground structures have been sited to avoid adverse geologic condi-
tions (i .e.,jointing and shear zones).
Although the magnitude and the orientation of the in situ stresses
were not performed for this study,the tectonic setting suggests
that the entire site region is in a compressional stress regime.
The stresses near valley walls ar~expected to have been relieved
and low horizontal stresses may exist.Considering the unconfined
strength of the intact rock,overstressing problems such as rock
spalling and slabbing are not anticipated.The rock support re-
quireme~ts will depend on the size and orientation of the openings
and the presence and character of the rock discontinuities
10-7
(c)
intersected.For the most part,conventional rock bolt support
using 3/4-inch to l-inch-diameter bolts has been assumed to be
adequate for openings less than 40 feet in span.For larger
spans,in areas of poor quality rock and where rock discontin-
uities are known to be adversely oriented,support requirements
have been determined on a case-by-case basis.The use of shot-
crete,welded wire fabric,and concrete lining will be required in
poor rock quality areas.For power tunnels,provisions have also
been made for concrete lining and contact/consolidation grouting.
Although rock permeabilities are generally low to moderate,inter-
section of rock discontinuities may lead to ground water inflow
problems during construction.High-pore water pressures may
develop within discontinuities after the reservoir is flooded.
Therefore,provisions have been made for grouting around tunnels
and caverns,and installation of suitably placed drain holes and
drainage galleries has also been provided upstream from the power-
house and surge chamber.
The spacing between long tunnels will be 2.5 times the diameter of
the largest tunnel and caverns will be kept spaced to maintain a
minimum pillar thickness of 1.5 times the span of the larger
cavern.
Stability of Soil and Rock Slopes
In most areas,the permanent excavation slopes will be within
rock,except on the left bank, where a deep buried channel exists.
The slopes within overburden will depend on the nature of soil,
ground water table,and the height of the slope.In general,
slopes within the overburden have been assumed as 2H:IV or less
below the water table and 1.5H:IV or less above the water table.
A bench of appropriate width will be provided at the overburden-
rock contact to accommodate any local slumping and to intercept
and dispose of ground/seepage water.
The slopes of excavations in rock have been selected in accordance
with the joi nt dips and ori entati ons and the shear strength of
~oGk.--a-long--o-i-s GO nt-i-nu-i-t-i-e-s-.--£lo pe-s--i-n--i-nt-aGt--~o Gk--or---wher-e-d-i-s--
continuities dip into the excavated face will usually stand steep-
ly without any structural support.Slopes paralleling the discon-
tinuity have,wherever possible,been laid back to the same angle
as the dip of the rock discontinuity or adequate rock support pro-
vided.Wherever possible,permanent cuts have been set at stable
s lopes wi thout the need for rock bo lt s.In areas where pore pres-
sures could develop behind the rock cuts,allowances have been
made for drain holes to relieve the pore pressures.In general,a
4V:IH overall slope is considered stable.Excavation of tunnel
portals includes pattern rock bolting and appropriate provision
for concrete/shotcrete to reduce the risk of unstable slopes.
Special details are required in areas where slopes will intersect
or cross larger shear zones or otherwise unstable rock.
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(d) Saddle Dam Foundation
The saddl e dam on the south bank wi 11 be constructed across the
buried channel.The thickness of overburden in this area reaches
up to 80 feet.The underlying bedrock is competent argill ite and
graywacke.The core,filters,and outer shells for the saddle dam
will be founded on sound rock.The prominent shear zone or fault
which was found in the saddle dam foundation,together with vari-
ous other shear and fracture zones,will require treatment by con-
solidation and curtain grouting under the core.
10.4 - Seismic Considerations
As discussed in Section ~.4 for Watana,the Devil Canyon project struc-
tures have been classified as either critical structures or noncritical
structures for earthquake engineering and design considerations.Crit-
ical structures include the dam and simil ar major structures whose
failure may result in sudden and uncontrolled release of large volumes
of water which may endanger property and 1 ives-downstream.The non-
critical structures are those structures whose failure can be assessed
as an economic or financial loss to the project in terms of lost rev-
enue,repair,and/or replacement cost.Critical structures will be
designed to safely withstand the effect of the "Safety Evaluation
Earthquake (SEE)for the site.No significant damage to these struc-
tures will be accepted under these conditions.
The design of noncritical structures for earthquake conditions will be
undertaken on the basis of conventional Uniform Building Code recommen-
dations.
The design of the saddle dam at Devil Canyon,as for Watana dam,is
based on the projected time history for the Benioff Zone SEE,magnitude
8.5.The distance from Devil Canyon in this case is 57 miles.
The design of the arch dam and other critical concrete structures is
based on the Terrain SEE as discussed for Watana.The appropriate re-
sponse spectra for ground motions for the magnitude 6.25 Terrain earth-
quake are shown in Figure 9.3.
10.5 -Selection of Reservoir Level
The selected normal maximum operating level at Devil Canyon dam is Ele-
vat ion 1455. Stud ies by the USBf<and CUI:::on the lJev i 1 Canyon Pr oject
were essentially based on a simil~r reservoir level,which corresponds
to the tailwater level selected at the Watana site.Although the nar-
row configuration of the Devil Canyon site and the relatively low costs
involved in increasing the dam height suggest that it might be economic
to do so,it is clear that the upper economic limit of reservoir level
at Devil Canyon is the Watana tailrace level.
The detailed studies of reservoir level at Watana (Section 9)indicated
little change in benefit-cost ratio over a 100-foot range of reservoir
10-9
10.6 -Selection of Installed Capacity
-Daily peaking is more effectively performed at Watana than at Devil
Canyon;and
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370
410
507
Capaci ty MW
at Devi 1 Canyon has been estab-
Th is wi 11 prov i de some margi n
possible accelerated growth in
2002
2005
2010
Demand Year
The selected total installed capacity
lished as 600 MW for design purposes.
for standby duri ng forced outage and
demand.
Excessi ve fl uctuat ions in discharge from the Devi 1 Canyon dam may
have an undesirable impact on mitigation measures incorporated in the
final design to project the downstream fisheries.
Given this mode of operation,the required installed capacity at Devil
Canyon has been determined as the maximum capacity needed to utilize
the available energy from the hydrological flows of record,as modified
by the reservoir operation rule curves.In years where the energy from
Watana and Devi 1 Canyon exceeds the system demand,the usable energy
has been reduced at both stations in proportion to the average net head
available,assuming that flows used to generate energy at Watana will
also be used to generate energy at Devil Canyon.
The total capacity required at Devil Canyon in-a--wet--year,-excluding
standby and spinning reserve capacity,is summarized below.As dis-
cussed in Section 9.6,the capacity shown is based on the December 1981
Battelle medium load growth forecast.
The methodology used for the preliminary selection of installed capa-
city at Watana and Devil Canyon is described in Section 9.6.
The decision to operate Devil Canyon primarily as a based loaded plant
was governed by the following main considerations:
level at the upper limit.Maximization of hydroelectric energy produc-
tion at the site was found to be an important objective which weighed
heavily in the selection of reservoir level at Watana.Although a de-
tailed determination has not been undertaken,the same is likely to be
true at Devil Canyon.
Although significantly lower reservoir levels at Devil Canyon would
lead to lower dam costs,it is clearly evident that the location of
adequate spillway facilities in the narrow gorge would become extremely
difficult and lead to offsetting increases in cost.In the extreme
case,a spillway discharging over the dam would raise concerns regard-
ing safety from scouring at the toe of the dam,which have already led
to rejection of such schemes.
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The major factors governing the selection of the unit size at Devil
Canyon are the rate of growth of system demand,the minimum station
output,and the requirement of standby capacity under forced outage
conditions.The above tabulation indicates that st at i on maximum load
in December will increase by about 50 percent from 2002 to 2010 (from
370 MW to 507 MW).Station minimum output in July during the same
period will vary from about 150 MW to 202 MW.
The power facilities at Devil Canyon have been developed using 4 units
at 150 MW each.This arrangement will provide for efficient station
operation during low load periods as well as during peak December
loads.During final design,consideration of phasing of installed
capacity to match the system demand may be desirable.However,the un-
certainty of load forecasts and the additional contractual costs of
mobilization for equipment installation are such that for this study it
has been assumed that all units will be commissioned by 2002.
The Devil Canyon reservoir will usually be full in December;hence,any
forced outage could result in spilling and a loss of available energy.
The units have been rated to deliver 150 MW at maximum December draw-
down occuring during an extremely dry year;this means that in an aver-
age year,with higher reservoir levels,the full station output can be.
maintained even with one unit on forced outage.
10.7 -Selection of Spillway Capacity
A flood frequency of 1:10,000 years was selected for the spillway de-
sign on the same basis as described for Watana.An emergency spillway
with an erodible fuse plug will also be provided to safely discharge
the probable maximum flood.The development plan envisages completion
of the Watana project prior to construction at Devi 1 Canyon.Accord-
ingly, the inflow flood peaks at Devil Canyon wi 11 be less than pre-
project flood peaks because of routing through the Watana reservoir.
Spillway design floods are:
Flood
1:10,000 years
Probable Maximum
Inflow Peak (cfs)
165,000
346,000
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The avoidance of nitrogen supersaturation in the downstream flow dis-
cussed in Section 9 for Watana also will apply to Devil Canyon.Thus,
the discharge of water possibly supersaturated with nitorgen from Devil
Canyon will be 1[mi t ed to a recurrence peri od of not 1ess than 1:50
years by the use of solid cone valves similar to Watana.
10.8 -Main Dam Alternatives
The location of the Devil Canyon damsite was examined during previous
studi es by the USSR and COE.These studi es focused on the narrow en-
trance to the canyon and led to the recommendation of a concrete arch
10-11
dam.Notwithstanding this initial appraisal,a comparative analysis
was undertaken as part of this feasibility study to evaluate the rela-
tive merits of the following types of structures at the same location:
- Concrete gravity dam;
- Thick concrete arch;
- Thin concrete arch;and
-Fi 11 embankment.
(a)Comparison of Embankment and Concrete Type Dams
This analysis was based on the thin concrete arch and thick con-
crete arch schemes developed by the COE in 1975 and 1978,together
with a rockfill dam alternative developed as part of this study.
The results of the analysis indicated a trend in favor of the con-
crete arch dam alternatives when compared to the concrete gravity
dam or rockfill dam alternatives.The assessment showed that a
concrete gravity dam in the narrow gorge would tend to behave sim-
ilarly to an arch dam but would not have the flexibility of such a
structure.The technical feasibi 1ity of a concrete gravity dam
was therefore questionable particularly under severe seismic shak-
ing conditions.This type of dam also tended to be more expensive
than either concrete arch and was,therefore,not considered fur-
ther.
Consideration of a central core rockfill dam at Devil Canyon indi-
cated relatively small cost differences from a conservative arch
dam cost estimate,based on a dam cross-section significantly
thicker than the finally selected design.Furthermore,no infor-
mation was available to indicate that impervious core material in
the necessary quantities could be found within a reasonable dis-
tance of the damsite.The rockfi 11 dam was accordingly dropped
from further consideration.Details of this evaluation are pre-
sented in Appendix B.
Neither of the concrete arch dam layouts were intended as the
final site arrangement, but were sufficiently representative of
the most suitable arrangement associ ated with each dam type to
provideanadequ at-e-basis fer cempar-i-sen,.Each type-ofd am was
located just downstream from where the river enters Devil Canyon
and close to the canyon's narrowest point,which is the optimum
location for all types of dams.A brief description of each dam
type and configuration is given below.
(i)Thick Arch Dam
The main concrete dam would be a single center arch struc-
ture,acting partly as a gravity dam,with a vertical cyl-
indrical upstream face and a sloping downstream face in-
clined at 1V:0.4H.The maximum height of the dam would be
635 feet with a 'uniform crest width of 30 feet,a crest
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length of approximately 1,400 feet,and a maximum founda-
tion width of 225 feet.The crest elevation would be 1460.
The center portion of the dam would be founded on a massive
mass concrete pad constructed in the excavated river bed.
This central section would incorporate the main spillway
with sidewalls anchored into solid bedrock and gated ori-
fice spillways discharging down the steeply inclined down-
stream face of the dam into a single large stilling basin
set below river level and spanning the valley.
The main dam would terminate in thrust blocks high on the
abutments.The left abutment thrust block would incorpor-
ate an emergency gated control spi llway structure which
would discharge into a rock channel running well downstream
and terminating at a level high above the river valley.
Beyond the control structure and thrust block, a low-lying
saddle on the left abutment would be closed by means of a
rockfi 11 dike founded on bedrock.The powerhouse would
house four 150 MW un its and wi 11 be located underground
within the right abutment.The intake would be constructed
integrally with the dam and connected to the powerhouse by
vertical steel-lined penstocks.
The main spillway would be designed to pass the 1:10,000-
year routed flood with larger floods discharged downstream
via the emergency spillway.
(ii)Thin Arch Dam
The main dam would be a two-center,double-curved arch
structure of simil arheight to the thick arch dam,but with
a 20-foot uniform crest and a maximum base width of 90
feet.The crest elevation would be 1460.The center sec-
t ion would be founded on a concrete pad,and the extreme
upper portion of the dam would terminate in concrete thrust
blocks located on the abutments.
The main spillway would be located on the right abutment
and would consist of a conventional gated control structure
discharging down a concrete-l ined chute terminating in a
fl ip bucket.The bucket would discharge into an unlined
plunge pool excavated in the riverbed alluvium and located
suffi c ient ly downstream to prevent undermin ing of the dam
and associated structures.
The main spillway would be supplemented by orifice type
spillways located high in the center portion of the dam
which would discharge into a concrete-lined plunge pool im-
mediately downstream from the dam.An emergency spillway,
consisting of a fuse plug discharging into an unlined rock
10-13
channel,terminating well downstream,would be located be-
yond the saddle dam on the left abutment.
The concrete dam would terminate in a massive thrust block
on each abutment which,on the left abutment,would adjoin
a rockfill saddle dam.
The main and auxiliary spillways would be designed to dis-
charge the 1:10,000-year flood.Larger floods for storms
up to the probable maximum flood would be discharged
through the emergency left abutment spillway.
(iii)Comparison of Arch Dam Types
Sand and gravel for concrete aggregates are bel ieved to be
available in sufficient quantities within economic distance
from the damsite.The gravel and sands are formed from the
granitic and metamorphic rocks of the area;at this time it
is anticipated that they will be suitable for the produc-
tion of aggregates after screening and washing.
The bedrock geology of the site is discussed in Sections
10.2 and 10.3.At this time it appears that there are no
geological or geotechnical concerns that would preclude
either of the dam types from consideration.
Under hydrostatic and temperature loadings,stresses within
the thick arch dam will be generally lower than for the
thin arch alternative.However,finite element analysis
has shown that the additional mass of the dam under seismic
loading will produce stresses of a greater mag~itude in the
thick arch dam than in the thin arch dam.If the surface
stresses approach the maximum allowable at a particular
section,the remaining understressed area of concrete will
be greater for the thick arch,and the factor of safety for
the dam will be correspondingly higher.The thin arch is,
__~__~___however,a more efficient design and better utilizes the
Tilnerent properti esof the l:oncfete-:---Tt .is-de-sigrre-daroun-d
acceptable predetermined factors of safety and requires a
much smaller volume of concrete for the actual dam struc-
ture.
The thick arch arrangement did not appear to have a dis-
tinct technical advantage compared to a thin arch dam and
woul d be more expensive because of the 1arger volume of
concrete needed ..Studies,therefore,continued on refining
the feasibility of the thin arch alternative.
10.9 -Diversion Scheme Alternatives
In this section the selection of general arrangement and the basis for
sizing of the diversion scheme are presented.
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(a) General Arrangements
The steep walled valley at the site essentially dictated that di-
version of the river during construction be accomplished using one
or two diversion tunnels,with upstream and downstream cofferdams
protecting the main construction area.
The selection process for establishing the final general arrange-
ment included examination of tunnel locations on both banks of the
river.Rock conditions for tunneling did not favor one bank over
the other.Access and ease of construction strongly favored the
left bank or abutment, the obvious approach being via the alluvial
fan.The total length of tunnel required for the left bank is ap-
proximately 300 feet greater;however,access to the right bank
could not be achieved without great difficulty.
Design Flood for Diversion
The recurrence interval of the design flood for diversion was es-
tablished in the same manner as for Watana dam.Accordingly., at
Devil Canyon a risk of exceedence of 10 percent per annum has been
adopted,equivalent to a design flood with a 1:10-year return per-
iod for each year of critical construction exposure.The critical
construction time is estimated at 2.5 years.The main dam could
be subjected to overtoppi ng duri ng construct i on without causi ng
serious damage,and the existence of the Watana facility upstream
will offer considerable assistance in flow regulation in case of
an emergency.These considerations led to the selection of the
design flood with a return frequency of 1:25 years.
The equivalent inflow,together with average flow characteristics
of the river significant to diversion,are presented below:
As at Watana,the considerable depth of riverbed alluvium at both
cofferdam sites indicates that embankment-type cofferdam struc-
tures would be the only technically and economically feasible al-
ternati ve at Devi 1.Canyon.For the purposes of estab 1ishi ng the
overall general arrangement of the project and for subsequent di-
version optimization studies,the upstream cofferdam section adop-
ted will comprise an initial closure section approximately 20 feet
high constructed in the wet, with a zoned embankment constructed
in the dry.The downstream cofferdam will comprise a closure dam
structure approximately 30 feet high placed in the wet. Control
of underseepage through the alluvium material may be required and
could be achi eved by means of a grouted zone.The coarse nature
of the alluvium at Devil Canyon led to the selection of a grouted
zone rather than a slurry wall.
9,040 cfs
37,800 cfs
Average annual flow:
Design flood inflow (1:25 years routed
through Watana reservoir):
Cofferdams(c)
(b)
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10-15
(d) Diversion Tunnels
Although stud 1es for the Wat ana project i nd i cated that concrete-
lined tunnels were the most economically and technically feasible
solution,this aspect was reexamined at Devil Canyon.Preliminary
hydraulic stuc i es i nd lcated that the design flood routed through
the dlversion scheme would result in a design discharge of approx-
imately 37,800 cfs.For concrete-lined tunnels,a design veloci-
t i es of approxlmately 50 ft/s would permit the use of one con-
crete-llned tunnel wi th an equlvalent diameter of 30 feet.Al-
ternatlvely,for unllned tunnels,a maximum design velocity of 10
ftls in good quality rock would require four unlined tunnels,each
with an equlvalent diameter of 35 feet,to pass the design flow.
As was the case for the Watana diversion scheme,considerations of
reliability and cost were considered sufflcient to eliminate
consideration of unlined tunnels for the diversion scheme.
For the purposes of optimlzation studies,only a pressure tunnel
was considered,since prevlous studies indicated that cofferdam
closure problems associated with free-flow tunnels would more than
offset thelr other advantages.
(e)Optimization of Diversion Scheme
Given the considerations described above relative to design flows,
cofferdam configuration,and alternative types of tunnels,an eco-
nomlc study was undertaken to determine the optimum combinatlon of
upstream cofferdam elevation (height)and tunnel diameter.
Capital costs were developed for a range of pressure tunnel diam-
eters and corresponoing upstream cofferdam embankment crest eleva-
t i ons with a 30-foot wide crest and exterior slopes of 2H:1V.A
freeboard allowance of 5 feet was included for settlement and wave
runup.
Capital costs for the tunnel alternatives included allowances for
excavation,concrete liner,rock bolts,and steel supports.Costs
were also developed for the upstream and downstream portals,in-
cludt ng excavation and support;The cost of an intake gate str-uc-
ture and associated gates was determined not to vary significantly
with tunnel diameter and was excluded from the analysis.
The centerline tunnel length in all cases was estimated to be
2,000 feet.
Rating curves for the single-pressure tunnel alternatives are pre-
sented in Figure 10.2.The relationship between capital costs for
the upstream cofferdam and var i ous tunnel diameters is given in
Figure 10.3.
The results of the optimizatlon study indlcated that a s i nq le,
30-foot-dl ameter pressure tunnel results in the overall least
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10.11 -Power Facilities Alternatives
cost (Figure 10.3).An upstream cofferdam 60 feet high, with a
crest elevation of 945,was carried forward as part of the
selected general arrangement.
10.10 -Spillway Alternatives
The project spillways have been designed to safely pass floods with the
following return frequencies:
165,000
365,000
Di scharge
(cfs)
165,000
346,000
Inflow Peak
(cfs)Frequency
1:10,000 years
Flood
Probable Maximum
Spillway Design
A number of alternatives were considered singly and in combination for
Devi 1 Canyon spi llway faci lities.These included gated orifices in the
main dam discharging into a plunge pool, chute or tunnel spillways with
either a flip bucket or stilling basin for energy dissipation,and open
channel spillways.As described for Watana,the selection of the type
of spi llway was infl uenced by the general arrangement of the major
structures.The main spillway facilities will discharge the spillway
desi gn flood through a gated spi llway contro 1 structure wi th energy
dissipation by a flip bucket which directs the spillway discharge in a
free fall jet into a plunge pool in the river.As noted in Section
10.7,restrictions with respect to limiting nitrogen supersaturation in
selecting acceptable spillway discharge structures have been applied.
The vari ous spi llway arrangements developed in accordance with these
considerations are discussed in Sections 10.13 and 10.14.
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The selection of the optimum arrangements for the power facilities in-
volved consideration of the same factors as described in Section 9.11
for Watana.The selection of the installed capacity of 600 MW at Devil
Canyon is described in Section 10.6.
(a)Comparison of Surface and Underground Powerhouses
A surface powerhouse at Devil Canyon would be located either at
the downstream toe of the dam or along the side of -the canyon
wall.As determined for Watana,costs favored an underground ar-
rangement. In addition to cost,the underground powerhouse layout
has been selected based on the following:
-Insufficient space is available in the steep-sided canyon for a
surface powerhouse at the base of the dam;
-The provision of an extensive intake at the crest of the arch
dam would be detrimental to stress conditions in the arch dam
10-17
particularly under earthquake loading,and would require signif-
icant changes in the arch dam geometry;and
-The outlet facilities located in the arch dam are designed to
discharge directly into the river valley;these would cause sig-
nificant winter icing and spray problems to any surface struc-
ture below the dam.
(b)Comparison of Alternative Locations
The underground powerhouse and rel ated facil ities have been lo-
cated on the right bank for the following reasons:
-Generally superior rock quality at depth;
-The left bank area behind the main dam thrust block is unsuit-
able for the construction of the power intake;and
-The river turns north downstream from the dam,and hence, the
right bank power development is more suitable for extending the
tailrace tunnel to develop extra head.
(c)Selection of Units
The turbine type selected for the Devil Canyon development is
governed by the design head and specific speed and by economic
considerations.Francis turbines have been adopted for reasons
similar to those discussed for Watana in Section 9.11.
The selection of the number and rating of individual units is dis-
cussed in detail in Section 10.6.The four units will be rated to
del iver 150 MW each at full gate opening and minimum reservoir
level in December (the peak demand month).
(d) Transformers
Tr an sf ormer se1ect i on iss im il ar to Wat an a and disc ussed in Sec-
(e)Power Intake and Water Passages
For flexibility of operation,individual penstocks are provided to
each of the four un its.Detailed cost stud ies showed that there
is no significant cost advantage in using two larger diameter pen-
stocks with bifurcation at the powerhouse compared to four separ-
ate penstocks.
A single tailrace tunnel with a length of 6,80U feet to develop 30
feet of additional head downstream from the dam has been incorpor-
ated in the design.Detailed design may indicate that two smaller
tailrace tunnels for improved reliability may be superior to one
10::18
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large tunnel since the extra cost involved is relatively small.
The surge chamber design would be essentially the same with one or
two tunnels.
The overall dimensions of the intake structure are governed by the
selected diameter and number of the penstocks ahd the minimum pen-
stock spacing.Detailed studies comparing construction cost to
the value of energy lost or gained were carried out to determine
the optimum diameter of the penstocks and the tailrace tunnel.
(f)Environmental Constraints
In addition to potential nitrogen-saturation problems caused by
spillway operation,the major impacts of the Devil Canyon power
facilities development are:
-Changes in the temperature regime of the river;and
-Fluctuations in downstream river flows and levels.
Temperature modeling has indicated that a multiple level varying
the intake design at Devil Canyon would.not significantly affect
downstream water temperatures,since these are effectively con-
trolled by the water released from Watana.Consequently, the in-
take design at Devil Canyon incorporates a single level draw-off
about 75 feet below maximum reservoir operating level (El 1455).
The Devil Canyon station will normally be operated as a base-
loaded plant throughout the year,to satisfy the requirement of no
siginificant daily variation in power flow.
10.12 -General Arrangement Selection
The approach to selection of a general arrangement for Devil Canyon was
a similar but simplified version of that used for Watana described in
Section 9.
(a)Selection Methodology
Preliminary alternative arrangements of the Devil Canyon project
were developed and selected using two rather than three review
stages.Topographic conditions at this site limited the develop-
ment of reasonably feasible layouts,and initially,four schemes
were developed and evaluated.During the final review, the
selected 1ayout was refined based on technical,.operational and
environmental considerations identified during the preliminary
review.
(b)Design Data and Criteria
The design data and design criteria on which the alternative lay-
outs were based is presented in Table 10.1.Subsequent to selec-
t ion of the preferred Devi 1 Canyon scheme,the information was
10-19
refined and updated as part of the on-going study program.The
description of the Devil Canyon project presented in Section 13
reflects the most recent design data for the project.
10.13 -Preliminary Review
Consideration of the options available for types and locations of vari-
ous structures led to the development of four primary layouts for exam-
ination at Devil Canyon in the prel iminary review phase.Previous
studies had led to the selection of a thin concrete arch structure for
the main dam,and indicated that the most acceptable technical and eco-
nomic location was at the upstream entrance to the canyon.The dam
axis has been fixed in this location for all alternatives.
(a)Description of Alternative Schemes
The schemes evaluated during the preliminary review are described
below. In each of the alternatives evaluated,the dam is founded
on the sound bedrock underlying the riverbed.The structure is
635 feet high,has a crest width of 20 feet,and a maximum base
width of 90 feet.Mass concrete thrust blocks are founded high on
the abutments,the left block extending approximately 100 feet
above the existing bedrock surface and supporting the upper arches
of the dam.The thrust block on the right abutment makes the
cross-river profile of the dam more symmetrical and contributes to
a more uniform stress distribution.
(i)Scheme DCl (See Plate 10.1)
In this scheme,diversion facilities comprise upstream and
downstream earthfi 11 and rockfi 11 cofferdams and two
24-foot-diameter tunnels beneath the left abutment.
A rockfill saddle dam occupies the lower lying area beyond
the left abutment running from the thrust block to the
higher ground beyond.The impervious fill cut-off for the
saddle dam is founded on bedrock approximately 80 feet
beneath the existing ground sl.lrfate~The maXimUm height of
this dam above the foundation is approximately 200 feet.
The routed 1:10,000-year design flood of 135,000 cfs is
passed by two spillways.The main spillway is located on
the right abutment.It has a design discharge of 90,000
cfs,and flows are controlled by a three-gated ogee control
structure.This discharges down a concrete-lined chute and
over flip bucket which ejects the water in a diverging jet
into a pre-excavated plunge pool in the riverbed.The flip
bucket is set at Elevation 925,approximately 35 feet above
the river level.An auxil iary spillway,discharging a to-
tal of 35,000 cf s,is located in the center of the dam,100
feet below the dam crest and is controlled by three wheel-
mounted gates.The orifices are designed to direct the
10':'20
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flow into a concrete-lined plunge pool just downstream from
the dam.
An emergency spillway is located in the sound rock south of
the saddle dam.This is designed to pass discharges in
excess of the 1:10,000-year flood up to a probable maximum
flood of 270,000 cfs,if such an event should ever occur.
The spillway is an unlined rock channel which discharges
into a valley downstream from the dam leading into the
Sus itna Ri ver.
The upstream end of the channel is closed by an earthfill
fuse plug.The plug is designed to be eroded if overtopped
by the reservoir.Thus, as the crest is lower than either
the main or saddle dams,the plug would be washed out prior
to overtopping of either of these structures.
The underground power facil ities are located on the right
bank of the river,within the bedrock forming the dam abut-
ment.The rock within this abutment is of better qual ity
with fewer shear zones and a lesser degree of jointing than
the rock on the left side of the canyon (see Section 10.3),
and hence more suitable for underground excavation.
The power intake is located just upstream from the bend in
the valley before it turns sharply to the right into Devil
Canyon.The intake structure is set deep into the rock at
the downstream end of the approach channel.Separate pen-
stocks for each unit lead to the powerhouse.
The powerhouse contains four 150 MW turbine/generator
units.The turbines are Francis type units coupled to
overhead umbrella type generators.The units are serviced
by an overhead crane running the length of the powerhouse
and into the end service bay.Offices,the control room,
switchgear room,maintenance room,etc.,are located beyond
the service bay.The transformers are housed in a separ-
ate,upstream gallery located above the lower horizontal
section of the penstocks.Two vertical cable shafts con-
nect the gallery to the surface.The draft tube gates are
housed above the draft tubes in separate annexes off the
main powerhall.The draft tubes converge in two bifurca-
tions at the tailrace tunnels which discharge,under free-
flow conditions,to the river.Access to the powerhouse is
by means of an unlined tunnel leading from an access portal
on the right side of the canyon.
The switchyard is located on the 1eft bank of the river
just downstream from the saddle dam,and the power cables
from the transformers are carried to it across the top of
the dam.
10-21
(ii)Scheme DC2 (See Plate 10.2)
The 1ayout is generally simil ar to Scheme Del except that
the chute spillway is located on the left side of the can-
yon.The concrete-lined chute terminates in a flip bucket
high on the left side of the canyon which drops the dis-
charges into the river below.The design flow is 90,000
cfs,and discharges are controlled by a 3-gated,ogee-
crested-control structure,similar to that for Scheme DC1,
which abuts the left side thrust block.
The saddle dam axis is straight,following the shortest
route between the control structure at one end and the
rising ground beyond the low-lying area at the other.
(iii)Scheme DC3 (See Plate 10.3)
The layout is similar to Scheme DC1 except that the right
side main spillway takes the form of a single tunnel rather
than an open chute.A 2-gated,ogee-contro 1 structure is
located at the head of the tunnel and discharges into an
inclined shaft 45 feet diameter at its upper end. The
structure will discharge up to a maximum of 90,00U cfs.
The concrete-l ined tunnel narrows to 35 feet diameter and
discharges into a flip bucket which directs the flows in a
jet into the river below as in Scheme DC1.
An auxiliary spillway is located in the center of the dam
and an emergency spi 11 way is excav ated on the 1eft abut-
ment.
The layout of dams and power facilities are the same as for
Scheme DCl.
(iv)Scheme DC4 (See Plate 10.4)
e am,power facTrn ies,-ana sacral ecfam for thE sc
are the same as those for Scheme DC1.The major difference
is the substitution of a stilling-basin type spillway on
the right bank for the chute and flip bucket.A 3-gated,
ogee-control structure is located at the end of the dam
thrust block and controls the discharges,up to a maximum
of 90,000 cfs.
The concrete-lined chute is built into the face of the can-
yon and discharges into a 500-feet-long by 115-feet-wide by
100-feet-high concrete sti 11 ing basin formed below river
level and deep within the right side of the canyon.Cen-
tral orifices in the dam and the left bank rock channel and
fuse plug form the auxiliary and emergency spillways,re-
spectively,as in the other alternative schemes.
10-22
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The downstream cofferdam is located beyond the stilling
basin,and the diversion tunnel outlets are located farther
downstream to enable construction of the stilling basin.
(b)Comparison of Alternatives
The arch dam,saddle dam,power facilities,and diversion vary
only in a minor degree among the four alternatives.Thus,the
comparison of the schemes rests solely on a comparison of the
spillway facilities.
As can be seen from a comparison of the costs in Table 10.2,the
flip bucket spillways are substantially less costly to construct
than the stilling-basin type of Scheme OC4.The left side spill-
way of Scheme UC2 runs at a sharp angle to the river and ejects
the discharge jet from high on the canyon face toward the opposite
side of the canyon.Over a longer period of operation,scour of
the heavily jointed rock could cause undermining of the canyon
sides and their subsequent instability.The possibility of depo-
sition of material in the downstream riverbed with a corresponding
elevation of the tailrace.Construction of a spillway on the
steep left side of the river could be more difficult than on the
right side because of the presence of deep fissures and large un-
stable blocks of rock which are present on the left side close to
the top of the canyon.
The two-right side flip bucket spillways schemes, based on either
an open chute or a tunnel,take advantage of a downstream bend in
the river to discharge parallel to the course of the river.This
will reduce the effects of erosion but could still present a prob-
lem if the estimated maximum possible scour hole would occur.
The tunnel type spillway could prove difficult to construct be-
cause of the large diameter inclined shaft and tunnel paralleling
the bedding planes.The high velocities encountered in the tunnel
spillway could cause problems with the possibility of spiraling
flows and severe cavitation both occuring.
The stilling basin type spillway of Scheme OC4 reduces downstream
erosion problems within the canyon.However,cavitation could be
a pr ob lem under the high-flow velocities experienced at the base
of the chute.This would be somewhat alleviated by aeration of
the flows. There is,however,little precedent for stilling basin
operation at heads of over 500 feet;and even where floods of much
less than the design capacity have been discharged,severe damage
has occurred.
10-23
(c)Selection of Final Scheme
The chute and fl ip bucket spillway of Scheme DC2 could generate
downstream erosion problems which could require considerable main-
tenance costs and cause reduced efficiency in operation of the
project at a future date.Hydraulic design problems exist with
Scheme DC3 which may also have severe cavitation problems.Also,
there is no cost advantage in Scheme DC3 over the open chute
Scheme DCl.In Scheme DC4,the operating characteristics of a
high head stilling basin are little known,and there are few ex-
amples of successful operation.Scheme lJC4 also costs consider-
ably more than any other scheme (Table 10.2).
All spillways operating at the required heads and discharges will
eventually cause some erosion.For all schemes,the use of solid
cone valve outlet facilities in the lower portion of the dam to
handle floods up to 1:50-year frequency is considered a more rea-
sonable approach to reduce erosion and el iminate nitrogen super-
saturation problems than the gated high level orifice outlets in
the dam.Since the cost of the flip bucket type spillway in the
scheme is considerably less than that of the stilling basin in
Scheme DC4,and since the latter offers no relative operational
advantage,Scheme Del has been selected for further study as the
selected scheme.
10.14 -Final Review
The layout selected in Section 10.13 was further developed in accor-
dance with updated engineering studies and criteria.The major change
compared to Scheme DC1 is the elimination of the high level gated ori-
fices and introduction of low level solid cone valves,but other modi-
fications that were introduced are described below.
The revised layout is shown on Plate 10.5.A description of the struc-
tures is as follows.
(a)Main Dam
The max irflUtfl operating 1evel of the reservoir was rai sed to Eleva-
tion 1455 in accordance with updated information relative to the
Watana tailwater level.This requires raising the dam crest to
El evat ion 1463 with the concrete parapet wall crest at El evat ion
1466.The saddle dam was raised to Elevation 1472.
(b)Spillways and Outlet Facilities
To eliminate the potential for nitrogen supersaturation problems,
the outlet fac il it ies were des igned to restrict supersaturated
flow to an average recurrence interval of greater than 50 years.
This led to the replacement of high level gated orifice spillway
by outlet facilities incorporating 7 fixed-cone valves,3 with a
diameter of 90 inches and 4 with a diameter of 102 inches,capable
of passing a design flow of 38,500 cfs.
10-24
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The chute spi 11 way and fl ip bucket are located on the ri ght bank,
as in Scheme DCI;however,the chute length was decreased and the
elevation of the flip bucket raised compared to Scheme DCl.
More recent site surveys indicated that the gr~und surface in the
vicinity of the saddle dam was lower than originally estimated.
The emergency spillway channel was relocated slightly to the south
to accommodate the larger dam.
(c)Diversion
The previous twin diversion tunnels were replaced by a single-
tunnel scheme.This was determined to provide all necessary
secur ity and wi 11 cost approximately one-half as much as the
two-tunnel alternative (see Section 10.9).
(d)Power Facilities
The drawdown range of the reservoir was reduced, allowing a reduc-
tion in height of the power intake.In order to locate the intake
within solid rock,it has been moved into the side of the valley,
requiring a slight rotation of the water passages,powerhouse,and
caverns comprising the power facilities.
10-25
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LIST OF REFERENCES
(1) Acres American Incorporated,Report on 1980-81 Geotechnical Inves-
tigations,Prepared for the Alaska Power Authority,February
1982.
(2)Woodward-Clyde Consultants,Interim Report of Seismic Studies for
the Susitna Hydroelectric Project,Prepared for Acres
American Incorporated,Uecember 1980.
(3)Woodward-Clyde Consultants,Final Report of Seismic Studies for
the Susitna Hydroelectric Project,Prepared for Acres
American Incorporated,February 1982.
TABLE 10.1:DESIGN DATA AND DESIGN CRITERIA FOR
REVIEW OF ALTERNATIVE LAYOUTS
River Flows
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Average flow (over 30 years of record):
Probable maximum flood:
Max.flood with return period of 1:10,000 years:
Maximum flood with return period of 1:500 years:
Maximum flood with return period of 1:50 years:
Reservoir
Normal maximum operating level:
Reservoir minimum operating level:
Area of reservoir at maximum operating level:
Reservoir live storage:
Reservoir full storage:
Dam
Type:
Crest elevat ion:
Crest length:
Maximum height above foundation:
Crest width:
Diversion
Cofferdam types:
Upstream cofferdam crest elevation:
Downstream cofferdam crest elevation:
Maximum pool level during construction:
Tunnels:
Outlet structures:
Final closure:
Releases during impounding:
Spillway
Design floods:
Service spillway -capacity:
-control structure:
-energy dissipat ion:
Secondary spillway -capacity:
-control structure:
-energy dissipation:
Emergency spillway -capacity:
-type:
8,960 cfs
270,000 cfs
135,000 cfs (after routing
through Watana
42,000 cfs (after routing
through Watana
1455 feet
1430 feet
21,000 acres
180,000 acre feet
1,100,000 acre feet
Concrete arch
1455 feet
635 feet
20 feet
Rock fill
960 feet
900 feet
955 feet
Concret e lined
Low-level structure with
slide closure gate
Mass concrete plugs in
line with dam grout curtain
2,000 cfs min.via fixed-cone
valves
Passes PMF,preserving
integrity of dam with no
loss of life
Passes routed 1:1o,000-year
flood with no damage to
structures
45,000 cfs
Fixed-cone valves
Five 108-inch diameter
fixed-cone valves
90,000 cfs
Gated,ogee crests
St illing basin
pmf minus routed 1:1o,000-year
flood
Fuse plug
TABLE 10.1:(Cont t d)
Power Intake
Type:
Transformer area:
Access
Type of turbines:
Number and rating:
Rated net head:
Maximum gross head:
Type of generator:
Rated output:
Power factor:
Underground
Separate gallery
Rock Tunnel
Francis
4 x 140 MW
550 feet
565 feet epprox ,
Vert ical synchronous
155 MVA
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TABLE 10.2:SUMMARY OF COMPARATIVE COST ESTIMATES
PRELIMINARY REVIEW OF ALTERNAT~VE ARRANGEMENTS
(January 1982 $X 10 )
Item DC1 DC2 DC3 DC4
Land Acquisition 22.1 22.1 22.1 22.1
Reservoir 10.5 10.5 10.5 10.5
Main Dam 468.7 468.7 468.7 468. 7
Emergency Spillway 25.2 25.2 25.2 25.2
Power Facilities 211.7 211.7 211.7 211.7
Switchyard 7.1 7.1 7.1 7.1
Miscellaneous Structures 9.5 9.5 9.5 9.5
Access Roads &Site Facilities 28.4 28.4 28.4 28.4
Common Items -Subtotal '7lU:'7 '7lU:'7 '7lU:'7 '7lU:'7
1 Diversion 32.1 32.1 32.1 34.9
I Service Spillway 46.8 53.3 50.1 85.2
Saddle Dam 19.9 18.6 18.6 19.9
Non-Common/Items Subtotal 9'B"':'1r 11JZi':'lJ 1'tl'l:r.1r 17ITf.1l"
Total 882.0 887.2 884.0 923.2
Camp &Support Costs (169~)141.1 141.9 141.4 147.7
Subtotal TO'2"3:T TlJ'2'9:T '"flJ2'5:7i "'f'U'7'lT:.""9
Contingency (20%)204.6 205.8 205.1 214.2
Subtotal T'l'lT:T 1234.9 T2'3'lJ:":5"TZ'lB":T
En(ineering &Administration
12.590 153.5 154.3 153.8 160.6
Total 1'3'lrr."2"'1"3'S'9':"2"T3'S"Zi:":'r "f'44'5:7
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JOINT STATION
GEOLOGIC SECTION LOCATION
GEOLOGIC FEATURE
MAFIC DIKE
FELSIC DIKE
BEDDING/FOLIATION, INCLINED, VERTICAL
OVERBURDEN,UNDIFFERENTIATED
ARGILLITE AND GRAYWACKE OUTCROP
FELSIC DIKE, WIDTH SHOWN WHERE GRESUER
THAN 10 FEET
MAFIC DIKE, WIDTH SHOWN WHERE GREATER
THAN 10 FEET
SHEAR,WIDTH SHOWN WHERE GREATER THAN
10 FEET, VERTICAL UNLESS DIP SHOWN
SHEAR, WIDTH LESS THAN 10 FEET, INCLINED,
VERTICAL, EXTENT WHERE KNOWN
FRACTURE ZONE, WIDTH SHOWN WHERE
GREATER THAN 10 FEET,VERTICAL UNLESS
DIP SHOWN
JOINTS, INCLINED,OPEN INCLINED,VERTICAL
(SETS I AND II ONLYI
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MI
FI
I.CONTOUR INTERVAL 50 FEET.
2.EXTENT OF SHEARS, FRACTURE ZONES AND
ALTERATION ZONES ARE INFERRED BASED ON
GEOLOGIC MAPPING AND SURFACEEXPLORATIONS,
AND ARE SUBJECT TO VERIFICATION THROUGH
FUTURE DETAILED INVESTIGATIONS.
3.DETAILS OF GEOLOGIC FEATURES PRESENTED
IN 19BO-BI GEOTECHNICAL REPORT.
----LIMIT OF OUTCROP
OTHER:
DC-I
t.t
STRUCTURE:
CONTACTS:
LEGEND
LITHOLOGY:
FIGURE 10.1
0~1!I!iI""'~~_iiiii4;i;l90 FEETSCALEi:,
15oo~
1550~
1650-:--------
1700~
ooo.;
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DEVIL CANYON
GEOLOGIC MAP
ooo
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8
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REFERENCE' BASE MAP FROM R ElM, 19BI -I"'200'
DEVIL CANYON TOPOGRAPHY.
COORDINATES IN FEET, ALASKA STATE PLANE (ZONE 4)
N 3,224,000 -
N 3,221,000 -
N 3,223,000 -
N3,222,oo0 -
1050
4035
I -PRESSURE TUNNEL
(36,000 CFS
25 30
TUNNEL DIAMETER (FT)
20
aao
1000
900
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i 0
TYP.TUNNEL
SECTION
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DEVIL CANYON DIVERSION
HEADWATER ELEVATION /TUNNEL DIAMETER
FIGURE 10.2
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SECTION
4
o 20 25 30
TUNNEL DIAMETER (FT.)
35 40
DEVIL CANYON DIVERSION
TOTAL COST I TUNNEL DIAMETER
FIGURE 10.3 •
--~--
GENERAL ARRANGEMENT
ELI370
-470'SWITCHYARD
DEVIL CANYON
SCHEME DCI
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
NOTE
POWERHOUSE LOCATION SUBJECT TO
OPTIMIZATION STUDIES OF QOWNSTREM LOCATIONs.
30'
SECTION A-A
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THIS DRAWING ILLUSTRATES A
PRELIMINARY CONCEPTUAL PROJECT LAYOUT
PREPARED FOR COMPARISON OF
ALTERNATIVE SITE DEVELOPMENTS n."y ~_
_.._----_._~..------------
1400
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SCALE !
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SUSITNA HYDROELECTRIC PROJECT
/
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DEVIL CANYON
SCHEME DC2
EMERGENCY SPILLWAY
NOTE
POWERHOUSE LOCATION SUBJECT TO
OPTIMIZATION STUDIES OF DOWNSTREAM
LOCATIONS.
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THiS DRAWING ILlUSTKA 11:.0 A
PREuMINARY CONCEPTUAL PROJECT LAYOUT
PREPARED FOR COMPARISON OF
ALTERttATlVE SITE DEVELOPMENTS ONLY ~
ACRESAMERJCAHi'NCORPmIJEO
PLATE:
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SCALE: B
GENERAL ARRANGEMENT
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SCHEME DC3
::SU:;)II~A nlDROB...ECTRIC PROJECT
ALASKA POWER AUTHOR~TY
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SECTION F-F
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THIS DRAWING ILLUSTRATES A
PRELIMINARY CONCEPTUA.L PROJECT LA.YOUT
PREPARED FOR COMPARISON OF
ALTERKATIVE SJTE DEVELOPtIEJfTS ont.:r ~~-----------ACRES AMERICAN INCORPORATED
PLATE
10.3
L_L....-...-'--L__._~
PLATE
10.4
rsoo 1700
DEVIL CANYON
SCHEME DC4
SECTION D-D
100 200 FEET
5iiiiiiiiiiiiii
ALASKA POWER,AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
1200
o
SCALE
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1100
ANCHORS
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NATURAL GROUND SURFACE
"{LEFT SIDE}
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SECTION C-C
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SECTION F-F
lmS DRA'R'1HG lLUJSlRATES A
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PREJWIED FOR COMmmsOH OF
~TER"lnlVE SITE DEVElOPlEHTS ONlY
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PLATE
10.5
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
~lm~~
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. DEVIL CANyON
SELECTED SCHEME
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NOTE
THIS DRAw:!HG rLLUSTRATES A
PREUMlnARY CONCEPTUAL PROJECT·LAYOUT
fl'PElIAR'ED FOR COIIIPllftlSOH OF ALTERNATIVE
SITE DEVELOPIlEHT ONLY.
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11 -SELECTION OF ACCESS PLAN
This section describes the process of formulation and selection of an
access plan for the Susitna Hydroelectric Project.The methodology for
comparison of alternative plans is outlined,and an evaluation of each
basic plan is presented,considering schedule;costs,and biological
and social impacts.The selected plan is described in detail,and
recommendations for measures to reduce impacts are presented.
Engineering studies conducted on the alternative routes consisted of
development of design criteria,layout of the alternative routes,pre-
liminary field investigations,estimated cost of constructing the
alternative routes and costs in transporting supplies and materials to
the damsites.Environmental studies included identification,field
investigations,and evaluation of biological impacts for each of the
alternative routes.Social,cultural,socioeconomic, and a public par~
ticipation program were included among the studies completed as part of
the Access Plan evaluation.Public concerns and preferences,particu-
larly those of the area that would be impacted the most directly,were
solicited and fully considered in the evaluation.
The evaluation of the alternative plans included evaluation criteria,
comparisons of the alternative plans,identification of conflicts among
the alternative plans relative to the evaluation criteria,resolution
of the conflicts in the evaluation criteria,and the tradeoffs made in
the evaluation process.
11.1 -Background
(a)Existing Access Facilities
The proposed Devil Canyon and Watana sites are located approxi-
mate ly 115 miles northeast of Anchorage and 140 mil es south of
Fairbanks.The Alaska Railroad,which links Anchorage and Fair-
banks, passes within 12 miles of the Devil Canyon site at Gold
Creek.The George Parks Highway (Route 3)parallels the Alaska
Railroad for much of its route,although between the communities
of Sunshine and Hurricane,the highway is routed to the west of
the railroad,so that Gold Creek is situated approximately 16
miles south of the intersection of the railroad and highway.A
portion of the highway between Lane and Hurricane passes through
Denali State Park.At Cantwell,51 miles north of Gold Creek,the
Denali Highway (Route 8) leads easterly approximately 116 miles to
Paxson,intersecting the Richardson Highway at this point.
To the south,the Glenn Highway (Route 1)provides the main access
to Gl enna11 en and intersects the Ri chardson Hi ghway wh ich 1eads
south to Valdez.
11-1
(b)Modifications to Plan of Study
The original POS proposed that a single route would be selected by
May 1981 to be followed by detailed environmental investigations
of thi s route.
Early in the study,three main access corridors were developed.
Consideration of these plans on the basis of available informa-
tion,comments,and concerns from various state agencies and a
recommendation from the Susitna Steering Committee,led to a deci-
sion to assess all three alternative routes in more detail
throughout 1981 and recommend a selected route later in the year.
Accordingly,this assessment included environmental studies,
engineering studies,aerial photography,and geologic mapping of
all three alternatives rather than the single route initially
envisaged.
11.2 -Objectives
The finally selected access plan must allow for the efficient and time-
ly undertaking of construction and maintenance activities in order that
the Susitna HYdroelectric Project can be completed and electric power
be reliably and continuously provided to the Railbelt area of Alaska.
In meeting this basic objective,several specific objectives were
developed as a basis for evaluation of the alternative access routes.
These objectives are:
-To allow the construction of the Susitna project to proceed on a
schedule that would supply the necessary power to the Railbelt Area
of Alaska where needed in 1993;
-To minimize total cost including construct ion costs of the access
facilities,logistics costs for supporting the construction of the
Susitna development as well as the logistics costs of subsequent
operation of the completed project;
-To allow for ease of operation and maintenance to insure reliability
----------~-+n~1;he~powers-upp-ly-;----~------,----~-~-~~-~-------------------------------
-To minimize adverse biological impacts;
-To accommodate the preferences of local communities;--and
-To accommodate the preferences of native landowners.
11-2
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11.3 -Approach
The approach utilized to arrive at an access plan recommendation was an
adaptation of the generic plan formulation and selection methodology
described elsewhere in the report.The methodology as specifically
applied to selection of the access plan is presented graphically in
Figure 11.1.
i)
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[]
[]
To aid in understanding the selection process and the various studies
conducted,the following definitions are provided:
(a)Corridor
A strip of land generally 2 miles or greater in width leading be-
tween two points or areas.
(b) Route
A strip of land generally 1/2 mile or less in width,leading be-
tween two points.
(c)Segment
Portions of a route which when combined constitute one alternative
route between two points.
(d)Alternative Route
One of several routes which will be evaluated between two points.
(e) Plan
The first step in the selection process involved identification of the
three general corridors described below (see Plate 11.1):
An access plan includes a single or a combination of existing and
new alternative routes.The plan will also define the logistics
involved in the transportation of supplies and materials.
11.4 -Corridor Selection and Evaluation
DescriptionCorridor
I II_J
1
2
3
From the Parks Hi ghway to the Watana site .
via the north side of the Susitna River.
From the Parks Highway to the Watana site
via the south side of the Susitna River.
From the Denal i Hi ghway to the Watana
site.
11-3
These corridors were selected based upon the use of existing transpor-
tation facilities within reasonable proximity to the Wataha and Devil
Canyon sites.
A general environmental analysis was undertaken for each corridor,and
discussions,evaluations,and results are presented elsewhere (2).The
maj or environmental constrai nts ident ifi ed withi n each corri dor are
potential impacts on the following:
(a)Corridor 1
Fishery resources in the Susitna and Indian Rivers;
-Cliff-nesting raptors near Portage Creek and Devil Canyon;
-Furbearer habitat near Portage Creek and High Lake;
-Moose habitat on the Susitna River;and
- Caribou habitat between Devil Creek and Deadman Creek.
(b)Corridor 2
-Fishery resources in the Susitna and Indian Rivers;
-Cliff-nesting raptors near south side of the Susitna River;
-Waterfowl habitat in the Stephan Lake-Fog.Lake areas;and
-Furbearer habitat in the Stephan Lake-Fog Lake areas.
(c)Corridor 3
- Caribou calving area near Butte Lake;
-Furbearer habitat;and
-Some waterfowl habitat.
In addition,increased access will cause various impacts which are com-
mon to all corridors.Archaeological resources could pose a con-
straint;at this time,the locations of such resources that may exist
are unknown.
Finally,socioeconomic impacts will vary both in magnitude and areas of
concentration,depending upon which access route or combination of
access routes is selected,and whether a road or railroad i-s-used.
·---~---~---W-i-th~the~soc-i-oec onom:i-cassessment--o-f-access-schemes-,~thel".e_ts __mor·_e_con~_~__~..
cern with the ori gin and type of access because these wi 11 affect the
communities more than the actual route.
With a road from the Parks Highway to the damsites (Corridors 1 and 2),
effects generally would be concentrated on the western side of the pro-
ject area along the Parks Highway.An easily accessible road corridor
would provide for transportation of construction materials,equipment,
and labor as well as post-construction uses of the upper Susitna basin
(such as recreation).The impact of a rai lroad from the same side
would likewise be concentrated on the western side.However,in every
soci oeconomi c category,impacts woul d be the same or 1ess with a rail-
road than with the road.The single exception would be in rail indus-
try activities,which would experience major changes.
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!]With a road constructed from the Denali Highway to the damsites (Corri-
dor 3),impacts along the Parks Highway-Alaska Railroad corridor would
depend upon whether materi a1s were to be shi pped by road or ra i1 to
Cantwell before being transported along the Denali Highway to the
access road.If Corridor 3 is used, impacts wou1 d occur in the Cant-
well area regardless of the transportation mode •.
11.5 -Route Selection and Evaluation
Following identification of three major corridors,a number of access
routes were selected and evaluated based on engineering and economic
criteria.The selected routes were then modified on the basis of an
environmental analysis.
Following corridor definition,various segments that met the
engineering criteria were mapped.These segments were then joint-
ed to form alternative routes which were compared on the basis of:
The preliminary design criteria adopted for the access road and
rail alternatives were selected on the basis of similar facilities
provi ded for other remote projects of thi s nature.Basic para-
meters were as follows:
overall length;
- average grade per mile;and
- average deflection per mile.
(b)Economic Criteria
Ra ilroad
2.5 percent
10 degrees
not appli-
cable
E-50
Access Road
6 percent
5 degrees
80k per axle and
200 k total
HS-20- After Construction
Maximum Grade
Maximum Curvature
Design Loading
-During Construction
(a)Design Criteria
Construction of the Susitna project wi 11 require a dependable,
safe,and efficient access route suitable for transporting person-
nel,consumable supplies and large pieces of equipment for an ex-
tended period,in adverse weather conditions.IIL
IJ
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For the early stages of corridor and route selection,the alterna-
tives were compared on the basis of total centerline length of
route,with mi nor adjustments for average grade and curvature.
Preliminary capital costs for construction were estimated at
$1,250,000 per mile.
11-5
(c)Results
A total of 16 segments,combined into 30 routes,were identified
within the three corridors.The alternatives identified as being
most favorable in terms of overall length,grade and alignment are
as follows (the routes are described and presented in greater
detail elsewhere [3J):
Corridor 1 Corridor 2 Corridor 3 Corridor 2
Parks Parks Denali Gol d Creek
Highway Highway Highway to Watana
to Watana to Watana to Watana south side
north side south side
Type Road Road Road Rail
Overall
length 64.9 mil es 66.5 miles 39.1 mil es 58.0 mil es
Average
Grade 2.4 percent 2.2 percent 1.3 percent 0.5 percent
Deflection
per Mi 1e 7° 06
1+4° 50°+1° 30
1+5°11 1 +
(d)Environmental Influences on Alternative Routes
After the engineering and economic assessment identified the 3
roads and 1 rail route described above,an initial screening was
made which resulted in several refinements to the alternative
routes under consideration.A major refinement involved the dele-
tion of a large portion of the road access corridor from the Parks
Highway on the north side of the river (Corridor 1).The segment
connect i ng the hi ghway and the Devi1 Canyon site routed around
Portage Creek was deleted mainly on the basis of potentially
severe environmental impacts on anadromous fish,furbearers,and
r aptor s, The topography in the Portage Creek area is furthermore
------"--.--------------.-.-.-----...",--.,....------.5 uc tr··--tnat"ttre---·o\rer-·,rl--'---"-erng't-h-"'-o-f--·-r-o-a-d~-n-e-c-e-s-s-·ary----t-o-·---me·et-"",·t-h"e----e-st--ab-,;;-.------
lished criteria was excessive.In addition,the construction of
the segment would be extremely difficult due to the.predominance
of steep sidehill cuts of considerable height.
Another major refinement to the corridors was the routing to the
west cf the northern portion of the Denali route (Corridor 3).
This routing was advocated on environmental grounds in an attempt
to reduce potential impacts on the caribou subherd calving area
near Butte Lake.A final refinement consisted of realignment of
the portion of the Corridor on the south side of the river (Corri-
dor 2)in the Stephan Lake-Fog Lakes area to reduce potential
environmental impacts to fur bearers and waterfowl.
11-6
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The main routes within the corridors remalnlng after the initial
screening are described below (see Plate 11,2):
(i)Parks Highway to Devil Canyon
This route follows the existing portion of the Alaska Rail-
road between Gold Creek and the intersection of the rail-
road with the Parks Highway just south of Hurricane.Trav-
eling southeast from Hurricane,this route passes through
Chulitna Pass and then parallels the Indian River to Gold
Creek.The existing river valley is sufficiently wide to
accommodate a road.From Gol d Creek to Devil Canyon,the
route lies south of the Susitna River,paralleling the
river on a high ridge.
(ii)Devil Canyon to Watana - South Side of Susitna River
This route generally parallels the Susitna Ri ver and tra-
verses west to east from Devil Canyon to Watana.The lnl-
tial topography is mountainous and the route involves the
most difficult construction of the three routes,requiring
a number of sidehill cuts in rock and soil.This route
also includes the environmentally sensitive Stephan Lake
and Fog Lake areas.
(iii)Devil Canyon to Watana - North Side of Susitna River
This route generally parallels the Susitna River and tra-
verses west to east from Devil Canyon to Watana.Thi s
route is mountainous and includes terrain at the highest
elevations of all routes;however,construction of the road
would not be as difficult as the route between the damsites
on the south side of the Susitna River.
(iv)Denali Highway to Watana
This route connects the Denali Highway with the Watana site
and runs in a north-south direction.This route is the
easiest to construct of the alternative routes.The ter-
rain is relatively flat with a few wetlands involved.This
route would not require any major bridges.
11.6 -Description of Basic Plans
From the three routes r emat m ng after the i nit ia1 screen ing, ei ght
plans were developed.These plans were evaluated in more detail than
originally planned, as a result of information and assessments conduc-
ted during the study program,the concerns of state agencies,and rec-
ommendati ons of the Sus itna Steeri ng Committee.The additi onal i nves-
tigation and evaluations consisted of environmental field work,geo-
logic and topographic mapplng,and subsurface borings.
11-7
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This plan would serve both damsites by a.rail line.This alterna-
tive would essentially preclude public access.Construction plan-
ning for this mode of access would be based on trains being broken
down and cars dropped on the siding at Gold Creek.An engine and
train crew would be stationed at Gold Creek which would allow
shuttle cars from Gold Creek to the project site on a daily basis.
Passenger rail service would be required daily.If public access
is desired after construction,the rails could be removed and the
road bed graded into a single lane road with turnouts.~
Thi s pl an serves Watana by truck from a railhead at Cantwell and
Devil Canyon by rail from Gold Creek.In the pl an,there is no
connection between dams.
Thi s pl ans uti 1 izes a roadway from the Parks Hi ghway to Watana
along the south side of the river.This access plan is based on
materials such as cement and steel being brought into the state
through the port of Whittier.Food and other camp supplies would
be imported through Anchorage vi a contai ners,and fUfi:!1 directly
from Kenai to Anchoraqe via existing pipel i ne.These materials
and supplies would then be carried by rail to a railhead and stor-
age area at Gold Creek.At Gold Creek,materials would be trans-
ferred to trucks for transport by road to the site.Other mate-
rials and supplies would be transported by truck from Anchorage
along the Parks Highway to the access road.An alternative for
fuel supply would be rail haul from the refinery at North Pol e,
Al ask a,
(b)Plan 2
(c)Plan 3
(d)Plan 4
The plans are presented below and are also shown s chemat t cal ly in
Fi gures 11.2 through 11.5.
(a)Plan 1
j
This plan envisages the use of a combination of rail and road!
transportation.Construction activities at Watana would be served
from a railhead and storage area at Cantwell by truck across the
Denal i Hi ghway and along a newly constructed road from the_J)enal i )
___~~~_~~~~_HighWg)'~CQJlstructiQlLat Devi~l~C~Dyon would be.served.by rOild
from a railhead at Gold Creek and road access --from Gof(f--Creek t-6-""~-~-----
the Parks Highway.This plan does not include a connection be-I
tween the two dams.
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(e) Plan 5
This plan serves both dams by road from a railhead at Gold Creek.
The route is located on the south side of the river to Devil Can-
yon with a major bridge downstream from the damsite,then follows
the north side of the river to Watana.There is a road connection
to the Parks Highway from Gold Creek.
(f)Plan 6
This plan is identical to Plan 4 except that a service road for
maintenance purposes is included on the north side of the river
between the two dams.
(g) Plan 7
This plan is the same as Plan 3 except that a service road would
be provid,ed along the north side of the river as in Plan 6.
(h) Plan 8
This plan is the same as Plan 5 except there is no road connection
to the Parks Hi ghway.A newly constructed road woul d servi ce
Devil Canyon from Gold Creek on the south side of the river.A
major bridge would be required downstream from Devil Canyon and a
new road on the north side of the river would connect the two
dams.This alternative plan precludes public access.
11.7 -Additional Plans
Following selection and evaluation of the eight plans described above,
presentations were made to the Power Authority and the Sus i t na Hydro-
e lectri c Project Steeri ng Committee.These presentations and subse-
quent discussions resulted in the addition of the three plans described
below and shown schematically in Figures 11.6 and 11.7.
(a) Plan 9
This plan is the same as Plan 8 except access between Gold Creek
and Devil Canyon is by rail along a similar route,and the rail-
head is located at Devil Canyon instead of Gold Creek.
(b) Plan 10
This plan is identical to PlaIT 9 except that the road conne~ting
Devil Canyon and Watana is on the south side of the Susitna
Ri ver ,
11-9
(c) Plan 11
This plan utilizes a railhead at Cantwell, road access via the
existing Denali Highway,a road from the Denali Highway to Watana
and a road from Watana to Devi 1 Canyon on the north si de of the
river.
Plans 9 and 10 were suggested by the Steering Committee as a means to
reduce accessibility to the area,thus avoiding the introduction of
adverse environmental impacts into the Susitna Basin.
Plan 11 was added as a possible way to provide access from only one
area while also alleviating the socioeconomic impacts the communities
near Hurricane would feel as a result of an access road from the west.
11.8 -Evaluation Criteria
The specific objectives of the selected access plan are described in
Section 11.2.The criteria used to assess the degree that any given
plan satisfies these objectives are described in the following para-
graphs.
(a)Construction Schedule
It is essential that the selected access plan be adequate to meet
the overall project scheduling requirements.The load f oreces ts
described in Section 5 together with the examination of the exist-
i ng system and future generati ng options i ndi cated a requirement
for first power from Watana in 1993.A delay in the on-line date
by one year would mean that another source of fossil fuel genera-
tion would have to be constructed,or the loss of load probability
must be violated.In terms of present worth costs,a delay of one
year would increase the present worth of the long-term costs of
the project by approximately $43 million.
Analysis of the construction schedule requirements for Watana dem-
onstrates that an all-weather access route to the site i sr~quired
by mid-1986 if the on-line date of 1993 is to be maintained.For'-the-purposesoffhese 'sfu(r;es~--Tf-n as been assumeo-nlat----aF ERC .
license to construct the project will be received at the beginning
of 1985,and the start of permanent work on the project will coin-
cide with this date.In order to meet all the mid-1986 require-
ments,it is obvious that an access route to the site would have
to be constructed within approximately 18 months.
A preliminary evaluation of the construction period for completion
of the access plans is presented below.
11-10
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The pioneer road scheme can be implemented with Plans 1, 2, 5, 8,
9 and 10.Therefore,all 11 plans can be considered equivalent in
terms of their ability to meet initial project requirements pro-
vided a pioneer road can be constructed.
Construction and Logistics Costs
For the purposes of this evaluation,construction costs include
the cost of constructing the access facilities,adjusted for any
differences in cost of constructi ng the Susitna project itsel f
which relate to the particular access plan under construction.
Logistic costs are the costs associated with transporting,labor,
fuel,equipment,materials and supplies to construct the two power
developments.
It is apparent from the above that only Plans 3, 4, 6, 7 and 11
could be constructed within the 18-month period required to main-
tain the overall project schedule.Since this would severely lim-
it the selection process,a scheme was developed to provide ini-
tial access to the Watana site within the framework of regulatory
and scheduling restraints.This scheme,described in more detail
elsewhere (1),involves construction of a pioneer road to Watana
from either Gold Creek or the Parks Highway.The pioneer road
would consist of a gravel based road with periodic passing turn-
outs and would be constructed on existing ground insofar as pos-
sible to avoid significant cuts or fills.Temporary floating
Bailey bridges would be used at river crossings,replaced by ice
crossings in the winter.The analysis indicates that the pioneer
road scheme will be sufficient to provide continuous access to the
site within 18 months, and will be sufficient to support construc-
tion activities until the permanent access route is completed.
Certain additional licensing and permiting requirements are asso-
ciated with this scheme;these are discussed in Section 11.12.
3-4
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1
1
3
3
3
1
Approximate
Construction
Peri od (years)
Parks Highway
Gold Creek
Denali Highway
Dena 1i Hi ghway
Parks Highway
Denali Highway,Gold Creek
Denali Highway,Parks Highway
Go 1d Creek
Gol d Creek
Gold Creek
Denali Highway
Origin for Watana Access
1
2
3
4
5
6
7
8
9
10
11
Plan
(b)
11-11
(c)Ease of Operation and Maintenance
This criterion relates to the relative ease of operation and main-
tenance of the two developments after constr uct ion is complete.
Initial planning envisages operation of both developments from
Watana for several years after Devi1 Ca nyon is brought on-l i ne,
after which time both projects will be operated remotely from a
central location.Maintenance of two projects of this size and
complexity will obviously be an important consideration.Duplica-
tion of maintenance facilities and staff at both sites would
result in a substantial increase in the annual costs of the over-
all development.The most economic scheme,given the sequenc~of
development,would be to establ ish an operati on and mai ntenance
facility at Watana,with a reliable means of access to Devil Can-
yon 32 miles downstream.In this regard,access plans with a road
connect ion between the two sites have been evaluated as bei ng
superior in terms of ease of operation and maintenance than plans
without a road connection.
(d)Flexibility in Construction Logistics and Transportation
This criterion is used to evaluate the extent to which an access
plan contributes to the maintenance of a reliable and flexible
logistic support system during construction of Watana and Devil
Canyon.
For the Susitna project,a fundamental consideration is whether or
not to provide a road connection to a major highway.For this
evaluation,the following alternatives have been considered:
- a road connection either to the Parks Hi ghway or Denali Hi gh-
way; and ..
-rail access only from Gold Creek.
Plans 1 through 10 described in Section 11.5 all include a rall-
head and storage area at Gold Creek.Accordingly,plans incorpor-
ati ng a road connecti on with the Parks or·Denal i HighwaYs obv i-
ously ·-pr-ov ide-gre-at·er-f-Yextb i-lity-a·n·d-r·elia·bi-Hty·-i-n---cas·e-of a
transportation disruption involving the Alaska Railroad,compared
to plans with "rail only"access.Specific considerations are as
foll ows:
Any breakdown in the rail system woul d result ina loss of all
ground transportation,in the absence of an a lternat ive road
system.The increased ri sk of del ays has an associ ated cost
penalty.An analysis has been undertaken to quantify the risks
associated with rail access only.Methodology for this risk
analysis is presented elsewhere (1).
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- The availability of two possible modes of transportation will
undoubtedly be reflected in lower and more competitive bids for
construction,supply and service contracts,since contractors
would otherwise include some contingency to cover transportation
disruptions.Although significant,this aspect is difficult to
quantify.
Environmental Considerations
Exclusive of socioeconomic considerations,the objective is to
develop an access plan which minimizes adverse changes to the
natural environment.The criteria used to assess the degree to
which any plan meets this objectives are described below.
(i)Effects on Big Game
In the case of resident fisheries,there are relatively
isolated lakes (Butte Lake,Big Lake)and streams in the
northwestern section of the Upper Susitna Basin,and the
Fog Lakes area that would receive additional angling pres-
sure if road access was provided.These impacts can be
1essened by avoi di ng access from the Denali Hi ghway and
along the south side of the Susitna River between the dam-
sites.
Since Devil Canyon acts as a natural barrier to anadromous
fish migration,there is no concern regarding the effect of
improved access on this resource upstream of Devil Canyon.
However,Indian River and the Susitna River below Portage
Creek,are important for salmon.Any access plans that
follow or cross these rivers could affect salmon directly
through habitat disruption (i.e.,sedimentation)or in-
directly through increased fishing pressure.These impacts
coul d be lessened by avoidi ng road access parallel i ng the
Indian River.
11-13
(iii)Effects on Furbearers
Wetlands, important to furbearers,have been identified be-
tween the Parks Highway and Gold Creek, near Deadman Moun-
tain,near Deadman and Big Lakes and the Upper Deadman
Creek. In addition,the Fog Lake - Stephan Lakes wetlands
complex is a valuable furbearer habitat.Ared fox denning
complex has also been identified south of Deadman Mountain.
Any access road crossing through these areas has the poten-
tial for negative impacts on furbearers.Impacts on fur-
bearers would be least by selecting access from Gold Creek
to Devil Canyon on the south side of the Susitna River and
on the north side of the River between the damsites.
(iv)Effects on Birds
Heavily forested areas between the Parks Hi ghway and Devil
Canyon along riverbanks are productive avian habitat.Con-
struction through these areas would disturb this habitat.
(v)Effects on Wilderness Setting
The Upper Susitna Basin is presently in a state of wilder-
ness to semi-wilderness.Although continued intrusion with
ATVs from Denali Highway,potential development of native
lands and the establishment of the Indian River disposal
sites have the potential of changing the character of sec-
tions of the basin.The improved public access associated
with construction of the Susitna Hydroelectric Project will
produce a major alteration in the remoteness of the area.
Natural resource agencies and the local public have expres-
sed a desire to maintain the status quo to the maximum ex-
tent possible.People from the urban centers of Anchorage
and Fairbanks have expressed a desire to provide road ac-
cess and open the area for recreati on development.The
factor used to assess the potential effect of a proposed
route on the wilderness setting was the ease by which the
ic would have access to the area•.._._~....._-._---_._-~--.-...~_.....
(vi)Effects on Archaeological Resources
Archaelogical resources are likely present aleng all access
routes.The segment with the least potential for affecting
archaeological sites is between Gold Creek and Devil Can-
yon. All other segments have a moderate to high potential
of di sturbing cultural resource sites.The segments from
the Denali Highway to Watana and from the Devil Canyon site
to Watana north of the Sus itna Ri ver have a hi gher poten-
tial for archaeological disturbance because of the treeless
topography and thin soils.
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(f)Social Considerations
(i)Preferences Expressed by Native Landowners
-CIRI
The CIRI organization has selected lands surrounding the
impoundment areas and south of the Susitna River between
the damsites.CIRI has officially expressed a preference
for a plan providing road access from Parks Highway to
both damsites along the south side of the Susitna River
(Plan 1).Unofficially,they have indicated that only
Plan 1 is fully acceptable to them.
-Ahtna
The Ahtna native corporation presently owns land boarder-
ing the Denali Highway.At a public meeting in Cantwell
in October 1981, a number of Ahtna members expressed a
preference for a route involving the Denali Highway;how-
ever,no official position from the Ahtna Corporation has
been documented.
In evaluating the compatability of a proposed route with
native landowner preference,it was considered that only
Plan 1 met the preference expressed by CIRI and that Plans
3, 4, 6, 7, or 11 woul d meet the preference of Ahtna.
Since CIRI is the largest native landowner in the area and
since they have officially expressed their preference,
greater importance was given to their preference.
(ii)Effects on Native Landowners
For the purposes of plan evaluation,distinction has been
made between the native preferences as expressed and Acres
evaluation as to how the various access plans would affect
the opportunity for the natives to develop their lands on
the south side of the river.
The aspects used to assess the effect of a proposed route
on the opportunity for 'CIRI to develop their lands were:
-The degree of access provided from a major transportation
corridor to native lands;
-The degree of access provided on native lands;and
-The type of access provided.
11-15
(iii)Preferences Expressed by Local .Communities
The local communities have expressed opinions relating to:
-The access plan they prefer;
-The general community lifestyle patterns they prefer;and
-The general setting in the surrounding area they prefer.
These preferences are discussed by community.This summary
refers mainly to'the opinion expressed by the majority of
residents within each community.Complete documentation of
community preferences is presented in the report submitted
by S.Braund (1).
-Cantwell
The majority of residents in Cantwell preferred the
Denali access route,provided stringent hunter control
was enforced.
The community desired economic stimulus and were in favor
of the economic changes that could result from having a
major construction project in the area.
They 'preferred the semi -wilderness setti ng of the Upper
Susitna Basin and expressed concern over the potential
effects of a Denali access on the fish and wildlife re-
sources of the area.
-Railroad Communities North of Talkeetna
The residents of these communities were unanimous in
their preference for no increase in access or development
of the area.If access was required,they preferred the
all-rail alternative.These communities also expressed a
strong preference for maintenance of the status quo with-
in their communities and the surrounding area.
Attitudes were somewhat divided within this community
(see S.Braund report [1J).However,the majority of
residents:
•Preferred to maintain their general lifestyle pat-
terns;
•Preferred the all-rail access plan;and
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•Preferred to maintain the semi-wilderness-wilderness
setting in the Upper Susitna Basin area.
- Trapper Creek
Although alternative access plans considered could affect
Trapper Creek differently from Talkeetna,the preferences
expressed by this community were similar to those out-
lined for Talkeetna.
-WillowjWasila Area
These communities were not contacted through Susitna com-
munity workshops or the sociocultural study.Data from a
study conducted in the Mat-Su Borough by the Overall Eco-
nomic Development Program,Inc.indicates that people in
Willow,Houston,Wasila, and Palmer tend to favor a
higher rate of development than the communities north of
Willow.
-Indian River Land Disposal Sites
In 1981,a total of 75 remote state 1and parcel s were
awarded by lottery in the Indian Ri ver area.Of these,
35 were staked in the summer of 1981.The 35 land hold-
ers were contacted by 1etter through t he Power Author-
ity's Public Participation Office.Of the 12 responses
received to date,11 favored retention of the remote sta-
tus of the area and one favored road access to the area.
This area would be most affected by road access from the
Parks Highway and least affected by access from the
Dena 1i Hi ghway.
-Effect on Local Communities
For the purposes of plan evaluation,distinction has been
made between the local community preferences as expressed
and Acres evaluation as to how the various access plans
would affect the local communities.
Preferences in regard to general lifestyle patterns were
used to assess whether or not the communities would view
projected socioeconomic changes as being positive or
negative.
Preferences in regard to the general setting in the sur-
rounding area were used to assess whether or not project
changes to this setting would be considered positive or
negative.
It is Acres evaluation that the Denali route with strin-
gent hunting regulations implemented and enforced would
11-17
best meet the preferences expressed by the majority of
the residents in Cantwell.
It is Acres evaluation that for the communities north of
Talkeetna, Talkeetna,and Trapper Creek,the all-rail
access,and the road access would be equal in meeting
their preferences for lithe general community 1ifestyl e
patterns.II The communities expressed preference for the
all-rail access assuming it would better maintain the
status quo.Acres assessment indicates that if rai 1
access only is provided,the practicality of a self-con-
tained family-status community at either of the sites
would be greatly diminished and a single-status only
facility would likely be established.If this were to be
the case,workers would tend to locate their families in
the nearest communiti es, thus i ncreasi ng the impacts on
these communities.
(g)Agency Concerns
Correspondence, meetings and interaction with the various agencies
involved with the Susitna Hydroelectric Project Steering Committee
occurred throughout the study.Agency comments have been consid-
ered in the evaluation.The concerns of the agencies have gener-
ally related to environmental issues,with the emphasis on biolog-
ical and land use impacts.Therefore,evaluation in terms of the
environmental criteria discussed previously is considered to gen-
erally include agency concerns.
The Susitna Hydro Steering Committee has expressed the following:
-Access corridors which serve a dual or triple purpose would be
highly desirable;
-If feasi ble,it generally prefers a rail mode of access to and
within the project site;
- Three environmentally sensitive areas that should be avoided
• Routes from the Denali Highway;
•The route crossing the Indian River and through wetlands to
the Parks Highway;and
•The route on the south side of the Susitna River from Devil
Canyon to the proposed Watana damsite.
- A pioneer road should not be built before FERC licensing.
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(h) Transmission
Access plan selection has been coordinated with the transmission
line studies.The transmission line studies to date have identi-
fied two corridors,one north of the Susitna River and one south
of the Susitna River from Watana to Gold Creek.Although corri-
dors run along the river,there is flexibility to expand the cor-
ridor to include the access road when the decision is made as to
which access route will be constructed.Due to more stringent en-
gineering criteria of lines and grades for road alignments,it was
decided that the selection of a transmission line route would oc-
cur subsequent to the access road selection.
The results of the transmission studies have also established that
if the northern Denali access route is selected,the transmission
line would not follow that route due to excessive cost and adverse
visual impacts.
(i )Recreation
In discussing and evaluating the recreation plans,it has become
apparent that the various recreation plans are sufficiently flexi-
ble to accommodate any access route selected.No single route was
identified which had superior recreational potential associated
with it.Therefore,compatability with recreational aspects was
essentially eliminated as an evaluation criteria.
11.9 -Evaluation of Access Plans
The 11 access plans evaluated on the basis of the criteria described in
Section 11.8 have been grouped in accordance with the following cate-
gories in order to clarify the presentation.
In addition to the specific considerations outlined in the following
paragraphs,a major concern with all of the access plans is the crea-
tion of access to areas previously inaccessible or relatively inacces-
sible.Such access would lead to impacts to furbearers through in-
creased trapping pressure and to big game through hunting pressure.In
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Category
Plans providing access from both
Parks and Denali Highways
Plans providing access from Parks
Hi ghway on ly
Plans providing access from
Denali Highway only
Access from Gold Creek only
Plan Numbers
3 and 7
1 and 5
4, 6 and 11
2, 8, 9 and 10
11-19
addition,detrimental effects could occur to all wildlife through dis-
turbance and destruction of habitat by ATVs.Cultural resources would
also be vulnerable to amateur collectors and ATV traffic.
(a) Access to Both Parks and Denali Highways (Plans 3 and 7)
(i ) Cost
The costs of the 11 aJternative access plans are summarized
in Table 11.1.Given the preliminary nature of the field
data used to develop construction costs,construction cost
differences of less than $10,000,000 (approximately 5 to 10
percent of the cost of the alternatives examined)should
not be considered significant.
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A roadway from the Parks Hi ghway woul d cross producti ve
furbearer wetlands habitat between the highway and Gold
Creek.The Denali segment of both these plans also crosses
Biological
The primary biological concerns for these two plans relate
to the effects the road would have on furbearers,big game,
and cultural resources.
-PTans-3--ancrr-Bottr·salisfy-tlfecriterfafbr-f1 exfoilTtyfbr-_-_._.
construction logistics and transportation by having a road
access connecting to a major highway.
Maintenance costs are a small portion of construction
costs,and large variations in maintenance costs will have
negligible influence on overall costs.The logistic costs
are based on current freight rates and vary by less than 10
percent for all plans.The personnel shuttle costs and
conti ngency ri sk costs are necessari ly approximate but are
adequate for comparison purposes.When comparing the total
costs,the plans were considered equal if the total costs
were within $20 million,and a definite cost advantage was
considered if there was a $50 million difference.
On the basis of the foregoing,Plan 3 is comparable in cost
to the minimum cost alternative plan. Plan 7 has approxi-
mately a $60 million cost disadvantage compared to Plan 3.
(ii)Ease of Operation,Maintenance and Construction Flexibility
Access Plan 3 does not meet the ease of operation and main-
tenance criterion because it does not have a connecting
road between Watana and Devil Canyon.Access Plan 7 does
meet the ease of operation criteria by having a connection
service road between the two sites.
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aquatic furbearer habitat near Deadman Mountai n,Deadman
and Big Lakes,and Upper Deadman Creek. In addition,a red
fox denning complex south of Deadman Mountain within one
mile of the proposed road is likely to be affected.
The primary concern relative to big game for both these
plans is the Denali segment,which would pass through an
area that has frequently been used by either major portions
or all of the Nelchina herd and includes the calving and
summer ranges of the northwestern subgroups of the Nelchina
caribou herd.The route also lies across the late summer
mi grati on route of cari bou movi ng toward Butte Lake and
Gold Creek and parallels a traditional spring migration
route southward to the Susitna River.
The direct effects upon this group of caribou,should Plan
3 be implemented,include disturbance to cows and calves
during the road construction period,a disturbance and pos-
sible impediment to caribou migration as a result of in-
creased traffic in the area,and the possibility of direct
mortality from road kills.However,the presence of the
road should not interfere with migration,since caribou are
known to cross roads.Moreover,interference with the cal-
ving areas could cause a major adverse impact on the fe-
males who show an affinity to traditional calving grounds.
Of greater importance than these factors,however,are the
indirect consequences to this group of caribou of increased
access to its range.An access road across this alpine
tundra would provide the opportunity for all terrain vehi-
cles to push a network of unplanned trails throughout the
range of this subherd. This new access would cause distur-
bance and increased mortality to these caribou from their
contact with hunters.Thus,there is a chance that this
route could lead to partial abandonment of important cari-
bou habitat.Since the caribou hunt is controlled through
permitting,increased hunting mortality caused by improved
access should be minimal,although additional controls may
be required.
The actual magnitude of impact is difficult to assess since
it depends on the somewhat unpredi ctable behavior of both
caribou and man.With an increased emphasis on management
of the area and stringent hunter control,it is technically
possible to lessen the potential extent of impact.It is
noted,however,that resource agencies are apprehensi ve
about the success of any mitigation plans and would resist
any road access from the Denali Highway.
(iv)Social Considerations
Without mitigating measures,access plans with a roadway
originating from the Parks Highway could significantly
11-21
impact the westside communities in terms of demand for in-
creased services,changes in population,housing availabil-
ity,government expenditures and revenues,1abor demand,
and unemployment.There will al so be si gnifi cant effects
on construction,retail trade,and tourism.
Many of these changes will occur as construction workers
attempt to relocate to the communities near the construc-
tion site.Depending upon commuting modes to the camp,
there could be a large increase in vehicular traffic in the
area.
These access plans also include a road from the Denali
Highway.As such,many of the impacts which would be felt
in the west side communities of Talkeetna,Trapper Creek,
and railroad communities north of Talkeetna would also
occur in Cantwell.With a road from the north,it is ex-
pected an increased number of workers would settle in Fair-
banks, thereby reducing some of the impacts which the west
side communities would experience.
These plans would create economic stimulus in Cantwell but
wi 11 not meet the preferences expressed by those in the
west side communities who desire no change.
However,road access connecting the Denali and Parks High-
ways woul d create extensive pub 1ic access fo 11 owi ng con-
struction thus creati ng the maximum change in the status
quo of the area.
As discussed under Section 11.13,it is considered that
mitigation measures can be implemented to lessen the ef-
fects on the west side communities of Talkeetna and Trapper
Creek.With road access from the Parks Highway,change in
the remoteness of Gold Creek and the Indian River Land Dis-
posal sites will occur regardless of mitigation.
___mn_JQ}Access from Parks Highway Only (Plans 1 and 5 L_m _
(i)Costs
Access Plan 1 is comparable to the minimum cost alternative
Plan 5 (Table 11.1).
(ii)Ease of Operation and Construction Flexibility
Both Access Plans 1 and 5 satisfy the ease of operation
criteria by having a road directly connecting both sites.
Both Access Plans 1 and 5 satisfy the flexibility criteria
by having a road connection with a major highway.
Access Plans 1 and 5 involve a shorter haul distance com-
pared to any alternative having access via Denali Highway.
IF-22
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(i v)
Anchorage has been identified as the most viable port of
entry for the majority of the materials and supplies.When
comparing Access Plans 1 and 5,with plans having access
only from the Denali Highway,Plans 1 and 5 have a logis-
tics cost advantage over any access from the Denali High-
way. With the majority of materials and supplies coming
from Anchorage,the access route from the Denal i Hi ghway
would involve an additional haul of approximately 52 miles
to Watana when compared to an access from the Parks High-
way. The additional 52 miles would be a disadvantage in
long-term operation and maintenance.
Biological Considerations
The primary concerns with access from only the Parks High-
way were discussed in (a)above.Briefly,the concerns are
the potential impact to furbearer habitat between the high-
way and Gold Creek and potential degradation of fisheries
habitat in "the Indian and Susitna Rivers.Of lesser con-
cern is the disturbance of moose and bear populations and
removal of their habitat caused by the northside connecting
road in Plan 5.
In addition to these,Plan 1 includes a connection on the
south side of the Susitna Ri ver between the two damsites.
This road would pass near and through extensive wetland
areas in the Stephan Lake-Fog Lake area.These wet 1ands
provide habitat for furbearers and waterfowl and support a
1arge,year-round concentration of moose.Because thi s
area is currently relatively inaccessible,potential im-
pacts i ncl ude removal of habitat and increased mortality
through hunting and trapping.
Social Considerations
Evaluation of these plans from a socioeconomic aspect re-
veals that Plans 1 and 5 will result in the greatest impact
to the west side communities.Because access is provided
from the west only,the majority of the impacts would be
felt in the west side communities.There would be a great-
er tendency for people to relocate in the communities and
perhaps in Anchorage and a 1 esser tendency to.1 ive in the
Fairbanks area.There would be some impacts to the Cant-
well area,but fewer than with a road from Denali.
In terms of public preference,these plans least meet the
desires of people living in the project area.The plans
would cause the greatest change in the Talkeetna-Trapper
Creek area (where residents have expressed negative atti-
tudes toward social change)and would minimize impacts to
the Cantwell area (where residents have expressed a desire
for change).The Indian River land disposal site.and Gold
11-23
Creek would experience the greatest change with the selec-
tion of one of these plans.
(c)Access from Denali Highway (Plans 4, 6 and 11)
(i ) Costs
Table 11.1 indicates that Plan 4 is comparable to the least
cost alternative (Plan 5).The costs of Plans 6 and 11 are
approximately $50 million greater than that of Plan 5.
(ii)Ease of Operation and Construction Flexibility
Plan 4 does not satisfy the ease of operation criterion due
to the absence of a road directly connecting the two dam-
sites.Plans 6 and 11 both have a road directly connecting
the damsites,therefore both plans satisfy the ease of op-
eration criterion.
Plan 4 only partially meets the construction flexibility
criterion.Plan 4 includes a road connect ion to a major
hi ghway for the Watana development but not for the Devi 1
Canyon development.Access Plans 6 and 11 both satisfy the
flexibility criteria by having a connection to a major
hi ghway.
(iii)Biological Considerations
These three plans all involve road access from Denali High-
way to Watana dams i t e,The potential biological and cul-
tura 1 impacts associ ated with thi s route were discussed
under (a) above.Basically,impacts could occur to por-
tions of the Nelchina caribou herd through increased hunt-
ing mortality and potential interference with migration and
calving.Increased access and trapping press4re could also
impact furbearers.In addition,because of treeless topo-
graphy and shallow soil,di sturbance and removal of any
~~-~~--~--~---~-cu-Uu~alxesources-could-resuJ-t.---------
Plans 4 and 6 involve construction of a r at l connecting
from Gold Creek to Devil Canyon.No major environmental
problems were identified along this portion of the route.
The connection road on the north side of the Susitna River
between the two dams was discussed under (b) above,the
only environmental concern bei ng the crossi ng of moose and
bear habitat.
(iv)Social Considerations
Plans 4, 6 and 11 involve access from the Denali Highway,
rather than the Railbelt Corridor.Workers'families would
tend to locate to more communities,including Cantwell and
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(d)
Fairbanks.Due to the rail access from Gold Creek,there
would still be some impact on the west side communities,
but less than with a road originating from the Parks High-
way.Plan 11,involving access from Denali Highway only,
would cause the greatest number of changes in the Cantwell
and Fairbanks area and essentially no impacts on west side
communities.
Access from Gold Creek Only (Plans 2, 8, 9 and 10)
(i)Costs
Table 11.1 indicates that the total costs of Plan 8 and 9
are respectively $15 and $30 million greater than the least
cost alternative,Plan 5.The substantial savings in con-
structi on costs are offset by increased personnel shutt1 e
costs and an allowance for contingency risk.The cost
comparison also shows that the total costs of Plans 2 and
10 are $55 million and $40 million more than that of the
least cost alternative.
(ii)Ease of Operation and Construction Flexibility
Access Plans 2, 8, 9 and 10 all only partially satisfy the
ease of operation and maintenance criteria.These plans
have either a road or a rai 1road directly connecti ng the
two damsites,however,none of them have a connection to a
major highway.This reduces the flexibility in operation
and maintenance of the sites as discussed in Section 11.8.
Access Plans 2, 8, 9 and 10 do not satisfy the flexibility
criteria for construction as they do not have a road con-
nection to a major highway.
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(i ii )Biological Considerations
These p1 ans all prec1 ude access from the Parks Hi ghway or
Denali Highway;therefore,the impacts associated with in-
creased access are substantially reduced.
Plans 2 and 10,which involve connections between Watana
and Devil Canyon on the south side of the Susitna River,
have as the major potential environmental impacts,the dis-
turbance of wet1 and areas near Stephan and Fog Lakes, as
discussed under (b) above.
The overall reduction in access and the fact there is no
access connecting with the Denali Highway to the north in-
dicates these plans would result in the least number of im-
pacts to biological and cultural resources.
11-25
(iv)Social Considerations
These plans all involve access from the west by rail only
to Gold Creek, then from Gold Creek the only difference be-
ing road or rail,and if rail,the distance into the basin
the railroad extends.As such, impacts would be concen-
trated in the Gold Creek area as well as Talkeetna and
Hurricane because of their location at rail-highway inter-
sections.The Cantwell and Fairbanks areas would be less
affected as there would be no northerly access.
The public has expressed a preference for a rail access and
a mai ntenance of the status quo.Al though rai 1 access
woul d best mai ntai n the status quo of the Upper Susitna
Basin in general with the rail access,significant changes
could occur in the Talkeetna/Trapper Creek area as discus-
sed in Section 11.8(f).
These plans would not meet the public preferences expressed
by Cantwell residents.
11.10 -Identification of Conflicts
From the evaluation presented in Section 11.9,it is apparent no single
plan meets all the objectives or satisfies all the criteria established
as part of the study.The basic conflicts identified were:
(a)Social and Biological Considerations vs
Construction and Operation Logistics
Rail or road access from a railhead at Gold Creek without road
access from a major highway would limit social and biological
changes in the immediate project area and retain the status quo to
the greatest extent possible.This option is in direct conflict
with the requirement to provide flexibility in construction logis-
tics and transportation and to provide ease of operation and main-
tenance.The selection of such an option would increase the risk
of high costs,schedule delays,and safety problems and decreaseproject _-_._.-
(b)Social vs Biological Considerations
Social and biological objectives are not in basic conflict since
limited access to the project area is most desirable in both
cases.If,however,the assumption is made that road access to a
major highway will be provided,then a conflict arises.From the
social/local public preference perspective,access from the Denali
Highway is preferred.This plan would create the economic stimu-
lus desired in Cantwell,reduce the potential for change in the
Trapper Creek/Talkeetna area,while retaining the remoteness of
the Indian Ri ver land disposal site and the railroad communities
north of Talkeetna.The Denali access,however,is in conflict
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with biological objectives since it would allow access by hunters
and ATVs to a large portion of the Upper Susitna Basin and create
potential impacts on the Ne1china Caribou,other big game species
including moose and bear,the fisheries in isolated lakes and
streams and furbearer habitat.In additi on,the potential for
disturbance of archaeological sites in this area is greatest.Al-
though mitigation measures can be employed to reduce these poten-
tial biological impacts,it is noted that government resource
agencies are apprehensi ve about the success of any control pro-
grams and would thus be opposed to access from the Denali Highway.
The selection of a Denali access plan could result in unacceptable
delays in license approval or a subsequent rejection of this plan
requiring a reassessment of access plans from the west.
Table 11.2 broadly summarizes the conflicts in the evaluation.
11.11 -Comparison of Access Plans
(a)Access from Railhead at Gold Creek (Plans 2, 8, 9 and 10)vs
Access from Major Highway (Plans 1,3,4,5,6, 7,11)
Considerable cost,schedule,safety and reliability risks are
associated with construction of a major project without road
access to a major highway.On the other hand, road access to a
major highway will create additional change in the status quo of
the Upper Susitna Basin.If the decision is made to develop a
large scale hydroelectric facility in the Upper Susitna Basin,it
is considered essential that the orderly development and mainten-
ance of the facility should be afforded a higher priority than
maintenance of the status quo. Thus, access plans originating at
a railhead at Gold Creek only are not recommended.
These considerations led to the rejection of plans not providing
road access to a major highway.
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Plans eliminated in this comparison:
Plans remaining:
2,8,9,10
1,3,4,5, 6, 7, 11
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(b)Access from Both Parks Highway and Denali Highway (Plans 3, 7)v~
Access from Only One Highway (Plans 1,4, 5, 6,11)
The plans which optimize transportation flexibility and ease of
operation,Plans 3 and 7, involve the initial construction of a
road from Denali Highway to Watana damsite.To allow for improved
logistics during the peak construction at Watana and throughout
the construction of Devil Canyon,road access would also be
created to the Parks Hi ghway.The disadvantages of these plans
are that they would create the maximum change in the status quo
produci ng both the bi 01 ogica1 impacts associ ated with the Denali
link and the social impacts associated with the Parks Highway
link.These impacts are further intensified with both roads since
11-27
These conclusions resulted in the rejection of the plans providing
road access to both the Parks and Denali Highway.
connection of the Parks and the Denali Highway would encourage
hunters and tourists to drive the complete loop.
Roadway Connecting the Damsites Directly (Plans 1,5, 6,11)vs
No Roadway Connecting the Damsites Directly (4)
Plans incorporating a road connecting the damsites directly are
clearly superior in terms of ease of operation and maintenance to
plans which do not directly connect the dams t tes,The access
plans which do not connect the damsites directly do not have ad-
vantages in any of the other,or combined criteria to warrant not
eliminating these alternatives from further consideration.
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3, 7
1,4,5,6,11
Plans eliminated in this comparison:
Plans remaining:
These plans are al so more costly than the mi nimum cost alterna-
tives.It is considered that the social and biological impacts
that woul d result from these plans cannot be just ifi ed by the
added transportati on fl exibi1ity and ease of operati on benefits
associated with road access to both the Parks and Denal i High-
ways.
(c)
These conclusions resulted in the rejection of plans not connect-
ing the damsites directly.
Plans eliminated in this comparison:
Plans remaining:
4
1,5,6,11
(d) Access to Denali Highway (Plans 6,11)vs
Access to Parks Highway (Plans 1,5)
The main concerns associated with the Denali access are the poten-
tial effects on the Nelchina caribou herd,increased access to a
large area of alpine tundra with the associated effects of distur-
.---------~-.-....-banceoyATVs and di slLlroi3.nc::e ()fp()fer'lfrarcunuraTr-esources~-
Although there are some fisheries and furbearer concerns in the
Indian River area associated with a Parks Highway access,from the
biological perspective,Parks Highway access is preferred to a
Denali Highway access.
In terms of construction logistics and long-term operation,the
access from the Parks Highway is preferred.Any access plan which
utilizes the Denali has an additional haul distance of 52 miles
for the majority of construction equipment and supplies and long-
term mai ntenance and resupply.With a Denal i road access,it is
still preferable to transport equipment and supplies to Devil
Canyon from Gold Creek,thus creating access to the area from both
11-28
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the north via Denali and the west from Gold Creek. In terms of
initial project scheduling,the Denali route or the Parks Highway
route with the pioneer road are considered similar.
From a perspective of social change, the Denali route is consid-
ered to have the advantage compared to the Parks Hi ghway route.
The Denali route would promote the economic stimulus desired in
Cantwell while reducing the influence on the communities of
Trapper Creek,Talkeetna,and north of Talkeetna,which have ex-
pressed a desire to maintain their general lifestyle patterns.It
is considered,however,that even with a Parks Highway access,
mitigation in the form of self-contained construction camp facil-
ities,regulation of commuter schedules,and control of
transportation modes can reduce or avoid many of the potential
changes in Talkeetna and Trapper Creek.It is also considered
that,with the Parks Highway access,changes to these communities
would be greater than changes that would occur with a Denali
access.These changes,however,are not considered significantly
greater,and therefore,for comparison purposes,the Denali route
is considered to have a slight advantage.
A Parks Highway route also allows the transmission line and access
road to be constructed in a common corridor.
Considering native landowner preferences,the Parks Highway route
is considered to have the advantage over the Denali route.
With any access plan from the west, a major railhead would be lo-
cated at Gold Creek creating local changes.With road access from
the Parks Highway to Gold Creek, changes will also occur at the
Indian River disposal sites.
Based on the above di scussi on,it is conc1 uded that the Parks
Highway access is preferable to the Denali access plan.This con-
clusion is based on the assumption that if a Denali route were
selected:
It would be Plan 6,which would still result in significant
social changes in the Gold Creek area;
-Mitigation planning,preparation of environmental impact state-
ments,and the permitting process itself could cause delays of 1
to 2 years,since there are a number of significant environmen-
tal concerns with the Denali route expressed by resource
agencies;
-Changes in local communities can,to a large degree,be miti-
gated through control s imposed on contractor and constr ucti on
workers;and
11-29
11.12 -Recommended Access Plan
Based on the above discussion,it is recommended that:
-Controls would be very difficult to impose upon hunters and ATV
operators who would utilize the Denali route after construction.
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6, 11
1,5
Plans eliminated in this comparison:
Plans remaining:
Plans 1 and 5 both commence on the Parks Hi ghway near Hurricane
and proceed through Chulitna Pass and along the Indian River to
Gold Creek.From Gold Creek, both plans proceed east on the south
side of the Susitna River to the Devil Canyon site.At Devil Can-
yon, Plan 1 proceeds east on the south side of the Susitna River
to the Watana site.Plan 5 crosses the Sus itna Ri ver at Devi 1
Canyon and proceeds east on the north side of the Susitna River to
the Watana site.Access Plan 1 has potential for greater environ-
mental impacts than Access Plan 5. This is because of extensive
wetland areas in the Stephan Lake -Fog Lake area.The wetlands
provide habitat for furbearers and waterfowl and support a large,
year-round concentration of moose.Providing road access:into
this area increases the potential for adverse impacts by removal
of habitat and increased mortality through hunting and trapping.
Access Plan 1 is more difficult to construct than Access Plan 5
because of the more difficult terrain in the segment between Devil
Canyon and Watana,south of the Susitna River.The difficult ter-
rain would require considerable steep sidehill construction and a
large bridge over Cheechacko Creek,just east of the Devil Canyon
dams t t e.
The foregoing considerations resulted in the elimination of plans
i nvol vi ng access'from the Denal i Hi ghway.
Plans eliminated in this comparison:1
Plans remaining:5
Based on the above considerations,it is concluded that Access
Plan 5 would better meet the overall projeet objectives than
Access Plan I.
Access Plan 1 has an advantage over Access Plan 5 in native land-
owner (CIRI)preference.Al though Plan 5 does not totally meet
the preference expressed by CIRI,it does create road access to
native lands,thus providing a major transportation link which
would allow the native landowners to develop their lands more
.eCfsi Iy than is presently possible';
-The selected access plan for the construction and operation of the
Susitna Hydroelectric Project should comprise a road commencing near
(e)Comparison of Plan 1 vs Plan 5
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MP 156 on the Parks Highway,proceeding southeast crossing the
Susitna River at Gold Creek,turning northeast to Devil Canyon dam-
site along the southern side of the Susitna River,crossing the
Susitna River at Devil Canyon,and proceeding along the north side of
the Susitna River to Watana damsite (see Plate 35).
-To allow for continued access for project construction by mid-1986,a
limited access pioneer road between Gold Creek and Watana damsite be
constr ucted commenci ng in mi d-1983.The app1 i cati on for permits to
construct this pioneer road be submitted to the State of Alaska and
the Bureau of Land Management by September 1982, independent of the
FERC license application.
-To mitigate against the possibility of unrestricted public access to
the area in the event that the project is not built,road access be-
tween the Parks Highway and Gold Creek not commence until after FERC
license approval.If the project does not proceed after the pioneer
road is constructed,the road as such should be rendered impassable
to future vehicular traffic.
-To minimize potential impacts to furbearers and fisheries resources
in the Indian River and Susitna River areas,special construction
techniques be utilized (including adequate bank stabilization,reveg-
etation and restoration)when crossing wet1 and areas or when con-
structing in proximity to any important stream,river or water body.
-To minimize the effects of public access during the operation phase
of the project consideration be given to controlling public access
across Devil Canyon Dam.If access is provided east of Devil Canyon
damsite,restrictions should be placed on the use of ATVs and hunt-
ing.
To assist in minimizing changes in the local communities of Tal-
keetna,Trapper Creek,Sherman and Curry,it is strongly recommended
that subsequent decisi on on constructi on camp faci1 it ies,commuter
modes,work incentives,and genera1 po 1icies i ncorpor ate a specia1
effort to minimize the effects of construction on these local commun-
ities.Specific mitigation recommendations are included in Section
11.13.
The foregoing is based on the following assumptions:
-The pioneer road concept wi 11 be approved by government regu1 atory
agencies since the pioneer road would not connect to any existing
road before the issuing of a FERC license,thus not making the prior
commitment to a11owlngpub1ic access to the Upper Susitna Basin.
-Although the native landowners (CIRI)have expressed a strong prefer-
ence for road access from Parks Hi ghway to both damsites along the
south side of the Susitna River, they would receive significant
benefits from the recommended road access to their existing land
holdings.
11-31
-Public access will be prohibited during the construction phase of the
project.Also, the selection of Plan 5 offers some flexibility in
regard to the degree and type of public access subsequent to 1993.
-Most biological and social impacts will be mitigated through adoption
of the recommendations presented in Section 11.13.
If the pioneer road concept ,receives institutional opposition from
agencies from which permits must be received,than a Denali route al-
ternative (preferably Plan 6)is the only means by which the overall
project schedule can be retai ned.If the required permits are not ob-
tained by mid-1983,it will be necessary to reevaluate the options and
possibly amend the FERC License Application to include an access plan
that retains the overall project schedule.
11.13 -Mitigation Recommendations
The plan recommended by Acres does not satisfy all the evaluation cri-
teria outlined in Section 11.2.In order to reduce potential impacts
to biological and cultural resources and to alleviate socioeconomic im-
pacts to the communities of Talkeetna,Trapper Creek,Sherman and
Curry,the following mitigation measures are recommended:
- Permit only on-duty construct ion workers to have access to both the
pioneer road and access road.
-After construction of the power development is complete,maintain a
controlled access route beyond the Devil Canyon Dam.It is antici-
pated a cooperative agreement could be reached with BLM and APF&G
concerni ng the number of people permitted access to the areas and
contro 1 measures could be i mpl emented by mai ntenance and secur ity
personne 1.
-The construction camp should be as self-contained as possible,thus
limiting the number of workers who might otherwise bring their fam-
ilies to a nearby community and commute daily.
- Provide incentives to encourage workers to work the longest time pos-
-------.-.-si-b-lebetween-leaves ·tominimize--commuter~i;raff-ic-.~A-l-i;h0 ugh~t-he ...------_.-.-
final schedule will not be known until labor agreements are estab-
lished and construction commences,longer work periods between breaks
can be advocated.
- Provide planning assistance if requested to the communities of Tal-
keetna and Trapper Creek and railroad communities north of Talkeetna
to aid them in preparing for the effects of potential increased
populations.
-Evaluate various commuter management policies and select the one
whi ch reduces impacts to the 1ccal.icomam Hies._Socioeconomi c impact
assessment studi es currently under way for the Sus itna Project wi 11
provide important input data for evaluating possible commuter manage-
ment policies.
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-Utilize excavated cuts and other construction techniques to prohibit
utilization of the pioneer road after construction of the access
road.Areas used for the pioneer road which do not follow final road
alignment should be reclaimed.
The total costs for the mitigation measures are estimated to be about
$3.5 million (1982 dollars).These capital costs are not considered to
influence the evaluation and comparison of alternatives.
11.14 -Tradeoffs Made in the Selection Process
(a) Basis of Selection Process
From the natural resource and local public preference perspective,
mai ntenance of their general 1ifestyl e patterns is probably most
favored.However,it is unrealistic to consider that a project
the size of Susitna can be implemented without changing the exist-
ing character of sections of the Upper Susitna Basin.
Access to the damsites is a complex and controversial issue.As
such,it has received considerable attention from the study team,
APA,resource agencies and the public.Although the studies have
determined that there is no single access plan that satisfies all
the project objectives and evaluation criteria,it has been pos-
sible to develop an access plan which provides a reasonable trade-
off of preference.These tradeoffs are essenti ally based on the
following compromises:
- All entities must present a degree of flexibility,otherwise a
satisfactory compromise is impossible.
-Whenever a specific objective is partially compromised,consid-
erable effort is made during subsequent decisions to compen-
sate.
-Any compromises made are clearly outlined such that decision
makers reviewing the final recommendation are aware of negotia-
tions to date.
(b)Tradeoffs Made in the Selection Process
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(i)Engineering
Concessions made include:
-No road access from Denali Highway which would include a
complete loop connecting Parks Highway with Denali High-
way;
11-33
No pioneer road to Parks Highway prior to the issuance of
a FERC license;
-Commitment to be prepared to make the pioneer road impas-
sible if FERC license not granted;and
-Restrictions to be placed on worker commuting schedules
and mode;worker incentives to be provided to minimize
effects on local communities.
Objectives retained include:
-Road access to both dams ites to allow for ease of con-
struction,operation and maintenance of the project;
-Maintenance of schedule through retention of the pioneer
road concept.
(t t )Biological
Concessions made include:
-Road access from Parks Highway affecting Indian River
area and providing partial public access to the upper
bas in.
Objectives retained include:
-No access from Denali Hi ghway wh ich was considered to
have the greatest potential for environmental impact;
-No route on the south side of the Susitna River between
the damsites,thus avoiding the sensitive Stephan Lake
and Fog Lakes area;
-Emphasis on construction mitigation when developing road
link between Parks Highway and Gold Creek; and
-Retention of a degree ofeontrolonfuturepubl-ic access
by accepti ng the Parks Hi ghway p1 an where,due to the
terrain,private vehicles are basically restricted to the
access corridor between Parks Highway and the Devil Can-
yon damsite.The degree and type of access east of Devil
Canyon can be somewhat controlled by regulation of access
across the Devil Canyon dam.
The alternative of not connecting to a major highway was
considered to have the 1ea~t net adverse biological impact.
The ease of operation and maintenance and the construction
flexibility criteria,as explained previously,was consid-
ered to outweigh this advantage.The mitigation measures
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and road management will reduce the adverse biological im-
pacts associated with an access connection to a major high-
way,to a minimum.
(iii)Social
Concessions made include:
-Road access to the Upper Susitna Basin;
-Road access from Parks Highway which creates greatest
potential for change in the Indian River land disposal
site.
Objectives retained include:
-Through the implementation of a relatively self-contained
construction camp,restriction of private vehicles from
the construction site,implementation of mass transit
modes for commuting workers,incentives to encourage
workers to remai n on site and controlled pub 1ic access
east of Devil Canyon following construction,it is con-
sidered that changes in the local communities of Trapper
Creek/Talkeetna area will be minimized;
-Although the western communities favored a rail access,
they also favored maintaining their general lifestyle
patterns.The recommended plan with its associated miti-
gation should produce less change in the Talkeetna/
Trapper Creek area than an all-rail access plan.
Overall consensus of the local community preference favored
access from the Denali Hi ghway.The advantages of the
Parks Highway access over the Denali access in reducing the
biological impacts is considered to outweigh the local com-
munity preference.In addition to the lessened biological
impacts,the recommended plan better meets the preferences
of Native landowners.
The recommended plan does not fully meet the preferences of
the Native landowners.They would prefer the access road
between Devi 1 Canyon and Watana be located on the south
side of the Susitna Ri ver,The advantages of the road
being located on the north side of the Susitna River,
include,reduced biological impacts,the actual construc-
tion of the road is easier than if located on the south
side.The recommended plan would,however,provide a major
transportation link which would allow the native landowners
to develop their land more easily than is presently pos-
si b1e. These advantages are considered to outwei gh the
native landowner preference to have the road located on the
south side of the Susitna River.
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LIST OF REFERENCES
1. Acres American Incorporated,Task 2 -Access Route Selection
Report,March 1982.
2.Terrestrial Environmental Specialists,Environmental, Socioeco-
nomic,and Land Use Analysis of Alternative Access Plans,
October 1981.
3.R&M Consultants,Subtask 2.10 -Access Planning Study,March 1982.
L-
TABLE 11.1:SUSITNA ACCESS PLANS
~._-
DESCRIPT ION:ROAIJiIAY:PARKS RAIL:GOLD ROAIJiIAY:DENALI ROAIJiIAY:DENALI ROAIJiIAY:PARKS ROAIJiIAY:DENALI RDAIJiIAY:DENALI RDAIJiIAY:GOLD RAIL:GOLD RAIL:GOLD RDAIJiIAY:DENALI
HIGHWAY TO DEVIL CREEK TO DEVIL HIGHWAY TO HIGHWAY TO HIGHWAY TO DEVIL HIGHWAY TO HIGHWAY TO CREEK TO DEVIL CREEK TO DEVIL CREEK TO DEVIL HIGHWAY TO WATANA
CANYON &WATANA CANYON &WATANA WATANA,PARKS WATANA,RAIL,GOLD CANYON ON SOUTH WATANA,RAIL,GOLD WATANA,PARKS CANYON ON SOUTH CANYON ON SOUTH CANYON ON SOUTH CONNECTING ROAD
ON SOUTH SlOE ON SOUTH SIDE HIGHWAY TO CREEK TO DEV IL SlOE OF SUSITNA,CREEK TO DEVIL HIGHWAY TO DEVIL SIDE OF SUSITNA, SlOE OF SUSITNA, SIDE OF SUSITNA.BETWEEN WATANA
OF SUSITNA OF SUSITNA DEVIL CANYON CANYON ON SOUTH DEVIL CANYON TO CANYON ON SOUTH CANYON ON SOUTH DEV IL CANYON TO ROAIJiIAY DEVIL ROAIJiIAY DEVIL ANO DEVIL CANYON
ON SOUTH SlOE SIDE OF SUSITNA.WAT ANA ON NORTH SIDE OF SUSITNA. SlOE OF SUSITNA.WATANA ON NORTH CANYON TO WATANA CANYON TO WATANA ON N,lJRTH SlOE
OF SUSITNA.NO NO CONNECTING SlOE OF SUSITNA.CONNECTING ROAD CONNEC TING ROAD SIDE OF SUSITNA.ON NORTH SIDE ON SOUTH SIDE OF SUSITNA.
CONNECTING ROAD ROAD ON NORTH SIDE OF ON NORTH SIDE OF SUSITNA.OF SUSITNA.
SUSITNA.OF SUSITNA.
MILEAGE OF NEW ROAD 62 5B 70 60 68 102 111 54 58 53 86
CONSTRUCT ION
COST ($x 1,000,000)15B 140 151 119 143 179 209 93 108 123 145
MAINTENANCE
COST rs x 1,000,000)5 4 6 5 B 8 9 7 5 5 11
LOGISTICS COST
($x 1 000,000)215 210 231 230 214 230 231 214 216 214 25B
SUBTOTAL
($x 1,000,000)378 354 3B8 354 365 417 449 314 329 342 414
PERSONNEL SHUTTLE
COST ($x 1,000,000)0 25 0 10 0 0 0 25 25 25 0
CONTINGENCY RISK
($x 1 000,000)0 40 0 15 0 0 0 40 40 40 0
TOTAL COSTS
($x 1,000 000)37B 419 3BB 379 365 417 449 379 394 407 414
CONSTRUCTION SCHEDULE 3-4 3-4 1 1 3-4 1 1 3 3 3 1
MAJOR BRIDGES 2 2 0/1 0 2 0 0/1 1 1 1 0
TABLE 11.2:IDENTIFICATION OF CONFLICTS I
CrIterla 2 3 4 5 6 7 8 9 10 11
Costs
Minimize Costs 3 3 3 3 3 2 2
Ease of Operation and
Construction Flexibility
Ease 0 f Ope r at ion and
Maintenance 3 2 3 3 3 2 2 2 3 .~Construct ion Flexibility 3 3 2 3 2 3 3
Biological
Minimize Biological Impacts 2 3 2 3 3 3 ,I
Social
Accommodate Preference of
Native Landowners 3 2 2
Accommodate Local
Community Preference 2 2 2 2 2
2 2 2 2
1 - Does not sat isfy cr iter ia
2 -Intermediate
3 -Satisfies criteria
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w w w w WDEFINE OBJECTIVES I--DESIGN PARAMETERS
SCREENING PROCESS PLAN FORMULATION EVALUATION
SELECT ACCESS ROADWAY AND RAIL .....TECHNICAL f-3 ROUTES ONE IN ADDITIONAL STUDIES r"II ALTERNATIVE PLANS
ROUTE TO HYDROPOWER ENGINEERING CRITERIA ECONOMIC EACH CORRIDOR SOILS DATA
ARE EVALUATED TO
SITES THAT ALLOWS i ENVIRONMENTAL AS A RESULT OF ENGINEERING THE FOLLOWING
CONSTRUCTION AND PUBLIC PREFERENCES THE SCREENING
.......CONSTRUCTION COSTS
-CRITERIA
OPERATION WHILE -bJ TRANSMISSION IMPACT PROCESS IN @]LOGISTICS COSTS ENGINEERINGBEST MEETING ARE ESTABLISHED TRANSMISSION IMPACT
ECONOMICOVERALLCRITERIAESTABLISH CANDIDATES t ENVIRONMENTALSTATED IN I]J A TOTAL OF 33 -H ENVIRONMENTAL I-SCHEDULINGROUTES ARE PORT FACILITIES DESIRED LEVEL OFESTABLISHEDINROADWAYOPTIONSHLABOR ORGANIZATION ~ACCESSTHE3CO~RIDORS RAIL OPTIONS CONCERNS AGENCY CONCERNS
+LOGISTIC REQUIREMENTS SOCIAL PREFERENCES
TRANSMISSION!AGENCY CONCERNS
2A AS A RESULT OF
PUBLIC PARTICIPATION 8 PLANS,WHICH f-t.AGENCY CONCERNS,
I-
PRESENT THE OPTIONS
~UTILIZED THE 3 ADDITIONAL PLANS
TO THE PUBLIC AND 3 ROUTES ARE
"-ARE ESTABLISHED
INVITE COMMENT ESTABLISHED HNATIVE LANDOWNERS ~PREFERENCES
LOCAL COMMUNITY
PREFERENCES
ACCESS PLAN SELECTION METHODOLOGY
FIGUREll.lm
PARKS
HWY.
ALASKA
RAILROAD
DENALI HWY.
HURRICANE
PROPOSEDl·ROAD
t ---~-__Ill
D.C.- -LWATANA
GOLD SITE SITE
CREEK
PLAN I
HURRICANE
DENALI HWY.
FIGURE 11.2 •
PLAN 2
ALASKA-~
RAILROAD
CANTWELL.
HURRICANE
PLAN 3
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tWATANA
SITE
-j
D.C.
SITE
DENALI HWY.
PROPOSED
~lLG~-
CREEK
!1II
[1
CANTWELL
HURRICANE
ALASKA
RAILROAD
DENALI HWY.
PLAN 4
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PROPOSED~I
ROAD ~
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tWATANA
SITE
FIGURE 11.31 ~~I!~1
CANTWELL
HURRICANE
ALASKA
RAILROAD
DENALI HWY.
PLAN 5
FIGURE 11.4 [81
DENALI HWY.
PLAN 6
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CREEK SITE SITE
CANTWELL
HURRICANE
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PLAN 7
FIGURE 11.5 [Ii]
DENALI HWY.
DENALI HWY.
PLAN 8
LPROPOSEDlROAD
---t:L~-UCJ ---lWATANA
CREEK SITE SITE
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FIGURE 11.6.
J PROPOSED
ROAD
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-'-WATANA
SITE
PLAN 10
PLAN 9
DENALI HWY.
DENALI HWY.
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ROAD
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- - -WATANA
SITE
CANTWELL
CANTWELL
HURRICANE
HURRICANE
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Docf WATANA
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PLAN 1\
FIGURE 11.7 m
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'LS;;;(~d '3 f·\~.(I !),1m
---'...'"R.9E..I : R.IOE.R.IIE. R.12E.:
U <t B MILES
SCALE
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
ALTERNATIVE ACCESS CORRIDORS
REFERENCE:BASE MAPFROM USGS.1:250,000
HEALY,ALASKA
TALKEETNAMOUNTAINS.ALASKA ~~
ACRESA'NERICANiNCORPORm"o
PLATE
11.1
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RAW.R.3W.
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LEGEND
----ACCESS ALTERNATE I==ACCESSALTERNATE 2
----ACCESS ALTERNATE 3
SCALE 0 4 8 MILES
ALASKA POWER AUTHORITY
SUSITNAHYDROELECTRIC PROJECT
ALTERNATIVE ACCESS ROUTES
REFERENCE:BASE MAP FROM USGS,'.250,000
HEALY,ALASKA
TALKEETNA MOUNTAINS,ALASKA
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12 -WATANA DEVELOPMENT
This section describes the various components of the Watana Develop-
ment,including diversion facilities,emergency release facilities,the
main dam,outlet facilities,reservoir,main and emergency spillways,
the power intake,penstocks and powerhouse complex including turbines,
generators,mechanical and electrical equipment, switchyard structures
and project lands.A description of the permanent and temporary access
and support facilities is also included.
12.1 - General Arrangement
The evolution of the Watana general arrangement is described in Section
9.The Watana reservoir and surrounding area is shown in Plate 2.The
site layout in relation to main access facilities,borrow areas and
camp facilities is shown in Plate 3. A more detailed arrangement of
the various site structures is presented in Plate 4.
The Watana dam will form a reservoir approximately 48 miles long, with
a surface area of 37,800 acres,and a total volume of 9,520,000 acre-
feet at a normal maximum operating elevation of 2185.During opera-
tion,the reservoir will be capable of being drawn down to a minimum
elevation of 2045.
The dam will be an embankment structure with a central core.The crest
elevation of the dam will be 2210,with a maximum height of 885 feet
and a crest length of 4,100 feet.The total volume of the structure
will be approximately 62,000,000 cubic yards.During construction,the
ri ver wi 11 be diverted around the mai n construct i on area by means of
two concrete-lined diversion tunnels,each 38 feet in diameter,on the
right bank of the river.
A power intake located on the right bank will comprise an approach
channel cut into the rock leading to a concrete intake structure
with multi-level gates capable of operation over the full 140 feet
drawdown range.From the.intake structure,si x concrete-l i ned pen-
stocks,each 17 feet in diameter,will lead to an underground power-
house complex housing six Francis turbines with a rated capacity of 170
MW and six semi-umbrella type generators each rated at 180 MVA.Access
to the powerhouse complex will be by means of an unlined access tunnel.
Turbine discharge will flow through six draft tube tunnels to two surge
chambers downstream of the powerhouse.Each surge chamber wi 11 dis-
charge to the river through a 34-foot diameter concrete-lined tailrace
tunnel.A separate transformer gallery just upstream from the power-
house cavern will house nine single-phase 15/345 kv transformers.The
transformers will be connected by 345 kV single-phase,oil-filled cable
through two cable shafts to the switchyard at the surface.
A tunnel spillway located on the right bank will be designed to dis-
charge all flows resulting from floods having a return frequency of
12-1
once in 50 years or less.This structure will be equipped with six
fixed-cone valves at the downstream end to eliminate undesirable
nitrogen supersaturat i on in the r i ver downstream from the dam duri ng
spillway operations.Flows resulting from floods with a frequency
greater than once in 50 years but less than once in 10,000 years will
be discharged by a chute spillway also located on the right bank.The
flow down the chute spillway will be controlled at the upstream end by
three fixed wheel gates leading to a reinforced concrete-lined chute
section and then to a flip bucket at the downstream end.An emergency
spillway on the right bank will provide sufficient additional capacity
to permit discharge of the PMF without overtopping the dam.An
emergency release facility will allow lowering of the reservoir over a
period of time to permit emergency inspection or repair.
12.2 -Site Access
(a)Roads
At Watana the main access road will enter the site from the north.
In addition to the main access,several additional roads will be
required to the camp,village,airstrip,and tank farm.Haul
roads to the borrow areas and construct i on roads to the dam and
all major structures will also be required.These roads with the
exception of the haul roads are shown on Plate 36.
The construction roads will be 40-foot wide gravel surfaced roads
with small radius curves and grades limited to 10 percent.Major
cut and fill work will be avoided. A gravel pad approximately 5
feet thick will be required for the roads.This gravel pad will
provide a drivable surface and also will protect against the
sporadic perffiafrost areas.
(b) Bridges
No major temporary bridges at the Watana site will be required for
the construction of the Watana development.The crests widths of
the upstream and downstream cofferdams will be planned to provide
suitable access to the south bank of the Susitna River during
con on.
The completed main dam crest will provide permanent access across
the Susitna River.
One area which may require a small temporary bridge is Tsusena
Creek near its confluence with the Susitna River.Currently it is
envisioned that this crossing can be accomplished using culverts.
(c)Airstrip
A permanent airstrip will be constructed approximately 2.5 miles
north of the mai n construct i on camp.The runway wi 11 be 6,000
feet in length and will be capable of accommodating the C-130
12-2
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Hercules aircraft,as well as small jet passenger aircraft.Roads
will connect the airstrip to the camp,village,and damsite.A
small building will be constructed to serve as a terminal and
tower and a fuel truck/maintenance facility will be constructed.
Atemporary airstrip will also be constructed to support the early
phases of mobilization and construction.This temporary runway
will be 2,500 feet in length and will be located in the vicinity
of the main construction camp.The airstrip will be capable of
supporting smaller type aircraft.
The temporary airstrip will eventually be incorporated into one of
the main haul roads for Borrow Site D.This will occur after the
permanent airstrip is in service.
(d)Access Tunnel
An access tunnel wi 11 be provided to the underground powerhouse
and associated works.The main access tunnel will be approximate-
ly 35 feet wide and 28 feet high.The tunnel will allow permanent
access to the operating development and will also be utilized
during construction as the main construction tunnel.Construction
adits will branch off to the various components of the development
during construction.
12.3 -Site Facilities
(a)General
The construct i on of the Watana development will require vari ous
facilities to support the construction activities throughout the
entire construction period.Following construction,the operation
of the Watana hydroelectric development will require certain
permanent staff and facilities to support the permanent operation
and maintenance program.
The most significant item among the site facilities will be a
combination camp and village that will be constructed and main-
tained at the project site.The camp/village will be largely a
self-sufficient community housing 4,000 people during construction
of the project.After construction is complete,it is planned to
dismantle and demobilize most of the facility and to reclaim the
area.The dismantled buildings and other items from the camp will
be used as much as possible during construction of the Devil Can-
yon development. Other site facilities include contractors'work
areas,site power,services,and communications.Items such as
power and communications will be required for construction opera-
t i on s independent of camp operat i on s.Th e same wi 11 be true re-
garding a hospital or first aid room.
12-3
Permanent f aci1it ies requi red wi 11 inc1ude a permanent town or
small community for approximately 130 staff members and their
f ami 1i es.Other permanent f aci 1it ies wi 11 inc1ude a mai ntenance
building for use during subsequent operation of the power plant.
A conceptual plan for the permanent town has been developed,how-
ever,it is recommended that the final design be deferred until
near the end of construction when more information as to the
design parameters is available.
(b) Temporary Camp and Village
The proposed location of the camp and village will be on the north
bank of the Susitna Ri ver between Deadman and Tsusena Creek,
approximately 2.5 mi 1es northeast of the Watana Dam.The north
side of the Susitna River was chosen because the main access will
be from the north and south-facing slopes can be used for siting
the structures.The location is shown in Plate 36.
The camp will consist of portable woodframe dormitories for bache-
lors with modular mess halls,recreational buildings,bank,post
office,fire station,warehouses,hospital,offices,etc.The
camp will be a single status camp for approximately 3,600 workers.
The village,accommodating approximately 350 families,will be
grouped around a service core containing a school,gymnasium,
stores,and recreation area.
The village and camp areas will be separated by approximately 1.5
miles to provide a buffer zone between areas.The hospital will
serve both the main camp and village.
The camp location will separate living areas from the work areas
by a mi 1e or more and keep travel time to work to 1ess th an 15
minutes for most personnel.
The camp/village will be constructed in stages to accommodate the
peak work force as presented in Table 12.1.The facilities have
Been designed forlnepeakwork force plus 10 percent for turn-
over.The turnover will include allowances for overlap of workers
and vacations.The conceptual layouts for the camp and village
are presented on Plate 37 and 38.
(i)Site Preparation
Both the c amp and the vi 11 age areas wi 11 be cleared in
select areas,fi lter fabric wi 11 be installed,and the
granular material will be placed over it.At the village
site,selected areas wi 11 be left with trees and natural
vegetation intact.Topsoil stripped from the adjacent
Borrow Site D will be utilized to reclaim camp and village
sites.
12-4
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Both the main camp and the village site have been selected
to provide well-drained land with natural slopes of 2 to 3
percent.
A granular pad varying in thickness up to 4 feet will be
placed at the main camp,covering most of the areas inside
the perimeter fence.This will provide a uniform working
surface for erection of the high density housing and ser-
vice buildings and will serve in certain areas to protect
the permafrost where it underlies the camp.In the village
area,a granular pad will be installed only as necessary to
support the housing units and to provide a suitable base
for construction of the temporary village center buildings.
All roadways within the camp/village areas will be flanked
by roads i de ditches,with cul verts carryi ng water across
the intersections.In general,drainage will be through
construction of a surface network of ditches.
(i 1)Faci 1it i es
Construction camp buildings will consist largely of
trai ler-type factory-bui It modules assembled at site to
provide the various facilities required.The modules will
be fabricated complete with heating,lighting and plumbing
services,interior finishes,furnishings,and equipment.
Larger structures such as the central utilities building,
warehouses and hospital will be pre-engineered,steel-
framed structures with metal cladding.
The 1arger structures wi 11 be erected on concrete-s 1ab
foundations.The slab will be cast on a non-frost suscep-
tible layer at least the thickness of the annual freeze/
thaw layer.
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Permawalks wi 11 connect the majority of the bui ldings and
dormitories.The various buildings in the camp are identi-
fied on Plate 37. A detailed description of the nature and
function of the buildings is presented in Appendix B7.
(c)Permanent Town
The permanent town will be located at the north end of the tempo-
rary village (see Plate 36)and be arranged around a small lake
for aesthetic purposes.
The permanent town will consist of permanently constructed build-
ings.The vari ous buildi ngs in the permanent town are 1i sted
below:
12-5
-Single family dwellings;
-Multifamily dwellings;
-Hospital;
- School;
-Fire station;
- A town center will be constructed and will contain the
followin.g:
a recreation center
. a gymnasium and swimming pool
. a shopping center
The concept of building the permanent town at the beginning of the
construction period and using it as part of the temporary village
was considered.This concept was not adopted,since its intended
occupancy and use is a minimum of 10 years away,and the require-
ments and preferences of the potential long-term occupants cannot
be predicted with any degree of accuracy.
(d)Site Power and Utilities
(i)Power
El ectr i cal power will be requi red to mai ntai n the campi
village and construction activities.A 345 kV transmission
1ine wi 11 be constructed and wi 11 serv i ce the site from
1987 onward.The 345 kV transmission line will be operated
at 138 kV during the construction phase. After the Watana
development is complete and in operation,the transmission
line will supply power to the Intertie from Watana and will
operate at 345 kV.
During the first two years of construction (1985 and 1986),
th1:!power supply will come from diesel generators.These
generators will remain on site after 1987 as standby power
supply.The peak demand during the peak camp population
year is estimated at 13 MW for the camp/village and 7 MW
for construction requirements totaling 20 MW of peak
demand.The distribution system in the camp/village and
construct i on area wi lJ .be-4-.16-kV.~.__.
Power for the permanent town wi 11 be supp 1ied from the
station service system after the power plant is in opera-
tion.
(i 1)Water
The water supply system will provide for potable water and
fire protection for the camp/village and selected contrac-
tors I work areas.The est imated peak popul at i on to be
served will be 4,720 (3,600 in the camp and 1,120 in the
vi 11 age).
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(iii)
The principal source of water will be Tsusena Creek, with a
back up system of wells drawing on ground water.The water
wi 11 be treated in accordance with the Environmental Pro-
tection Agency's (EPA)primary and secondary requirements.
A system of pumps and storage reservoirs will provide the
necessary system capacity.The distribution system will be
contai ned wi thi n ut il i dors constructed usi ng plywood box
sections integral with the permawalks.The distribution
and location of major components of the water supply system
are presented in Plate 36.Details of the utilidors are
presented in Plate 39.
Waste Water
A waste water co 11 ect ion and treatment system wi 11 serve
the camp/village.One treatment plant will serve the
camp/village using gravity flow lines with lift stations
wi 11 be used to co 11 ect the waste water from all of the
camp and village facilities.The "in-camp"and "in-
village"collection systems will be run through the utili-
dors so that the collection system will be protected from
freezing.
The chemical toi lets located around the construction site
will be serviced by sewage trucks,which will discharge
direct ly into the sewage treatment plant.The sewage
treatment system will be a biological system with lagoons
designed to meet Al askan and EPA standards.The sewage
plant wi 11 di scharge its treated effl uent through a force
main to Deadman Creek. All treated sludge will be disposed
in a solid waste sanitary landfill.
The location of the treatment plant is/shown in Plate 37.
The location was selected to avoid unnecessary odors in the
camp as the wi nds are from the SE only 4 percent of the
time,which is considered minimal.
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(e)Contractor's Area
The onsite contractors will require office,shop,and general work
areas.Partial space required by the contractors for fabrication
shops,mai ntenance shops,storage or warehouses,and work areas,
will be located between the main camp and the main access road.
12.4 -Diversion
(a) General
Diversion of the river flow during construction will be accom-
I)plished with two 38 foot diameter circular diversion tunnels.The
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12-7
tunnels wi 11 be concrete-l ined and located on the right bank of
the river.The tunnels are 4,050 feet and 4,140 feet in length.
The diversion tunnels are shown in plan and profile on Plate 11.
The tunnels are designed to pass a flood with a return frequency
of 1:50 years,equivalent to peak inflow of 81,~00 cfs.Routing
effects are small and thus,at peak flow the tunnels will dis-
charge 80,500 cfs.The maximum water surface elevation upstream
of the cofferdam is EL 1536. A rating curve is presented in
Figure 12.1.
The upper tunnel or Tunnel No.2 will be converted the permanent
low level outlet after construction.The local enlarging of the
tunnel diameter to 45 feet is to accommodate the low level outlet
gates and expansion chamber.
(b) Cofferdams
The upstream Eofferdam will be a zoned embankment founded on the
closure dam (see Pl ate 12).The closure dam wi 11 be constructed
to Elevation 1475 based on a low water elevation of 1470, and will
consist of coarse material on the upstream side grading to finer
materi a 1 on the downstream side.For purposes of feas i bil ity
design,it has been assumed that a cut-off through the river bed
alluvium to bedrock will be required.A cement/bentonite slurry
wall supplemented by downstream pumping has been shown on Pl ate
12.Further investigations at the cofferdam site may indicate
that the insitu materi als are such that seepage flows can be
controlled solely by pumping without the need for a cutoff.
Above Elevation 1475 the cofferdam will be a zoned embankment con-
sisting of a central core,fine and coarse upstream and downstream
fi lters,and rock and/or gravel supporting shell zones with rip-
rap on the upstream face to resist ice action.This cofferdam is
shown with a 9 foot freeboard for wave runup and ice protection.
The downstream cofferdam will consist of only a closure d~m con-
structed from approximate Elevation 1440 to 1472,and consisting
arse mater-i-al-on the downstreams-ide g~ading·tofi-nermater
ial on the upstream side.Control of underseepage similar to that
for the upstream cofferdam will be required.
(c) Tunnel Portals and Gate Structures
A rei nforced concrete gate structure wi 11 be located at the up-
stream end of each tunnel,housing two closure gates (see Plate
13) .
Each gate wi 11 be 38 foot high by 15 foot wi de separated by a
center concrete pi er.The gates wi 11 be of the fi xed roll er ver-
tical lift type operated by a wire rope hoist.The gate hoist
will be located in an enclosed,heated housing.Provision will be
12-8
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made for heating the gates and gate guides.The gate in Tunnel
No.1 will be designed to operate with the reservoir at Elevation
1540, a 50 foot operating head.The gate in Tunnel No.2 will be
desi gned to operate with the reservoi r at E1 evat ion 1540, a 120
foot operating head.The gate structures for Tunnels No.1 and 2
will be designated to withstand external (static)heads of 130 and
520 feet,respectively.The downstream portals will be reinforced
concrete structures with guides for stoplogs.
(d) Final Closure and Reservoir Filling
As discussed in Section 9 one of the diversion tunnels will be
converted to a low level outlet or emergency release facility
during construction.
It is estimated one year will be required to construct and install
the permanent low level outlet in the existing diversion Tunnel
No.1.This will require that the lower Tunnel No.2 pass all
flows during this period.The main dam will be at an elevation
sufficient to allow a 100 year recurrence interval flood (90,000
cfs)to pass through Tunnel No.2.Th is flow wi 11 result ina
reservoir elevation of 1625.During the construction of the low
level outlet,the intake operating gate in the upper Tunnel No.1
will be closed.Prior to commencing operation of the low level
outlet,coarse trashracks will be installed in the Tunnel No.1
intake structure in the slots provided.
Upon commencing operation of the low level outlet,the lower Tun-
nel No.2 will be closed with the intake gates and construction of
the permanent plug and filling of the reservoir will commence.
When the lower Tunnel No.2 is closed the main dam crest will have
reached an elevation sufficient to start filling the reservoir
and sti 11 have adequate storage avai 1ab1e to store a 250 year
recurrence period flood.
During the filling operation,the low level outlet will be passing
the summer flow of 6,000 cfs and a winter flow of 800 cfs.In
case of a large flood occuring during the filling operation,the
low level outlet would be opened to its maximum capacity of 30,000
cfs until the reservoir pool was lowered to a safe level.
The filling of the reservoir will take 4 years to complete to full
reservoir operating elevation of 2185.After 3 years of filling
the reservoir will be at Elevation 2150 and will allow operation
of the powerplant to commence.
The filling sequence is based on the main dam elevation at any
time during constructiun and the capability of the reservoir
storage to absorb the infl ow vo 1ume from a 250 year recurrence
period flood without overtopping the main dam.
This information is presented graphically in Figure 12.2.
12-9
12.5 -Emergency Release Facilities
The upper diversion Tunnel No.1 will be converted to a permanent low
level outlet,or emergency release facility.These facilities will be
used to pass the required minimum discharge during the reservoir fill-
ing period and will also be used for draining the reservoir in an
emergency.
The facility will have a capacity of 30,000 cfs at full reservoir pool
and wi 11 be capable of drawing the reservoir dam in 14 months.The
reservoir drawdown time incorporating the low level outlet is presented
graphically in Figure 12.3 for various "start"times during the year.
Duri ng operat i on, energy will be di spated by means of two gated con-
crete plugs separated by a 340 foot length of tunnel (see Plate 21).
Bonnetted type high pressure slide gates will be installed in the tun-
nel plugs.The gate arrangement will consist of one upstream emergency
gate and one operating gate in the upstream plug and one operating gate
in the downstream plug. A 340 foot length of tunnel between plugs will
act as an energy dissipating expansion chamber.
The 7.5 feet by 11.5 feet gates will be designed to withstand a total
static head of about 740 feet,however,they will only be operated with
a maximum head of about 600 feet or less.
During operation,the operating gate opening in the upstream plug will
be equal to the opening of the corresponding gate in the downstream
plug. This shou16 effectively balance the head across the gates.The
maximum operating head across a gate should not exceed 340 feet.
Each gate will have a hydraulic cylinder operator designed to raise or
lower gate against a maximum head of 560 feet.Three hydraulic units
wi 11 be installed,one for the emergency gates,one for the upstream
operating gates and one for the downstream operating gates.Each gate
will have an opening/closing time of about 30 minutes. A grease injec-
tion system will be installed in each gate to reduce frictional forces
when the gates are operated.
--------~~~Th-e-desi gn of the gate wlll be such tJlafTheh-ydraUTfC-c:yrrn-aer--as-wel r
as the cylinder packing may be inspected and repaired without dewater~
ing the area around the gate.All gates may be locally or remotely
operated.
To prevent concrete erosion,the conduits in each of the tunnel plugs
will be steel lined.An air vent will be installed at the downstream
side of the operating gate in the downstream plug.
12.6 -Mai n Dam
(a)Comparison with Precedent Structures
The main dam at Watana,as currently proposed with a height of 885
feet will be among the highest in the world.The highest embank-
12"'10
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ment dams completed in North America are Mica Creek in British
Columbia (794 feet)and Oroville in California (771 feet).Two
dams under construction in the USSR will exceed 1,000 feet,but
the only dam completed to a height in excess of 800 feet is Sulak
in the USSR.A list of embankment (earth and rockfill)dams in
excess of 500 feet completed, under construction or proposed is
given in Table 12.2.
The Watana site is located in a seismically active area and the
major design features of 24 embankment dams between 350 and 795
feet in height constructed in seismic areas are summarized in
Table 12.3.The characteristics of the Watana design,which will
be developed in this section,are included in this table for com-
parison.Special site conditions,purpose of development, depth
to bedrock,availability of materials,size of reservoir,site
location,for example,all have an impact on the design and such
factors account for some of the extremes quoted in the table.
A further comparison is given in Table 12.4 which includes the
principal geometrical parameters of the core and outer slopes for
high dams in seismically active areas.Considering these various
parameters:
-The freeboard ranges between 13 and 62 feet,with seven of the
eleven cases quoted being less than the 25 feet proposed for
Watana.
-The crest width ranges between 33 and 111 feet.Wide crests are
usually the result of non-structural requirements,i.e.,a road-
way across the dam.Neglecting extreme widths,seven of the ten
cases quoted are between 30 and 40 feet compared with the 35-
foot width proposed for Watana.
-The core wi dth to water depth rati 0 ranges between 0.29 and
0.56,with only one example higher than the 0.50 ratio proposed
for Watana.
-The upstream slopes range between 2.0:1 and 2.7:1.The Japanese
dams tend to have flatter slopes (within the range 2.5 to 2.7),
while the North American dams are in the range of 2.0 to 2.6.
The Watana slope of 2.4:1 is among the steepest,but is flatter
than the next two highest dams,Mica at 2.25:1 and Chicoasen at
2.2:1.However,special features are included in the Watana
design,primarily the use of free-draining processed alluvial
gravel in the upstream shell,to minimize the effects of earth-
quakes on the stability of the upstream face of the dam.
-The downstream slopes range between 1.8:1 and 2.7:1.Ten of the
15 cases quoted are equal to or steeper than the 2:1 slope pro-
posed for Watana,while only one case is flatter than 2.2:1.
12-11
Complete details of the core materials used in all the dams listed
in the accompanying tables are not available in the literature.
However a number of 1arge dams have been constructed in Canada
using similar glacial deposits as core material.The mean grading
curves for these materials including that used for the core of the
Mica Creek dam,the existing dam generally comparable to Watana in
size,materials,and location,are compared with the mean grading
curve for the core material proposed for the Watana dam in Figure
12.4.It is apparent from this figure that the Watana core
material is well within the range of materials used successfully
for other large dams in North America.
In summary,the proposed Watana design is generally conservative
with respect to precedent design.However,special features which
are di scussed in more detail later in this section are incorpo-
rated in the Watana section to provide additional safeguards
against seismic loading.
(b) Excavation and Foundation Preparation -General
The geology of the Watana site is described in Section 9".In
summary,the existing conditions at the damsite comprise alluvial
deposits in the r i verbed up to 100 feet deep overlyi ng bedrock,
while the lower slopes of the valley are covered with talus and
there is overburden on the upper slopes.The bedrock is jointed
and weathered at the surface with weathering along joints extend-
ing to considerable depths.Locally in shear zones and drainage
gullies the rock is weathered throughout to depths in excess of 40
feet.The frequency of joi nts and fractures generally decreases
with depth but fractured and weathered zones have been identified
1oca lly at depths up to 200 feet.Zones of permafrost occur,
particularly in the south abutment.
The dam foundation must satisfy the following basic requirements:
-The foundation under the core must be stable and capable of
supporting the weight of the core under all loading conditions,
rnust not erode under the seepage gradi ents whl ch will develop
under the .core;.and must not allow excessive seepage···losses
under the core.
-The foundation under the upstream and downstream shells must be
stable and capable of supporting the weight of the dam without
excessive movement under all loading conditions.
-The core mat erla1 must be prevented from movi ng down into the
foundation (e.g.into cracks or joints)and then through the
foundation under the transition zone into the downstream shell
or beyond.
-There must be positive contact between the core and its founda-
tion despite the distortions that will occur in the dam because
of its own weight and the thrust of the reservoir.
12-12
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-Any seepage through the foundation must be controlled and dis-
charged so that excessive seepage pressures do not develop in
the downstream portion of the core,in the materials beneath the
shell,or downstream of the dam.
The excavation and foundation preparation necessary to meet these
objectives are outlined in the following paragraphs.
(c) Excavation
(i)River Excavation
The properties of the river alluvium are not well defined
but it is expected to include sands,gravels,cobbles,and
boulders up to 3 feet or more.Such materi als are not
suitable as a foundation for the core,primarily because of
their relatively high permeability.Similar deposits have
been 1eft in place under both the upstream and downstream
shells of many of the world's largest dams (see Table
12.4).However,at Watana these granular materials could
undergo liquefaction under seismic loading with potentially
catastrophic results.Insufficient data is available to
demonstrate that there is no possible risk of liquefaction
of the alluvium,but further investigations may provide
data to support the concept of removing the alluvium only
under the central portion of the shells and of incorporat-
ing the cofferdams within the shells.However,in view of
the high seismicity of the area it is proposed at this time
that the river alluvium be removed over the whole founda-
tion area.
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(i i)Under Core and Filters
The core and filters must be founded on sound rock to en-
sure that no material can wash through open joints.This
will require excavation of overburden and talus on the
slopes and weathered rock in the valley bottom and on the
abutments.The tal us thi ckness on the abutments perpendi-
cular to the ~lope varies from zero to an estimated 20 feet
and weathered rock to 40 feet or more in some areas.
Weathered rock is here defined as closely jointed or frac-
tured rock with weatheri ng and i nfi 11 i ng of the joi nts.
The final foundation will be sound hard rock with only
minor weathering,which can be treated by slush grouting
and/or consolidation grouting to ensure that core material
cannot be washed through joints in the rock.
The maximum rock slope along the abutments is determined to
some extent by the valley shape. In general,1H:1V slope
or flatter is ideally preferred although steeper slopes
have been used.At Watana damsite,the natural slopes at
12-13
(iii)
(i v)
(v)
lower elevations are steeper but still generally less than
1H :2V.It is therefore proposed that the overa11 core
foundation slopes will be no steeper than 1H:2V below
elevation 1800 and 1H:1V above elevation 1800.The cross
cut slopes will be 1H:10V.
Local shaping of the rock foundation will be necessary to
eliminate irregularities which might otherwise induce local
cracking of the core due to differential settlements or
strains in the core or would impede proper compaction of
the core at the foundation contact.
The depth of excavation required to remove unsuitable rock
will vary considerably over the core contact area.In some
areas very little or no excavation may be needed, while in
shear or altered zones excav at i on may extend to 50 or 60
feet.
Under Upstream and Downstream Shells
The she 11 s wi 11 be founded on competent rock.Loose or
detached rock or rock r i bs and highly weathered rock wi 11
be removed to expose sound rock.'The actual thickness of
loose rock to be excavated will vary across the site,but
it is estimated that the average will not exceed 10 feet.
Dental Excavation
Dental excavation over and above normal excavation will be
required in zones of intense shearing or highly irregular
surfaces.Such excavations wi 11 normally be backfi lled
with concrete.
Excavation Methods
It is expected that the excavation of the overburden mate-
ri al within the dam foundation wi 11 be performed as a
multi-level operation using wheeled loaders working with
dozers-~-Boulders that--cannot-be--removed---byexcavat ion
equi pment wi 11 be blasted.On the steep slopes work i ng
areas will be formed with material excavated from the
slopes above.These working areas will be progressively
lowered removing overburden and weathered rock in one
operation.
To ensure a safe operation,the excavation of the founda-
tion will need to be complete from about Elevation 1800
down to the ri verbed before p1aci ng of fi 11 is commenced.
Trimming of the rock surface to acceptable slopes may re-
quire blasting and the excavation on the upper slopes will
require to be kept sufficiently in advance of grouting and
fill placement to avoid interference with these activities
by any blasting.
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Dental excavation will be done by small backhoes and final
cleanup of the area under the core and filters wi 11 be
carried out to a high standard by hand with high pressure
air and water jetting prior to grouting.The rock surface
under the core and filters should be clean enough for de-
tailed geological mapping.Final surface preparation will
include slush grouting were necessary to seal exposed open
joints.
Selected alluvial material from the riverbed and sound rock
may be used in the downstream shell of the dam but the re-
maining material,generally a mixture of weathered rock and
overburden,will be wasted or used for road, cofferdam or
temporary facility construction.Spoil areas will gener-
ally be below final water level in the reservoir area.
(d) Grouting and Pressure Relief
A combination of consolidation grouting and cutoff curtain grout-
i ng under the core and a downstream pressure re1i ef (drai nage)
system are proposed for the Watana site.Those systems wi 11
result in:
-Improved stability of the foundation;
-Reduct i on in rock mass permeab i l ity and hence seepage through
the foundation;
Reduct i on in the risk of movement of so i 1 part i c1es through
joints in the rock;and
- Control and safe d i scharge of any seepage flows through the
grout curtain.
It is proposed that the curtain grouting and drilling for the
pressure relief system are carried out from galleries in the rock
foundation in the abutments and beneath the dam.Details of the
grouting,pressure relief and galleries are shown on Plate 10.
The purpose of grouting is to improve foundation and abutment rock
conditions with respect to load bearing and seepage considera-
t ions.The need,extent,and detai 1 of grout i ng is dependent on
site geological conditions,type and character of rock,reservoir
head,and location of specific structures.The diorite bedrock at
Watana is competent as far as load carrying capacity is concerned.
However,numerous shear zones from a few inches to several feet in
width,have been identified in a general NW-SE direction.Occa-
sionally,the width of shear zones may be several tens of feet
locally.Most of these zones,which are found both in the river
channel and in abutments,contain gouge material and under appro-
priate conditions,may be susceptible to piping.These features
are discussed in more detail in Section 9.
12-15
The permeability tests in boreholes indicate the rock mass perme-
ability at the Watana site to be generally in the range from 1 x
10-6 cm/sec to 1 x 10-
4 cm/sec,indicating a maximum seep-
age rate through the foundation of the order of 4 cubic feet per
second.However,these permeabi lity values may not properly
account for shear zones.For example, in Borehole BH-2 on the
north abutment,circulation was lost during drilling when the
bori ng encountered a shear zone.Al so,because of heavy vegeta-
tion,talus cover,and limited access,it is possible that there
may be other shear zones not yet identified.A primary grouting
program of an exploratory nature will be required under the dam
and in the abutments,and the results of this program will form
the basis for final grout curtain design.
(i)Consolidation Grouting
The rock under the core,upstream fi lter,and downstream
filter will be consolidation grouted to provide a zone of
relatively impermeable rock under the entire contact.
Locally,the rock may be sound and free of any discontinui-
ties resulting in virtually no grout take;nevertheless,
the joints and shear zones are generally steeply dipping
and any particular vertical plane is likely to intersect
these zones which are estimated to be 15 to 20 feet apart.
Consolidation grouting is estimated to require 30 foot deep
holes on a 10 foot by 10 foot grid.
(ii)Curtain Grouting
The design of grout curtains under dams is largely emplrl-
cal,though based on data from boreholes.At the Watana
site,only Borehole DH-21 extends to a significant depth
below the river to Elevation 876,approximately 500 feet
below dam foundation level.Sheared and highly fractured
zones are indicated at an average of 50 feet intervals to
the bottom of the hole and the upper zones should be
grouted to reduce seepage losses.The average rock perme-
ability decreases significantly around 200 feet depth.
For the purposes of this study,a double row grout curtain
to a depth of 0.7H, where H is the head of water behind the
dam at a particular location,with a maximum depth of grout
curtain of 350 feet has been assumed.Grouting will be
carried out from a series of underground galleries which
will also serve the drainage system pressure relief.
It is likely that in some areas the grout take at depth
will be very low. Primary holes will be considered as
exploratory holes and wi 11 be core dri lled.On the basis
of the core and water pressure tests in the exploratory
holes,the depth of secondary holes can be decided.The
exploratory holes may also identify areas that need addi-
tional grouting.
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All holes will be water pressure tested in stages and the
grout i ng program wi 11 be determi ned usi ng these results.
Grouting will be carried out using split spacing with the
primary holes at 40 feet spacing.The secondary,tertiary
and quaternary holes would bring the final hole spacing to
5 feet if required.
Any permafrost in the area to be grouted wi 11 have to be
thawed before water pressure test i ng and grout i ng can be
done.The greatest depth of permafrost so far recorded was
in BH-8 where the ho 1e froze to a depth of 175 feet.
Permafrost will be thawed by circulating clean river water
through dri 11 holes.
The effectiveness of the initial thawing and grouting may
be difficult to assess but the permanent galleries under
the dam will enable additional grouting to be carried out
at any time during and following reservoir filling and
subsequent thawing of the foundation and abutments.
It is desirable for the grout holes to intersect as many
discontinuities as possible.The dip of the main joint
sets and shear zones range from 80° to 60°and it is there-
fore considered most efficient to drill the boreholes ver-
tically or at an angle of 45°.
A major shear zone approximately 600 feet wide trending in
a NW direction intersects the left edge of the dam and
reservoir area and the curtain should extend into the abut-
ment to provide a positive cutoff of this zone.The ground
surface rises to the south of the dam and the surface ex-
pression of any shears to the south of the major zone will
be outside the reservoir area and are unlikely to cause
appreciable seepage.The extent of the grout curtain
through the shear zone wi 11 be determi ned by exp1orat i on
from the grout gallery.
No major shears have been found on the right abutment where
the rock is Qf good quality.The grout curtain will extend
from the spillway intake structure 400 feet into the abut-
ment with the depth of the curtain set at a maximum of 200
feet.
The spillway control structure is located on the dam cen-
terline and the grout curtain will extend beneath the
structure with drilling and grouting carried out from the
gallery formed within the concrete rollway.
Drainage will be provided behind the grout curtain with
holes drilled from the gallery.
12-17
(iii)Drainage and Pressure Relief
Drainage features are included beneath the dam foundation
and the abutments to intercept seepage through the grout
curtain and to relieve pressure.Common drainage and
grout ing wi 11 be constructed with grout i ng from the up-
stream side and drai nage from the downstream side of the
galleries.The use of galleries is recommended for the
following reasons:
-Curtain grouting from the gallery can be carried out
independently of the construction of the dam.
- The grouting can continue longer into the winter than
would be possible with surface grouting.
- Permanent access is available under the dam for inspec-
tion and maintenance.Additional grouting or drainage
holes can be drilled after construction of the dam when,
far example,the thawing effect of the reservoir may lead
to increased seepage requiring remedial grouting.
-Higher grout pressures may be used because of the weight
of the overlying embankment.
-Drainage holes drilled downstream of the grout curtain
will be discharged into the gallery enabling flow from
individual holes to be monitored.This system will
prevent the outlets of the drainage holes from freezing.
- The galleries may be used for the installation of instru-
mentation and provide access for the repair and replace-
ment'of instrumentation.
The drai nage/pressure re 1i ef holes wi 11 be dr i 11 ed after
all grouting is complete.They will be approximately 3
inches in diameter spaced at about 10 foot centers.Gener-
ally the holes will be open but any penetrating fractured
orsheal"edrockmaY-·l"equ·i·l"e~·perf0rated·G·as·i·ngt0prevent
caving.
(iv)Construction Methods -Grouting and Pressure Relief
The schedule of work is of particular importance in this
phase of the work. The excavation for the galleries must
be carried out before consolidation grouting because the
grouted rock may be disturbed by tunnel blasting.It will
also be preferable to complete excavation of the dam foun-
dation in a particular section before excavation of the
gallery so that the surface rock profile may be confirmed
before tunnelling.
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(v)
Rock temperatures will be measured in any areas of perma-
frost thawed prior to grouting.Grout holes will generally
be approximately 1-1/2 inch in diameter.Large hole sizes
will be drilled where exploratory cored holes are required
or downthe-hole hammer equipment is used.
All holes will be washed and pressure tested before grout-
i ng.Grout i ng wi 11 be done wi th Type II Port 1and cement
with 2 percent addition of bentonite (by weight of cement).
The water/cement ratio and grouting pressures will be
vari ed accordi ng to the cond it ions encountered.Grouting
will be carried out in stages using packers.Some redrill-
i ng between st ages wi 11 be requ ired.To allow greatest
flexibility of the schedule,most curtain grouting,which
will include up-hole grouting,will be done from the
galleries.In the inclined galleries special platforms
will be required for drilling and grouting equipment.
Primary grout holes will be treated as exploratory holes
and core drilled,with further core-drilled holes as
requi red to test the effect iveness of the grout ing.The
grout i ng program wi 11 be modi fi ed accordi ng to the rock
conditions encountered as the work proceeds.
Gallery Construction
The layout of the galleries are shown on Plate 10.It is
expected that the majority of the gallery length will not
require any support but from available geologic data it is
estimated that about 25 percent will require rock bolt and
shotcrete support.Steel arches may be requi red at the
portals and at tunnel junctions or in highly fractured or
sheared zones. A concrete slab will be cast in the tunnel
invert to provide an even working surface and to form the
drainage channel.
Measuri ng wei rs wi 11 be constructed in the drai nage chan-
ne 1sin order that the vo 1ume of seepage water may be
monitored.The seepage water wi 11 be discharged from the
gallery just above tai lwater level into drainage tunnels
extending to the downstream toe of the dam and discharging
below tailwater level to prevent icing up of the outlet.
Inspection access will be provided at the downstream toe of
the dam but from a separate portal above water level.
Light i ng for inspect i on of the gall eri es and venti 1ation
will be required when personnel are in the tunnels.The
fresh air intake during the winter must be heated to pre-
vent freezing of seepage water within the tunnels.Eleva-
tors and emergency stairs will be installed in the vertical
shafts and cable hoists will be installed in the inclined
tunnels for movement of equipment.
12-19
(e)Main Dam Embankment
The main dam will consist of a central compacted core protected by
fine and coarse fi lters on the upstream end downstream slopes.
The downstream outer shell will consist of rock fill and alluvium
gravel;and the upstream outer shell of clean alluvium gravel.A
typical cross section is shown on Plate 9.
(i)Comparison of Vertical and Inclined Cores
The des i gn of the embankment is dependent on the type of
core chosen,either a vertical core or an inclined core,
and its location,upstream or central in the embankment.
The advantages to each type of core are as follows:
-Vertical Core
Provides better contact with the foundation;
Provides slightly more thickness of core for the same
quantity of the core material;and
Settlement of the core will be independent of the post-
construction or seismic displacement settlement of the
downstream shell.
-Inclined Core
Can place 1arge proport i on of downstream shell before
placing core material;and
Can carry out foundation treatment during placement of
shell materi al.
The major disadvantages for each type of core are as fol-
lows:
Vertical Core
Placement of core material controls placement of filters
and shell materials;and
-Inclined Core
Excessive post-construction settlement or seismic dis-
placement of downstream shell may cause rupture of core;
and
Location of core may affect the upstream slope by requiring
a flatter slope for stability reasons.
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The proposed core material is a combination of glacial out-
wash and alluvial/fluvial deposits with a wide grain size
distribution.This material might tend to crack rather
than deform under tensi le stress and hence could be sus-
ceptible to erosion.For a sloping core there is a risk of
cracks developing in core constructed of nonplastic materi-
al because of lateral settlement or displacement during a
seismic event.
A central vert ica1 core was therefore selected for the
embankment based on a revi ew of precedent structures dis-
cussed above and the nature of the proposed impervious
materi a1.
Earthquake Resistance Design Features
Because of the apparent low plasticity of the material to
be used in the core and the requirement for an earthquake
resistant design,the following design features will be
incorporated into the main dam cross section:
-The core-foundation contact will be widened near the ends
of the embankment to ensure seepage control during normal
operating conditions and any seismic event.
-Th ick fi lter zones wi 11 be placed upstream and downstream
from the core to prevent breachi ng of the core from
either post-construction settlement and cracking or from
any cracking resulting from a seismic event.
-The filters will be designed to flow into and seal any
transverse cracks which might develop in the core,as a
result of either post-construction settlement or a seis-
mic event,thus preventing the formation of an open seep-
age path through the core.
-The downstream filters will be designed to be capable of
handling any abnormal flows which could result from
t ransverse-cracki ng of the core from post-construct ion
settlement or a seismic event.
-The proposed wi dth of the core wi 11 prevent archi ng of
the core caused by transfer of load to the shell or fil-
ter materials.
Compacted processed clean river alluvium gravel of high
permeability will be used to construct the upstream
outershell to minimize settlement displacement and the
build up of pore pressures during a seismic event,and to
ensure rapid dissipation of any pressures which may
develop.
12-21
Freeboard and Static Settlement
If for any reason the crest settles below 2210 feet,more
material should be added to maintain the safety margin of 5
feet to allow for seismic settlement.
The minimum required crest elevation of the Watana dam,not
including static and seismic settlement,was determined for
each of the following conditions:
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2185
17
2202
2202
3
2205
Probab 1e
Maximum
Flood
2185
8
2193
6
3
2202
3
2205
1:10,000
Year
Storm
2185
6
2191
6
3
2200
3
2203
1:50 Year
Storm
Minimum crest elevation
Elevation top of core
Ro adway th i ckness
Water elevation
This YS the lowest elevation acceptable for the dam crest
and allowances must be made for static settlement of the
dam following its completion,settlement on saturation of
the upstream shell,and possible settlement because of
seismic loading.It has not been possible to perform
detailed calculations at this time to determine the likely
settlements since little test data is available.
Wave runup allowance
Dry freeboard allowance
For purposes of this feasibility study,it has been assumed
that settlement due to seismic loading could be up to 0.5
percent of the height of the dam and the desi gn crest
elevation at the center of the dam is,therefore,shown at
2210.An allowance of 2 feet has been made at both abut-
ments and hence the design crest elevation rises from 2207
at the abutments to 2210 at the center.Under normal
operating conditions the minimum freeboard relative to the
maximum operating pool elevation of 2185 will be 22 feet at
the abutments and 25 feet at the center of the dam.
Normal maximum reservoir
e1evat ion
Storm surcharge
These elevations refer to the maximum section of the dam
and are based on a normal operating reservoir level of 2185
feet.The governing minimum crest elevation excluding
static and seismic settlement is seen to be 2205 feet at
the maximum section and at the abutments.
(iii)
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An additional allowance must also be made for post-con-
struction settlement of the dam under its own weight and
for the effects of saturation on the upstream gravel fill
when the reservoir is first filled.This allowance is not
shown on the drawings since it is not a permanent require-
ment.However,for initial estimating purposes,1 percent
of the height of the dam has been allowed.Hence,at the
end of construction the dam crest elevation at the center
of the dam would be at 2210 feet plus 9, or 2219 feet.The
additional height constructed into the dam would be
achieved by steepening both slopes above approximately
elevation 1850. This 1 percent allowance is conservative
when compared with observed settlements of similar
structures,and may be revi sed when more data is
available.
Further margin against overtopping of the main dam is pro-
vided by the emergency spillway.Under normal operation
this spillway is sealed by a fuse plug.or dam across the
entrance channel.This plug is simply a gravel dam with
special design of the core and strict control of the shell
materials to ensure that it will erode rapidly when over-
topped, allowing flood flows to be discharged freely down
the emergency spi llway.The location and typical cross
section through the fuse plug are shown on Plate 53.
(iv)Typical Cross Section
The typical cross section of the main dam is shown in Plate
45.The central core slopes are 1H:4V with a top width of
35 feet.The thickness of the core at any section will be
s 1ightly more than 0.5 times the head of water at that
section.Minimum core-foundation contact will be 50 feet
requiring flaring of the cross section at each end of the
embankment.
The upstream and downstream filter zones increase in thick-
ness from 15 or 30 feet near the crest of the dam to a max-
imum in excess of 60 feet.They are sized to provide pro-
tection against possible piping through transverse cracks
in the core that could occur because of settlement or re-
sulting from displacement during a seismic event.
The shells of the dam will consist of compacted alluvial
gravels.To minimize pore pressure generation and ensure
rapid dissipation during a seismic event,the saturated
upstream shell will consist of compacted clean alluvial
gravels processed to remove fines so that not more than 10
percent of the materials is less than 3/8-inch in size.
The downstream shell will consist of compacted unprocessed
alluvial gravels and rockfill from the excavations for
underground work,si nce it wi 11 not be effected by pore
pressure generation during a seismic event.
12-23
Protection against wave and ice action on the upstream
slope will consist of a 10 foot layer of riprap comprising
quarried rock between 18 and 36 inches in size.
The typical crest detail is shown in Plate 9.Because of
the narrowi ng of the crest dam,the fi lter zones are re-
duced in width and the upstream and downstream coarse fil-
ters are eliminated.A layer of filter fabric is incorpo-
rated to protect the core material from damage from frost
penetration and dessication,and to act as a coarse filter
where required.
(v)Core Material Properties
The core material will be obtained from Borrow Site D,
located on the right bank of the river,upstream from the
dam.The area consists of a series of glacial deposits
separated by alluvial and lacustrine deposits.A gener-
alized surficial stratigraphic column in Area D,based on
all investigations to date including seismic lines and deep
drilling,is given in Table 12.5.
Complete details of these deposits together with results of
laboratory test results are given in the 1980-81 Geotechni-
cal Report.
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-Compact ion:
Atterberg Limits:Liquid Limit -7 to 18
Plasticity Index -Non-plastic to 4.2
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127.6 pcf
10.4 percent
<3/4 inch
135.5 pcf
7.5 percent
Modififed Proctor Standard Proctor
Materia1
Maximum Dry Density
Optimum W/C
- Shear Strength:
-Permeability:
10-6 em/sec (test on <3/4 inch material,2 percent
wet of Standard Proctor optimum).
It is proposed that materials from the upper outwash,allu-
vial and fluvial deposits,designated C,D,E,and F in
Table 12.5,are blended to produce core material within the
gradation band indicated on Figure 12.5.The actual
grading curve for a composite sample used in the testing
program is shown in Figure 12.6 and the laboratory test
results are summarized as follows:
o =37°;c =0 (in terms of effective stresses,on mate-
rial 2 percent wet of Modified Proctor optimum).
-Pinhole dispersion test:non-dispersive
The natural water contents of samples tested ranged from 7
to 21 percent with an average in the range of 10 to 12
percent.Unit G (Table 12.5)includes clay layers with
relatively high plasticity and water contents in excess of
40 percent.Such materials cannot be blended with coarser
materi a1s to form a homogeneous materi a1,and Un i t Gis
not,therefore,considered suitable for inclusion in the
core materi a1s.
(vi)Excavation,Placement,and Compaction of Core Material
The borrow area wi 11 be excavated to a depth of approxi-
mately 30 feet working vertical faces.Processing and
blending of the material will be done during excavation.
Oversize material (greater than 6 inches)will be removed
by gri zzl i es or raked out of the fi 11 dur lng spreadi ng.
Frozen material will,where possible,be allowed to pro-
gressively thaw insitu,with a system of surface ditches to
accelerate drainage of the thawed materi al.Where t h i sis
not pract i cal for schedul ing reasons or other consi dera-
tions,the frozen material will be loosened by ripping or
blasting and hauled to a disposal area.
It is presently contemplated that the core material will be
placed in lifts of 8 to 12 inches compacted thickness with
the water content wet of optimum to a maximum of plus 3
percent.The f t nal requi rements for compacti on wi 11 be
based on field tests of the actual materials and compaction
equi pment.
(vii)Fine and Coarse Filter Materials
Fine and coarse filter material will be obtained from Bor-
row Site E. The required gradations of the fine and coarse
filter material to satisfy the following criteria are shown
in Figure 12.6:_
Criterion 1:The 15 percent (015)of a filter material
must be not more than five times the 85
percent size (085)of a protected soil.
Criterion 2:The 15 percent slze (015)of a fi lter mate-
rial should be at least five times the 15
percent size (015)of a protected soil.
Criterion 3: The 50 percent size (050)of a filter materi-
al must be not more than 25 times the 50
percent size (050)of a protected soil.
12-25
Permeability of the fine filter and coarse filter is esti-
mated to be greater than 1 em/sec and 10 em/sec,respec-
tively.Permeability will be verified by large scale field
or laboratory tests.
The fine and coarse fi lter materi als have been assumed to
have an angle of shearing resistance in terms of effective
stresses (0)of 35°for the purposes of these studies.
Actual properties will be determined from large scale
triaxial tests and/or modeling the gradation for standard
triaxial tests for final design.
(viii)Excavation,Placement,and Compaction of Filter Material
The borrow areas wi 11 be developed utilizing scrapers and
draglines.Material will be processed by screening and
blending using wet screening methods.Any oversized
material will be either used as an aggregate source or
in the outershell of the dam.
The method of placement and compact i on wi 11 depend on the
results of field tests to be done prior to construction
using the proposed equipment and materi also It has been
assumed that 12-i nch 1i fts wi th four passes of a 1arge
vibratory roller will provide the required compaction.
(i x) Alluvial Fi 11 Material
The alluvial fill will be obtained from Borrow Sites E and
I.The upstream shell of the dam will be constructed using
processed alluvial gravel and the downstream shell of un-
processed alluvial fill material mixed with rock from the
various excavations,when available.Any oversized materi-
al will be either used in the riprap zones or crushed for
concrete aggregate.
The required grading limits for the upstream shell are
shown in Figure 12.5.The downstream shell material will
not r-equire processing.
On the basis of the proposed operation,the permeability of
the processed alluvial fill in the upstream shell is esti-
mated to be greater than 100 em/sec.
An angle of shearing resistance in terms of effective
stresses of 35°has been assumed for the all uv ia1 fi 11
materi a1.
Actual properties will be determined from large scale tri-
axial tets and/or modeling the gradation for standard tri-
axial tests for final design.
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(x)Excavation,Placement,and Compaction of Alluvial Fill
Materials
The alluvial fill material will be obtained from the main
dam foundation excavation and from downstream from the dam.
Excavation will likely be by scraper operations above the
water table and dragline operation below the water table to
a max i mum depth of 50 feet.The materi a1 wi 11 have to be
processed to remove the undersized and oversize materi a1
for the upstream shell .
All material in the shells must be well compacted to mini-
mize post-construction settlement and seismic slumping.
The method of placement and compaction will be based on the
results of test fills but it has been assumed that 24-inch
lifts for alluvium fill material with four passes of a
1arge vibratory roller wi 11 provide the required compac-
tion.
(xi)Rip-Rap Material
The rip-rap material (slope protection)comprising exca-
vated rock 18 to 36 inches in size,will be obtained from
the oversize material from the various borrow areas,Quarry
A and any other rock excavations.The rip-rap materi al
will be placed on the upstream slopes and in certain areas
on the downstream slopes of the dam exposed to wave and ice
action.
(f)Stability Analysis
(i)Methodology
Static and dynamic stability analyses were performed to
confirm the stability of the upstream and downstream slopes
of the Watana dam.The analyses indicated stable slopes
under all conditions for a 2.4 horizontal to 1.0 vertical
upstream slope and a 2.0 horizontal to 1.0 vertical
downstream slope.
The static analyses were done using the STABL computer
program developed to handle general slope stabi lity prob-
lems by adaptation of the Modified Bishop method,and a
finite element program for static analysis of earth and
rockfill dams (FEADAM)to determine the initial stresses in
the dam during normal operating conditions.The detailed
results and conclusions from both the static and dynamic
analyses are given in Appendix B.
The dynamic analyses were done using the QUAD 4 finite ele-
ment program which incorporates strain dependent shear
modulus and damping parameters.The design earthquake for
the dynamic analyses was developed for a Benioff zone
event.
12-27
The assessment of the stat ic and sei smi c response of the
Watana dam for the stat ic and postul ated sei smi c loadi ng
involved the following:
-Finite Element Model
The finite element model consisted of 20 layers of ele-
ments with 546 nodes and 520 elements.Different soil
parameters as described in the following sections were
chosen for the core,transition material,and the shell
material.The transition material comprised the fine and
coarse filter lones.
-Static Analysis
The slope stability analyses were done using the STABL
computer program for the general solution of slope sta-
bility problems by a two-dimensional limiting equilibrium
method. The calculation of the factor of safety against
instability of a slope was performed by an adaptation of
the Modified Bishop method of slices which aJlows the
analysis of trial failure surfaces other than those of a
circular slope.Soil properties used in the analysis are
given in Table 12.6.
The calculated factors of safety are in the range of 1.7
to 2.2 indicating no general slope stability problems
under static loading.
Further analysis,using the finite element program for
static analyses of earth and rockfi 11 dams (FEADAM),
determined the initial stresses in the dam during normal
operating conditions.The program calculates the
stresses,strains,and displacements in the dam simu-
lating the actual sequence of construction operations.
Two analyses were performed to show the effects of
relatively soft versus stiff core material.
s
The dynamic analysis was done using the QUAD 4 computer
program. The initial values of shear modulus and damping
ratio used in the analyses were derived from typical
values available in Banerjee et al (1979) and are as
follows:
Damping Shear
ZONE K2 Type Curve
Core Materi a 1
-Soft 90 sand
-St iff 120 sand
12-28
I.)
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-Piezometers
Instrumentation
sand
sand
150
180
Transition Material
Shell Material
Taut-wire arrangements.
Cross-arm devices .
.Inclinometers.
Strain meters.
.Hydraulic-settlement devices of various kinds.
Various versions of the taut-wire devices which have been
developed to measure internal settlement .
12-29
Stress meters.
Surface monuments and alignment markers.
Seismographic records and seismoscopes.
Flow meters to record d i scharge from drai nage and pressure
relief system.
The design earthquake time history was developed by Wood-
ward-Clyde Consultants and is shown in Figure 12.8.The
significant features are as follows:
Piezometers are used to measure static pressure of fluid in the
pore spaces of soil,rockfill and in the rock foundation.
-Magnitude 8.5 Richter;
- Location 25 miles (40 km)from the site (Benioff
Zone);
-Maximum acceleration of 0.55g;
- Duration of strong motion - 45 seconds;and
-Significant number of cycles - 25.
Cross-arm settlement devices as developed by the USBR.
-Internal Horizontal Movement Devices
- Other Measuring Devices
-Internal Vertical Movement Devices
Instrumentation will be installed to provide monitoring during
construction as well as during operation.Instruments for measur-
ing internal vertical and horizontal displacements,stresses and
strains,and total and fluid pressures,as well as surface monu-
ments and markers will be installed.The quantity and location
will be decided during final design.Typical instrumentation is
as follows:
(g)
(h) Conclus1ons
The stat1c stabil1ty of the embankment was assessed by comparing
the 1nduced stresses at any locat 1on with the shear strength
avai lable within the materi al.The results of the analyses for
both the soft and st1ff core cases indicate no failure zones and a
more than adequate st at lc factor of safety for all cases con-
s i dered.Vert1cal and conf1ning stresses from the analyses show
the expected results cons1dering the reservo1r load and the
var1ation 1n materials within the dam.
The se1sm1c stab1l1ty of the embankment was assessed by comparing
the Induced dynamic stresses at any location with the available
st at i c stresses.The results of the analyses indicate limited
zones of shear stress exceedance adjacent to the toe of the up-
stream shell,near the upstream crest,and on the surface of the
downstream shell.However,these are 1oca 11 zed zones not extend-
ing 1nto the embankment,and overall stability will not be jeopar-
dized.The results of the analyses are presented in Appendix B.
12.7 -Rel1ct Channel Treatment
(a)Site Cond1t1ons
Earl1er studies 1dent1f1ed a buried channel runn1ng from the Su-
sitna River gorge immediately upstream from the proposed damsite
to Tsusena Creek, a d1stance of about 1.5 m1les.A boring by the
Corps of Engineers penetrated 454 feet of glacial deposits over-
lying bedrock wh1ch was encountered at El evat i.on 1775, while the
surface elevation of the lowest saddle 1S approximately 2205.
Additional 1nvestigations dur1ng the current study further delin-
eated the channel,and full details are given in the 1980-81 Geo-
technical Report.The channel represents a potent i al source of
leakage from the Watana reservoir.Along the buried channel thal-
weg,the highest bedrock surface 1S some 450 feet below reservoir
level,while along the shortest leakage path between the reservoir
and Tsusena Creek the highest rock surface is some 250 feet below
reservoir level.The maximum hydraulic gradient along the buried
charirieTffom the·e~d-g-e (Jfp-oolto-TSTJSena-~ereekisapprox+mately9
percent,while between existing riverbed levels it is about 6 per-
cent.There are surface lakes with1n the channel area,and while
some drill holes encountered artesian water,others penetrated
highly permeable zones resulting in complete loss of drilling
fluid.Zones of permafrost have also been identified throughout
the channel area.
Although the glacial h1story of the area 1S not clearly under-
stood,a sequence of events has been postul ated 1n the 1980-81
Geotechnical Report,based primarily on the invest1gation of the
Borrow Site D adjacent to the buried channel.The generalized
surfic1al strat1graphic column is given in Table 12.5.
12-30
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Of particular relevance to the buried channel problems are the
alluvium at the base of the channel,encountered in one deep bore-
hole between 292 feet and bedrock at 454 feet below ground,and
the unconsolidated outwash,alluvial and fluvial deposits.The
deep alluvium offers a potential leakage path,its high permeabil-
ity being indicated by loss of drilling fluid,while the unconsol-
i dated,primari ly sandy deposits may be subject to 1i quefact ion
following saturation.
(b)Potential Problems
The major potential problems associated with the buried channel
are leakage,both surface and subsurface flows;piping at down-
stream outlets to Tsusena Creek;the impact of permafrost and the
long-term effects as heat from the reservoir thaws the ground
through the channel area;and instability of soil slopes on sat-
uration,thawing,or seismic loading leading to a breach of the
rim of the reservoir.
(i)Surface Flows
During the study of alternative layouts for Watana,the
maximum operating reservoir level was higher than the
critical ground elevation of 2205 in the buried channel
area.These layouts,therefore,incorporated a saddle dam
about 40 feet high and 2,500 feet long across the critical
section of the channel.The foundation conditions for such
a saddle dam are not well defined at this time but because
of the variable nature of the glacial deposits,the effects
of permafrost and potential for liquifaction within the
foundation were addressed.It was concluded,however,that
in any event there was a strong possibility that settle-
ment of such a dam could not be adequately controlled and
there would be a real risk of transverse cracking occurring
through the dam.With the reservoir level above ground
surface,any such cracking could lead to 8urface flows and
subsequent channeling through the unconsolidated deposits.
(ii)Subsurface Leakage
No field permeability tests have been conducted,but it is
anticipated that the total subsurface leakage will be rela-
tively small and economically insignificant.For example,
if the average permeability of all material in the channel
were 10-
2 cm/sec,the total leakage flow would be less
than 100 cubic feet per second.By inspection of the grad-
ing curves,the actual permeability is certainly less than
10-2 cm/sec,except possibly in the channel bed alluvi-
um,Unit K,Table 12.5,and a more realistic leakage flow
would be about 10 cubic feet per second.The capital value
of this leakage,in terms of lost energy,is about $4
12-31
million.However,any leakage may be concentrated in the
discharge zone in Tsusena Creek,and there is potential for
piping which could lead to large-scale erosion cutting back
to the high ground forming the rim of the reservoir.
(iii)Permafrost
Thawing of permafrost will result in higher seepage rates
and possibly settlement of the surface as excess water
drains from the thawed soils.
(iv)Liquefaction
Filling the reservoir will lead to the saturation of some
of the glacial deposits within the buried channel area,
including the upper slopes of the Susitna River valley,and
produce the potent i al for l t quefact i on of these deposits
under seismic loading.Under extreme circumstances,lique-
faction could lead to mass movements of so i ls into the
reservoi r and breach of the reservoi r r i min the area of
the freeboard dike.
For this situation to occur,it would require a large,con-
tinuous deposit of loose,saturated,granular material with
sufficient ground surface slope so that the soil above the
liquefied zone would move under its own weight.Although
such a scenario is considered most unlikely,the investiga-
tions to date are not sufficiently detailed to preclude the
possibility.In view of the potentially catastrophic
failure that would result from a breach of the reservoir
rim,further investigations must be carried out prior to
construct i on to confi rm the strat i graphy and provi de ade-
quate data to properly assess the need for and desi gn of
remedial treatment.
(c)Remedial Measures
Since the stability of the section of the buried channel forming
the rim-aT theWatana reservoir i sessent i al .for the feasibility
of the Watana development as outlined in this report,practical
solutions to all possible scenarios,including extreme combina-
tions of the problems outlined above, must be identified.
(i)Surface Flows
To eliminate the potential problems associated with settle-
ment and breach of a saddle dam allowing surface flows
through the buried channel area,the maximum operating
level of the reservoir has been lowered to 2185 feet
leaving a width of at least 1,500 feet of "dr y"ground at
the saddle above this elevation.A freeboard dike with a
crest elevation of 2210 is required to provide protection
12-32
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against extreme reservoir levels under probable maximum
flood conditions.The shortest distance between the toe of
the dike and the edge of the Elevation 2185 reservoir pool
is at least 450 feet,and under PMF flood,the water level
w111 just reach the toe of the d1ke.
(ii)Subsurface Flows
Progressive piping and erosion in the area of discharge
into the Tsusena Creek will be controlled by the placement
of properly graded granular materials to form a f i l t er
blanket over the zones of emergence.Field i nves t lqat l on
will be carried out to define critical areas,and only such
areas will be treated.Continuous monitoring of the outlet
area will be necessary,since it may take many years for
equi 1ibri um with respect to permafrost to become est ab-
lished in the buried channel area.
If the permeab 11 i ty of the base all uv i um is found to be
excessive,grouting of the upstream inlet zone could be
carried out to reduce the total leakage.
(1i 1)Permafrost
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Thawing of permafrost will occur that may have an impact on
subsurface flows and ground settlement.No specific reme-
dial work 1s necessary,but flows,ground water elevation,
and ground surface elevation in the buried channel area
must be monitored and any necessary maintenance work
carried out to maintain freeboard and control seepage dis-
charge.
(iv)Liquefaction
To guarantee the integrity of the reservoir rim through the
channel area requires that either:
- There is no potential for a liquefact10n slide into the
reservoir which could cut back and breach the r1m,or
-If there is such potent1al,there is a sufficient volume
of stable mater1al at the crit1cal section that even if
the upstream materials were to slide into the reservoir,
the fai lure zone could not cut back to the reservoir
rim.
Any remedial treatment required will depend on the location
and extent of cr1t1cal zones and could range from stabili-
zation by comp act i on (vibroflotation)or grout1ng tech-
n i ques,either cement or chemical grouting,or in the
11mit,removal of material.
12-33
The stratigraphic column 1ndicates that the two lower till
deposits I and J have been overconsolidated by glaciat10n,
and it is unlikely that these deposits could liquefy under
any circumstances.The overlying Unit H is a medium fine
sand wi th silt and is probably the most susceptible to
l i quet act i on of all the materials sampled. This unit has
been 1dentif1ed up to 40 feet thick in places,with the top
of the layer est1mated to be about 100 feet below ground
surface at the deepest point,as shown in the 1980-81 Geo-
technical Report.All materials above th t s unit are nor-
mally consolidated water-lain till,outwash,alluvium,and
fluv1al deposits which could include zones of cr i t i cal
materials.
There are 1nsuffic1ent data ava1lable to 1dent1fy the full
extent of such cr t t i cal materials;hence,It i s not poss-
i ble to precisely deflne the remed1al work necessary at
this time.Available alternative methods include:
-Densification
Layers within about 100 feet of the surface could be com-
pacted by vibroflotation techniques to eliminate the risk
of liquefact10n and provide a stable zone.
-Stab111zation
Critical layers at any depth could be grouted,either
with cement for fine gravels and coarse sands or by chem-
ical grouting for f1ne sands and silts.
-Removal
This could range from the replacement of cr1tical materi-
al near the valley slopes with high-quality,processed
material,which would stabilize the toe of a potential
slide and so prevent the 1nitiation of failure that might
otherw1 se cut back and cause major f cl.1lUres,to the ex-
··caljation~·blendtn-g;'-and--rep-l-acement-of-+arge volumes of
material to provide a stable zone.
The ultimate treatment w1ll be based on an engineering and
cost analys1s study of the appropr1ate alternatives during
the design phase of the project when the site conditions
have been more closely defined.However,to confirm the
technical and overall financ1al feasibility of the project
at this t1me,it is necessary to cons1der a solut10n to the
worst conditions deemed poss1ble.
On the basis of ava1lable data,such conditions are:
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- That the alluvium Unit H encountered between elevations
2100 and 2140 in drill hole DR22 is a homogeneous loose,
silty,fine sand.
-Th at it is of 1arge areal extent and cont i nuous from
beyond the saddle out to the Susitna valley slopes.
- That is of such thickness that a failure plane could be
contained fully within its boundaries.
With these conditions,liquefaction of the unit under
seismic loading following saturation from the reservoir
could result in the overlying material sliding on the
liquefied zone into the reservoir.
Catastrophic failure would develop if the back scarp of the
failure surface through the overlying materials broke
ground surface on the downstream-side of the saddle below
reservoir water level.
The most positive solution to such a situation would be the
replacement of the critical zone with material that would
not liquefy.This would involve,in effect,the rearrange-
ment of the in-place materials to create an underground dam
sect i on constructed of se 1ected materi a 1s founded on the
dense till layer beneath the critical alluvium.Such an
operation would require the excavation of a trench up to
135 feet deep with a surface width up to 1,000 feet.
Selected materials would be compacted to form a central
stable zone while surplus and unsuitable materials would be
placed on both sides of this central "dam"to complete
backfilling to ground surface.The central zone would,be
designed to remain stable in the event that all material
upstream did slide into the reservoir.Preliminary esti-
mates indicate that such a structure would need to be about
5,000 feet long, with a total cut volume of about 13
million cubic yards,of which 4-112 million cubic yards
could be used in the compacted center zone.The cost of
such work is est imated to be about $100 mi 11 ion.The need
of such expenditure is considered to be most unlikely and
is deemed to be covered by the overall project contingency
cost.
(d)Further Investigations
Additional site investigations are necessary in the relict channel
area to more closely define the following:
-Confirm and/or refine the stratigraphy throughout the area.
-Thickness,extent,density,continuity,and permeability of the
alluvium identified in DR22 immediately above bedrock.The
12-35
investigations should include pumping tests and possibly dye in-
jection tests to check the continuity of this unit along the
buried channel,since this is deemed to have the greatest
potential for leakage.
-Dens ity of the lowest till 1ayers I and J wh i ch have been sub-
jected to overconsolidation by glaciation,to confirm that they
would not liquefy under earthquake loading.
-Density,gradation,extent,and continuity of the sandy silt
alluvium,Unit H.
- Extent of any other units which may be subject to liquefaction.
-Conditions in the outlet area of the relict channel into Tsusena
Creek.
-Ground water regime throughout the channel area with particular
reference to the source of artesian or confined aquifers and the
drainage outlets from such aquifers.
12.8 -Outlet Facilities
The primary function of the outlet facilities will be to discharge
floods with recurrence frequencies of up to once in 50 years after they
have been routed through the Watana reservoir.Downstream erosion will
be minimal and the dissolved nitrogen content in the discharges will be
restricted as much as possible to avoid harmful effects on the down-
stream fish population.A secondary function of outlet facilities will
be to provide the capability to rapidly draw down the reservoir during
an extreme emergency situation.
The facilities will be located on the right abutment, as shown on Plate
18,and will consist of an intake structure,pressure tunnel,and an
energy dissipation and control structure housing six fixed-cone valves
which will discharge into the river 100 feet below.
(a)Approach Channel and Intake
The approach channel to the outlet facilities will be shared with
the power intake.The channel will be 400 feet wide and excavated
to a depth of approximately 150 feet in the bedrock with an invert
elevation of 2010.The intake structure will be founded deep in
the rock at the end of the channel.The single intake passage
will have an invert elevation of 2012.It will be divided
upstream by a central concrete pier whi ch wi 11 support steel
trashracks located on the face of the structure,spanni ng the
openings to the water passage.The racks wi 11 be mounted in
vertical guides and can be raised and lowered for cleaning and
maintenance by a mobile gantry crane monitored at deck level.
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Downstream of the racks,located between the pier and each of the
sidewalls,will be two fixed wheel gates operated by a mechanical
hoist mounted above the deck of the structure.The purpose of the
fixed wheel gates will not be to control flows through the outlet,
but to isolate the downstream tunnel to allow dewatering for main-
tenance of the tunnel or ring gates located in the discharge
structure.Stoplog guides will be provided just upstream of the
two fixed wheel gates to permit dewatering of the structure and
access to the gate guides for maintenance.
(b)Intake Gates and Trashracks
The gates will be of the fixed wheel vertical lift type with down-
stream skinplate and seals.The nominal gate size will be 18 feet
wide by 30 feet high.Each gate will be operated by a single drum
wire rope hoist mounted in an enclo~ed tower structure at the top
of the intake.The height of the tower structure will permit
raising the gates clear of the intake concrete for inspection and
maintenance.
The gates will be capable of being lowered either from a remote
control room or locally from the hoist area.Gate raising will be
from the hoist area only.
The trashracks will have a bar spacing of about 7 inches,and will
be designed for a maximum differential head of 40 feet.The maxi-
mum net velocity through the racks wi 11 be about 6 ft/s.Provi-
sion will be made for monitoring the head loss across the trash-
racks.
(c)Shaft and Tunnel
Discharges will be conveyed from the upstream gate structure by a
concrete-lined tunnel terminating in a steel liner and manifold.
The manifold will branch into six steel-lined tunnels which will
run through the main spillway flip bucket structure to the fixed
cone valves mounted on the downstream face.
The water passages wi 11 be 28 feet in diameter up to the steel
manifold.The upstream concrete-l ined portion wi 11 run a short
distance horizontally from the back of the intake structure before
dipping at an angle of 55° to a lower level tunnel of similar
cross section.This angle of 55°is considered the flattest slope
at which the tunnel can be "self-mucking"during construction.
The lower tunnel will run at a gradient of 1:10 to the point where
the overlying rock is insufficient to withstand the large hydro-
static pressure which will occur within the tunnel.Downstream of
this point the tunnel will be steel lined.The steel liner will
be 26 feet in diameter and surrounded by mass concrete filling the
space between the liner and the surrounding rock.The area be-
tween the outs ide face of the 1i ner and the concrete wi 11 be
grouted to fill all voids and reduce external ground water pres-
sure build up.
12-37
The majority of the tunnel length is on bearing 065 0
•This align-
ment is intersected by Joint set II at acute angle of about 10
0
•
This may cause some greater than normal overbreak but conventional
support measures will be sufficient for stability.
At the upstream end,the tunnel parallels the trend of the main
shear and fracture zones and is intersected by a mi nor fract ion
and shear zone some 80 feet wide. The tunnelling over this length
is expected to be difficult.Extensive rock bolting and shotcrete
or steel sets will be required.
For hydraulic consideration the tunnel is required to be concrete
1 ined.
A rock pillar width of 1.0 times excavated diameter is required.
With this spacing requirement considerable control and care will
have to be exercised in this section of the tunnel.Steel set
support will be required through this section and the manifold
tunnel.
The portal is located in a shear and fracture zone.Extensive
rock support will be required both on the portal face and within
the tunnel.
Steel arch support wi 11 probably be required in the first 50-100
feet of tunnel,depending on the extent of the shear and fracture
zone.
The excavation will probably be carried out by driving a pilot
tunnel first and enlarg ng to full size.
Upstream from the discharge structure the liner will terminate in
a steel manifold with six parallel 8 foot diameter steel-lined
branches.These wi 11 cont inue through the back face of the di s-
charge structure,and terminate in fixed cone discharge valves
mounted at the downstream end of the structure.
(d)Discharge Structure
The concrete di scharge structure is shown on Pl ate 17.It wi 11
form the fl iP bucket for the mai n spi llway and wi 11 house the
fixed cone valves and individual upstream ring follower gates.
The valves will be set with a centerline elevation of 1560 and
will discharge into the river approximately 105 feet below.
Openings for the valves will be formed in the concrete and the
valves will be recessed within these openings sufficiently to
allow enclosure for ease of maintenance and heating of the move-
able valve sleeves.An access gallery upstream from the valves
will run the length of the discharge structure,and will terminate
in the access tunnel and access road on either side of the struc-
ture.Housing for the ring follower gates will be located up-
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stream from the fixed cone gate chambers.The ring follower gates
will operate in the steel liners and will serve to isolate the
discharge valves.A common monorail hoist will be located above
each valve and gate assembly to provide for their removal and
transportation to the access gallery.
Fixed Cone Discharge Valves
Eight 78-inch diameter fixed-cone discharge valves will be in-
stalled at the downstream end of the outlet manifold,qenerally as
shown on Plate 17.The valves were selected to be within current
experience,considering the valve size and operating head (see
Figure 12.20).The fixed-cone valves are a further development of
Howell Bunger valves with the cone support vanes of the fixed-cone
valve extending further upstream and are more streaml ined.The
valves have a slightly higher discharge coefficient than Howell
Bunger valves and are less prone to vibration.During final
design,careful consideration must be given to prevent vibration.
Considerable research will be carried out concerning experience
and design of existing installations,and model tests will be
necessary to help ensure satisfactory valve operation.
The valves will be operated either by two hydraulic cylinder
operators or by a screw stem hoist.For preliminary design
purposes,hydraul ic operators have been assumed.The valves may
be operated either locally or remotely.
In sizing the valves it has been assumed that the valve gate
openi ng wi 11 be restri cted to 80 percent full stroke to reduce
vibration.
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(f)Ring Follower Gates
A ring follower gate will be installed upstream of each valve and
will be used:
-To permit inspection and maintenance of the fixed-cone valves;
-To relieve the hydrostatic pressure from the fixed-cone valves
when they are in the closed position;and
-To close against fl owi ng water in the event of mal funct ion or
failure of the valves.
The ring follower gates will have a nominal diameter of 90 inches
and will be designed to withstand a total static head of about 630
feet.Existing large diameter high head ring follower gates are
summarized in Table 12.6.
The ring follower gates will be designed to be lowered under flow-
ing water conditions and raised under balanced head conditions.A
grease injection system will be installed in each gate to reduce
fri ct iona 1 forces when the gates are operated.The gates wi 11 be
operated by hydraulic cylinders from either a local or remote
location.
12-39
(g)Discharge Area
Immediately downstream of the discharge structure,the rock will
be cut at a slope of 2H:3V to a lower elevation of 1510.This
face will be heavily reinforced by rock bolts and protected by a
concrete slab anchored to the face.The lower level will consist
of un1ined rock extendi ng to the ri ver.Because of the high
degree of di spers ion of the disch arges and the infrequency of
operation of the valves,it is anticipated that erosion will not
be a problem.
12.9 -Main Spillway
(a)General
The main spillway will provide discharge capability for floods
.exceeding the capacity of the outlet facilities.The combined
total capacity of the main spillway and outlet facilities will be
sufficient to pass routed floods with recurrence frequencies up to
once in 10,000 years.
The main spillway,shown on Plate 14,is located on the right
abutment and consists of an approach channel,a gated ogee control
structure,a concrete-lined chute,and a flip bucket.
The spillway is designed to discharge flows of up to 115,000 cfs
with a corresponding reservoir e levat i'on of 2192. The total head
dissipated by the spillway is approximately 730 feet making it
among the wor lcs highest.A major concern with large spillways
is the total energy to be dissipated during discharge.It is to
be noted that there are a number of spi llways wi th energi es of
discharge several times higher than that at Watana.
A comparable spillway in North America is that at the Mica Project
on the Columbia River in British Columbia. This spillway was con-
structed in 1974 and has operated successfully at flows approach-
ing its design flow with only minor damage occurring in the upper
part of the chute.A comparison of data for the two schemes is
Tota 1 Head
Reservoir to Energy
Di scharge .to Tai lwater Dissipated
(cfs)(ft )(MW)
Watana 115,000 730 6,700
Mica 150,000 600 7,300
(b) Approach Channel and Control Structure
The approach channel is excavated to a depth of approximately 100
feet into rock.It is adjacent to the power facilities approach
channel,and in order to minimize its length,it is integrated
with the power channel.
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The control structure is a mass ive concrete structure set at the
end of the approach channe 1.Flows are contro 11 ed by three 47
feet high by 36 feet wide vertical lift gates.As shown on Plate
15, each gate is contained within a separate unit consisting of an
ogee overflow weir,pier,and a partially precast integral roadway
deck.The units are of individual amonolithic structures
separated by construction joints.
Model tests will be necessary during the final design stage to
dotermine final geometry and dimensions of the control structure.
The structure will be located adjacent to the right dam abutment
in 1ine wi th the dam crest.The mai n access route wi 11 pass
across the spillway deck and along the crest.
The approach channel is located to the south side of the intake
structure and intersects the intake channel upstream of the intake
structure.The rock cuts up to 100 feet in height should be
excavated to 1H:4V slopes.Only localized rock bolting and shot-
crete support will be required.
The structure is to be founded on sound rock. Since the excava-
tion is likely to extend well into sound rock,consolidation
grout i ng is not antici pated to be requi red.However shear or
fracture zones passing through the foundation may require dental
excavation,concrete backfill and/or consolidation grouting.The
slope of the contact surface between the dam core and the spillway
control structure is required to be 1H:3V to ensure sufficient
contact stress and therefore prevent leakage.
The mai n dam grout curtai nand drai nage system wi 11 pass beneath
the structure.Access to the grouting tunnels will be via a shaft
within the structure and a gallery running through the ogee weir.
(c)Spillway Gates and Stoplogs
The three spillway gates will be of the fixed wheel vertical lift
type operated by double drum wire rope hoists located in an en-
closed bridge structure.The gate size has been selected as 36
feet wide by 47 feet high,including freeboard allowance.The
gates will have upstream skinplates.The seals will be totally
enclosed to permit gate heating in the event that winter operation
is necessary.Provision will also be made for heating the gate
guides.
The height of the tower and bridge structure will permit raising
of the gates above the top of the spillway pier for gate inspec-
tion and maintenance.
An emergency gasoline engine will be provided to enable the gates
to be raised in the event of loss of power to the spillway gate
hoist motors.
12-41
Stoplog guides will be installed upstream of each of the three
spillway gates.One set of stoplogs will be provided to permit
servicing of the gate guides.
(d)Spillway Chute
The control structure will discharge down an inclined chute that
tapers slightly until a width of 80 feet is reached. A constant
width of 80 feet is maintained over the remainder of its length.
Convergence of the chute walls wi 11 be gradual to minimize any
shock wave development.
The maximum depth of overburden in the area of the spillway is
generally 20 feet.The depth of overburden in boreholes BH-l,3,
4 and DH 10 and 11 average 12 feet.Seismic line 80-2 indicates
an overburden thickness of 15 to 20 feet.
Weathering of the rock surface is generally only slight to moder-
ate and poor rock qualities and RQD values less than 50 percent
exist up to 15 feet below top of rock.However towards the lower
end of the spillway chute,surface features indicate minor shears
and fracture zone and the depth to sound rock is expected to be up
to 50 feet or more in places.
The spillway foundation is intersected by several shear and frac-
ture zones up to 60 feet wide.Joint sets I, II and III mapped in
the spillway area are all vertical or near vertical.
The structure wi 11 requi re to be founded on sound rock. Areas
where shear and fracture zones extend for considerable depths may
require dental excavation and backfilling with concrete.
The major joint sets in the area of the spillway are generally
vertical or steeply dipping.Stability of the rock slopes on the
south side of the excavation are not generally a problem.How-
ever,towards the downstream end of the chute the rock condition
on the north side deteriorates towards the "Ff nqerbust er-",An
overall excavation slope for this area of IH:4Vhas been adopted.
_Theexcavated filc::es'\:Q be~ubseguent ly~g_\l~g(:LwU1L cOY1c::ret~c::i11J
be excavated vertical or near vertical.Joint set II parallels
the excavation and joints sets I and III could give rise to some
wedge instability.An allowance has accordingly been made for
rockbolt support over 24 percent of the face area.
The chute section will be rectangular in cross section,excavated
in rock,and 1i ned wi th concrete anchored to the rock.Adequate
underdrainage of the spillway chute is essential for stability of
the structure.Uplift pressure will develop from reservoir
seepage under the control structure,from ground water and seepage
from the high velocity flows within the spillway itself.Seepage
from the spillway flow will generate high pressure within the rock
through cracks in the concrete and wi th sudden c 1osi ng of the
spillway gates,residual unbalanced water pressures under the slab
wi 11 result.
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An extensive drainage system is therefore proposed.The dam grout
curtain and drainage system is continued under the spillway
control structure utilizing a gallery through the mass concrete
rollway.A system of box drains on the rock surface under the
concrete slab in a herringbone pattern at 20 feet spacing is
proposed for the entire length of the spillway.To avoid blockage
of the system by freezing of the surface drains a drainage gallery
is proposed at 30 feet depth into rock over the entire length of
the spillway.Drain holes from the surface drains will intersect
the gallery.
Since complete drainage of the underside of the slab cannot be
assumed,some freezing or blockage of the drains could occur at
some time.Additional resistance to uplift pressure must there-
fore be provided by rock anchors.To ensure adequate foundation
quality for anchorage,consolidation grouting is proposed to a
depth of 20 feet.This grouted zone will also restrict seepage
below the spillway and improve the quality of the flip bucket rock
foundation.
Drainage holes drilled into the base of the high rock cuts will
ensure increased stability of excavations.
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(e)
Provision will be made at four locations along the chute
the flows and prevent cavitation of the concrete floor.
will be attained by means of a small inclined step with
drawn from a transverse lower gallery.
Flip Bucket
to aerate
Aeration
air being
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The funct ion of the fl iP bucket wi 11 be to di rect the spi llway
flow clear of the spillway and well downstream into the river
below.The jet issuing from the flip bucket will be partly dis-
persed during its passage through the air with a corresponding
loss of energy.The remainder of the energy will be dissipated on
impact in the plunge pool.
A mass concrete block wi 11 form the fl ip bucket for the main
spillway.Final geometry of the bucket,as well as dynamic pres-
sures on the floor and walls of the structure,will be determined
by model studies.Although the structure shown on Plate 17 shows
a simple,cylindrical type of bucket,it it is foreseen that a
more effective,dispersive type bucket will be developed during
model tests.
12.10 - Emergency Spillway
The emergency spillway will be located on the right .side of the river
beyond the mai n spi llway and power intake structure (see Pl ate 20).
The emergency spillway will consist of a long straight chute cut in the
rock and leading in the direction of Tsusena Creek.An erodible fuse
12-43
plug,consisting of fine gravel materials,will be constructed at the
upstream end. The plug will be designed to wash away when overtopped,
releasing flows of up to 160,000 cfs in excess of the combined main
spillway and outlet facility capacities,thus preventing overtopping of
the mai n dam.
(a) Fuse Plug and Approach Channel
The approach channel to the fuse plug will be excavated in rock
and will have a width of 310 feet and invert elevation of 2170.
The mai n access road to the dam and powerhouse wi 11 cross the
channel by means of a bridge.The fuse plug wi 11 close the
approach channel,and will have a maximum height of 31.5 feet with
a crest elevation of 2201.5 feet.The plug will have a core up to
10 feet wide,steeply inclined in the downstream direction,with
fine filter zones upstream and downstream.It will be supported
on a downstream erodible shell of crushed stone or gravel up to
1.5 inches in diameter.The crest of the plug will be 10 feet
wide and wi 11 be traversed by a 1.5 foot deep pi lot channel.The
principle of the plug is based on erosion progressing rapidly
downward and laterally from the pilot channel as soon as it is
overtopped.
The channel section at the fuse plug is considered as a broad
crested weir.A gated control structure was considered as an
alternative to the fuse plug,but this would give higher construc-
tion and maintenance costs and would not provide an discharge
response like plug.
Water'velocities in the approach channel are expected to be in the
order of 30 ft/s but will occur very infrequently,if ever,during
the life of the project.
Localized rock bolting only will be required and rock slopes of
IH:4V will be used.
(b)Discharge Channel
.Ihe rock channe 1 downstreamoft.befu.s.e.pJ.u9_wJJJ..JJ.ar.r.o.w__t,o..200
feet and continue in a straight line over a distance of 5,000 feet
at gradi ent s of 1. 5 percent to 5 percent in the direct ion of
Tsusena Creek.The flow will discharge into a small valley on the
south side of and separated from relict channel.It is estimated
that flows down the channel will continue for a period of 20 days
under probable maximum flood conditions.Some erosion in the
channel will occur,but the integrity of the main darn will be
maintained.The reservoir will be drawn down to Elevation 2170.
Reconstruction of the fuse plug will be required prior to refill-
ing of the reservoir.
12=44
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The spillway channel is straight,bearing 115°.The channel will
be generally unlined and the base of the channel will be excavated
into rock to provide a minimum side wall height of 50 feet in
rock.At the downstream end of the channel the height of this
rock wall decreases to zero.
The depth of overburden has been determined mainly by seismic in-
vestigation and surface expressions and is expected to be 30 -40
feet deep.The depth increases towards the downstream end of the
channe 1.
The trend of major shear and fracture zones intersects the emer-
gency spillway channel at angle of 10°.The side wall excavations
parallel joint set I and some wedge instability is expected.The
sides of the excavation are designed for 1H:4V slopes.No provi-
sion for rockbolting within the channel excavation has been made.
Since the channel will be used only infrequently,if ever,during
.the 1ife of the project and small rock falls wi 11 not endanger
personnel or the spillway operation,a low factor of safety for
wall stability in some locations is considered.
A zone of consolidation grouting 20 feet deep under the fuse plug
is required to ensure there is no seepage through the foundation
that could cause piping of the fuse plug material into the founda-
tion.
12.11 -Intake
(a) General
The intake structure at Watana will satisfy the following design
conditions:
-To provide independent power flow of 3,870 cfs to each of the
six Francis turbines,for any reservoir level from elevation
2200 (maximum flood level)to the maximum drawdown level of
elevation 2045;
-To provide an upstream closure gate on each penstock to permit
dewatering of the penstock and turbine water passages for rou-
tine inspection and maintenance;and
-To control the temperature of the water di scharged from the
reservoir within acceptable limits to mitigate the environmental
impacts of the Susitna development on downstream fisheries.
(b) Environmental Constraints
The operation of the Watana reservoir will effect the temperature
of the downstream flows:
- In summer,the temperature of downstream releases will be cooler
than the normal river regime;and
12-45
- In winter,the temperatures will be warmer than the normal river
regime.
If the temperature of the summer flow is below the acceptable
range for salmon spawning,the cooler water in the summer months
would have an impact on downstream fisheries,particularly in July
and August when salmon are moving into the sloughs downstream from
Devi 1 Canyon to spawn.Warmer water in wi nter wi 11 affect the
formation of ice,resulting in extensive open water downstream
from the reservoirs.
Temperature s imu 1at i on was undertaken usi ng a Corps of Engi neers
Hydraulic Engineering Center (HEC)program to model the downstream
effects of reservoir operation.A variety of different power in-
take designs at Watana and Devil Canyon were tested in the model.
These studies indicated that the temperature of the discharge in
the winter is sensitive to the intake design and would be approxi-
mately 39°F.However,the downstream river temperatures in the
summer months can be significantly effected by the power intake
design at Watana.The flow to the turbine should be drawn fr.om
the reservoir surface at all times.
The selected power intake design at Watana will permit water to be
drawn from the reservoir at four distinct levels through the anti-
cipated range of drawdown to mitigate the environmental impacts on
downstream river temperatures (see Volume 2).
Detai 1s of the reservoi r temperature mode 1i ng are presented in
Appendix A.
(c)Dr awdown
The allowable drawdown of the reservoir level controls the live
storage volume usable for river regulation.With no drawdown,the
development becomes a run-of-the-river plant and the dependable
energy from Watana would be determined by the unregulated river
flow.As the maximum allowable drawdown is increased,the flow
from the development during a dry year will be increased relative
~-to t henatura+-flow-by-water-drawn-from~st'orage-;-~[)r'awdowns ranq-
ing from 100 to 220 feet were analyzed to determine the relation-
ship between firm energy,average annual energy and cost.The
following results were obtained:
- For drawdowns less than 140 feet,the average annual energy (sum
of energy produced during each of the 32 years divided by by 32)
is essentially constant.
- For drawdowns greater than 140 feet,the average annual energy
decreses approximately 1 GWH per foot of increased drawdown.
- For drawdowns of the order of 100 feet the energy generated in
the driest and second driest years are significantly different.
12-46
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As the drawdown is increased from 100 feet to 140 feet duri ng
these two years,the difference in firm energy decreases.
-The technical feasibility of a multi-level intake structure
designed to accommodate 220 feet of drawdown is marginal and the
costs are considerable (compared to a 140 foot drawdown).
Based on the above results a 140 feet drawdown was selected as the
maximum allowable for the Watana reservoir.
(d) Design
The power intake will be a concrete structure located deep in the
rock at the upstream end of the approach channel.Access to the
structure will be the same as access to the intake for the outlet
f aci 1i ties.
In order to draw from the reservoir surface over a drawdown range
of 140 feet,four openings will be provided in the upstream con-
crete wall of the structure for each of the six independent power
intakes.The upper opening will always be open, but the lower
three openings can be closed off by sliding steel shutters
operated in a common guide.All openings wi 11 be protected by
upstream trashracks.A heated bulkhead wi 11 operate in guides
upstream of the racks fo 11 owi ng the water surf ace, keepi ng the
racks ice free.
A lower control gate will be provided in each intake unit.A
single upstream bulkhead gate will be provided for routine mainte-
nance of the six intake control gates.In an emergency,stoplogs
can be installed on the upstream wall of the power intake for work
on the trashracks or shutter guides.
The width of the intake will be controlled by the minimum spacing
of penstock tunnel excavations,taken as 2.5 times the excavated
diameter.
The upper level of the_concrete structure will be set at elevation
2202,corresponding to the maximum anticipated flood level.The
level of the lowest intake will be governed by the vortex criter-
ion for flow into the penstock from the minimum reservoir level EL
2045.The foundat i on of the structure wi 11 be about 200 feet
below existing ground level and will be expected to be generally
in sound rock.
Mechanical equipment will be housed in a steel-frame building on
the upper level of the concrete structure.The general arrange-
ment of the power intake is shown on Plate 26.
12-47
(e)Approach Channel
The width of the approach channel will be governed by the combined
width of the power intake and the intake to the outlet facilities.
The overall width of the channel will be about 350 feet.
The intake channel is bounded by two shear zones: to the north
the extension of liThe Fins",and to the south a fracture zone with
shearing approximately 80 feet wide."The Fins"feature strikes
at 120
0 parallel to the intake excavation and the feature to the
south stri kes at 1300,intersect i ng the excavated face of the
intake channel at an acute angle.
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(f)
The major joint set I strikes approximately parallel to the shear
zones and joint set II strikes at right angles to joint set l.
Both joint sets dip vertically.
Because of the proximity of both shear zones to the excavations,
the excavated slopes of the channel should be IH:4V,with local
rockbolting and shotcrete where required.Water velocity in this
channel will be in the order of 5 ftls and,will not cause erosion
problems.
In the adjacent main spi llway approach channel,however,higher
flows in the order of 30 ftl s are expected,and at the port a1 of
the service spi 11way tunnel a water velocity of 50 ft/s wi 11
occur.Since the junction of the main spillway approach channel
and the intake channel is in a zone of sheared and fractured rock,
the excavated slopes will require to be IH:4V with 10 foot benches
at 40 foot intervals.Extensive rock support will be required in
this area ef poor rock to prevent erosion.
The maximum flow in the intake approach channel wi 11 occur when
six machines are operating and the outlet facilities are discharg-
ing at maximum design capacity.With the reservoir drawdown to
elevation 2045,the velocity in the approach channel will be
3.5 ft/s,which will not cause any erosion problems.Velocities
of 10 cfs may occur where the intake approach channel intersects
..the .ap prQa.chc.h.almel ..to..the..maln.spJJJ.w.aJ,..
Excavations in overburden are expected to be up to 75 feet in
depth and will generally be trimmed at 2H:IV;riprap protection
will be required in the areas where high~flow velocities are
anticipated.
Geotechnical Considerations
The excavation for the intake structure will be over 200 feet deep
in rock in the northwest corner,with a total excavation depth of
240 feet.The southern end of the structure will be located in a
shear and fracture zone with an approximate excavation depth of 80
feet in rock.The excavation depth at the north end of the struc-
ture will be 120 feet.
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With sufficient rock support,mainly from rock bolting,the rock
slopes can be cut nearly vertical,with the possible exception of
the southern end,where the excavation will intersect the fracture
and shear zone.If it proves impracticable to support this face
nearly vertically,it will have to be trimmed back to a stable
slope.The intake structure would then be partially free-stand-
ing.The spillway tunnel portal will also be located in this zone
of fractured rock and will require substantial rock support in-
stalled in the portal face.Since the intake structure will,when
complete,support this rock face,the required support will be
temporary.
The foundation will be in sound rock,but the shear and fracture
zones at the southern end may requi re conso 1i dat ion grouting.
Minor shears and fractures exposed in the remainder of the founda-
tion area may require local grouting and/or dental concrete.
(g) Mechanical Arrangement
(i)Ice Bulkhead
A heated bulkhead will be installed in guides immediately
upstream of the trashracks for each of the six power
intakes.The bulkhead will be operated by a movable hoist
and will automatically follow the reservoir level.The
bulkhead will serve to minimize ice accumulation in the
trashrack and intake shutter area,and prevent thermal
ice-loading on the trashracks.
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(i i )Trashracks
Each of the six power intakes will have four sets of trash-
racks,one set in front each intake openings.Each set of
trashracks will be in two sections to facilitate handling
by the intake servi ce crane.Each set of trashracks wi 11
cover an opening 30 feet wide by 24 feet high.The trash-
racks will have a bar spacing of about 6 inches and will be
designed for a maximum differential h~ad of 20 feet.
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(i ii)Intake Shutters
Each of the six power intakes will have three intake shut-
ters which wi 11 serve to prevent flow through the intake
openi ngs behind whi ch the shutters wi 11 be i nst all ed.As
the reservoir level drops,the sliding shutters will be
removed as necessary using the intake service crane.
Each of the shutters will be designed for a differential
head of 25 feet.The lowest shutter at each power intake
will incorporate a flap gate which,with 25 feet differen-
tial head across the shutter,will allow maximum turbine
12-49
flow through the gate.Th i s wi 11 prevent fai lure of the
shutters in the event of accidental blocking of all intake
openings.
The shutter guides will be heated to facilitate removal in
sub-freezing weather.In addition,a bubbler system will
be provided in the intake behind the shutters to keep the
intake structure water surface free of ice.
(iv)Intake Service Crane
A single,overhead,traveling-bridge type intake service
crane will be provided in the intake service buildings.
The crane will be used for:
-Servicing the ice bulkhead and ice bulkhead hoist;
-Handling and cleaning the trashracks;
-Handling the intake shutters;
- Handling the intake bulkhead gates;and
-Servicing the intake gate and hoist.
The overhead crane will have a double point lift and fol-
lowers for handling the trashrack shutters and bulkhead
gates.The crane wi 11 be radio-controlled with a pendant
or cab control for backup.
(v)Intake Bulkhead Gates
One set of intake bulkheads will be provided for closing
anyone of the six intake openings upstream from the intake
gates.The bulkheads will be used to permit inspection and
mai ntenance of the intake shutters and intake guides.The
gate will be designed to withstand full differential
pressure.
(vi)Intake Gates
The intake gates will close a clear opening approximately
-1-7-·squ are-f.eet-...They wi 11 be ef--the--vel"-t-iGa-l--f-i-xed whee 1
lift with an upstream seals and skinplate.
Each gate wi 11 be operated by a hydraulic cylinder type
hoist.The length of a cylinder will allow withdrawal of
the gate from the water flow.The intake service crane
will be used to raise the gate.The gat~s will normally be
closed under balanced flow conditions to permit dewatering
of the penstock and turbine water passages for inspection
and maintenance of the turbines.The gates will also be
designed to close in an emergency with full turbine flow
conditions in the event of loss of control of the turbine.
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12.12 -Penstocks
The general arrangement of the penstocks is shown on Plates 23 and 25.
The desi gn stat ic head on each penstock is 763 feet at di stri butor
1eve1 (e1evat ion 1422).An allowance of 35 percent has been made for
pressure rise in the penstock caused by hydraulic transients.
(a)Steel Liner
The rock adjacent to the powerhouse cavern will be incapable of
restraining the internal hydraulic forces within the penstocks.
Consequently,the first 50 feet of a steel liner will be required
to resist the maximum design head,without support from the sur-
round rock.Beyond th is sect ion the steel 1iner wi 11 be extended
a further 150 feet.For preliminary design purposes it is assumed
that not more than 50 percent of the maximum design head will be
taken by the surrounding rock over this length.
The steel 1iner wi 11 be surrounded by a concrete infi 11, with a
minimum thickness of 24 inches.The internal diameter of the
steel lining will be 15 feet based on the minimum total cost of
construction and the capitalized value of annual energy losses.A
steel transition will be provided between the liner and the 17
feet diameter concrete-lined penstock.
LJ
(b)
(c)
Concrete Lining
The penstocks will be fully lined with concrete from the intake to
the steel lined section,the thickness of lining varying with the
external hydrostatic head.The internal di ameter of the concrete
lined penstock will be 17 feet,based on the minimum total cost of
construction and the capitalized value of annual energy losses.
The minimum lining thickness will be 12 inches.
Geotechnical Considerations
The orientation of the penstock tunnels is generally at right
angles to the powerhouse i.e.,70°but at the upstream end near
the intake,the orientation is 115°.
Generally,good rock quality is expected in this area and the
tunnels over the majority of this length in the lower section will
require only light support.Joint set II intersects the tunnel at
an acute angle of 20°and this may cause some wedge instability.
However,in the upper part of the penstocks with an orientation of
115°,the tunnels parallel joint set I and this will probably make
tunneling more difficult in this section.An 80 feet wide shear
and fracture zone intersects the penstocks 200 feet to 600 feet
from the intake structure.The tunnels intersect the zone at an
angle of 60°in plan but at this point,the penstocks are inclined
12-51
at 55°therefore the length of tunnel affected by this zone may be
up to 150 feet in length.Fairly extensive support may be
required in this section.However,the shear and fracture zone is
expected to narrow with depth and would lessen the length of the
tunnel affected.
There is a minimum of 200 feet of rock cover to the penstock.The
rock has a high modulus and therefore deformation of the rock
around the penstock will be negligible.Highly fractured zones
may require consolidation grouting,but this will be in localized
areas only.
(d) Grouting and Pressure Relief
A comprehensive pressure relief system will be required to protect
the underground caverns agai nst seepage from the high pressure
penstock.The system will comprise small diameter boreholes set
out to intercept the jointing in the rock.
Grouting around the penstocks will be provided to:
- Seal and fill any voids between the concrete lining and the
steel liner,which may be left after the concrete placing and
curing;and
-Fill joints or fractures in the rock surrounding the penstocks
to reduce flow into the pressure relief system and to consoli-
d ate the rock.
A grouti~g drainage gallery will be located upstream of the trans-
former gallery,from which curtain grouting may be performed to
intersect the grout i ng from the penstock tunnels and from wh i ch
drainage holes may be drilled.
12.13 -Powerhouse
(a) General
nder.ground powerhouse.complex wi Ll.Jie..constnuct.ed.benaath.rthe
right abutment.This will require the excavation in rock of three
major caverns,the powerhouse,transformer gallery,and surge
chambers with interconnecting rock tunnels for the draft tubes and
isolated phase bus ducts.
Unlined rock tunnels will be required for vehicular access to the
three main rock caverns and the penstock construction adit.Ver-
tical shafts will be required for personnel access to the under-
ground powerhouse,for cable ducts from the transformer gallery,
for surge chamber venting and for the heating and ventilation
system.
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The general layout of the powerhouse complex is shown in plan and
section in Plates 54 and 55,and in isometric projection in Plate
56.The transformer gallery will be located on the upstream side
of the powerhouse cavern;the surge chamber will be located on the
downstream side.Clear dimensions between major rock excavations
have been set at 1.5 times the main span of the larger excavation.
This criterion controls not only the minimum distance between
caverns,but also the spaci ng between transformer gallery and
penstock,between bus shaft and penstock,and the minimum spacing
of penstock and tailrace tunnels.
The draft tube gate gallery and crane will be located in the surge
chamber cavern,above the maximum anticipated surge level.Provi-
si on wi 11 a1so be made in the surge chamber for t ail race tunnel
intake stoplogs,which will be handled by the draft tube crane.
(b) Layout Considerations
The location of the powerhouse was selected from consideration of
the following data:
Plots of the known major faults and shear zones on the right
abutment;
-Estimated cost of approach channel excavation,intake structure,
penstocks,and tailrace;and
-An assumed angle of 55°to the horizontal for the inclined
section of penstock.
Preliminary cost estimates indicate that the intake structure and
approach channel excavation are the most significant items in the
overall arrangement of the power facilities;the underground
powerhouse costs are dependent only on installed capacity.The
optimum arrangement has therefore been determined by adjusting the
position of the intake to give the least cost for intake,pen-
stocks,and tailrace.Since the costs of tunne l i nq are small
compared to the intake costs,the intake wi 11 be sited as far
upstream as possible,consistent with the required minimum
drawdown level,and a reasonable length of access tunnels.
The underground transformer gallery will be located on the
upstream side of the powerhouse.Thi s arrangement gives the
minimum possible distance between the turbines and the surge
chamber,for maximum protection of the draft tubes under transient
load conditions.The transformer gallery and the powerhouse
cavern wi 11 be protected against high pressure seepage from the
penstocks by a 200 foot long steel-lined section and an extensive
pressure relief system (see Section 12.12).
12-53
(c)Access Tunnels and Shafts
Vehicular access to the underground facilities at Watana will be
provided by a single unlined rock tunnel from the right bank area
adjacent to the diversion tunnel portal.The access tunnel will
cross over the diversion tunnels and then descend at a uniform
gradient to the south end of the powerhouse cavern at generator
floor level,at EL 1463.Separate branch tunnels from the main
tunnel will give access to the transformer gallery at EL 1507,the
penstock construction adit at EL 1420,and the draft tube gate
gallery at EL 1500.The maximum gradients will be 6.1 percent on
the construction access tunnel,and 6.9 percent on the permanent
access tunnels.
The common access tunnel will be sized to provide passing clear-
ance for the construction plant used during penstock construction.
The size of an articulated trailer required to deliver heavy items
of machinery such as the turbine runner,turbine spiral case,and
generator rotor,wi 11 be less critical with respect to tunnel
size,but will dictate the minimum radius of vertical and
horizontal curves.For preliminary design,the cross section of
the access tunnel has a modified horseshoe shape,35 feet wide by
28 feet high.The access tunnel branch to the surge chamber and
draft tube gallery will have a reduced section,consistent with
the anticipated size of vehicle and loading required.
The alignment of the access tunnel intersects the trend of major
shears and fracture zones at angle of about 80
0
•The tunnel will
therefore be driven through these zones for only a minimum dis-
tance.The features as mapped on the surface,are up to 60 feet
wide but are expected to be less extensive at depth.
Joint sets II and III intersect the tunnel aliqnment at angles ofzrand250
•Some unstable rock wedges may'occur due to this
pattern of jointing but can be supported by normal support techni-
ques.The tunnel parallels joint set II at the powerhouse end.
Since joint set II is vertical or near vertical,this will not be
a major problem.Some additional overbreak due to this parallel
joint set may ace-uri
With rock permeabi 1it ies at depth of 1 x 10-
5 to 1 x 10-
6,
little if any water inflow into the tunnel is expected.At major
shear and fracture zones,some minor seepage may occur which can
be controlled by simple drainage techniques.Grouting is not
expected to be required.Borings have shown high RQD values for
over 60 percent of the tunnel length for which only spot bolting
rock support is required.
It is est imated from the bori ngs and from the mapped shear and
fracture zones that 9 percent of the tunnel length will be in very
poor rock with RQDs less than 25 percent.In this zone,it is
anticipated that extensive shotcrete and rockbolt support or steel
sets and insitu concrete lining will be required.
12-54
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(d)
Additional supports will be required for all junctions,the amount
required will depend on the local rock conditions.
At the portal,as a general rule,1.5 multiplied by the tunnel
span is required for rock cover to the tunnel.The side slopes to
the portal cut are expected to be 1H:4V with localized support
only.The portal face may be excavated steeply at 1H:10V but will
require more extensive rockbolting.
For safety,chainlink mesh will be installed over the length of
the tunnel crown that is not shotcreted or concreted.Hith good
scaling of the rock,the amount of rock caught by this mesh is
expected to be minimal.
The main access shaft will be at the north end of the powerhouse
cavern,providing personnel access from the surface control
building by elevator.Access tunnels will be provided from this
shaft for pedestri an access to the transformer gallery and the
draft tube gate gallery.Elevator access will also be provided to
the fire protection head tank,located about 250 feet above power-
house level.
The shaft 20 feet in internal diameter will probably be raised
bored or excavated by a pilot raise bore and enlarged to full
diameter by drill and blast.Depending on the method of excava-
tion,a concrete lining 9 to 18 inches in thickness will be
installed.As in the cable shafts,little rockbolt support is
expected to be required for stability,the concrete lining is
required mainly for smoothing the profile and providing protection
against small pieces of rock falling from the rock walls.The
concrete is not required for structural stability of the shaft.
Powerhouse Cavern
The main powerhouse cavern is designed to accommodate six vertical
shaft Francis turbines,in line,with direct coupling to coverhung
generators.Each unit is designed to generate 170 MW at a rated
head of 680 feet.
The vertical dimension of the powerhouse cavern is determined by
the physical size of turbine and generator,the crane height
required for routine maintenance,and the design dimensions of the
turbi ne draft tube.The length of the cavern wi 11 allow for a
unit spacing of 60 feet,with a 110-foot long service bay at the
south end for rout ine mai ntenance and for construct ion erect ion.
The width of the cavern allows for the physical size of the gen-
erator plus galleries for piping and air-conditioning,electrical
cables,isolated phase bus ducts,and generator circuit breakers.
Continuous drainage galleries will be provided to a low level
sump.
12-55
Vehicular access will be by tunnel to the generator floor at the
south end of the cavern;pedestrian access will be by elevator
from the surface control building to the north end of the cavern.
Multiple stairway access points will be available from the main
floor to each gallery level.Access to the transformer gallery
from the powerhouse will be by tunnel from the main access shaft,
or by stai rway through each of the iso 1ated phase bus shafts.A
service elevator will be provided from the maintenance area on the
main floor level to the machine shop and stores area on the
turbine floor level.
Hatches will be provided through all main floors for installation
and mai ntenance of heavy equi pment usi ng the overhead travel i ng
cranes.
(e)Transformer Gallery
The transformers will be located under9round in a separate
gallery,120 feet upstream from the main powerhouse cavern,with
three connecting tunnels for the isolated phase bus. There will
be nine single-phase transformers rated at 15/345 kV,122 MVA,
installed in groups of three one group for each pair of turbines.
Generator circuit breakers will be required,and will be installed
in the powerhouse on the lower generator floor level.
High voltage cables will be taken to the surface by two cable
shafts,each with an internal diameter of 7.5 feet.Provision has
been made for installation of an inspection hoist in each shaft.
A spare transformer wi 11 be located in the transformer gallery,
and a spare HV circuit will also be provided for improved reli-
ability.The station service auxiliary transformers (2 MVA)and
the camp services auxiliary transformer (7.5/10 MVA)will be
located in the bus tunnels.Generator excitation transformers
will be located in the powerhouse on the main floor.
Vehicle access to the transformer gallery will be the main power-
house access tunnel at the south end.Pedestri an access wi 11 be
from the main access shaft or through each of the three isolated
(f)Surge Chamber
A surge chamber wi 11 be provided 120 feet downstream from the
powerhouse cavern to control pressure fluctuations in the turbine
draft tubes and tailrace tunnels under transient load conditions,
and to provide storage of water for the machine start-up sequence.
The chamber will be common to all six draft tubes,and under
normal operation will discharge equally to the two tailrace
tunnels.
The draft tube gates gallery and crane will be located in the same
cavern,above the maximum anticipated surge level.The draft tube
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gate crane has also been designed to allow installation of
tai lrace tunnel intake stoplogs for emergency closure of either
tai lrace tunnel.
The chamber will generally be an unlined rock excavation,with
localized rock support as necessary for stability of the roof arch
and walls.The gate guides for the draft tube gates and tailrace
stoplogs will be of reinforced concrete,anchored to the rock by
rockbo lt s.
Access to the draft tube gate gallery will be by an adit from the
main access tunnel;the tunnel will be widened locally for storage
of draft tube bulkhead gates and stoplogs.
Geotechnical Consideration for Caverns
The orientation of the powerhouse cavern was selected to avoid
paralleling major joint sets I and II and the trend of shear and
fracture zones. Problems of block release into the excavation
will be minimal if the major cavern axis is made normal to the
strike of the predominant joint sets of the caverns but this
arrangement is not practical for power generation considerations.
A compromise orientation with powerhouse cavern 165
0 was therefore
adopted to avoid paralleling the trend of major shears.
BH-4 intersected a fracture zone at elevation 1567 just above the
cavern crown of about 20 feet along the hole where RQDs were
around 30 percent.In BH-3,a 56 feet length of borehole inter-
sected a shear/alteration zone with RQDs of zero at an elevation
about 200 feet above the powerhouse.
Further investigations will be carried out to locate similar zones
if they exist and in final design,the caverns,where possible,
would be arranged to avoid the altered and fractured zones.
However,this may not be possible and an allowance has been made
in the cavern support to deal with these difficult conditions.
The rock quality at depth is generally good to excellent.Water
pressure tests show permeabi 1it i es in the range of 1 x 10-5 to
1 x 10-6 .Little seepage into the excavation from the
surrounding rock is expected.
Preliminary design of the support of the cavern roof has been done
using the empirical rule:pi =n B
IJ
Where pi =
n =
B =
=
support pressure
constant,generally between 0.1 and 0.3
span of cavern
density of rock
12-57
Using an average value for n =0.2,which is considered reasonable
value for the quality of rock at Watana,this correlates well with
other design methods (2).
Similar preliminary design for wall support was carried out with
modified factors in each case.
The lengths of rockbolts have been designed considering:
-Average block size;
-Span dimension;and
-Anchor spacings.
The design of large underground excavations in jointed rock
requi res an appreci at i on of the effects of stresses both on the
rock and its discontinuities.Rock is,in general,a non-homogen-
eous discontinuous medium with complex behavior under load.No
generalized design method has been evolved which is applicable to
all potential situations.Final design studies will be'based on
the following methods:
-Precedent practice,observational methods and empirical rules;
-Stability studies us~ng the results of stress analyses based on
the principles of continuum mechanics;and
- Analyses using limit equilibrium techniques applied to specific
failure mechanisms.
Each of the three methods of design have substantial limitations.
Design of reinforcement requires input from all three methods and
a considerable amount of engineering judgement.
Final desi gn of the underground caverns wi 11 requi re further
investigation of:
-Rock jointing;
-Joint shear strength;
_-",,-.Ro.ck.mas.5_deformaUDn prnpert jes;~
-Insitu stress field;and
-Distribution of rock types.
This information can most likely be obtained from an exploration
adit driven fin the powerhouse location.Construction of this
adit at an early stage will be a design requirement.
Although in final design,every effort will be made to locate the
powerhouse away from altered zones, such as described earlier
encountered in BH-3;an allowance has been made in the cost esti-
mates for very substantial support for a portion of the cavern
1ength.
12...58
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Allowances have been made in cost estimates for additional rock-
bolting at the junctions of the penstock tunnels,draft tube
tunnels,bus galleries and access tunnels with the main cavern.
A cavern spacing (i.e.,rock pillar width)criteria at 1.5 times
the 1arger of the adjacent cavern spans has been adopted.In good
rock,this may be somewhat conservative but considering the shear
and fracture zones known to exist in the area,this spacing
requirement was considered necessary.The spacing of the caverns
will be considered in the stress analyses program in final design.
The excavation will be carried out by conventional drill and blast
techniques.Particular attention will be paid to obtaining an
even excavation profile.This contributes to the stability of the
cavern wh i1e reduced overbreak decreases the amount of concrete
requi red in the powerhouse structure.It is expected that the
excavation will be done in several stages starting with a top
heading which would be subsequently enlarged to the full width of
the cavern.The rock support to the cavern roof will be installed
progressively as the excavation is carried out.During this
stage,multiple point borehole extensometers and rockbolt load
cells will be installed to monitor the support performance.The
support design will be modified if necessary in light of the
performance measurements.The excavation will then be lowered in
benches with wall supports being installed as the excavation is
lowered.In the initial stages,access will be by ramps within
the powerhouse from the main access tunnel level.As the excava-
tion is lowered,muck removal will be through the draft tube and
tailrace tunnels.Chain link mesh will be installed on all ex-
posed overhead rock surf aces for protect ion agai nst small rock
falls.
The geotechnical considerations for the transformer gallery and
surge chamber are simi lar to those of the powerhouse cavern.
Seepage into the transformer gallery may be greater because this
gallery is the most upstream cavern and is close to the section of
penstock tunnel which is not steel lined.The grout and drainage
gallery located upstream of the transformer gallery wi 11 control
this seepage.Seepage-will be channeled into a drainage system
through the bus galleries and conducted into the powerhouse drain-
age system.
Grouting and Pressure Relief
During construction,the seepage into the excavation is expected
to be very low.However,with the reservoir full and the penstock
tunnels operating under full head of water,there may be signifi-
cant 1eakage into the powerhouse areas.Seepage into the under-
ground structures effects the overall stability of the cavern and
also would create difficult operating conditions.
12-59
Control of this seepage will be achieved by a grout curtain up-
stream of the transformer gallery and an arrangement of drainage
holes downstream of this curtain.In addition,drain holes will
be drilled from the caverns extending to a depth greater than the
rock anchors.
Seepage water wi 11 be collected by surface drainage channels and
directed into the powerhouse drainage system.
It is not anticipated that rock grouting from the caverns to con-
trol water inflows will be required.
(i)Cable Shafts
Cable shafts are 8.5 feet in excavated diameter.Although not
required for rock stability,a 6-inch thick concrete lining has
been specified for convenience of installing hoist,stairway and
cable supports.It is expected that these shafts will be raise
bored,and the resulting smooth profile will require little rock
support.Allowance has been made for rock bolting at the upper
and lower sections.
(j)Draft Tube Tunnels
The orientation of the draft tube tunnels is determined from the
powerhouse alignment.The draft tube tunnels bear 075 0
•Joint
set II intersects these tunnels at an acute angle of 20 0
•This is
not expected to be a problem except that on the south side of the
junction with the surface chamber and the northside of the junc-
tion with'the powerhouse where the rock corner may spall off~The
tunnel,with excavated diameter of 23 feet,will require only
light rock support.When the joint set II tends to parallel the
tunnel greater than normal overbreak may occur.
The draft tube tunnel will be lined with concrete,2 feet in
thickness to embed the steel draft tube liner.The initial rock
support will therefore be temporary and concentrated at the junc-
tions with the powerhouse and single chamber where the two free
._.-f-aces-g i-v e~gr-e ates-tp at ent i a-l-f or--b-lo ek--i~nst aoi li-t-y.~~
The contact between tunnel crown and concrete tunnel lining will
be grouted.Consolidation rock grouting will only be requlred if
a highly fractured zone is encountered.
12.14 -Reservoir
The Watana reservoir,at normal operating level of 2185 feet,will be
approximately 48 miles long with a maximum width in the order of 5
miles.The total water surface area at normal operating level is
37,800 acres.Just upstream from the dam,the maximum water depth will
12-60
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be approximately 680 feet.The mi rnmum reservoir level will be 2045
feet during normal operation,resulting in a maximum drawdown of 140
feet.The reservoir will have a total capacity of 9,470,000 acre-feet
of which 4,400,000 acre-feet will be live storage.
Prior to reservoir filling,the area below Elevation 2190 will be
cleared of all trees and brush.A field reconnaissance of the proposed
reservoir area included examination of aerial photographs and maps,an
aerial overflight of the reservoir and collection or recent (1980 field
season)forest inventory data from the U.S.Forest Service.Most of
the vegetatal material within the reservoir consists of trees,with
very little undergrowth.The trees are quite small,and the stands are
not very dense.In the Watana reservoir area,an estimated 18,000,000
cubic feet of wood exists.Approximately 87 percent of the available
timber are soft woods.The combination of steep terrain,moderate-
light tree stocking levels,small trees,erosive potential of the
reservoir slopes,remoteness,and very restricted access to the reser-
voirs are major factors affecting the choice of harvesting systems to
be utilized for this project.
Present market demand for the timber at Susitna is low,however the
worldwide demand wood fluctuates considerably.It is anticipated that
use of the harvested material would be limited to either sale as wood -
waste products and as fuel.
Slash material including brush and small trees,which will be unsuit-
able for either of the above uses,will be either burned in a carefully
controlled manner consistent with applicable laws and regulations,or
hauled to a disposal site.Material placed in disposal areas will be
covered with a earthfill cover sufficient to prevent erosion and subse-
quent exposure.
12.15 - Tai lrace
Two tailrace pressure tunnels will be provided at Watana to carry water
from the surge chamber to the river.The tunnels will have a modified
horseshoe cross-section with a major internal dimension of 34 feet.
For preliminary design the tunnels are assumed to be fully concrete-
lined throughout,with a minimum concrete thickness of 12 inches and a
length of 1,800 feet.
The tailrace tunnels will be arranged to discharge into the river
between the mai n dam and the mai n spi llway. In vi ew of the severe
limitations on space in this area,one tailrace tunnel will be designed
to discharge through one of the diversion tunnel portals.The cross
section of the tailrace tunnel will be modified over the common length
of 300 feet to the shape of the diversion tunnel in order not to impair
the hydraulic performance of the tai lrace tunnel.After diversion clo-
sure,the diversion tunnel upstream section will be plugged with
concrete.
The size of the two tai lrace tunnels was selected after an economic
study of the cost of construction and the capitalized value of average
12-61
annual energy losses caused by friction,bends,and changes of section.
In an emergency,however,the station can be operated using one tail-
race tunne 1,wi th increased head losses.For such an emergency condi-
tion'tailrace intake stoplog guides will be provided in the surge
chamber.The surge chamber will be designed for full plant load rejec-
tion with either one or two tailrace tunnels in operation.
The upstream section of the tailrace is on bearing 018 0 and parallels
the main access tunnel.
The northern tunnel joins the lower diversion tunnel and utilizes the
diversion portal for the tailrace outlet.
The northern tunnel changes direction on downstream end to bear 60
0 and
the portal is situated between the diversion tunnel portals and the
spillway flip bucket.
Alternative alignments for the diversion tunnels were examined down-
stream of the flip bucket but this would require tunnelling through the
"Fingerbuster"area in which very poor rock quality has been found.
The tunnels are favorably oriented with respect to major joint sets and
shears.The rock at depth is of good quality and little support will
be requi red except for a number of shear,fracture'and a lterat i on
zones.An allowance has been made for rockbo It and shotcrete support
for 17 percent of the tunnel length and steel set supports for 8
percent.
The tunnels are concrete-lined for hydraulic considerations.
The downstream portal of the northern tunnel is located between the
spillway flip bucket and diversion tunnel portal.A rock berm is
required to be left to the south of the portal to allow construction of
a cofferdam to permit access to the tailrace tunnel which the diversion
tunnels are operating.
It was necessary to locate the tai lrace portal as far downstream as
ossible to avoid undercutti the southside of the spillway flip
Major joint set I and the trend of the major shears intersect the por-
tal face and an acute angle about 10
0
•Therefore it may be desirable
to excavate the portal face bank to a natural discontinuity within the
rock.
The rock berm left between the tailrace portal and diversion portal has
been made as wide as possible for stability and to ensure a good con-
nection for the tailrace tunnel cofferdam,but the arrangement is
restri cted by the downstream cofferdam and the spi llway fl i p bucket.
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It is realized that this berm may be unstable because of the jointing
and considerable rock support and mass concrete wi 11 be required to
maintain it.
The rock slope between the tailrace portal and the flip bucket will
also require extensive rock support to ensure stability of the flip
bucket foundation.
The tailrace portals will be reinforced concrete structures designed to
reduce the outlet flow velocity,and hence the velocity head loss at
the exit to the river.The minimum rock cover required above the
tunnels will be 1.5 times the major excavated dimension (about 54
feet).
12.16 -Turbines and Generators
(a) Unit Capacity
The Watana powerhouse will have six generating units with a nomi-
nal capacity of 170 MW corresponding to the minimum December
reservoir level (elevation 2117)and a corresponding gross head of
662 feet on the station.
The head on the plant will vary from 590 feet to approximately 735
feet.The maximum unit output will change with head, as shown on
Figure 12.8.
The rated head for the turbine has been established at 680 feet,
which is the weighted average operating head on the station.
Allowing for generator losses,the rated turbine output is 250,000
hp (186.5 MW)at full gate.
The generator rating has been selected as 190 MVA with a 90 per-
cent power factor.The generators will be capable of a continuous
15 percent overload allowing a unit output of 196 MW.At maximum
reservoir water level,the turbines will be operated below maximum
output to avoid overloading of the generators.
(b)Turbines
The turbines wi 11 be of the vertical shaft Francis type with steel
spiral casing and a concrete elbow-type draft tube.The draft
tube will comprise a single water passage without a center pier.
The rated output of the turbines will be 250,000 hp at 680 feet
rated net head.Maximum Mnd minimum heads on the units will be 728
feet and 576 feet respectively.The full gate output of the tur-
bines will be about 275,000 hp ar 728 feet net head and 195,000 hp
at 576 feet net head.Overgating of the turbines may be possible,
providing approximately 5 percent additional power; however, at
high heads the turb i ne output wi 11 be restri cted to avoid over-
12-63
loading the generators.The best efficiency point of the turbines
will be established at the time of preparation of bid documents
for the generating equipment and will be based on a detailed
analysis of the anticipated operating range of the turbines.For
preliminary design purposes,the best efficiency (best gate)
output of the units has been assumed as 85 percent of the full
gate turbine output.This percentage may vary from about 80
percent to 90 percent;in general,a lower percentage reduces
t urb i ne cost.
The full gate and best gate efficiencies of the turbines will be
about 91 percent and 94 percent respectively at rated head.The
efficiency will be about 0.5 percent lower at maximum head and 1
percent lower at minimum head.The preliminary performance curve
for the turbine is shown on Figure 12.9.
A speed of 225 rpm has been selected for the unit for preliminary
design purposes.The resulting turbine specific speed (N s)is
32.4.As shown on Figure 12.10,this is within present day
pract ice for turb ines operat i ng under a head of 680 feet.The
turbine data are summarized in Table 12.7.
On the basis of information from turbine manufacturers and the
studies on the power plant layout,the centerline of the turbine
distributor has been set at 30 feet below minimum tailwater level.
The final setting of the unit will be established in conjunction
with the turbine manufacturer when the contract for the supply of
the turbine equipment has been awarded.
Bulkhead domes will be provided with two of the turbines (Units 3
and 4) to be installed at the bottom of the draft tube liner at
the time of turbine installation.The domes permit work to con-
tinue on turbine installation after the tailrace,surge chamber,
and draft tubes are flooded (prior to startup of Unit 1),without
installing draft tUbe gates.
Because of the relatively short length of the intake penstock and
a surge tank location immediately downstream of the powerhouse,
.....the hydraulic transient characteristics.oftbet!J.r!:LLDJ~~.9r~
favorable.The regulating ratio is above the minimum recommended
by the USBR for good regulating capacity.Also,unit speed rise
and penstock pressure rise are all well with in normal accepted
values.Because of the deep unit setting and the relatively short
distance between the turbine and the tailrace surge tank,there
will be no problems with draft tUbe water column separation.
The potential problems associated with partial loads must be given
serious consideration in the final design.
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Generators
The generators are rated as follows:
(i)Type and Rating
190 MVA,0.9 power factor
170 MW
15 kV,3 phase,60 Hertz
225 rpm
3.5 MW-sec/MVA
28 percent (maximum)
1.1 (minimum)
98 percent (minimum)
The generators will be of the air-cooled type,with water-
to-air heat exchangers located on the stator periphery.
The ratings given above are for a temperature rise of the
stator and rotor windings not exceeding 60°C with cooling
air at 40°C.
The generators will be capable of continuous operation as
synchronous condensers when the turbine is unwatered, with
an underexcited reactive power rating of 140 MVAR and an
overexcited rat i ng of 110 MVAR.Each generator wi 11 be
capable of energizing the transmission system without risk
of self-excitation.
The generators will be capable of delivery 115 percent of
rated MVA continuously (195.5 MW)at a voltage of +5 per-
cent without exceeding 80°C temperature rise in accordance
with ANSI Standard C50.10.
Rated Capac i ty:
Rated Power:
Rated Voltage:
Synchronous Speed:
Inertia Constant:
Transient Reactance:
Short Circuit Ratio:
Efficiency at Full Load:
The optimum arrangement at Watana will consist of two gen-
erators per transformer bank, with each transformer bank
compri sing three si ngl e-phase transformers.(Development
of this scheme is described in Section 12.18).The genera-
tors wi 11 be connected to the transformers by iso 1ated
phase bus through generator circuit breakers directly
connected to the isolated phase bus ducts.
Each generator will be provided with a high initial re-
sponse static excitation system.The units will be con-
trolled from the Watana surface control room,with local
control facility also provided at the powerhouse floor.
The units will be designed for black start operation.
The six generators in the Watana powerhouse will be of the
vertical shaft,overhung type directly connected to the
vertical Francis turbines.The arrangement of the units is
shown in Plates 27 and 28 and the single line diagram is
shown in Plate 32.
(c)
12-65
Generator Construction
Generator Excitation System
Approximate dimensions and weights of the principal parts
of the generator are given below:
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36 feet
22 feet
7 feet
385 tons
740 tons
Stator pit diameter:
Rotor di ameter:
Rotor length (without shaft):
Rotor weight:
Total weight:
It shaul d be noted that these are appro)(imate fi gures and
they will vary between manufacturers,sometimes consider-
ably.However,at this stage of design feasibility and
planning,the dimensions and weights are considered appro-
priate and representative.
The generator will be provided with a high initial response
type static excitation system supplied with rectified exc i-
t ation~powe~~~f.romt rans£ormers~~connected-d~i-~ect~l-j'-~to .the~
generator terminals.The excitation system will be capable
of supplying 200 percent of rated excitation field (ceiling
va ltage)with a generator termi na1 va ltage of 70 percent.
The power rectifiers will have a one-third spare capacity
to maintain generation even during failure of a complete
rectifier module.
The design data of the generators stated above should be
reviewed during the detailed design stage for overall
economic and technical design and performance requirements
of the power plant and the power system.
The generator will be of a modified umbrella type overhung
construction,with a combined thrust and guide bearing
be low the rotor and a gu ide beari ng above the rotor.The
lower beari ng bracket wi 11 support the rotor and turbi ne
runner weights and the unbalanced hydraulic thrust of the
runner.All removable parts,fncluding turbine parts,will
be designed for removal through the generator stator.
The rotating parts of the generator and turbine wi 11 be
designed so that the critical speed exceeds the runaway
speed of the unit by at least 20 percent.
(i i )
(i i 1)
The excitation system will be equipped with a fully static
voltage regulating system maintaining output from 30 per-
cent to 115 percent,within +0.5 percent accuracy of the
voltage setting.Manual control will be possible at the
excitation board located on the powerhouse floor,although
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the un it wi 11 norma 11 y be under remote contro 1,as de-
scribed in Section 12.18 covering the control systems of
the plant.
(iv)Erection and Tests
As is normal for large hydroelectric generators,the
machines will not be assembled completely and tested in the
factory.The erect i on and tests of the generators at the
powerhouse,therefore,wi 11 assume greater importance in
the successful commissioning of the station and should be
carefully coordinated with that of the turbines and civil
works.
The assemb ly of the stator sect ions wi 11 be done in the
pit.The rotor will be assembled in the erection bay.The
powerhouse cranes will be capable of lifting the completed
rotor assembly and lowering it into the stator,and onto
the thrust bearing and shaft assembly on the bracket
supports.Al ignment and tests of the rotor,turbine
runner,and shaft will be done to tolerances specified in
NEMA/ANSI Standards.
The generators wi 11 be fully tested after assemb ly and
mechanical run tests,including dielectric tests,satura-
tion tests,heat run,efficiency,and full-load rejection
tests.Ceiling voltage and response of the excitation
system will be tested.Operation of the unit within
specified vibration limits will be checked.
(d)Governor System
The governor system which control the generating unit will include
a governor actuator and a governor pumping unit.A single system
will be provided for each unit.The governor actuator will be the
electric hydraulic type and will be connected to the computerized
station control system.
12.17 -Miscellaneous Mechanical Equipment
(a)Powerhouse Cranes
Two overhead trave 1i ng br i dge type powerhouse cranes wi 11 be i n-
stalled in the powerhouse.The cranes will be used for:
-Installation of turbines,generators,and other powerhouse
equipment;and
- Subsequent dismantling and reassembly of equipment during main-
tenance overhauls.
12-67
Each crane will have a main and auxiliary hoist.The combined
capacity of the main hoist for both cranes will be sufficient for
the heavi est equi pment 1i ft,wh ich wi 11 be the generator rotor,
plus an equalizing beam.A tentative crane capacity of 205 tons
has been established.The auxiliary hoist capacity will be about
25 tons.
(b)Draft Tube Gates
Draft tube gates will be provided to permit dewatering of the tur-
bine water passages for inspect ion and mai ntenance of the tur-
bines.The draft tube gate openings (one opening per unit)will
be located in the surge chamber. The gates will be of the bulk-
head type,installed under balanced head conditions using the
surge chamber crane.Four sets of gates have been assumed for the
six units,with each gate 20 feet wide by 10 feet high.
When Unit 1 is ready for startup,the gates will be installed in
Units 2, 5, and 6,with one gate available for Unit 1.Turbine
bulkhead domes will be installed in Units 3 and 4.
(c) Surge Chamber Gate Crane
A crane will be installed in the surge chamber for installation
and removal of the draft tube gates as well as the tailrace tunnel
intake stoplogs.The crane will either be a monorail (or twin
monorai 1)crane,a top runni ng crane,or a gantry crane.For the
preliminary design,a twin monorail crane has been assumed. The
crane will be about 30 tons in capacity,and will have a two point
1i ft.
(d)Miscellaneous Cranes and Hoists
In addition to the powerhouse cranes and surge chamber gate crane,
the following cranes and hoists will be provided in the power
plant:
- A 5-ton monorail hoist in the transformer gallery for transfor-
- A 4-ton monorail hoist in the circuit breaker gallery for
handling the main circuit breakers;
Small overhead jib or A-frame type hoists in the machine shop
for handling material;and
- A-frame or monorail hoists for handling miscellaneous small
equipment in the powerhouse.
(e)Elevators
Access and service elevators will be provided for the power plant
as follows:
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-An access elevator from control buildings to powerhouse;
- A service elevator in the powerhouse service bay;and
-Inspection hoists in the cable shafts.
Power Plant Mechanical Service Systems
The mechanical service systems for the power plant can be grouped
into six major categories:
-Station water systems;
-Fire protection;
-Compressed air;
-Oi 1 storage and handling;
- Drainage and dewatering;and
-Heating,ventilation and cooling.
(i)Station Water Systems
The station water systems will include the water intake,
cooling water systems,turbine seal water systems,and
domestic water systems.The water intakes wi 11 supply
water for the various station water systems in addition to'
fire protection water.The water can be taken from the
penstock;however,pressure-reducing valves will be neces-
sary because of the high pressure of the water (about 330
psig maximum).Alternatively,water can be supplied from
the draft tube using pumps to provide suitable pressure.
On a unit basis,cooling water will be required for genera-
tor air coolers,turbine and generator bearing coolers,
transformers,and powerhouse unit air coo1ers.The total
cool ing water requirements for each unit wi 11 be about
4,000 gpm.In addition,the compressed air systems in the
service bay will require approximately 100 gpm of cooling
water.One coo1i ng water pump wi 11 be provi ded per unit
which will take water from downstream from the water intake
strainer.To ensure suitable reliability,the cooling
water pumps for two units will be interconnected,with each
pump capable of handling the flow for both units.Two
cooling water pumps in the service bay will handle compres-
sor cooling water requirements.The cooling water for each
unit will discharge into the turbine draft tube,while the
compressor cooling water will flow into the station drain-
age system.
Turbine seal water will be supplied to the seal on the main
shaft and to the runner seals when the unit is spinning in
air (i .e.,in spinning reserve mode).Fi ltered water may
or may not be required,depending on the type of shaft
seal.If no fi ltration is needed,the seal water will be
12-69
(i i)
taken directly from the high-pressure side of the cooling
water pumps.If filtration is necessary,a single system
will be provided for the powerhouse.The system will have
two fi lters and two pumps whi ch wi 11 take water from
downstream from the water intake strai ner and di stri bute
the water to each unit via a looped header.
Domest ic water wi 11 be requi red for the washrooms,1unch
rooms,drinking fountains,and a service sink and emergency
eyewash in the battery room.Peak domestic water require-
ments are expected to be about 30 gpm.The system wi 11
have two pumps and a hydropneumatic tank.Water will be
t akenfrom the water intake system and wi 11 be treated by
chlorination or other means as necessary.
Fire Protection System
The power plant fire protection system will consist of a
fire protection water system with fire hose stations
located throughout the powerhouse and transformer gallery;
sprinkler systems for the generators,transformers,and the
oil rooms;and portable fire extinguishers located in
strategic areas of the powerhouse and transformer gallery.
Fire hose stations will be provided on all floors of the
powerhouse,in the transformer gallery,and in the bus
tunnels.
Fire protection water will be taken from the station water
intakes.Pressuri zed water wi 11 be provi ded by a pumped
system with two main fire pumps as well as a jockey pump,
or alternatively by a head tank with two supply pumps which
keep the head tank full.For preliminary design purposes,
a system with a head tank has been selected because of the
increased re1i ab i1i ty of the system.Wi th an underground
powerhouse,a head tank can be provided quite easily at a
suitable elevation as an adit to the access shaft.
The capacity of the head tank wi 11 be about 100,000
9 a11orf$~;--th-etanks-wi ll-have--two-comp-artments--to--permH-
draining of half the water for inspection and maintenance.
For reliability,the water supply pumps will have two
e1ectrica.1 power sources.
Service water outlets will be installed at the various fire
hose stations to supply water for washing downs floors or
equipment.The sprinkler systems for generators,transfor-
mers,and oil rooms will be the dry deluge type,operated
by a solenoid valve which in turn will be activated by
detectors in the respective area.
The portable fire extinquishers will generally be carbon
dioxide or a dry chemical type.
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(iii)Compressed Air Systems
Compressed air will be required in the powerhouse for the
following:
-Service air;
-Instrument air;
-Generator brakes;
-Draft tube water level depression;
-Air blast circuit breakers;and
-Governor accumulator tanks.
For the preliminary design,two compressed air systems have
been assumed:a 100-psig air system for service air,brake
ai r,and air for draft tube water 1eve 1 depressi on;and a
1,OOO-psi g hi gh-pressure air system for governor ai rand
circuit breaker air.For detailed plant design,a separate
governor air system and c t rcuit-breaker air system may be
provided.
The service air systems will have three air compressors of
the rotary screw or rec i procat i ng type,each wi th a capa-
city of about 200 cfm.The system wi 11 have four air
receivers,two with approximately 800 ft3 capacity used
for the draft tube water 1eve 1 depress ion system,and two
with approximately 150 ft 3 used for service and brake
air.The system will be designed to give priority to the
brake air system.Service air piping with air hose sta-
tions will be located on all floors of the powerhouse and
in the transformer gallery.
The high-pressure governor/circuit~breaker air system will
have three reciprocating air compressors with approximately
30-cfm capacity each,and three small air receivers.The
governor air system will supply air for initial filling of
the governor system accumulator tanks and for makeup air to
replace air lost through leakage and air dissolved in the
governor system oil.
The circuit breaker air system will provide compressed air
for operation of the main breakers.To insure dry air for
the breakers,the air will be stored at 1,000 psig and then
reduced to about 350 psig for operation of the breakers.
Instrument air wi 11 also be taken from the high-pressure
air system.
(i v)Oi 1 Storage and Handl i ng
Facilities will be provided for replacing oil in the trans-
formers and for topping-up or replacing oil in the turbine
and generator beari ngs and the governor pumpi ng system.
12-71
For preliminary design purposes,two oil rooms have been
assumed, one in the transformer gallery and one in the
powerhouse service bay.
The transformer gallery wi 11 have two o i 1 storage tanks,
one for fi ltered oi 1 and the other for unfi ltered oi 1.
Each tank will have a capacity at least equal to the volume
of ol1 in one transformer (about 8,000 gallons).A header
with valve stations at each transformer wi 11 be used for
transferring oil to and from the transformers.Oi 1 will be
transferred by a portable pump and filter unit.
A similar system will be provided in the powerhouse with a
filtered and unfiltered oil tank and distribution header
with valve stations at each unit.The o i 1 tank capacity
will be equal to the total oil volume for one unit (about
3,000 gallons).
During the detailed design stages,consideration should be
given to the use of mobile oil tanks lo~ated in a parking
area near the powerhouse and transformer gallery,near the
access tunnel.
(v)Drainage and Dewatering Systems
The drainage and dewatering systems will consist of:
- A unit dewatering and filling system;
- A clear water discharge system;and
- A sanitary drainage system.
The unit dewatering and filling systems will consist of two
sumps each with two dewatering pumps and associated piping
and valves from each of the units.To prevent station
floodi ng,the sump wi 11 be desi gned to withstand maximum
tailwater pressure.For preliminary design purposes,
submersible dewatering pumps have been assumed.Vertical
turbine type pumps can also be considered;however,since
the dewatering system .acts as anemergenGy~dr-a·inage-s:y-stem,
the pump columns would have to be extended so that the
motors are above maximum tailwater level.Another option
is turbine-driven pumps,but these are generally very
costly.A valved draft tube drain line will connect to a
dewatering header running along the dewatering gallery.
The spiral case will be drained by a valved line connecting
the spiral case to the draft tube.Suitable provisions
will be necessary to insure that the spiral case drain
valve is not open when the spiral case is pressurized to
headwater 1eve 1.The dewateri ng pump di scharge 1i ne wi 11
discharge water into the surge chamber.The general proce-
dure for dewateri ng a unit wi 11 be to close the intake
gate,drai n the penstock to t ai lwater 1eve1 through the
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unit,then open the draft tube and spiral case drains to
dewater the unit.Unless the drainage gallery is below the
bottom of the draft tube elbow,it will not be possible to
comp 1ete 1y dewater the draft tube through the dewateri ng
header.If necessary,the remainder of the draft tube can
be unwatered using a submersible pump lowered through the
draft tube access door.Unit filling to tailwater level
wi 11 be accompl ished from the surge chamber through the
dewateri ng pump discharge 1ine (with a bypass around the
pumps)and then through the draft tube and spiral case
drain lines.Alternatively,the unit can be filled to
t ai lwater 1eve1 through the draft tube drain 1ine from an
adjacent unit.Fi lling the unit to headwater pressure will
be accomplished by "cracking"the intake gate and raising
it about 2 to 4 inches.
The clearwater drainage system will handle normal drainage
into the power plant.Drainage will be collected by a
network of floor drai ns,trench drai ns,pressure re 1i ef
drains,and equipment drains which discharge into gravity
drainage sumps from which the water will be pumped to the
surge chamber.
The sumps in the powerhouse will have submersible pumps for
the same reasons as di scussed above for the dewateri ng
system.The transformer gallery will have vertical turbine
type pumps.The drainage sumps in the powerhouse will have
an overflow line which will discharge water into the adja-
cent dewatering sump should inflow into the drainage sumps
exceed the capaci ty of the drai nage pumps.The overflow
line will have a flap valve to prevent reverse flow from
the dewatering sump.
Particular care will be taken to prevent accidental oil
spi 11 s from bei ng discharged into the powerhouse.The
following provisions will be made:
- All three main sumps will have oil contamination detec-
tors to obtain the pressure of oil in the sumps;
-Drainage into the sumps will first pass through an oil
separator;
-Controls for the drai nage pumps·into the transformer
gallery will be interlocked with the transformer fire
protection sprinkler system.Activation of the
sprinklers,which signifies a transformer fire and the
possibility of a major oil spill,will prevent the
drai nage pumps from st art ing unt i 1 the drai nage sump is
almost full.It will be possible to retain about 40,000
gallons of oi l/water in the sump before the pump start
12-73
(each transformer holds about 8,000 gallons of oil).In
this manner,it will be possible to retain a large amount
of oil inthe sump where it may be skimmed off;and
-Suitable oil retention curbs will be provided in the oil
rooms.
Sanitary drainage from the washrooms, lunch room,and
drinking fountains will drain to a packaged sewage treat-
ment plant and then wi 11 be di scharged into the surge
chamber via sewage lift pumps.
(vi)Heating,Ventilation and Cooling
The heating,ventilation and cooling system for the under-
ground power plant will be designed primarily to maintain
sui tab 1e temperatures for equi pment operat ion and to pro-
vide a safe and comfortable atmosphere for operating and
maintenance personnel.Air will be drawn into the power
facilities through one or more shafts,cirtulated through-
out the power plant,and discharged from the power pl ant
through other shafts.For preliminary design purposes it
has been assumed that air will be drawn down the access and
the cable shafts,and discharged out through the access
tunnel;however,the actual arrangement wi 11 depend upon
the final design.
The power plant will be located in mass rock which has a
constant year around temperature.of about 40°F.Consi der-
ing heat given off from the generators and other equipment,
the primary requirement will be for air cooling.Ini-
tially,some heating will be required to offset the heat
loss to the rock,but after the first few years of opera-
tion an equilibrium will be reached with a powerhouse rock
surface temperature of about 60 to lOaF.
Air cooling will be accomplished by providing suitable air
changes incorporating cooling coils in the air circulation
_..~--~-_._..__._--~~-.-s.ystem.-···-G001ingwa·ter--t~0m--the-s~tat-i-0n·-serv+eewater-··
supply will be circulated through the cooling coils.In
winter,some heating may be required to moderate the
temperature of the incoming air into the power plant.
Allowance must be made in the design for the possibility
that large quantities of air (up to about 5,000 cfm per
unit)may be required for turbine aeration.
Other factors which must be considered or incorporated in
the design are:
-To prevent or minimize the circulation of combustion
products in the event of a fire,powerhouse ventilation
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should be separate from transformer gallery ventilation
and provision should be made for isolating the two areas;
and
-Suitable air locks will be necessary to preclude adverse
chimney effects in the shafts.
Surface Facilities Mechanical Service Systems
The mechanical services at the control building on the surface
will include:
A heating,ventilation,and air conditioning system for the
control room;
-Domestic water and washroom facilities;and
- A halon type fire protection system for the control room.
Domestic water will be supplied from the powerhouse domestic water
system, with pumps located in the powerhouse and piping up through
the access shaft.Sanitary drainage from the control bu i ld i nq
will drain to the sewage treatment plant in the powerhouse through
piping in the access tunnel.
The standby generator bUilding will have the following services:
- A heating and ventilation system;
- A fuel oil system with buried fuel oil storage tanks outside the
building,and transfer pumps and a day tank within the building;
and
- A fire protection system of the carbon dioxide or halon type.
Machine Shop Facilities
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A mach ine shop and too1 room wi 11 be located in the powerhouse
service bay area with sufficient equipment to take care of all
normal maintenance work at the plant,as well as machine shop work
for the larger components at Devil Canyon.For preliminary design
purposes,an area of about 1,500 ft 2 has been allocated for the
machine shop and tool room.The actual equipment to be installed
in the machine shop will be decided during the design stages of
the project;however,it will generally include drill presses,
lathes,arbor press,power hacksaw,shaper,and grinders.
12.18 -Accessory Electrical Equipment
The accessory electrical equipment described in this section includes
the following:
12-75
Main generator step-up 15/345 kV transformers;
Isolated phase bus connecting the generator and transformers;
Generator circuit breakers;
345 kV oil-filled cables from the transformer terminals to the
switchyard;
Control systems of the entire hydro plant complex;and
Station service auxiliary AC and DC systems.
Other equipment and systems described include grounding,lighting
system,and communications.
The main equipment and connections in the power plant are shown in the
single line diagram,Plate 32.The arrangement of equipment in the
powerhouse,transformer gallery,and cable shafts is shown on Plates 27
through 29.
(a)Selection of Transformers and H.V.Connections
(i)General
Ni ne single-phase transformers and one spare transformer
will be located in the transformer gallery.Each bank of
three s i ngl e-phase transformers wi 11 be connected to two
generators through generator ci rcui t breakers by iso 1ated
phase bus located in individual bus tunnels.The HV
terminals of the transformer will be connected to the 345
kV switchyard by 345 kV single-phase oil-filled cable
installed in 700-footlong vertical shafts.There will be
two sets of three s i ngle-phase 345 kV oi l-fi lled cables
installed in each cable shaft.One set will be maintained
as a spare three phase cable circuit in the second cable
shaft.These cable shafts will also contain the control
and power cables between the powerhouse and the surface
contra 1 room,as well as emergency power cab 1es from the
diesel generators at the surface to the underground facili-
ties.
A number of considerations led tothecho~ce~of the above
sys-temoftransform at-i-on .and eonnee-t+ons-;--l3i-f-ferent--a-lter-
native methods and equipment designs were also considered.
In summary,these are:
-One transformer per generator vs one transformer for two
generators;
-Underground transformers vs surface transformers;
-Direct transformation from generator voltage to 345 kV vs
intermediate step transformation to 230 kV or 161 kV,and
then to 345 kV;
-Single-phase vs three-phase transformers for each alter-
native method considered;and
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-Oi l-fi lled cable vs solid dielectric cable for SF6 gas-
insulated bus.
Reliability Considerations
Reliability considerations will be based on the general
reliability requirements for generation and transmission
described in Section 15 regarding the forced outage of a
single generator,transformer,bus or cable in addition to
planned or scheduled outages in a single contingency situa-
tion,or a subsequent outage of equipment in the double
contingency situation.The system should be capable of
readjustment after the outage for loading within normal
ratings and for loading within emergency ratings.
The generators will be rated with a 115 percent continuous
overload capability.All main connections and equipment
including the transformers,circuit breakers,isolated
phase bus,and 345 kV cables will be rated for continuous
operation at the 115 percent overload rating of the genera-
tors.
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Emergency ratings are different for different items of
equipment and emergency periods.It generally varies
between 110 to 130 percent in summer to 120 to 140 percent
in winter for a 4 to 12 hour period,with somewhat higher
values for very short (1 hour)emergency periods.
(iii)Technical and Economic Considerations
The use of surface transformers connected directly to the
underground generators by isolated phase buses was ruled
out at the outset due to significantly higher costs and
higher losses associated with generator isolated phase
bus.The incremental cost could be decreased if three
units were connected to one transformer,but such a compro-
mise is not acceptable due to reliability considerations.
In general,3-phase transformers are preferred to single-
phase transformers because of their lower overall costs,
smaller overall dimensions and smaller underground gallery
dimensions.However,transport limitations within the
Railbelt seriously affect the use of the larger size
3-phase transformers,both in di mens ions and wei ght.The
following are the road and rail data available:
- Parks and Denali Hi~hways
Maximum load - 150,000 lb
Overweights require special permits.
12-77
-Ra i lway
Maximum Weight -263,000 lb
Dimension Limits - 16 feet high,10 feet wide
A further check of these design limitations for the
selected sizes of transformers is recommended during the
detailed design stage.A careful route reconnaissance
study is also required.
Single-phase transformers are therefore recommended for the
6-unit power plant.One advantage of single-phase trans-
formers is that a spare transformer can be provided at a
fairly low incremental cost.
The grouped unit arrangement with two generators per trans-
former will allow a smaller gallery length,with center-to-
center spacing comparable to the generator spacing.The
grouped un it arrangement is the recommended arrangement.
The alternative with one transformer per generator will
require a gallery about 300 feet longer.
The double~step transformation scheme (15/161 KV generator-
transformer,161 KV cable and 161/345 KV auto-transformer
at the switchyard)is economicallly competitive with the
direct transformation scheme (15/345 KV),resulting from a
number of tradeoffs:cost/MVA per transformer is lower;
also dimensions,weights and cavern dimensions are lower;
but the i ntermedi ate..voltage transformer costs are
add it i ona 1.
Di rect transformat i on (15/345 KV)is best from system
transient stability viewpoint since the overall impedance
of the generator unit to the 345 KV bus is lower.Further-
more,it has a better overall reliability since there is
one less voltage level and,therefore,less equipment in
the generat ing "chat nil of equi pment.Th is scheme costs
about·$2 million less in overall costs compared to the
.....-~-~.....····-doub+e-s-t·ep·transformation scheme;------··~···~_·-·
The comparison between 345 KV oil-filled cables and other
345 KV cable and bus system is made in Section 12.18.The
SF6 bus is about 5 to 6 times the cost of the oi l-fi lled
cables.It also requires a larger diameter cable shaft.
The oil-filled cable is well proven at a number of under-
ground power i nsta 11 at ions and was therefore selected for
both technical and economic considerations.
f1IJ
(c)Main Transformer
(i)Rating and Characteristics
The nine single-phase transformers (three transformers per
group of two generators)and one spare transformer,will be
of the two winding,oi l-immersed,forced-oi 1 water-cooled
(FOW)type,with rating and electric characteristics as
follows:
The temperature rise above air ambient temperature of 40°C
is 55°C for the windings for continuous operation at the
rated kVA.
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Rated capac i t y:
High voltage winding:
Basic insulation level (BIL)
of H.V.winding:
Low voltage winding:
Transformer impedance:
145 MVA
345 /-V3 kV,Grounded Y
1300 kV
15 kV,De lta
15 percent
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( i i )Construction
The transformers will be of the FOW type with water-cooled
heat exchangers whi ch wi 11 remove the heat from the oi 1
circulating through the windings.A one-third spare cooler
capacity wi 11 be provided.The transformer wi 11 be of the
forced oil directed type with a design aimed to achieve
minimum dimensions and weight for shipping purposes.The
low voltage terminals will be connected to the isolated
phase bus,and the high voltage terminals to the 345 kV
oil-filled cable box termination at the transformer.
Lightning arresters will be connected directly to the high
voltage terminals.The transformer installation in the
gallery will be designed to provide the necessary ground
and safety clearances from the live 345 kV terminals to all
nearby equipment and structures.
The tank underbase will be provided with flanged wheels for
transport on rails.The spare single-phase transformer
will be exactly identical to the remaining nine single-
phase transformers.It wi 11 be mai ntai ned ina state of
maximum readiness,for connection in the shortest practical
time to replace any of the main transformers.
The transformers will be fully tested and inspected in the
factor y accord ing to ANSI!NEMA St andards.They wi 11 be
shipped without oil and filled with inert gas for protec-
tion.At the site,erection would be mainly for external
fittings such as bushings,lightning arresters,heat
exchangers,piping,and electrical connections.
12-79
Generator Isolated Phase Bus
(i)Ratings and Characteristics
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18,000
240,000
150,000
150
Transformer
Connection
to the surge protect ion
excitation transformers,
Bus duct ratings are as
9,000
240,000
150,000
150
Generator
Connection
Rated current,amps
Short circuit current
moment ary,amp s
Short circuit current,
symmetrical,amps
Basic insulation level,kV (BIL)
The bus will be of standard self-cooled design with conduc-
tor and tubular enclosure of aluminum.The current rating
is such that either a self-cooled or forced cooled design
will be.poss ibJe.With ..aforcedcooled-desjgn,the size
and costs will be lower;however,if the forced-cooling
plant fails,the bus would be severely derated to a rating
less than 50 percent of the forced cooling rating.The
self-cooled designs are used up to 30,000 amps rated
current and are therefore recommended for this installation
where the ratings will not exceed 18,000 amps.
The enclosure will be of welded construction and each bus
will be grounded.The construction is highly reliable;
will eliminate phase-to-phase faults,neutralize the magne-
tic field outside the enclosure,and provide protection
against contamination and moisture,with consequent minimum
maintenance requirements.
The iso 1ated phase bus mai n connect ions wi 11 be located
between the generator,generator ci rcui t breaker,and the
transformer.
Fire walls wi 11 separate each single-phase transformer.
Each transformer will be provided with fog-spray water fire
protection equipment,automatically operated from heat
detectors located on the transformer.
Tap-off connect ions wi 11 be made
and potential transformer cubicle,
and station service transformers.
fo 11 ows:
The bus conductors will be designed for a temperature rise
of 65°C above 40°C ambient temperature.
(ii)Construction
(iii)Fire Protection
(d)
(e)Generator Circuit Breakers
The generator circuit breakers will be of the enclosed air circuit
breaker design suitable for mounting in line with the generator
isolated phase bus ducts.They are rated as follows:
The short circuit rating is tentative and will depend on detailed
analysis in the design stage.
The breakers will be designed and constructed with a high degree
of reliability.The phase spacing of the breakers will be
genera 11y the same as the iso1ated phase bus duct.The breakers
will be mounted on strong foundations on the generator floor
designed to absorb the reaction forces when the breaker operates.
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Rated Current:
Voltage:
Breaking capacity,
symmetrical,amps
9,000 Amps
23 kV class,3-phase,60 Hertz
150,000
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(f)345 kV Oil-Filled Cable
(1)General
The recommended 345 kV connection is a 345 kV oil-filled
cable system between the high voltage terminals of the
transformer and the surface switchyard.The cable wi 11 be
installed in a vertical cable shaft.Cables from two
transformers will be installed in a single cable shaft.
This system of 345 kV connection was chosen after a techni-
cal and economic analysis of alternative methods of connec-
tion,including:
-SF6 isolated bus system;
-High pressure oil pipe cable system;and
-Solid dielectric cable system.
The SF6 bus system is considered to be the best alterna-
tive to the oil-filled cable system.Its advantages are a
generally better overall reliability,including a low fire
hazard.However,it costs approximately 5 to 6 times that
of the oil-filled cable installation,and requires almost
twice the diameter cable shaft of the cable installation.
The overall cost difference is approximately $7,000,000 in
direct costs.
The oil pipe cable will consist of three conductors con-
tained within an oil-filled steel pipe.This system has
the highest potential fire hazard of all the cable systems
and is not recommended for high head vert ical cab 1e in-
12-81
(g)
st al lat lons.The solid dielectric (polymeric)cables are
still under development at the 345 kV to 500 kV voltage
class.
It is recommended that further detailed study of the oil-
filled cable in comparison with the SF6 bus and other
more recent SF6 cable designs under development be
undertaken at the design stage.
By far the greatest number of high voltage,high capacity
installations utilize oil-filled cables.A formidable
experience record is evident for the oil-filled cable
installations associated with large power plants all over
the world.Typical installations include the 525 kV/650
MVA units at Grand Coulee III,the 345 kV/550 MVA units at
Churchill Falls in Canada,the 400 kV/2640 MVA cables at
Severn River crossing in Great Britain,and the 400 kV/2340
MVA cables at Dinorwic pumped storage plant in Great
Britain.
(i1)Rating and Characteristics
The cable will be rated for a continuous maximum current of
800 amps at 345 kV +5 percent.The maximum conductor
temperature at the maxTmum rating will be 70°C over a maxi-
mum ambient of 35°C.This rating will correspond to 115
percent of the generator overload rating.Tbe normal
operating rating of the cable will be .87 percent,with a
corresponding lower conductor temperature which wi llim-
prove the overall performance and lower cable aging over
its project operating life.Depending on the ambient air
temperature,a further overload emergency rating of about
10 to 20 percent will be available during winter condi-
tions.
The cables wi 11 be of single-core construction with oi 1
flow through a central oil duct within the copper conduc-
tor.Cables will have an aluminum sheath and PVC over-
sheath.~~'No-cable jointingwill be required--for-the 70-o--{0
800 feet length cable installation.
Control Systems
(i)General
A Susitna Area Control Center will be located at Watana to
control both the Watana and the Devil Canyon power plants
as shown in Pl ate 34.The control center wi 11 be 1inked
through the superv i sory system to the Central Di spatch
Control Center at Willow as described in Section 14.
12-82
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The supervisory control of the entire Alaska Railbelt sys-
tem will be done at the Central Dispatch Center at Willow.
A high level of control automation with the aid of digital
computers wi 11 be sought but not a complete computerized
direct digital control of the Watana and Devil Canyon power
plants.Independent operator controlled local-manual and
local-auto operations will still be possible at Watana and
Devil Canyon power plants for testing/commissioning or
during emergencies.The control system will be designed to
perform the following functions at both power plants:
-Start/stop and loading of units by operator;
- Load-frequency control of units;
-Reservoir/water flow control;
- Continuous monitoring and data logging;
-Alarm annunciation;and
-Man-machine communication through visual display units
(VDU)and console.
In addition,the computer system will be capable of
retrieval of technical data,design criteria,equipment
characteristics and operating limitations,schematic
diagrams,and operating/maintenance records of the unit.
The Susitna Area Control Center wi 11 be capable of com-
pletely independent control of the Central Dispatch Center
in case of system emergencies.Similarly it will be possi-
ble to operate the Susitna units in an emergency situation
from the Central Di spatch Center,although thi s should be
an unlikely operation considering the size,complexity,and
impact of the Susitna generating plants on the system.
The Watana and Devil Canyon plants will be capable of
"black s t ar t "operation in the event of a complete black
out or co 11 apse of the power system.The contro 1 systems
of the two plants and the Susitna Area Control Center
complex will be supplied by a non-interruptible power
supply.
(ii)Unit Control System
The unit control system will permit the operator to initi-
ate an entire sequence of actions by pushing one button at
the control console,provided all preliminary plant condi-
t ions have been fi rst checked by the operator,and system
security and unit commitment have been cleared through the
central dispatch control supervisor.Unit control will be
designed to:
-Start a unit and synchronize it with the system;
-Load the unit;
- Stop a unit;
12-83
Operate a unit as spinning reserve (runner in air with
water blown down in turbine and draft tube);and
- Operate as a synchronous condenser (runner in air as
above).
Unit control will be essentially possible at four different
levels in a hierarchical organization of the control sys-
tem:
-Local control at the machine floor at individual turbine-
generator control boards (primarily designed for commis-
sioning and recommissioning of units).It will be the
responsibility of the operator for performing individual
control operations in the correct sequence,and monitor-
ing instrumentation during local control operations.
-Automatic ot semi-automatic system for start-up and
shut-down of generat i ng uni t at the 1oca1 board at the
machine floor.
-Fully automatic system at Sdsitna Area Control (at
Watana)for Watana and Dev i l Canyon power plants.(Thi s
will be the normal Susitna operation.)
-Fu lly automat i c system through superv i sory contro 1 from
Central Dispatch Center at Willow.(Abnormal or emer-
gency situations only).
(iii)Computer-Aided Control System
Traditionally,control systems for power plants in general,
and hydro plants in particular,have utilized hard-wired
switchboard type equipment (such as electro-mechanical
relays,instruments,alarm annunciators,signal lamps,
mimic diagram and control switches) for the operation,
indication,alarm and control of the power plant.Such
equipment was installed both at the plant local control
area on the machine floor as well as in the control room,
with a HmHed degreeofmi-niaturizati on of equipment .at
the control desks in the control room.
While traditional switchboard type equipment is still
utilized at the local control level,supplemented with
programmable control systems at many plants,the design of
control and display equipment at modern central control
rooms has been rapi dly mov l ng towards computer-ai ded or
fully computer-controlled systems,especially where remote
control operations are contemplated.One of the problems
encountered by utilities is the necessity for operating
personnel familiar with the conventional control systems to
adapt to the new computer-aided control systems. In this
context,establishing a modern computer-aided control
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system in the Alaska Power Authority electrical system for
the Susitna Project complex should not pose any special
problems for the adaption and training of operators.
The computer-aided control system at the Susitna Area
Control Center at Watana will provide for the following:
- Data acquisition and monitoring of unit (MW,MVAR,speed,
gate position,temperatures,etc.);
Data acquisition and monitoring of reservoir headwater
and t ail water 1eve1s;
- Data acquisition and monitoring of electrical system
voltage and frequency;
- Load-frequency control;
- Unit start/stop control;
- Unit loading;
-Plant operation alarm and trip conditions (audible and
visual alarm on control board,full alarm details on VDU
on demand);
- General visual plant operation status on VDU and on giant
wall mimic diagram;
- Data logging,plant operation records;
-Plant abnormal operation or disturbance automatic
recording;and
-Water management (reservoir control).
The block diagram of the computer-aided control system is
shown in Plate 34.The supervisory control and telemeter-
i ng system and central dispatch center system det ai1s are
described in Section 14.
(iv)Local Control and Relay Boards
Local boards will be provided at the powerhouse floor
equipped with local controls,alarms,and indications for
all unit control functions.These boards will be located
near each unit and will be utilized mainly during testing,
commissioning,and maintenance of the turbines and genera-
tors.It will also be utilized as needed during emergen-
cies if there is a total failure of the remote or computer-
aided control systems.
12-85
The unit electrical protective relays will be mounted on
re 1ay boards,wi th one board for each generator located
near the unit.Differential protection will be provided
for each generator and transformer.The differential zones
of protection overlap will include all electrical equipment
and connections.The 345 kV ol l-fi lled cable to the sur-
face switchyard will be protected by a pilot-wire differen-
tial protection relay.The overall differential relay
protects the generators,transformers,and 345 kV cable.
Sensitive ground fault stator protection will be provided
for the generator.Protect i on wi 11 also be provi ded for
negative phase sequence operation,loss of excitation,
overvoltage,and under frequency.A phase impedance relay
will provide backup protection for the generator.
(v) Load-Frequency Control
The load frequency control system will provide remote
control of the output of the generator at Watana and Devil
Canyon from the central dispatch control center through the
supervi sory and computer-ai ded control system.at Watana.
The bas i c method of load frequency control wi 11 use the
plant error (differential)signals from the load d i sp'atch
center and wi 11 allocate these errors to the power pl ant
generators automatically through speed-level motors.Pro-
vi si on wi 11 be made in the control system for the more
advanced scheme of a closed-loop control system with digi-
tal control to control generator pow~r.
The control system wi 11 be designed to take into account
the digital nature of the controller-timed pulses as well
as the inherent time delays caused by the speed-level motor
run-up and turbine-generator time-constants.
The load set-point for the Susitna area generation will be
set at the Central Di spatch Center.The summated power
will be telemetered from the Susitna Area Control center to
the Central Dispatch Center,from which the required
~~-~----~~---dtfferent+a-l--p+ant--g e ner-at-io n---(--'J-errorJL)-w-i-l--l-be--dete~mi-n ed---
and transmitted by the supervisory system to Susitna Area
Control Center.From this point,the remaining functions
for the automatic generation control will be carried out by
the plant supervisory control systems to load the individ-
ual generating units at Watana and Devi 1 Canyon.
The unit will be automatically removed from load-frequency
control for various conditions including failure of super-
vi sory system,unit contro 11 er or computer'system, abnor-
mally high plant frequency,unit shut-down,and dc power
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failure.When the unit is taken off automatic load-fre-
quency control,it will be returned to manual load and
frequency control by the operator at Watana Control room.
(h)Station Service Auxiliary AC and DC Systems
(i)Auxiliary AC System
The station service system will be designed to achieve a
re 1i ab1e and economi c di stri but ion system for the power
plant and switchyard,in order to satisfy the following
requirments:
-Station service power at 480 volts will be obtained from
two 2,000 kVA auxi 1i ary transformers connected direct ly
to the generator circuit breaker outgoing leads of Units
1 and 3;
-Surface auxiliary power at 34.5 kV will be supplied by
two separate 7.5/10 MVA transformers connected to the
generator leads of Units 1 and 3;
-Station service power will be maintained even when all
the units are shut down and the generator circuit
breakers are open;
- 100 percent standby transformer capaci ty wi 11 be
available;
- A spare auxiliary transformer will be maintained,
connected to Unit 5; and
-1181 ack st ar-t"capabi 1 ity wi 11 be provided for the power
plant in the event of total failure of the auxiliary
supply system,500 kW emergency diesel generators will be
automatically started up to supply the power plant and
switchyard with auxiliary power to the essential services
to enable startup of the generators.
The main ac auxiliary switchboard will be provided with two
bus sections separated by bus-tie circuit breakers.Under
normal operating conditions,the station-service load is
divided and connected to each of the two end i ncomi ng
transformers.In the event of failure of one end supply,
the tie breakers will close automatically.If both end
supplies fail,the emergency diesel generator will be
automatically connected to the station service bus.
Each unit will be provided with a unit auxiliary board
supplied by separate feeders from the two bus sections of
the main switchboard interlocked to prevent parallel opera-
12-87
tiona Separate ac swltchboards will furnish the auxiliary
power to essential and general services in the power
plant.
The unit auxiliary board will supply the auxiliaries neces-
sary for starting,running,and stoppi ng the generating
unit.These supplies will include those to the governor
and o i 1 pressure system,bearing oi 1 pumps,cooling pumps
and fans,generator circuit breaker,excitation system,and
miscellaneous pumps and devices connected with un i t
operation.
The station essential service supplies will include power-
house sump pumps,drainage pumps,compressors for circuit
breakers,and generator brakes,dc battery chargers,con-
trol and metering devices,communications,fire pumps,and
other miscellaneous essential power requirements.
The station general supplies will include powerhouse light-
ing, heating,ventilating and air-condltioning,elevators,
cranes,machine shop and tools,and other miscellaneous
pumps and general requirements.
The 34.5 kV supply to the surface facilities will be dis-
tributed from a 34.5 kV switchboard located in the surface
control and administration building.Power supplies to the
swltchyard,power intake,and spi llway as well as the
11 ght i ng systems for the access roads and tunnels wi 11 be
obtained from the 34.5 kV switchboard.
The unit auxiliary board will supply the auxiliaries neces-
sary for starting,running,and stopping the generator-tur-
bine unit.These supplies will include those to the gover-
nor and oil pressure system, bearing oil pumps,cooling
water pumps and fans,generator circuit breaker,excitation
system,and miscellaneous pumps and devices connected with
unit operation.
,_Ih,e_st,atjDn,._,e,s,s,entj_aJ~s,eLvjc,e_,s,upp_LLes~wjJJ_"j_ncJ,ude__p,ower.~.,."
house sump pumps,drainage pumps,compressors for circuit
breaker,air and generator brakes,dc battery chargers,
control and metering devices,communications,fire protec-
tion pumps,and other miscellaneous essential power
requirements.
The station general supplies will include powerhouse light-
ing,heating,ventilating and air-conditioning,elevators,
cranes,mach ine shop and too1s,and other mi sce 11 aneous
pumps and general requirements.
The 34.5 kV supply to the surface facilities will be dis-
tributed from a 34.5 kV switchboard located in the surface
12-88
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control and administration building.Power supplies to the
switchyard power intake,and spillway as well as the 1ight-
i ng systems for the access roads and tunnels wi 11 be ob-
tained from the 34.5 kV switchboard.
The two 2000 kVA,15000/480 volt stations service transfor-
mers and the spare transformer wi 11 be of the 3-phase,
dry-type,sealed gas-filled design.The two 7.5/10 MVA,
15/34.5 kV transformers will be of the 3-phase oil-immersed
OA!FA type.
Emergency diesel generators,each rated 500 kW,will sepa-
rately supply the 480 volt and 34.5 kV auxiliary switch-
boards during emergencies.Both diesel generators will be
located in the surface control building.
An uninteruptib1e high security power supply will be pro-
vided for the computer control system.
(ii)DC Auxiliary Station Service System
The dc auxiliary system will supply the protective relay-
ing,supervisory,alarm,control,tripping and indication
circuit in the power plant.The generator static excita-
tion system will be started with "f lashinq"power from the
de battery.It will also supply the emergency lighting
system at critical plant locations.
Separate duplicate lead-acid batteries for 125 volt dc will
be provided in the powerhouse.The 48 volt battery supply
for the supervisory and computer aided control system and
microwave communications will be located in the surface
control building.
The main battery system will be supplied by double charging
equipment consisting of a full wave rectifier system with
regulated output voltage which normally will supply the
continuous dc load in the system.The battery capacity
will be suitable for an emergency loading based on a fail-
ure of ac station service lasting 5 hours.
(iii)IIB1ack Start ll Capability
The Watana power plant will have a built-in capability of
starting up a completely blacked-out power system in a very
short time.Only a few basic requirements will have to be
sat i sfi ed:
-Sufficient water will be available in the reservoir for
the minimum generation required for "bl ack st ar t"opera-
tion;
12-89
-The governor oil system will have sufficient stored
energy capable of operating the turbine wicket gates to
full open position;
-The generators wi l le be equipped with static exciters
capable of being flash-started from the station battery
system
-Dc control power will be available for the startup cir-
cuits.
The above described emergency power requirements will not
exceed about 200 kW for one unit and will be easily sup-
plied from the emergency diesel generator.With the
startup of a single unit,the complete power plant and
switchyard auxiliary power will be immediately available,
enabling all the units in the power plant to be started up
sequentially within the hour.
(i)Grounding System
The power plant grounding system will consist of one mat under·the
power plant,one mat under the transformer gallery,risers,and
connection ground wires.Grounding grids will also be included in
each powerhouse floor.The power plant grounding system will be
connected to the swt tchyard groundi ng system by three 500 MCM
copper ground conductors to mi ni mi ze the overall re's i st ance to
ground.The grounding system will be designed to provide a ground
resistance of 1 ohm or lower.All exposed metal part and neutral
connect ions of generators and transformers will be connected to
the ground i ng system for the purpose of protect i ng personnel and
equipment from injury or damage.
(j)Lighting System
The lighting system in the powerhouse will be supplied from 480/
208-120 volts llghting transformers connected to the general ac
aux ill ary stat ion servi ce system.The l i ghtingsystem will be all
_______~.t.luocescent__and_j_nc_andescentJj_xt_u~es_op_e~atj_n_g_on-l2Dv-OJt_s and
a 11 outdoor type high pressure sodt um fi xtures operat i ng on 208
volts.The lighting level varies generally from 20 to 50 foot
candles depending upon the powerhouse area;the higher levels will
be at control areas.Adequate illumination will be provided on
vertical switchboards with local lighting canopies.
An emergency lighting system will be provided at the power plant
and at the control room at all critical operating locations with
an illumination level of 2 foot candles.The emergency lighting
system will operate from a separate 120 volt ac circuit which, by
means of automatic transfer switches,will be automatically
connected to the 125 volt dc system upon failure of the ac
system.
I_........•.._-
J
1
I
1
1
J
1
j
[1
.1
IJ
(k)Communications
The power plant will be furnished with an internal communications
system,including an automatic telephone switchboard system. A
communication system will be provided at all powerhouse floors and
galleries,transformer gallery,access tunnels and cable shafts,
and structures at the power intake,draft tube gate area,mai n
spillway,and dam.
The communications system for the central dispatch control system,
telemetering,supervisory and protective relaying system is de-
scribed in Section 15.
(1)Insulation Coordination and Lightning and Switching Surge
Protection
The electrical insulation and protective devices will be selected
and coordinated to provide a safe margin of insulation strength
above the maximum abnormal voltages permitted during lightning,
switching,and short-circuit surges.The 1300 kV basic insulation
level (BIL)specified for the transformer and other BIL values
stated for the electrical equipment and connections are tentative
and are subject to detailed study in the design stage of the pro-
ject.
In principle,lightning arresters will be mounted on or adjacent
to all major electrical equipment having wound-type internal con-
struct ion,and wi 11 be provi ded at the generator 15 kV termi na1s
and the main transformer 345 kV terminals.
12.19 -Switchyard Structures and Equipment
[J
LJ
11
LJ
(a)Single Line Diagram
The e1ectri c system stud i es recommended a "breaker-and-a-ha lf"
single line arrangement.This arrangement was recommended for
reliability and security of the power system.Plate 61 shows the
details of the switchyard single line diagram.
(i)Control and Metering
All control and metering functions are handled by the
Watana control center.The Wi llow System Center can also
initiate a control function through the Watana control cen-
ter,thus allowing the system center considerable flexibil-
ity in operating the total system.
(ii)Relay Protection
Relay protection for transmission lines is similar to that
described in Section 14.5.In addition relay protection is
provided for the 345 kV cable from the powerhouse to the
12-91
switchyard.This protection will consist of differential
relays,and as a backup the overall differential protection
zone of the generator and unit transformer relay wi 11 also
include the 345 kV cable circuit.
(b)Switchyard Equipment
The number of 345 kV circuit breakers is determined by the number
of elements to be switched such as lines or in-feeds from the
powerhouse.Each breaker wi 11 have two di sconnect switches to
allow safe maintenance.
The auxiliary power for the switchyard will be derived from the
generator bus vi a a 15 -34.5 kV transformer and 34.5 kV cable.
The voltage wi 11 then be stepped down to 480 V for use in the
swi tchyard.
(c)Switchyard Structures and Layout
The switchyard layout will be based on a conventional outdoor type
desi gn.The desi gn adopted for thi s project wi 11 provi de a two
level bus arrangement.This design is commonly known as a low
station profile.
The two level bus arrangement is desirable because it is less
prone to extensive damage in case of an earthquake.It is also
easier to maintain low level busses.
Although the present studies are based on conventional switchyard
layouts,it is recommended that SF6 gas-insulated equipment be
considered in the design stage.For a more detailed description
see Section 14.
12.20 -Project Lands
Project lands acquired for the project will be the minimum necessary to
construct access and site facilities,construct permanent facilities,
to clear the reservoir,and to operate the project.
A large amount of public land in the Watana area is managed by the
Bureau of Land Management.There are 1arge blocks of pri vate Native
Village Corporation Lands along the river.Other private holdings
consist of widely scattered remote parcels.The state has selected
much of the federal 1and in th is area and is expected to recei ve a
patent.
I
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LIST OF REFERENCES
(1) Acres American Incorporated,Susitna Hydroelectric Project 1980-81
Geotechnical Report,prepared for the Alaska Power Authority,
February 1982.
(2)Barton,et al.,Engineering Classification of Rock Masses for the
Design of Tunnel Support.
I
I I
i1II
1
I
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lJ
j
Calendar Year
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
TABLE 12.1:WATANA PEAK WORK FORCE AND CAMP/VILLAGE
DESIGN POPULATION
Camp/Village
Yearly Peak Work Force Facilities Design
900 1000
1600 1760
2300 2530
2900 3200
3200 3520
3600 3970
3400 3740
2600 2860
1000 1100
200 220
TABLE 12.2:ROCKFILL AND EARTH DAMS IN EXCESS OF 500 FEET
Dam Country Feet
Rogun USSR 1,066
-lNurekUSSR1,040
Watana USA 885
Tehri India 856
Kishaw India 830
Sulak USSR 802
Mica Canada 794
Patia Colombia 787
Chicoasen Mexico 787
Chivor Colombia 778
Oroville USA 771
Esmeradla Colombia 754
Sayansk USSR 738
Keban Turkey 679
Altinkaya Turkey 640
New Melones USA 626
Don Pedro USA 614
Swift USA 610
Portage Mountain Canada 600 lNewBullardsBarUSA590.I
Dartmouth Australia 590 -.J
Okoy Turkey 590
Ayvacik Turkey 587
Takase Japan 577 '\
Hasan Ugurlu Turkey 574 INader Shah Iran 574
Gura Apelor Retezat Romania 568
Magarin Jordan 561
Charvak USSR 551
Boruca Costa Rica 548
Kremasta Greece 541
Trinity USA 538
Thomson Australia 530
Talbingo Australia 530
Tokujama Japan 528
LaGrande No.2 Canada 525
Palo Quemado S. America 525 IGrand Maison France 525
Sao Felix Brazil 525
Fierze Albania 519
Cougar USA 519
Yacambu Venezuela 519
Emborcacao Brazil 519
Einster.tal
Cumberland Australia 510
Canales Spain 510
Narmata Japan 508
Goeschenenalp Switzer land 508
Salrajina Colombia 505
Gepatsch Austria 503
Foz do Areia Brazil 503
Tedorigawa Japan 503
Carter USA 500
f
I
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TABLE 12.3:SUMMARY OF DESIGN DATA FOR LARGE EMBANKMENT DAMS
IN SEISMICALLY ACTIVE AREAS
11 Crest Ratio of
Height Freeboard Width Core Width Upstream Downstream
Dam Feet Feet Feet to Dam Height Slope Slope
Watana (US)885 25* 35 0.50 2.4 2.0
Mica (C)794 26 111 0.45 2.25 2.0
fl Chicoasen (M)787 33 82 0.42 2.2 2.0
Oroville (US)771 22 80 0.34 2.6 2.0
f]Don Pedro (US)614 2.4 2.1
Ayvacik (T)587 17 50 0.34 2.5 1.8
11
Takase (J)577 17 46 0.40 2.6 2.1
Tedorigawa (J)503 13 40 0.31 2.6 1.85
Netzahualcoyotl (M)453 18 50 0.43 2.0 2.0
Iwaya (J)413 62 33 0.33 2.5 2.0
Kazurya (J)413 39 2.6 1.8
Narakura (J)410 16 39 0.56 2.7 2.7
Pyramid (J).(US)400 36 2.5 2.0
\)Tamahara (J)380 13 39 0.43 2.7 2.2
Seto (J)364 20 36 0.29 2.5 2.0
*Watana freeboard - normal maximum operations level to nominal crest
(additional height allowed for seismic settlement)
US - United States
C -Canada
M -Mexico
T - Turkey
J - Japan
!J
I \U
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LJ
I
TABLE 12.4:'DAMS IN SEISMIC AREAS
Jt UK!:.t ,K~UUJ'UH I .U"
Core
Crest Free-Crest Width Ratio Core Slopes Unified
Seismic Height Length board Width Core at Base Width to of Core Classi-Liquid Plastic U/S Thick-D/S Thick-Treat-Under
Name Country Activity (ft)(f't )(ftl)(ft )Type (f't )Dam Heiqht Zone fication Limit Limit ness (f't )ness (f't )Type ment Shells
Watana USA H BB5 25:35 CV 440 0.50 0.25:1 SM 23 8 60 60 R CG R/UD
Mica Canada L 794 2,600 26' 111 S 360 0.45 ------R CG A/UD
Chicoasen Mexico H 787 1,640 33 82 CV 330 0.42 0.15:1 CL 40 20 25 25 CB CG A/UD
Oroville USA L-M 771 .5,600 22 80 S 263 0.34 -GC -----CB -
Ayvacik Turkey M-H 587 1,400 17 50 C 197 0.34 -CL --50 50 R CB R/UD
Takase Japan M-H 577 1,200 17 46 CV 230 0.40 0.15:1 ----50 R -A/UD
Palo Quemado S.Americe H 525 1,215 26 40 CV 295 0.56 0.25:1 ML 33 7.5 13 13 R CG R/UD
Tedorigawa Japan M-H 503 1,380 13 40 CV 157 0.31 0.15:1 - --26 26 R -A/UD
EI Infiernilla Mexico H 486 1,100 25 40 CV 164 0.34 0.15:1 CL 49 25 8 8 R CG A/UD
Tarbela Pakistan M-H 469 9,000 18 40 S 262 0.56 -GW/SM ----A -A/UD
Netza~ualcoyotl Mexico H 453 1,570 18 50 CV 197 0.43 0.15:1 ML/MH 50 20 -13 R CG A/U
Mangla Pakistan H 453 3,400 32 41 S 230 0.51 -CL ---13 R CG A/UD
Derbendi Khan Iraq M 443 1,460 33 56 CV 330 0.74 0.3:1 CH/CL 50 26 20 30 R -R/UD
Tsengwen Taiwan H 436 1,440 33 33 CV 410 0.94 0.4:1 SM/GM 22 8 --R CG.R/UD
Pueblo Viejo C.Americe H 436 820 49 43 CV 157 0.36 0.15:1 CL 41 19 23 23 R CG R/UD
8eas India M-H 435 6,400 3D.45 CV 131 0.30 0.1:1 CL 30 12 20 20 R -A/UD
Alicura Argentina H 426 2,620 1~39 CV 275 0.65 0.3:1 CL 35 15 10 10 R -A/UD
Ramga'i'ga India M-H 413 -22 39 CV 197 0.48 0.2:1 CL --98 79 R -A/UD
Iwaya Japan H 413 1,200 62 33 C 138 0.33 ----33 65 R -R/UD
Narakura Japan M-H 410 820 1~39 CV 230 0.56 0.2:1 ---20 49 R -A/UD
Shimokotori Japan M-H 390 915 13.36 C 151 0.39 ----39 39 --R/UD
Bao C.Amerd cs H 388 1,312 24 26 CV 184 0.47 0.2:1 CL 40 20 20 20 R -CB &CG
Tamahara Japan H 380 2,000 13 39 CV 164 0.43 ----79 79 R CG R/UD
Seto Japan H 364 1,120 13 36 C 105 0.29 ----39 39 R -R/UD
Guri Venezuela L 361 1,970 20 36 CV 180 0.50 0.2:1 ML 50 15 5 6.5 R CG R/UD
Impervious Core:
cv -Central vertical
C -Central very slightly sloped
S -Sloping
Foundation:
R -Rock
A -Alluvium
D -Downstream
U - Upstream
CG -Consolidation grouting
CB -Concrete block over rock
,----~....;~''':',...
TABLE 12.5:GENERALIZED SURFICIAL STRATIGRAPHIC COLUMN
AREA "0"AND RELICT CHANNEL
[1
1
1,J
[J
[J
[J
lJ
u
Column
C
o
E
and
F
G
H
I
and
J
Unit
Surficial
Outwash
Alluvium &
Fluvial
Deposits
Outwash
Till/Water lain
Till
Alluvium
Till
Alluvium
Estimated
Thickness
0-5'
0-18'
12'average
0-15'
0-35'
15'average,
2-50'
12'average
0-40'
>10'to 65'
20'average
to 160'
Description
Boulders,organic silts and sands.
Silty sand with some gravel and cobbles
occasionally.Usually brown although becomes
gray in limited areas.Thickest in northern
portions of area,thickening southward,often
absent near Susitna River.
Sand with some silt,occasional gravel.
Generally brown, found only along course of
limited drainage channels formed in outwash
"E".Generally sorted.
Sand,silt,gravel and cobbles,partly sorted,
with fragments sub-angular to rounded.Silt
and sand lenses often present.Brown to gray
brown with a cobble/boulder zone often present
at the base of Unit "F".Contact between "E"
and "F"is often poorly defined.
Clayey,silty sand,usually gray,often
plastic.Contains cobbles and gravel in many
areas.Occasionally present as a lacustrine
deposit showing laminations and/or varves.
Generally a till deposited through or near
standing water.
Sand,silt,gravel,partly to well sorted.
Often absent between Units "I"and "G". Unit
represents period of melting producing
alluvium/outwash between these deposits.
Appears as narrow bands representing channel
fillings.ThicKest in western portion of the
area.
Poorly sorted sand,silt,gravel and cobbles,
occasionally with clay.Generally gray to gray
brown.Continuity uncertain due to lack of
information at depth.Silt or sand layer
2 inches -6 inches thick often found in
center of Unit "I".Base unit on top of
bedrock,except in buried channel.Contact
between "I"and "J"often poorly defined.
Sand,gravel,cobbles,boulders,few fines,
permeable.Found only in bottom of buried
channel.Top at 292 feet extending to rock at
454 feet.
Note:Letters used to define units are arbitrary and were used for
correlation purposes.Two letters may define parts of the same unit.
TABLE 12.6:RING FOLLOWER GATES
DESIGN YEAH OF
PROJECT LOCATION SIZE (IN.)HEAD (FT)INITIAL OPERATION
(1)New Melones California 96 607 1979
(2)New Melones California 72 591 1979
(3)Portage Mountain Canada 84 550 1967
(4)Hungry Horse Montana 96 495 1952
(5)Yellowtail Dam Montana 84 470 1967
(6)Trinity Dam California 84 450 1962
(7)Grand Coulee Washington 102 354*1940
(8) Glen Canyon Colorado 96 337 1965
(9) Green Mountain Colorado 102 261 1943
*Maximum static head;maximum operating head - 250 feet.
I
·1
TABLE 12.7:PRELIMINARY UNIT DATA
1 -GENERAL DATA
-Number of Units •••••••••••••••••••••••••••••••••6
-Nominal Unit Output 170 MW
fl
- Headwater Levels:
--normal maximum •••••••••••••••••••••••••••••••El ,2185
--minimum El.2045
-Tailwater Levels:
--mlnlmum ••••••••••••••••••••••••••••••••••••••El. 1452
--normal ....•.••...•.•..•...••.••.......••.•...El. 1455
--maXlmum El. 1475
2 -TURBINE DATA
-Type ••••••••••••••••••••••••••••••••••••••••••••Vertical Francis
- Rated Net Head ••••••••••••••••••••••••••••••••••680 feet
-Maximum Head
-Minimum Head
728 feet
576 feet
[]
-Full Gate Output:
--at rated head 250,000 hp
--at maximum head ••••••••••••••••••••••••••••••275,000 hp
--at minimum head 195,000 hp
- Best Gate Output ••••••••••••••••••••••••••••••••85 percent full
-Full Gate Discharge at Rated Head •••••••••••••••3560 cfs
- Speed •••••••••••••••••••••••••••••••••••••••••••225 rpm
-Specific Speed 32.4
-Runner Discharge Diameter •••••••••••••••••••••••132 in
-Runaway Speed •••••••••••••••••••••••••••••••••••400 rpm
-Cavitation Coefficient (sigma)••••••••••••••••••0.088[1 -Centerline Distributor E1.1422
IJ
3 -GENERATOR DATA
- Type ••••••••••••••••••••••••••••••••••••••••••••Vertical Semi-Umbrella
[]
- Rated Output
-Power Factor
190 MVA
0.90
u
-Voltage •••••••••••••••••••••••••••••••••••••••••15 kV
- Synchronous Speed •••••••••••••••••••••••••••••••225 rpm
-Inertia Constant (H)*•••••••••••••••••••••••••••3.5 MW/sec/MVA
- Flywheel Effect (WR 2)*••••••••••••••••••••••••••57 x 10
6 Ib-ft 2
-Heaviest Lift 780,000 Ib
*Including turbine
TABLE 12~8:ASSUMED PROPERTIES FOR STATIC ANALYSES OF WATANA DAM
1
MatenaI K Kur n Rf Kb m C Ko
CORE:
--Soft(1)140 200 300 .8 .6 60 .8 0 35 0 .43
--Stiff(2)140 700 800 .35 .8 280 .2 0 35 0 .43
TRANSIT IoN(3) 145 1300 1500 .4 .72 900 .22 0 35 6 .43
SHELLS (4) 145 1800 2000 .4 .67 1300 .16 0 35 6 .43
where:
=Unit weight,pcf
K =Modulus nun~er,ksf
1;1Kur=Elastic unloading modulus number,ksf
n =Modulus exponent
Rf =Failure ratio
Kb =Bulk modulus number,ksf
m =Bulk modulus exponent
C =Cohesion,psf
=Friction angle,degrees
=Decrease in friction angle per log cycle increase in 3'degrees
Ko =Earth pressure coefficient ~
Note: Values taken from Duncan et al.,1980,"Strength,Stress-Strain and Bulk Modulus
Parameters for Finite Element Analyses of Stress and Movements in Soil Masses,"Report
No.UCB/GT/8o-o1,University of California,Berkeley.
(1)MicaCteek Dam Cote,2 percent wet of optimum
(2) Mica Creek Dam Core, 2 percent dry of optimum
(3)Oroville Dam silty sandy gravel
(4)Oroville Dam Shell -Amphibolite gravel
..j
I
II
il TABLE 12.9:WATANA DAM -CREST ELEVATION AND FREEBOARD
.m SO Year
River Inflow Storm
Normal maximum reservoir
elevation 2185
Storm surcharge 6[J
Still water elevation
Wave runup allowance
Dry freeboard allowance
Elevation top of core
Roadway over core
Minimum crest elevation
2191
6)
__3_)
2200
3
2203
1 an 10,000 Probable
Year Storm Maximum Flood
2185 2185
8 17
2193 2202
6 NIL
2199 2202
3 3
2202 2205
[j
Governing elevation for crest of main dam
Highest still water level to be 2 feet above
fuse plug pilot channel
Sill of pilot channel in fuse plug
2205
2200
[J
u
u
u
Note: The above elevations do not include allowances for static settlement and
seismic slumping.
TABLE 12.10:RECENT HIGH HEAD FRANCIS TURBINES
Ii:)
i 1
Year of Head Output Speed Specl.fl.c Speed
Number Plant Order (ft)(hp) (rpm)(Ns)
1 Albi 1972 1141 49,100 750 25.1 :-12AltoAnchicaya1970 1312 158,000 450 22.6
3 Big Creek 1976 737 50,600 450 26.4
4 El Chocon 1971 192 274,000 88.3 64.7
5 Hendrik-Verwoerd 1972 225 137,000 136.4 57.9
6 Estreito 1970 208 239,000 112.5 69.6
7 Grand Coulee III 1973 285 808,000 72 55.3
8 Grand Coulee IV 1973 285 938,000 85.7 70.9
9 Grimsel II 1974 1502 142,000 750 30.2 i
1
10 Harspranget V 1974 338 629,000 107.1 58.6
11 Hermillon 1971 535 82,300 333 37.1
12 Inga II 1972 205 239,000 107.1 67.5
13 Kargamakis 1970 443 185,000 214 45.3
14 Langsan 1972 590 70,500 428 39.1
1-115LaSuassaz1970 679 109,000 333 31.7
16 LG-2 1975 450 454,000 133 43.2 I·
17 Libby 1970 300 163,000 128.6 41.5
18 Loentsch 1970 1178 54,200 750 25.3 I
1
19 Magisano 1972 1215 52,800 750 24.0
20 Malpaso 1974 313 293,000 128.6 52.9
21 Marimbondo 1972 236 248,000 100 53.8
22 Mica 1975 560 595,000 128.6 36.4
23 Mitt a 1971 666 132,000 333.3 35.7
-J24NewMelones1974 460 205,000 171.4 36.4
25 Nurek 1970 754 416,000 200 32.6
26 Oldan 1972 827 92,400 500 34.3
27 Passo Fundo 1972 853 151,000 300 25.3 I28Porjus1971 195 323,000 83.3 65.0 I
29 Peace River 1971 450 410,000 150 36.9
30 Reza Shah-Kabir 1970 541 373,000 166.7 39.0
31 Ritsem 1973 476 442,000 166.7 49.8
32 Revelstoke 1977 427 664,000 112.5 47.2 !J33Salas19'70 862 73,000 500 28.9
34 SaIto Osorio 1972 236 212,000 120 59.7
35 Sarelli 1973 1149 65,700 750 28.7
36 Sirikit 1972 277 202,000 125 49.7
I 'j37 Sodusu II 1973 1246 55,200 600 19.0
38 Tumut 3 1971 530 379,000 187.5 45.3
39 Ust-Ilim 1972 296 328,000 125 58.5
40 Verbano II 1970 932 84,200 500 28.1
41 Waldeck II 1970 1104 295,000 375 32.0
42 Yarnvagsforsen 1973 278.8 72,900 214.3 50.8
!'I
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~0 (!)
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e::{l-
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<l:I-~0 ~e::{
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o 0 0
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I r--
'~--'L--.J ---'~I
--------'
SPILLWAY1.1 SERVICE OUTLETS +MAIN
L LLO +SERVICE OUTLETS
LOW LEVEL OUTLET (LLO]LOWER D.T. ONLY2DIVERSIONTUNNELS (D.T.)
FINAL CREST ELEVATION \
NORMAL MAXIMU':'L\
OPERATING LEVEL 2210
~i-L2185 ._
2130 -=-./
//./o_--r o 1-----.//~--~--.,.-..,//~
100 YR.FLOOD \-EVEL7 ,f"'-1 2150 \.-?RY SEQUENCE
WET SEQUENCE
1~50.//I L POWER INTAKE
/'~1938 INUNDATED
//1865 J
1810 No. OF UNITS
DAM CONSTRUCTION SrQUENCEV ~AVAILABLE.
222334
IJ I I I I I
D
1660 /"--WATER SURFACE ELEVATION (JULY- DEC.)
NORMAL POWER....-/(AVERAGE YEAR)OPERATIONU/S COFFERDAM-100 YR. FLOOD LEVEL
1545 i\-:
50 YR. FLOOD TEVEL
1460 I
I
2000
2300
2100
2200
,..:
u,-z 1900
0
~>w 1800...Jw
1700
1600
1500
1400
AVAILABLE 1
DISCHARGE
FACILITIES
DDJDJDJDJDJDJ
I I
I I
I I
I I
I I I
I I./WETTEST SEQUENCE RECORD....,: :REyORDED
'1"1-1 ,.I L,DRIEST SEQUENCE7rei~io I I RECORDED
I •
I I
I
:1:!"1 I
,ri,I I
I I I
I I :
I I
I
J t,ei --:j.J.,I r-'.
~I I . L,I II.1 !III I ..,
I ' I
'-'I I r ~/~EQUIRED DOWNSTREAM AVERAGE MONTHLY~I L.~I • I
FLOW-TYPICAL INFLOW-TYPICAL I I II I ..,
I ..,I • I .-r i,~I L~,I 1....;",I !I I -.I 1:=t.1:.:.L.'!-I I I I I I in .........,.::.~...:r...~:=.:r.-I •....i
35000
30000
25000
~
~
z 20000
0
i=:;
w 15000...Jw
10000
5000
0
19BB 1989 1990 1991 1992 1993 1994
WATANA RESERVOIR FILLING SEQUENCE
FIGURE 12.2
L-~L ~
'--------L.-..-.i ______.-.I --,
~_--1
161412108
MONTHS
642
-,
1\
\
~
.\WET EAR
\
V 1\
\
1\
\
\
-_..-._........_--...--
1900
2300
2100
2200
1500
1700
1800
1600
2000
MONTHS
MJJASONO JFMAMJJA
2 4 6 8 10 12 14 16
)...........r-.
1\
\
)
1\
1\WET Y AR
\
1\
\/1\
\J
\7
2100
2200
2300
1800
1900
2000
1500
1700
1600
MONTHS
J F M A M J J A SON 0 J F M"A M J J A
2 4 6 8 10 12 14 16 18 20
-,,
\
\~~~
'\r WE YEAR
\
\\~AVE AGE .:
MON HLY-'
\\
\i\\/\,I,
I
I
1,II
I
! /
2300
1800
1700
1600
2100
1900
2200
1500
po 2000
u,
JANUARY START MAY START
WATANA RESERVOIR
EMERGENCY DRAW DOWN
SEPTEM8ER START
FIGURE 12.3 •
-'--L-r--,
~:.-.....----l
I ~I II T 1 T !
.....~~lo.."'01 1 r-r~.....1 ~B~RSI.MI~!:
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U.S.STANDARD SIEVE SIZE
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GRAIN SIZE IN MILLIMETERS
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WATANA
COMPARISON OF GRAIN SIZE
CURVES FOR VARIOUS CORE MATERIALS
FIGURE 12.4 •
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SOlLDERS I COBBLES GRAVEL
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SAND
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FINES
Silt Sizes
WATANA
REQUIRED GRAIN SIZE CURVES
MAIN DAM
FIGURE 12.5 m
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WATANA
COMPOSITE GRAIN SIZE CURVE -BORROW SITE D
FIGURE 12.6
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BEST EFFI(IENCV-!FULL GATE
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RESERVOIR EL.2045...,--7 --
100 120 140 160
UNIT OUTPUT- MW
180 200 220
WATANA-UNIT OUTPUT
FIGURE 12.8
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IL.
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TURBINE OUTPUT (HP)
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WATANA -TURBINE PERFORMANCE
(AT RATED HEAD)
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FIGURE 12.9
,
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N S =950/v'li (USSR RECOMMENDED
UPPER LIMIT I
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SPECIFIC SPEED EXPERIENCE CURVE
FOR RECENT UNITS
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13 -DEVIL CANYON UEVELOPMENT
This section describes the various components of the Devil Canyon
development,including diversion facilities,emergency release facili-
ties,main dam,primary outlet facilities,reservoir,main and emer-
gency spillway,saddle dam,the power intake,penstocks,and the power-
house complex,including turbines,generators,mechanical and electri-
cal equipment,switchyard structures,and equipment and project lands.
A description of permanent and temporary access and support facilities
is also included.
13.1 -General Arrangement
The evolution of the Devil Canyon general arrangement is described in
Section 10.The Devil Canyon reservoir and surrounding area is shown
on Plate 4U.The site layout in relation to main access facilities and
camp fac il ities is Shown on Pl ate 72. A more detailed arrangement of
the various site structures is presented in Plate 41.
The Dev il Canyon darn wi 11 form a reservo ir approximate 1y 26 miles long
with a surface area of 7,8UO acres and a total volume of 1,092,00U acre
feet at a normal maximum operating elevation of 1455.The operating
level of the Devil Canyon reservoir is controlled by the tailwater
level of the upstream Watana development.During operation,the reser-
voir will be capable of being drawn down to a minimum elevation of
1400.
The dam will be a thin arch concrete structure with a crest elevation
of 1463 and max imum height of 645 feet.The dam wi 11 be supported by
mass concrete thrust blocks on each abutment.On the left bank,the
lower bedrock surface will require.the construction of a substantial
thrust block.Adj acent to th is thrust block,an earth-and rockfi 11
saddle dam will provide closure to the left bank. The saddle dam will
be a central core type generally similar in cross section to the Watana
dam.The dam will have a maximum height above foundation level of
approximately 245 feet.
During construction,the reservoir will be diverted around the main
construction area by means of a single 30-foot-diameter concrete-lined
diversion tunnel on the left bank of the river.
A power intake,located on the right bank,will comprise an approach
channel in rock leading to a reinforced concrete gate structure.From
the intake structure four 20-foot-diameter concrete-lined penstock tun-
nels will lead to an underground powerhouse complex housing four
Francis turbines each with a rated capacity of 15U MW ana four semi-
umbrell a type generators each rated at 180 MVA.Access to the power-
house complex will be by means of an unlined access tunnel approxi-
mately 3,200 feet long as well as by a YoU-foot deep vertical access
13-1
shaft.Turbine discharge will be conducted to the river by means of a
single 38-foot-diameter tailrace tunnel leading from a surge chamber
downstream from the powerhouse cavern.Compensation flow pumps at the
power plant will ensure suitable flow in the river between the dam and
tailrace tunnel outlet portal.A separate transformer gallery just up-
stream from the powerhouse cavern will house six single-phase 15/345 KV
transformers.The transformers will be connected by 345-KV,single-
phase,oil-filled cable through a cable shaft to the switchyard at the
surface.
The primary outlet facility will consist of seven individual outlet
conduits located in the lower part of the main dam.These will be
designed to discharge all floods with a frequency of 1:50 years or
less.Each outlet conduit will have a fixed-cone valve similar to
those prov ided at Watana to min imize undes irab 1e nitrogen supersatura-
tion in the flows downstream. Flows resulting from floods with a fre-
quency greater than 1: 50 years but 1ess than 1:10,000 years wi 11 be
discharged by a chute spillway on the right bank,also similar in
design to that provided for Watana.An emergency spillway on the left
bank will provide sufficient additional capacity to permit discharge of
the PMF without overtopping the dam.
13.2 -Site Access
(a) Roads
At Devil Canyon the main access road will enter the site from the
south.A low level bridge crossing the Susitna River will be
located just upstream of the dam.In addition to the main access,
several auxiliary roads will be required to the camp,village,
tank farm,borrow sites,and construction areas.These roads,
with the exception of temporary haul roads,are shown on Pl ate
72.
The construction roads will be gravel-surfaced roads 40 feet wide
with small radius curves.Grades will be 1 imited to 10 percent.
IVlajor cut and fill work will be avoided where possible.A gravel
PClclLapRr()xjm(J:t§.Jy ...t.tve feet .tbjcK,.wjJJ._.b.erequjJ"ed._.forthe
roads.This will provide a drivable surface and also will protect
against settlements and heaving caused by localized permafrost.
(b)Bridges
The existing low level bridge upstream of the dam will be used
during abutment excavation.Once construction of the cofferdams
is complete,the crests of these structures will be used for river
crossing.
After compl et ion of the main dam,the crest of the dam wi 11 pro-
vide access across the Susitna River.
13-2
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(c)Airstrip
The permanent airstrip at the Watana site,approximately 30 miles
west of the Dev i 1 Canyon site,will be used for the Dev il Canyon
development.The airstrip will be capable of accommodating both
C-130 Hercules aircraft;as well as small jet passenger aircraft.
(d) Access Tunnel
An access tunnel wi 11 be provided to the underground powerhouse
and associated works.The main access tunnel will be unlined and
approximately 35 feet wide and 28 feet high.The tunnel will be
utilized during construction as the main construction access.
Ad its wi 11 br-anch off from th is tunnel to other areas of under-
ground development.
( e)Access Shaft
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A vertical 20-foot diameter access shaft with an elevator will
also be provided for access to the underground facil ities.The
shaft will be sited at the end of the access tunnel.
13.3 -Site Facilities
(a)General
The construction of the Devil Canyon development will require var-
ious facilities to support the construction activities throughout
the entire construction period.Following construction,the
pl anned operat ion and maintenance of the development will be
centered at the Watana development;therefore,minimum facilities
at the site will be required to maintain the power facil ity.
As described for Watana (Section 12),a camp and construction
village will be constructed and maintained at the project site.
The camp/village will provide housing and living facilities for
2,300 people during construction.Other site facil ities include
contractor's work areas,site power,services,and communications.
Items such as power and communications and hospital services will
a 1so be requ ired for construct ion operat ions independent of camp
operations.
su i ld tnps used for the Watana development will be used where pos-
sible in the Devil Canyon development.Current planning calls for
dismantling and reclaiming the site after construction.Electric
power will be provided from the watana development.The salvaged
building modules used from the Watana camp/village will be retro-
fitted from fuel oil heating to electric heat.
(b) Temporary Camp and Village
The proposed location of the camp/village'is on the south bank of
the Susitna River between the damsite and Portage Creek,approxi-
mately 2.5 miles southwest of the Devil Canyon dam (see Plate 72).
13-3
The south side of the Susitna was chosen because the main access
road is from the south.South-facing slopes will be used for the
camp/village location.
The camp will consist of portable woodframe dormitories for single
status workers with modular mess halls,recreational buildings,
bank,post office,fire station,warehouses,hospital,offices,
etc.The camp wi 11 be a si ng1 e status camp for appr oxtmately
1,780 workers.
The village,designed for approximately 170 families,will be
grouped around a service core containing a school,gymnasium,
stores,and recreation area.
The two areas will be separated by approximately 1/2 mile to pro-
vi de a buffer zone between areas.The hospital wi 11 serve both
the main camp and the village.
This camp location will be separated from the work areas by
approximately a mile.Travel time to the work .area will generally
be less than 15 minutes.
The camp/village will be constructed in stages to accommodate the
peak work force as presented in Table 13.1.Table 13.1 also pre-
sents the camp/vi 11 age facil ity desi gn numbers.The facil iti es
have been designed for the peak work force plus 10 percent for
"turnover ",The "tur-nover"includes provisions or buffers for
overlap of workers and vacations.The conceptual layouts for the
camp/village are presented in Plates 73 and 74.
(i)Site Preparation
Both the camp and the vi 11age areas wi11 be cleared in
select areas of topsoil,and the topsoil will be stockpiled
for future use in reclamation operations.At the village
site,selected areas will be left with trees and natural
vegetation intact.
Both the mai n camp and the vil 1age5tt~grejn weJJ-c:Irainecl
land with natural slopes of 2 to 3 percent.A granular pad
varying in thickness up to 8 feet will be placed in select-
ed areas at the main camp to provide a uniform working sur-
face for erection of the high density housing and service
buildings as well as serving as a protective barrier for
underlying permafrost.In the village area,a granular pad
will be placed only as necessary to support the housing
units and to provide a suitable base for construction of
the temporary towncenter buildings.
All roadways within the camp/village areas will be flanked
by roadside ditches,with CMP culverts carrying water
across the intersections.In general,drainage will be
through a surface network of ditches.Peripheral ditches
will intercept surface flow from adjacent non-cleared land
and divert it around the camps.
13 ..4
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Runoff will ultimately be directed to existing drainage
channels leading to the Susitna River for the village and
the main camp.
(ii)Facilities
Construction camp buildings will consist largely of trai-
ler-type factory-built modules assembled at site to provide
the various facilities required.The modules will be fab-
ricated with heating,lighting,and plumbing services,
interior finishes,furnishings,and equipment.Trailer
modules will be supported on timber cribbing or blocking
approximately two feet above grade.
Larger structures,such as the central utilities building,
gym,and warehouses,wi 11 be pre-engi neered,steel-framed
structures with metal cladding.
The 1arger structures wi 11 be erected on concrete-s1 ab
foundations.The slab will be cast on a non-frost suscep-
tible layer at least equal to the thickness of the annual
freeze/thaw 1ayer.Heated permawa1ks wi 11 connect the
majority of the buildings and dorms.
The various buildings in the camp are identified on Plate
73.
(c)Site Power and Utilities
(i)Power
A 345 kV transmission line and substation will be in
service during the construction activities.Two transfor-
mers will be installed at the substation to reduce the line
voltage to the desired voltage levels.One of these trans-
formers will be the same used during the Watana develop-
ment.
Power will be sold to the contractors by the Power Author-
ity.The peak demand during construction is estimated at
20 MW for the camp/village and 4 MW for construction
requirements for a total of 24 MW.The distribution system
for the camp/village will be 4.16 kV.
(i i)Water
The water supply system will serve the entire camp/village
and selected contractor's work areas.The water supply
system will provide for potable water and fire protection.
The estimated peak population to be served wi 11 be 2,300
(1,780 in the camp and 520 in the village).
13-5
A system of pumps and constructed storage reservoirs will
provide the necessary system demand capacity.
The principal source of water will be the Susitna River.
The water wi 11 be treated in accordance with the Env iron-
mental Protection Agency (EPA)primary and secondary re-
quirements.
-f
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Chemical toilets located around the site will be serviced
by sewage trucks,which will discharge directly into the
sewage treatment plant.
At the village,an aerated collection basin will be instal-
led to collect the sewage. The sewage will be pumped from
this collection basin through a force main to the sewage
treatment pl ant.
Wastewater
One waste water collection and treatment system will serve
the camp/village.Gravity flow lines with lift stations
will be used to collect the wastewater from all of the camp
and village facilities.The "in-camp"and "invillage"col-
lection systems will be run through the permawalks and
utilidors so that the collection system will always be pro-
tected from the elements.
The sewage treatment system will be a biological system
with lagoons.The system will be designed to meet Alaskan
state water law secondary treatment standards.The lagoons
and system will be modular to allow for growth and contrac-
tion of the camp/village.
The location of the treatmen plant is shown on Plates 72
ancf 73~·--TI'IeT6ca-ri6n·was ·seTecfecr-tcY-avoio I..Hfnec·essat-y
odors in the camp.
The water distribution system will be by a ductile iron
pipe system contained in ut i l idors as described in Section
12.3.
(iii)
The contractors on the site will require office,shop and general
work areas.Partial space required by the contractors for fabrf-
cat ion shops,storage or warehouses,and work areas wi 11 be lo-
cated on the south side of the Susitna River near the owner/
manager's office.Additional space required by the contractor
will be in the area between the access road and the camp.
The sewage plant will discharge its treated effluent to the
Susitna River.All treated sludge will be disposed of in a
solid waste sanitary landfill.
(d)Contractor's Area
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13.4 -Diversion
(a) Genera 1
Diversion of the river flow during construction will be through a
single 30-foot-diameter concrete-l ined diversion tunnel on the
south bank.The tunnel will have a horseshoe-shaped cross-section
and be 1,490 feet in length.The diversion tunnel plan and pro-
file is shown on Plate 54.
The tunnel is designed to pass a flood with a return frequency of
1:25 years routed through the Watana Reservoir.The peak flow
that the tunnel will discharge will be 37,800 cf s .The maximum
water surface elevation upstream of the cofferdam will be Eleva-
tion ~44.A rating curve is presented in Figure 13.1.
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(b)Cofferdams
The upstream cofferdam will consist of a zoned embankment founded
on a closure dam (see Pl ate 54).The closure dam will be con-
structed to Elevation 915 based on a low water elevation of 910
and will consist of coarse material on the upstream side grading
to finer material on the downstream side.When the closure dam is
completed,a cut-off may be constructed to minimize seepage into
the main dam excavation if required.Further investigations in
later design studies will be necessary to define the type and
properties of river alluvium before a cut-off system can be
designed.
Cut-offs commonly used for cofferdams are grout curtains and
slurry walls.Whichever method is used will be constructed
through the closure dam and alluvium material.The abutment areas
will be excavated to sound rock prior to placement of any coffer-
d am mater ia 1.
The cofferdam,from tlevation ~15 to 947,will be a zoned embank-
ment consist ing of a central core,fine and coarse upstream and
downstream filters,and rock and/or gravel shells with riprap on
the upstream face.
The downstream cofferdam will be a similar closure dam constructed
from tlevation ~60 to 895,with a cut-off to bedrock,if required.
The upstream cofferdam crest elevation will have a 3 foot free-
board allowance for settlement and wave runup.Under the proposed
schedule,the Watana development will be operational when this
cofferd am is constructed . Thermal stud ies conducted show that
discharge from the Watana reservoir wi 11 be at 34°F when pass ing
through Dev i 1 Canyon.Therefore,an ice cover wi 11 not form up-
stream of the cofferd am,and no freeboard allowance for ice wi 11
be necessary.
13-7
{c)Tunnel Portals and Gates
A gated concrete intake structure will be located at the upstream
end of the tunnel (see Plate 55).The portal and gate will be
designed for an external pressure {static)head of 250 feet.
Two 30 feet high by 15 feet wide water passages will be formed in
the intake structure,separated by a central concrete pier.Gate
guides will be provided within the passages for the operation of
30-foot high by 15-foot wide fixed wheel closure/control gates.
tach gate,which will be operated by a wire rope hoist in an
enclosed housing,will be designed to operate with a 75-foot oper-
ating head (Elevation 945).
Stoplog guides will be installed in the diversion tunnel to permit
dewatering of the diversion tunnel for plugging operations.
The stoplogs will be in sections to facilitate relatively easy
handling,with a mobile crane using a follower beam.
(d)Operation During Diversion
The rating curve for the diversion tunnel is shown in Figure
13.1.
(e)Final Closure and Keservoir Filling
Upon completion of the main dam to a height sufficient to allow
ponding to a level above the primary outlet facilities (Section
13.7),the intake gates will be partially closed,allowing for a
discharge of minimum environmental flows while raising the up-
stream water level.Once the level rises above the lower level of
discharge valves,the diversion gates will be permanently closed
and discharge will be through the 90-inch-diameter fixed cone
valves in the dam.The diversion tunnel will be plugged with con-
crete and curtain grout ing performed around the pl ug.Construct ion
will take approximately 1 year.During this time the reservoir
will not be allowed to rise above Elevation 1135.
The filling of the reservoir from this elevation will take approx-
imately 2 to 3 weeks to operating Elevation 1455.
13.5 - Arch Dam
(a)General
The basis for selection of a concrete arch dam for Devil Canyon is
presented in detail in Appendix B.
The shape of the canyon gives a crest length-to-height ratio of
approximately 2. The proposed height of the dam,at 645 feet,is
well within precedent.A list of several comparable large arch
dams constructed throughout the world is given in Table 13.2.
13-8
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(b)
The Devil Canyon dam will be designed to withstand dynamic load-
ings from intense seismic shaking.Examples of high arch dams
constructed throughout the world in high earthquake areas incl ude
the 741-foot high El Cajon Dam in Honduras,the 696-foot high
Mohamed Reza Shah Pahl avi Dam in Iran,and the 548-foot high
Vidraru Arges Dam in Romania.The Vidraru Arges Dam and the 372-
foot high Pacoima Dam in Cal ifornia have both withstood high
earthquake load ings,with the 1 atter exper ienc ing a peak ground
acceleration of between 0.6 to 0.8 g.
Green Lake dam is presently being constructed to a height of 210
feet in Sitka,Alaska.
The design of the arch dam is described in Appendix B.
Locat ion
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The arch dam will be located at the upstream entrance of the can-
yon. Bedrock is well exposed along the gorge walls.Detailed
discussion of the rock conditions in the damsite area are pre-
sented in the 1980-Hl Geotechnical Report (1).
(c)Foundations
The arch d am wi 11 be founded on sound bedrock.Approx imate 1y 20
to 40 feet of weathered and/or loose rock will be removed beneath
the dam foundation.All bedrock irregularities will be removed
beneath the foundat ion to eliminate high stress concentrat ions
within the concrete.During excavation the rock will also be
trimmed,as far as is practical,to increase the symmetry of the
centerline profile and provide a comparatively uniform stress dis-
tribution across the dam.Areas of dikes and the local areas of
poorer quality rock will be excavated and supplemented with dental
concrete.
The foundation will be consolidation grouted over its entire area,
and a double grout curta in up to 300 feet deep wi 11 run beneath
the dam and its adj acent structures as shown in Pl ate 51.Grout-
ing will be done from a system of galleries which will run through
the dam and into the rock.Within the rock these galleries will
also serve as collectors for drainage holes which will be drilled
just downstream of the grout curtain and intercept any seepage
passing through the curtain.
Un the right abutment a mass concrete thrust block will be founded
at the end of the dam to match the left block and improve the dam
symmetry.
(d)Arch uam Geometry
The design philosophy of the dam is described in detail in Appen-
dix B and is briefly summarized here.The dam geometry is shown
in Plates 47 and 4H.The crown section at the center of the river
will be of a double curved cupola shape inclined downstream.The
static load from the reservoir will be taken primarily in the
13-9
13.6 -Saddle Dam
(e)Thrust Blocks
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Construction and Schedule
13-10
The thrust blocks are shown on Pl ate 50.The massi ve concrete
block on the left abutment will be formed to take the thrust from
the upper part of the dam above the existing sound rock level.
It will also serve as a transition between the concrete dam and
the adjacent rockfi 11 saddle dam.The incli ned end face of the
block will abut and seal against the impervious saddle dam core
and be wrapped by the supporting rock shell.
A thrust block will also be formed high on the right abutment at
the end of the dam and adjacent to the spillway control structure.
This block,which will improve the symmetry of the dam profile,
wi 11 transmit thrust from the dam through the intake control
structure and into the rock.
Placing of concrete for the dam will be completed oVer a five-year
period·as descr iDed in Sect i-on--l'7-.--Eonstracti-onwi-l-lt-akepl ace
throughout the year with cooling coils built into the concrete to
dissipate the heat of hydration and special heating and insulation
precautions taken in the winter to prevent excessive cooling of
concrete surfaces.Concrete aggregates will be obtained from the
alluvial deposits in the terraces upstream of the dam (1).
Concrete will be placed by means of three highlines strung above
the dam between the abutments.
A two-center configuration will be adopted for the arches to coun-
teract the slight assymetry of the valley and give a more uniform
stress distribution across the dam.The arches will be formed by
circles with centers located on the vertical axis plane running
along the center of the canyon.The radi i of the arches on the
right (wider)side of the canyon will be greater than those on the
left.The thrust will be directed more nearly normal to the rock
abutment rather than parallel to the face,as would occur with a
smaller radius arch.The radii of the intrados or downstream face
will be smaller than those of the extrados,producing a thickening
of the dam at the abutments and reducing stress at the rock/con-
crete interface and within the abutments.
arches.The three-dimensional action of the structure wi 11 tend
to induce tension in the downstream face of the cantilever.This
will be offset,however,by the gravity forces of the overhanging
section which will also counteract any seismic loadings produced
by downstream ground motion.
(f)
The design philosophy for the saddle dam at Devil Canyon is essentially
the same as that for the main dam at Watana described in Section 12.6.
The most significant difference is the use of rockfill in the shells
instead of river gravels used at Watana.The use of gravels in the
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upstream shell at Watana is to mlnlrnlze settlement of the shell on sat-
uration during filling of the reservoir and to ensure a free draining
material.These aspects of the design are not as significant for the
much smaller structure at Devil Canyon.The amount of settlement will
be less and the drainage paths for the dissipation of any excess pore
pressures wi 11 be much reduced.Many dams of equal or 1arger dimen-
sions have been constructed of similar materials and the design is well
within precedent.
(a) Proposed Dam Cross Section
Detail s of the proposed saddle dam are shown in Pl ate 53.The
central vertical core will be protected by fine and coarse filters
on both upstream and downstream slopes and supported by gravel and
rockfill shells.The core will have a crest width of 15 feet and
side slopes of 1H:4V to provide a core thickness to dam height
ratio slightly in excess of 0.5.
The wide filter zones will provide sufficient material to seal any
cracks which might occur in the core due to settlement or as the
result of seismic displacement.
The saturated sections of both shells will be constructed of com-
pacted clean gravel or rockfill,processed to remove fine material
in order to minimize pore pressure generation and ensure rapid
dissipat ion duri ng and after a sei smi c event.Si nce pore pres-
sures cannot develop in the unsaturated section of the downstream
shell,the material in that zone will be unprocessed rockfill from
surface or underground excavations.
Protection on the upstream slope will consist of a 10-foot layer
of ri prap.
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(b)Sources of Construction Material
No source of material suitable for the core of the saddle dam has
been identified closer than the borrow areas at Watana (Sites 0
and H)(l).The current proposal is to develop Site D for core
material at Watana and,since access roads will be established to
that area,the same source will be used for the Devil Canyon core.
Investigations to date indicate that suitable core material can be
obtai ned from areas above the Watana reservoir level.In the un-
likely event that insufficient material is available from Site D,
then Site H would be developed.The in-place volume of core
material is 306,000 cubic yards.
The filter material will be obtained from the river deposits (Site
G)immediately upstream of the main arch dam at Devil Canyon (1).
This area will also be exploited for concrete aggregates.The
total volume available in Site G is estimated to be 6 million
cubic yards,while the concrete aggregate demand is some 2.7 mil-
lion cubic yards.The estimated volumes required for the dam are
228,000 and 181,000 cubic yards for the fine and coarse filters,
respectively.Surplus material from Site G will be used in the
13-11
upstream shell.The bal ance of the shell material will be rock-
fill obtained primarily from the excavations for the spillways.
The total rockfill required will be approximately 1.2 million
cubic yards.The proportion of sound rock suitable for use in the
dam,which can be obtained from the excavations,cannot be accur-
ately assessed at this stage,but it is proposed to make up any
shortfall by deepening and extending the emergency spillway cut.
This will be more economical and environmentally acceptable than
developing Quarry Site K,some 2 miles from the damsite (1).
(c)Excavation and Foundation Preparation
The excavation and foundation preparation will be as for the
Watana site with all all uvium and other unconsol idated deposits
under the dam removed to expose sound bedrock to el iminate any
risk of 1 i quef ac t ion of the dam foundation under earthquake load-
ing.Weathered and fractured rock will be removed from beneath
the core and filters,and local irregul arities in the rock surface
either trimmed back or concrete added to provide a suitable con-
tact surface for placing the core.
(d)Grouting and Pressure Relief
The rock foundation will be improved by consolidation grouting
over the core contact area and by a grouted cutoff along the cen-
terline of the core.The cutoff at any location will extend to a
depth of at least 0.7 of the water head at that location as shown
on Pl ate 51.
A grouting and drainage tunnel will be excavated in bedrock
beneath the dam along the centerline of the core and will connect
with a simil ar tunnel beneath the adjacent concrete arch dam.
Pressure relief and drainage holes will be drilled from this
tunnel and seepage from the drainage system will be discharged
into the arch dam drainage system and ultimately downstream below
tai lwater level.
(e)Impervious Core and Filters
The requirements for impervious core and both fine and coarse fil-
ters will be as for the Watana dam (Section 12.6).
(f)Shells
The processed gravel and rockfi 11 to be pl aced in the saturated
zones of the dam will have the same grading as the processed allu-
vium used at Watana. The maximum size snall not exceed lti inches
and not more than 10 percent of the material shall be finer than
3/8 inch size.This restriction on fine material will not apply
to rockfill in the unsaturated zone above Elevation 1375 in the
downstream shell.
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(g)Freeboard and Superelevation
The highest reservoir level will be Elevation 1466 under maximum
probable flood (PMF)flows.At this elevation the fuse plug in
the emergency spillway will be breached and the reservoir level
will fall to the spillway sill elevation of 1434.The normal max-
imum pool elevation is 1455.
A minimum freeboard of tnree feet will be provided for the PMF;
hence,the crest of the saddle dam will be Elevation 1469.In
addition,an allowance of one percent of the height of the dam
will be made for potential settlement of the rockfill shells under
seismic loading.An allowance of one foot has been made for set-
tlement of both abutments;hence,the final crest elevations of
the saddle dam will be 1470 at the abutments,rising in proportion
to the total height of the dam to Elevation 1472 at the maximum
section.Under normal operating conditions,the freeboard will
range from 15 feet at the abutments to 17 feet at the center of
the dam.Further allowances will be made to compensate for static
settlement of the dam after completion due to its own weight and
the effect of saturation of the upstream shell,Which will tend to
produce add it iona1 breakdown of the rock fill at po int contacts.
Therefore,one percent of the dam height will be allowed for such
settlement,giving a maximum crest elevation on completion of the
construction of 1475 at the maximum height,and 1471 at the abut-
ments.
The allowances for post-construction settlement and seismic slump-
ing will be achieved by steepening both slopes of the dam above
Elevation 1400.These allowances are considered conservative and
should be reviewed as more relevant data are obtained during
detailed design studies.
(h)Instrumentation
Instrumentation will be installed within all parts of the dam to
provide monitoring during construction as well as during opera-
tion.Instruments for measuring internal vertical ana horizontal
displacements,stresses and strains,and total and fluid pres-
sures,as well as surface monuments and markers similar to those
proposed for the Watana dam,will be installed.
(i)Stability Analyses
As at Watana,special precaut ions have been taken to ensure sta-
bil ity under earthquake loading by the use of processed free
draining gravel and rockfill in the saturated zones of the dam,
the incorporation of very wide filter zones,and the removal of
all unconsolidated natural material from beneath the dam.
Static and dynamic stability analyses of the upstream slopes of
the Watana dam (Section 12.6),have confirmed stable slopes under
all conditions for a 2.4H:1V upstream slope and a 2H:IV downstream
slope.
13-13
Since these same slopes have been used for the Devil Canyon saddle
dam and the construction materials are essentially similar,it was
considered unnecessary to carry out further analysis for the spec-
ific details of the saddle dam to confirm feasibility,though such
analyses will be required during the final design phase.
13.7 -Primary Outlet Facilities
(a)General
The prime function of the outlet facilities is to provide for dis-
charge through the main dam,in conjunction with the power facili-
ties,of routed floods with up to f:50 years recurrence period at
the Devil Canyon reservoir.This will require a total discharge
capacity of 38,500 cfs through the valves.Downstream erosion will
be minimal and nitrogen supersaturation of the releases will be
restricted as much as possible as in the case of the Watana
development.A further function of these releases is to provide
an emergency drawdown for the reservoir,shou1d mai ntenance be
necessary on the main dam or low level submerged structures,and
also to act as a diversion during the latter part of the construc~
tion period as described in Section 13.4.
The facilities will be located in the lower portion of the main
dam, as shown on Plate 52,and will consist of seven free dis-
charge valves set in the lower part of the arch dam.
(b)Outlet
The di scharge val ves wi 11 be the fi xed-cone type located at two
elevations:the upper group,consisting of four 102-inch diameter
valves,will be set at Elevation 1050,and the lower group of
three 9.0-inch diameter valves will be set at Elevation 930.The
valves will be installed nearly radially (normal to the dam cen-
terline)with the points of impact of the issuing jets staggered
as shown in Plate 52.
The fixed-cone valves will be installed on individual conduits
----------------------.---pass-;-ng--through-the-dam,.set c-lose t-o-t-hedowns-t-ream-faee,and
protected by upstream ring follower gates located in separate
chambers within the dam.Monorail hoists will be located above
each val ve and gate assembly to provide for their withdrawal and
maintenance.The gates and val ves will be linked by a 20 foot
hi gh tunnel runni ng across the dam and into the 1 eft abutment
where access will be provided by means of a vertical shaft exiting
through the thrust block.Although secondary access will be pro-
vided via a similar shaft from the right abutment,access and in-
stallation are both from the left side.
The valve and gate assemblies will be protected by individual
trashracks installed on the upstream face.The racks will be
removable along guides running on the upstream dam face.The
racks will be raised by a travelling gantry crane operating at
deck revel.Guides will be installed for the installation of
stop1ogs,if required,at the upstream face.
13-14
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(c)Fixed-Cone Valves
The 102-inch diameter valves operating at a gross head of 420 feet
and the gO-inch diameter valves operating at a head of 525 feet
have been selected to be within current precedent considering the
valve size and the static head on the valve.The valves will be
located in ind iv idua 11y heated rooms and wi 11 be prov ided with
electric jacket heaters installed around the cylindrical sleeve of
each valve.The valves will be capable of year round operation,
although winter operation is not contemplated.Normally,when the
valves are closed,the upstream ring follower gates will also be
closed to minimize leakage and freezing of water through the valve
seats.
The valves will be operated remotely by two hydraulic operators.
Operation of the valves will be from either Watana or by local
operation.
In sizing the valves it has been assumed that the valve gate open-
ing wi 11 be restr icted to 80 percent full stroke to reduce poss i-
bilities of vibration.
(d)Ring Follower Gates
Ring follower gates will be installed upstream of each valve and
will be used:
- To permit inspection and maintenance of the fixed-cone valves;
-To rel ieve hydrostatic pressure on the valves when they are in
the closed position;and
To close against flowing water in the event of malfunction or
failure of the valves.
The ring follower gates will have nominal diameters of 102 and 9U
inches and will be of welded or cast steel construction.The
gates wi 11 be designed to withstand the total stat ic head under
full reservoir.Existing large diameter,high head ring follower
gates are summarized in Table 12.6.
The design and arrangement of the ring follower gates will be as
discussed for Watana in Section 10.8.
(e)Trashracks
A steel trashrack will be installed at the upstream entrance to
each water passage to prevent debris from being drawn into the
discharge valves.The bar spacing on the racks will be approxi-
mately 9 inches.Provision will be made for monitoring head loss
across the racks.
13-15
(f)Hulkhead Gates
The bulkhead gates will be installed only under balanced head con-
ditions using a gantry crane.The gates will be 13 feet and 11
feet square for the upper and lower valves,respectively.
Each gate will be designed to withstand full differential head
under maximum reservoir water level.One gate for each valve size
has been assumed.The gates wi 11 be stored at the dam crest
level.
A temporary cover will be placed in the bulkhead gate check at
trashrack level to prevent debris from getting behind the trash-
racks.
The bulkhead gates and trashracks will be handled by an electric
travelling gantry type crane located on the main dam crest at Ele-
vation 1468.The crane and lifting arrangement will have provi-
sion for lowering a gate around the curved face of the dam.
13.8 -Main Spillway
(a) General
The main spillway at Devil Canyon will be locatea on the right
side of the canyon (see Plate 56).The upstream control structure
will be aajacent to the arch dam thrust block and will discharge
down an incl ined concrete-l ined chute constructed on the steep
face of the canyon.The chute will terminate in a flip bucket
Which will traject flows downstream and into the river.
The right bank location for the spillway facilities is considered
preferable to the left because Df the better quality of the rock,
and better downstream alignment for spillway discharges.
The spillway will be designed to pass the 1:10,000 year routed
flood at Watana in conjunction with the outlet facilities.The
.spi llwa.y .wi 11 have a designcapaci-ty-~.o.£-125,000 cfsdischarged
over a total head drop of 550 feet.No surcharge will occur above
the normal maximum reservoir operating level of 1,455 feet.This
discharge will be below the design discharge of 150,OUU cfs over
600 feet for the Mica Project in British Columbia,which has oper-
ated successfully for a number of years.
(b)Approach Channel and Control Structure
The approach channel will be excavated to a depth of approximately
100 feet in the rock with a width of Just over 130 feet and an
invert elevation of 1375.
The control structure,as shown in Plate 57,will be a three-bay
concrete structure set at the end of the channel.Each bay wi 11
incorporate a 56-foot-high by 30-foot-wide gate on an ogee-crested
weir and, in conjunction with the other gates,will control the
13-16
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flows passing though the spillway.The gates will be fixed wheel
gates operated by individual rope hoists.
A gallery is provided within the mass concrete weir from which
grouting can be carried out and drain holes can be drilled as a
continuation of the grout curtain and drain beneath the main dam.
The main access route will cross the dam across the control struc-
ture deck upstream of the gate tower and bridge structure.
(c)Spillway Chute
The spi 11way chute wi 11 cut across the steep north face of the
canyon for a distance of approximately 900 feet,terminating at
Elevation 1000.The chute will taper uniformly over its length
from 122 feet at the upstream end to HO feet downstream.
The overburden in the spillway area is expected to be generally
less than lU feet,but local depressions may be encountered up to
00 or 60 feet deep.Where such features extend below excavation
grades,they will be excavated to sound rock and filled with con-
crete as required.
The orientation of the spillway is generally parallel to the
strike of the bedding planes,and the stability of the northern
excavation face is controlled by the bedding. For stability,the
rock will be cut back to an angle of 5So to 60°,or parallel to
the rock dip.Minimum rock bolting may be required to prevent
slabs of rock spalling off the face in closely jointed areas.
Wire mesh will be provided over the majority of the face to
control small rock falls.
Joint Set I and the major shears are generally vertically dipping
and are perpendicular to the spillway axis and will not effect the
stability of slopes or structures .
The chute itself will be concrete-lined with invert and wall slabs
anchored back to the rock.The profile of the chute will be such
that the invert slabs wi 11 be founded on sound rock.Part way
down the chute on the side closest to the river,the depth of cut
will be insufficient to provide the supporting rock to the slabs.
In this area the side wall will take the form of a gravity section
over approximately a 200 foot length.
The velocity at the bottom of the chute will be approximately 150
ft/s.In order to prevent cavitation of the chute surfaces,air
will be introduced into the discharges.Air will be drawn in
along the chute via an underlying aeration gallery and offshoot
ducts extending to the downstream side of a raised step running
transverse to the chute,similar to that provided at Watana.
Adequate underdrainage of the spillway chute is essential for sta-
bility of the structure.Uplift pressure will develop from reser-
voir seepage under the control structure and from ground water and
seepage from the high velocity flows within the spillway itself.
13-17
Seepage from the spillway flow will generate high pressure within
the rock through cracks in the concrete,and with sudden closing
of the spillway gates,res idual unbal anced water pressures under
the slab will result.
An extensive drainage system is therefore proposed similar to that
described for Watana.The dam grout curtain and drainage system
is continued under the spillway control structure utilizing a
gallery through the rollway.A system of box drains is proposed
for the entire length of the spillway under the concrete slab.To
avoid blockage of the system by freezing of the surface drains,a
30-foot deep drainage gallery is proposed along the entire length
of the spillway.Dr ain holes from the surface arains will inter-
sect the gallery.
Complete drainage of the underside of the slab cannot be assured,
and some freezing or blockage of the drains will occur at times.
Adaitional resistance to uplift pressures must,therefore,be pro-
vided by means of rock anchors.To ensure adequate foundation
quality for anchorage,consolidation grouting is proposed' to a
depth of 20 feet.This grouted zone will also restrict seepage
below the spillway and improve the deformation characteristics of
the flip bucket rock foundation.
Drainage holes drilled into the base of the high rock cuts will
ensure increased stability of the excavation.
(d) Flip Bucket
The spi llway chute wi 11 terminate in a mass concrete fl ip bucket
founded on sound rock at Elevation 1000,approximately 100 feet
above the river.The curve of the flow surface of the bucket will
be adjusted to confine the issuing discharge,but at present it is
assumed to be cylindrical and will be mOdified at the final design
stage following model tests.A grouting/drainage gallery will be
provided within the bucket to allow for foundation consol idation
.and relief o~uplift pre5sures~
The jet issuing from the bucket will be trajected downstream and
parallel to the river below.
(e) Plunge Pool
The impact area of the issuing spillway discharge will be limited
to the area of the downstream river surface to prevent excess ive
erosion of the canyon walls.This will be done by modification of
the flow surface of the flip bucket as described above.Over this
impact area the alluvial material in the riverbed will be exca-
vated down to sound rock to provide a plunge pool in which most of
the inherent energy of the discharges will be dissipated,although
some energy will already have been dissipated by friction in the
chute,and in dispersion and friction through the air.
13-18
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The river material in the plunge pool area will be excavated to
prevent excessive erosion and random downstream deposition of
material which might occur if discharges were allowed to form
their own pool.
13.9 -Emergency Spillway
(a)General
The emergency spillway will be located on the left side of the
river beyond the rockfill saddle dam.It will be set within the
rock underlying the left side of the saddle ana will continue
downstream for approximately 2,00U feet.
An erodible fuse plug,consisting of impervious material and fine
gravels,will be constructed at the upstream end ana will be
designed to wash out when overtopped by tne reservoir,releasing
floods of up to 160,00U cfs in excess of the combined main spill-
way and outlet capacities and thus preventing overtopping of the
main dam.
(b) Fuse Plug and Approach Channel
The approach channel to the fuse plug will be cut in the rock and
will have a width of 310 feet and an invert elevation of 217U.
The channel will be crossed by the main access road to the dam on
a bridge consisting of concrete piers,precast beams, and an in
situ concrete bridge deck.The fuse plug will fill the approach
channel and will have a maximum height of 31.5 feet with a crest
elevation of 1465.5.The plug will be located on top of a flat-
crested weir excavated in the rock and protected ·with a concrete
slab.Since the rock surface slopes steeply at the channel loca-
tion,it is desirable to keep the spillway chute as narrow as pos-
sible to reduce the excavation quality.For this reason a drop
section downstream of the plug has been introduced to increase the
discharge coefficients at the plug sections and thus enable a
reduction in the length of the plug.
The plug will be traversed by a pilot channel with an invert ele-
vation of 1464, and will have a similar zoning to that described
in Section 12.10 for Watana.
(c)Discharge Channel
The channel wi 11 narrow downstream,discharging into a steep
valley tributary above the Susitna River.This channel will
r apid ly erode under high flows but wi 11 serve the purpose of
training the initial flows in the direction of the valley.
(d)Geotechnical Considerations
Uverburden depth in the area of the emergency spillway will be in
the order of 10 to 20 feet in thickness.Local depressions in the
rock surface may have greater thicknesses of overburden.
13-19
The spillway is generally orientated parallel to the strike of the
bedding planes on the northside of the canyon.
The northern excavation faces will therefore be controlled by the
dip of the bedding planes which varies from 50° to 60° in this
area.The excavation will be cut back parallel to the bedding.
In the area of the fuse plug,the sides of the excavation will be
1H:3V to provide a suitable contact slope for the fuse plug em-
bankment.
I~o allowance for rock support has been made for the excavat ion
faces of the spillway.In some areas the excavated faces without
additional rock bolting will have factors of safety approaching
unity,but since this channel will be rarely,if ever,used this
risk is considered acceptable.A rock fall into the spillway
channel wi 11 not endanger equipment or personnel and can be
removed if sufficient quantity accumulates to effect water flow in
the channel.
The consolidation grouting similar to that required under the core
of the saddle dam will be carried out over the foundation area of
the fuse plug.This grouting will prevent seepage in the slightly
weathered rock under the fuse pl ug and prevent piping of fines
from the core of the plug into open rock fissures.
Rock support with some form of rock bolting may be required on the
excavation slope in the vicinity of the bridge upstream of the
use plug.
13.10 - Devil Canyon Power Facilities
(a)Intake
The intake structure is located on the right bank as shown on
Plate 64.Separate intakes are provided for each turbine.Reser-
voir levels will vary between Elevations 145Sand 1405.Each in-
.....······---·--·----t·akehasasingle .intake gate,a set of-steel-trasnr-a0ks,anEl pro-··
vision for placing a bulkhead gate upstream from the intake gate.
A traveling gantry crane on the intake deck at Elevation 1466 will
service all four intakes.The mechanical equipment is described
in more detail below.
The intake is located at the end of a 200-foot-long un 1 ined
approach channel.The overburden in this area is estimated to be
approximately 10 feet deep.
The excavation in rock is up to 170 feet in depth.Since the side
excavation slopes are at an angle of 60° to the strike of control-
ling bedding plane,no major stability problems are expected.
Since this is a water channel in which rock falls could obstruct
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flow and cause damage to intake structures or power facil ities,
slopes of 1H:4V are required with an allowance for rock bolting
over 25 percent of the face area to achieve a satisfactory factor
of safety.
The excavation for the intake structure requires four tunnel por-
tals on tiO foot centers.Rock pillars 32 feet wide and 38 feet
deep separate the portals.If Joint Sets II ana III are signifi-
cant in this area,these rock pillars may be unstable.Uuring ex-
cavation of the portal by blasting,it is likely that portions of
these pi 11 ars will be loosened and will have to be removed for
safety.Rock bolting at 3 foot centers (high yield bolts 1 inch
diameter)over the entire face area of the pillars will be re-
quired.Bolts will range in length from 32 feet extending right
through the pillar to 50 feet long to anchor the pillar back to
sound rock.Concrete will be pl aced where overexcavation has
occurred.
The rock face between intakes wi 11 be 1 ined with concrete to sta-
bil ize the rock surface.The grout curtain and drainage holes
will continue beyond the main dam and beneath this structure.
The drainage holes downstream of the grout curtain will be termin-
ated adjacent to the spillway control structure,since the flow
paths in this area of the abutment are considerably longer than
under the dam and at low head of water pressure.
(b)Intake Gates
The four power intakes will have a single fixed wheel intake gate
with a nominal operating size of 20-feet-wide by 2!:i-feet-high.
The gates will have an upstream skinplate and seal and will be
operated by hydraulic or wire rope hoists located in heated enclo-
sures immediately below deck level.The gates,which will normal-
ly close under balanced head conaitions to permit dewatering of
the penstock ana turbine water passages for turbine inspection and
maintenance,will also be capable of closing under tneir own
weight with full flow conditions and maximum reservoir water level
in the event of runaway of the turbines.A heated air vent will
be provided at the intake deck to satisfy air demand requirements
when the intake gate is closed with flowing water conditions.
(c)Intake Bulkhead Gates
One set of intake bulkhead consisting of two gate sections will be
provided for closing the intake openings.The gate will be used
to permit inspection and maintenance of the intake gate and intake
gate guides.The gates will be raised and lowered under balanced
water conditions only.
13-21
(d) Trashr acks
Each of the four intakes wi 11 have trashracks at the upstream
face.The trashrack will have a bar spacing of about 6 inches and
be designed for a maximum differential head of about 20 feet.each
trashrack will be constructed in two sections for removal by means
of a follower suspended from the intake gantry crane.
(e)Intake Gantry Crane
A 50-ton capacity (approximately)electrical traveling gantry
crane will be provided on the intake deck at Elevation 1466 for
handling the trashracks,maintenance gates and intake gates.
13.11 -Penstocks
The power plant will have four penstocks,one for each unit.The maxi-
mum static head on each penstock will be 638 feet,as measured from
normal maximum operating level (Elevation 1455)to centerl ine distribu-
tor level (Elevation 817).An allowance of 35 percent has been made
for pressure rise in the penstock under transient conditions,giving a
maximum head of 861 feet.Maximum extreme head,corresponding to maxi-
mum reservoir flood level will be 876 feet.
The penstock tunnel s are fully concrete-l ined except for a ~5U-foot
section upstream of the powerhouse which is steel-l ined.The incl ined
sections of the concrete-lined penstocks will be at 55°to the hori-
zontal.
(a)Steel Liner
The first SO feet of steel 1 iner immediately upstream of the
powerhouse wi 11 be designed to res i st the full internal pressure.
The remainder of the steel liner,extending another 200 feet up-
stream,will require reduced steel assuming a minimum of rock sup-
port in this area.For prel iminary design,it is assumed that not
more than 50 percent of the design head is taken by the surround-.rn~iro-cK--over-fhisl r ansftTon·Tengffi-:--.--~~_.--_.___._._----.
Beyond the steel 1 iner,the hydraul ic loads are taken solely by
the rock tunnel with a concrete liner.
The steel 1iner is surrounded by a concrete infill with a min irmm
thickness of 24 inches.A preliminary analysis has resulted in an
optimum internal diameter of the steel lining of 15 feet,based on
the minimum total cost of construction and the capitalized value
of energy reduction due to head loss.A tapered steel transition
wi 11 be provided at the j unct i on between the steel 1 iner and the
concrete liner to increase the internal diameter from 15 feet to
20 feet.
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(b)Concrete Liner
(c)
The thickness of the concrete 1 ining wi 11 vary with the design
head,with the minimum thickness of lining being 12 inches.
Based on preliminary'analyses,the optimum internal diameter of
the concrete liner is 20 feet.
Geotechnical Considerations
The penstock tunnels will have the same orientation as the draft
tube tunnels.
Since the tunnels will be concrete lined for hydraulic considera-
tions,the initial rock support required will generally be minor.
However,for estimating,approximately 12 percent of the tunnel
length is assumed to have poor rock quality that will require
pattern rock bolting and shotcrete rock support.
The spacing of the tunnels is limited to 2.50,center to center,
where U is the excavated diameter of the tunnels.For penstock
tunnels of 20 foot internal diameter with 2 foot thick concrete
lining,the spacing required is bU feet.
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The contact between tunnel crown and concrete tunnel lining will
be grouted.Generally,the rock has a high mocul us, and deforma-
tion of the rock around the penstock will be negligible.Highly
fractured zones,however,may require consolidation grouting but
this will be in localized areas only.
(d)Grouting and Pressure Relief
A comprehensive pressure relief system is required to protect the
underground caverns against seepage from the high pressure pen-
stocks.The system will consist of small diameter boreholes set
out in an array to intercept the jointing in the rock.
Grouting round the penstocks will be provided to:
Fi 11 and seal any voias between the concrete infi 11 and the
steel liner or rock which may be left after the concrete placing
and curing;and
Fi 11 joints or fractures in the rock surrounding the penstocks
to reduce flow into the pressure rel ief system and to conso1 i-
date the rock.
13.12 -Powerhouse and Related Structures
(a) Genera1
The underground powerhouse complex wi 11 be constructed in the
right abutment.This will require the excavation of three major
caverns (powerhouse,transformer gallery and surge chamber),with
13-23
interconnecting rock tunnels for the draft tubes and isolated
phase bus ducts.
An unlined rock tunnel will be constructed for vehicular access to
the three main rock caverns.A second unl ined rock tunnel will
provide access from the powerhouse to the foot of the arch dam.
Vertical shafts will be required for personnel access by elevator
to the underground powerhouse;for oil filled cable from the
transformer gallery;and for surge chamber venting.
The draft tube gate gallery and cavern will be located in the
surge chamber cavern,above maximum design surge level.
The general 1ayout of the powerhouse compl ex is shown on Pl ates
85, 86 and 87.The transformer gallery will be located upstream
of the powerhouse cavern and the surge chamber located downstream
of the powerhouse cavern.The spac ing between the underground
caverns will be at least 1.0 times the main span of the larger ex-
cavat ion.
(b) Layout Considerations
The powerhouse is located underground in the right abutment.
Water for power generat ion is taken from an intake structure to
the right of the main spillway,and carried through individual
penstocks to the turbines.Water is discharged to the river by a
single tailrace tunnel 6800 feet in length.The draft tubes and
tailrace tunnel are protected against excessive transient pressure
rise by a downstream surge chamber, which also provides storage
for the turbine start-up sequence.
The intake structure is aesigned for a maximum drawdown of 50 feet
and is located close to the main arch dam thrust block for ease of
access.The powerhouse is located to provide the minimum total
length of penstock,assuming an inclination of 55°to the horizon-
tal for the sloping section of penstock.The orientation of the
powerhouse.Jtas beens_elected ..a.s....g corJ1RrQmi~g betW~J~n ...the....ct~sirE?cl
orientation for power flow (E-W)and the geotechnical data on
known shear zones and joint sets.Minimum clear spacing between
major rock excavations is at least 1.5 times the span of the
larger excavation.This is considered a conservative estimate for
preliminary design purposes.
The downstream surge chamber will be constructed as close as pos-
sible to the powerhouse for maximum protection to the draft tubes
under transient load conditions.For this reason the undergrouna
transformer gallery will be located upstream from the powerhouse.
The rock around the powerhouse cavern and transformer gallery is
protected against high pressure seepage from the penstocks by a
200-foot continuous steel-lining and an extensive pressure relief
system.
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(c)Access Tunnels and Shafts
The 3,000-foot long main access tunnel connects the powerhouse
cavern at Elevation 852 with the canyon access road on the right
bank. A secondary access tunnel runs from the main powerhouse
access tunnel to the foot of the arch dam,for routine maintenance
of the fixed cone valves.Br anch tunnels from the secondary
access tunnel will provide construction access to the lower sec-
tion of the penstocks at Elevation 820.Separate branch tunnels
from the main access tunnel give vehicle access to the transformer
gallery at Elevation ~9ti and the draft tube gate gallery at Eleva-
tion 908.The maximum gradient on the permanent access tunnel is
8 percent;the maximum gradient on the secondary access tunnel is
9 percent.
The cross section of the access tunnels is dictated by require-
ments for construction plant.For preliminary design a modified
horseshoe shape 35-feet wide by 28-feet high has been used.
The alignment of the access tunnel parallels Joint Sets II and III
(1).Geologic surface mapping indicates that the tunnel may in-
tersect 10 shear zones but only three of these are greater than 10
feet in width.Generally,the rock quality is such that excava-
tion and support are not anticipated to be problems.
Based on borings and mapping,it has been assumed that 8 percent
of the tunnel length will be in poor rock with RQDs less than 25
percent.In these zones,it is anticipated that extensive shot-
crete and rockbolt support and/or steel sets and in situ concrete
1 ining may be required.Additional support may be required for
all junctions depending on local rock conditions.
A minimum rock cover to the tunnel will be 1.5 multipl ied by the
tunnel span.The side slopes of the portal cut are expected to be
1H:4V with localized support as required.The portal face may be
excavated at 1H:10V,requiring more extensive rock bolting.
For final design,detailed mapping of the portal area is required.
If possible,for economy of excavation a natural rock face should
be selected in the canyon wall for the tunnel portals.
The main access shaft will be located at the north end of the
powerhouse cavern,providing personnel access by elevator from the
surface.Horizontal tunnels will be provided from this shaft for
pedestrian access to the transformer gallery and the draft tube
gate gallery.At a higher level,access will also be available to
the fire protection head tank.
Access to the upstream grouting gallery will be from the transfor-
mer gallery main access tunnel,at a maximum gradient of 13.5
percent.
13-25
(d)Powerhouse Cavern
The main powerhouse cavern is designed to accommodate four verti-
cal shaft Francis turbines,in line,with direct coupling to over-
hung generators.Each unit is rated at 150 MW at 57t>-foot net
head.
The overall height of the cavern is governed by the physical size
of the turbine and generator,the design dimensions of the turbine
draft tube,the overhead travell ing crane clearance and size,and
the rise of the roof arch.The unit spacing will be 6U feet with
an additional 11U-foot service bay at the south end of the power-
house for routine maintenance and construction erection.The
control room will be located at the north end of the main power-
house floor.The width of the cavern will be sufficient for the
physical size of the generator plus galleries for piping,air-
conditioning ducts,electrical cables,and isolated phase bus.
Compensation flow of 500 cfs will be required to the river immedi-
ately downstream of the arch dam,in order to provide env iron-
mental flows along the approximate 7000 foot length of canyon.up-
stream of the tailrace outlet.This flow will be provided by two
No.1300 hp vertical shaft mixed flow pumps,installed in a gal-
lery below the service bay.Each pump is rated at 115,000 gpm at
35-foot head.Water wi 11 be taken from the base of the surge
chamber and pumped 1000 feet to the dam through a discharge pipe
1 aid partly in the secondary access tunnel and partly in a sep-
arate outlet tunnel.
Multiple stairway access points will be available from the power-
house main floor to each gallery level.Access to the transformer
gallery from the powerhouse will be by a tunnel from the access
shaft or by a stairway through each of the four bus tunnels.
Access will also be available to the draft tube gate gallery by a
tunnel from the main access shaft.
A serv ice e 1ev ator will be provided for access from the serv ice
bay area on the main floor to the machine shop,and the dewatering
---------_~_---~~an (j--err-a-in agegallerTe s --drrt ffe -ldweY'--floo r s;-flatCl1eswil lljeprd=
vided through all main floors for installation and routine main-
tenance of pumps,valves and other heavy equipment using the main
powerhouse crane.
(e)Transformer Gallery
The transformers will be located underground in a separate unlined
rock cavern,120 feet upstream of the powerhouse cavern,with four
interconnecting tunnels for the isolated phase bus. There will be
12 s ingle-phase transformers in four groups of 3, one group for
each generating unit.Each transformer is rated at 13/345,70
MVA.For increased rel iabil ity,one spare transformer and one
spare HV circuit will be provided.The station service transfor-
mers and the surface facilities transformers will be located in
the bus tunnels.Generator excitation transformers will be
located on the main powerhouse floor.
13-26
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High voltage cables will be taken to the surface in two 7.5 foot
interval diameter cable shafts,and provision will be made for an
inspection hoist in each shaft.
Vehicle access to the transformer gallery will be from the south
end via the main powerhouse access tunnel.Personnel access will
be from the main access shaft or through each of the four isolated
phase bus tunnels.
(f)Surge Chamber
A simple surge chamber will be constructed 120 feet downstream of
the powerhouse to control pressure fl uctuat ions in the turbine
draft tubes and tailrace tunnel under transient load conditions,
and on mach i ne start-up.The chamber wi 11 be common to all four
draft tubes and the in1et pipe to Hie compensat ion flow pumps.
The chamber design will be governed by an assumed full load rejec-
tion surge and the requirement for incipient stability under part
load operation,together with estimated floor levels from the
tailwater rating curve.
The draft tube gate gallery and crane will be located in the same
cavern,above the max imum ant ici pated surge 1eve 1.Access to the
draft tube gate gallery will be by a rock tunnel from the main
access tunnel.The tunnel wi 11 be widened locally for storage of
the draft tube gates.
The chamber will be an unlined rock excavation with localized rock
support as necessary for stability of the roof arch and walls.
The guide blocks for the draft tube gates wi 11 be of reinforced
concrete anchored to the rock excavation by rock bolts.
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(g)Geotechnical Considerations for Powerhouse Caverns
The proposed orientation of the powerhouse cavern has been influ-
enced by the orientation of major Joint Set I and the trend of
major shears,which are roughly perpenaicul ar to the long ax is of
caverns.Joint Sets II and III intersect the cavern at about 35°.
This may cause some possible wedge block instabil ity in the
cavern,but with the gOOd quality rock conaition at depth,this is
not expected to be a problem.
boreholes drilled in the vicinity of the powerhouse showed the
rock to be good to excellent quality (I).
It has been assumed, however,for cost est imating that a major
shear will intersect the powerhouse cavern requiring substantial
support over 10 percent of the cavern length.
Preliminary design indicates that a 6-foot by 6-foot pattern of
high yield anchors 25 feet long will be adequate in the cavern
roof support.
13-27
~ock p~rmeabil ities are expected.to be low, in the order of
1 x 10-cm/s at cavern depth.IVlin imal seepage into the exca-
vation from the surrounding rock is expected during construction.
The in situ stress of the rock is expected to be low,No evidence
has been found to indicate high residual stress.Further investi-
gations are required to determine the rock stress in the power-
house cavern area for final design.However,it is expected that
the in situ stress will not affect orientation of the cavern.
The prel imnary design of the caverns has been carried out in the
same manner as for Watana.
Grouting ana pressure relief will be similar to that described for
Watana.
The compensation flow tunnel is orientated at 020 0 and will be
intersected by Joint Sets II and III at 35 0
•These joint sets
are not expected to cause any tunnel ing instabil ity.The tunnel
is similar in size and shape to the majn access tunnel and it is
expected that the similar rock support will be required.
Since the portal will be in a very steep sided part of the canyon,
the exact location can be optimized utilizing the natural rock
face so that very little portal excavation is required.
Near the portal,the compensation flow tunnel intersects the right
abutment drainage tunnel.Access will be maintained to upstream
and downstream port ions of the drainage tunnel by a secondary
incl ined shaft.
(h)Draft Tube Tunnels
The 120
0 orientation of the draft tube tunnels has been determined
from the powerhouse alignment.Joint Sets I,II and III and the
major shears all intersect the tunnel s at about 50
0 to the tunnel
axis.Little rock support is expected to be required in these
tunnels.
The tunnels will be 23 feet in diameter ana steel and concrete
1 ined,with the concrete having a thickness of about 2 feet.
Rock support will be required mainly at the junctions with power-
house and surge chamber,where the two free faces give greatest
potential for instability.
The contact between tunnel crown and concrete tunnel 1 ining will
be grouted.Consol idation grouting will only be required if a
highly fractured zone is encountered.
13.13 -Reservoir
The Uevil Canyon reservoir,at a normal operating level of 1455 feet,
will be approximately 26 miles long with a maximum width on the order
of 1/2 mile.The total surface area at normal operating level is 7800
13-28
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acres.Immediately upstream of the dam,the maximum water depth will
be approximately 580 feet.The minimum reservoir level will be 1405
feet during normal operation,resulting in a maximum drawdown of 50
feet.The reservoir will have a total capacity of 1,090,000 acre feet
of which 350,000 acre feet will be live storage.
Filling of the reservoir will result in local slope instability.A
reconnaissance mapping program performed for this study identified
existing and potential areas of slope instability as well as areas of
permafrost.Details of this work are presented in the 19~0-81
Geotechnical Report (1).
Prior to reservoir filling,the area below Elevation 1460 will be
cleared of all trees and brush.A field reconnaissance of the proposed
reservoir area was undertaken.This work included examination of aeri-
al photographs and maps, and a collection of recent forest inventory
data from the U.S.Forest Service.As described for the Watana reser-
voir,most of the vegetation within the reservoir consists of trees
with very 1 ittle undergrowth.The trees are generally small spruce.
In the Watana reservoir area,an estimated 3,200,000 cubic feet of wood
exists.Approximately 87 percent of the available timber are soft
woods.
The steep terrain,moderate-light tree stocking levels,small trees,
erosive potential of the reservoir slopes,remoteness,and very re-
stricted access to the reservoirs will affect the choice of harvesting
to be utilized for this project.
Present market demand for the timber at Sus itna is
worldwide demand for wood'fluctuates considerably.
that use of the harvested material would be limited
wood-waste products or as fuel.
low;however,the
It is ant ic i pated
to either sale as
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Sl ash material including brush and small trees,which will be suitable
for either of the above uses,will be either burned in a controlled
manner consistent with applicable laws and regulations,or hauled to a
disposal site.Material pl aced in disposal areas will be covered with
an 'earthfi 11 cover adequate to prevent eros ion and subsequent expo-
sure.
13.14 -Tailrace Tunnel
The tailrace pressure tunnel carries power plant discharge from the
surge chamber to the river.The tunnel has a modified horseshoe cross-
section with an internal dimension of 38 feet.For preliminary design,
it is assumed to be concrete lined throughout with a minimum thickness
of 12 inches.The length of the tunnel is 6800 feet.
The size of the tunnel and surge chamber was selected after an economic
study of the cost of construction and the capitalized value of average
annual energy losses caused by friction,bends and changes of section.
13-29
The tailrace portal site will be located at a prominent steep rock face
on the right bank of the river.The portal out1et is rectangul ar in
section,which reduces both the maximum outlet velocity (8 ft/s)as
well as the velocity head losses.Vertical stoplog guides are provided
for closure of the tunnel for tunnel inspection and/or maintenance.
13.15 -Turbines and Generators
(a) Unit Capacity
The Oevil Canyon powerhouse will have four generating units with a
nominal capacity of 150 MW based on the minimum December reservoir
level (Elevation 1405)and a corresponding gross head of 555 feet
in the station.
The head on the plant will vary from 555 feet to 605 feet.The
maximum unit output will change with head as shown in Figure
13.2.
The rated average operating head for the turbine has been estab-
1ished at 575 feet.Allowing for generator losses,this results
in a rated turbine output of 225,000 hp (168 MW)at full gate.
The generator rating has been selected as 180 MVA with a 90 per-
cent power factor.The generators will be capable of continuous
operat ion at 115 percent rated power.f3ecause of the high capa-
city factor for the Devil Canyon station,the generators will,
therefore,be sized on the basis of maximum turbine output at max-
imum head,allowing for a possible 5 percent addition in power
from the turbine.This maximum turbine output (250,000 hp) is
within the continuous overload rating of the generator.
(b)Turbines
The turbines will be of the vertical shaft Francis type with steel
spiral casing and a concrete elbow type draft tube.The draft
tube will have a single water passage (no center pier).
Max imum and min imum heads on the un its will be 542 feet and 600
feet,respectively.The full gate output of the turbines will be
about 240,000 hp at maximum net head and 205,000 hp at minimum net
head.Overgating of the turbines may be possible,providing
approximately 5 percent additional power.For preliminary design
purposes,the best efficiency (best gate)output of the units has
been assumed at 85 percent of the full gate turbine output.
The full gate and best gate efficiencies of the turbines will be
about 91 percent and 94 percent,respectively,at rated head.The
efficiency will be about 0.2 percent lower at maximum head and 0.5
percent lower at minimum head.The preliminary performance curve
for the turbine is shown in Figure 13.3.
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(c)
A speed of 2L5 rpm has been selected for the unit for preliminary
design purposes.The resulting turbine specific speed (Ns ) is
37.9,which is within present day practice for turbines operating
under 575 feet head.
On the basis of information from turbine manufacturers and the
studies on the power plant layout,the centerline of the turbine
distributor has been set at 30 feet below minimum tailwater level.
The final setting of the unit will be established in conjunction
with the turbine manufacturer after the contract for the supply of
the turbine equipment has been awarded.
Because of the relatively short penstocks and the surge tank loca-
tion immediately downstream from the powerhouse,the hydraulic
transient characteristics of the turbines are favorable.
The regulating ratio is above the minimum recommended by the USHR
for good regulating.The unit speed rise and penstock capacity
pressure rise are within normal accepted values.Because of the
relatively short distance between the turbine and the tailrace
surge tank and the deep unit setting,no problems with draft tube
column separation are expected.
As discussed in Section 12.16 for Watana,the units will be cap-
able of operation from about 5(J to 100 percent load.Considera-
tions for draft tube surges and corresponding power swings as men-
tioned for Watana also will apply to uevil Canyon.
As with watana,the relationship between generator natural fre-
quency and the possible draft tube surge frequency will require
stUdy in later design stages.Because of the high capacity factor
for the Devil Canyon units,part load operation for these turbines
is not as critical as at Watana;therefore,the possibility of
prob 1ems wi th power swi ngs wi 11 be 1ess of a concern than at
Watana.
Generators
The four generators in the Devil Canyon powerhouse will be of the
vertical shaft,overhung semi-umbrella type directly connected to
the vertical Francis turbines.
The generators will be similar in construction and design to the
Watana generators and the general features described in Section
12.16 for the stator,rotor,excitation system,and other details
which apply for the Devil Canyon generators.
The rating and characteristics of the generators are as follows:
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Rated Capac ity:
Rated Power:
180 MVA,0.9 power factor with over-
load rating of 115 percent.
162 MW
13-31
A governor system with electric hydraulic governor actuators will
be provided for each of the Dev il Canyon un its.The system wi 11
be the same as for Watana.
Pumping operation will be continuous;therefore,pumping equipment
wi 11 be conservat ively designed to provide effic ient operat ion
with minimal maintenance.Crane access will be provided for the
pumps,motors,and valves to permit equipment servicing.
A single pump intake will be located in the surge chamber with an
8-foot-diameter intake tunnel leading to the powerhouse.The in-
take tunnel will bifurcate into individual pump intake conduits
within the powerhouse.The pump discharges will converge into a
single pump discharge line.
13.16 -Miscellaneous Mechanical Equipment
(a)Compensation Flow Pumps
The two pumps for providing nnn mum discharge into the Susitna
River between the dam and the tailrace tunnel outlet portal will
be vertical mixed flow type located in the powerhouse service bay
below the main erection floor,as shown on Plate 66.Each pump
will be rated at 250 cfs (115,000 gal/min)at 35 feet total head,
and will be driven by 1,400-hp induction motors.
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225 rpm
3.5 MW -Sec/MVA
15 kV,3 phase,60 Hertz
1.1 (minimum)
98 percent (minimum)
Rated Voltage:
Inertia Constant:
Short Circuit Ratio:
Synchronous Speed:
Efficiency at Full Load:
(d) Governor System
Butterfly type valves will be installed in the intake and dis-
charge 1 ines of each pump to permit isolation of a pump for in-
spection and maintenance.Trash screen guides and a trash screen
will be provided in the surge chamber at the pump intake.It will
------be-poss-ible-to-r-emove --the-trashscreen--using-the-draft -tube-gate
crane discussed below.The width of the guides will be selected
so that one of the turb ine draft tube gates may be install ed in
the intake to permit dewatering the pump intake tunnel for inspec-
tion and/or maintenance of the tunnel or the intake butterfly
valves.Stoplog guides and a set of stoplogs will also be pro-
vided at the downstream end of the pump discharge tunnel to allow
the discharge tunnel to be dewatered.The stoplogs will be
handled with a mobile crane and a follower.
In the detailed design stages,consideration will also be given to
turbine-driven rather than electric motor-driven pumps.A header
from at least two of the main turbine penstocks would supply water
to the turbines,with the turbine draft tubes connected to the
pump discharge.
(b)Powerhouse Cranes
Two overhead type powerhouse cranes will be provided at Devil Can-
yon as at Watana.The estimated crane capacity will be 200 tons.
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(c)
( d)
(e)
Draft Tube Gates
Draft tube gates will be provided to permit dewatering of the tur-
bine water passages for inspection and maintenance of the tur-
b ines.The arrangement of the draft tube gates wi 11 be the same
as for Watana,except that only two sets of gates will be pro-
vided,each set with two 2l-foot-wide by lO.5-foot-high sections.
At the time of starting of Unit 1,one gate will be installed in
Unit 4 with the other gate available for Unit 1.Bulkhead domes
will be installed in Units 2 and 3.
Draft Tube Gate Crane
A crane will be installed in the surge chamber for installation
and removal of the draft tube gates.The crane will be either a
monorail (or twin monorail)crane or a gantry crane.For the pre-
liminary design,a twin monorail crane of approximately 30-ton
capacity has been assumed.The crane will be pendant-operated and
have a two point lift.A follower will be used with the crane for
handl ing the gates.The crane runway will be located along the
upstream side of the surge chamber and will extend over the intake
for the compensation flow pumps,as well as a gate unloading area
at one end of the surge chamber.
Miscellaneous Cranes and Hoists
In add it ion to the powerhouse cranes and draft tube gate cranes,
the following cranes and hoists will be provided in the power
plant:
- A 5-ton monorail hoist in the transformer gallery for transfor-
mer ma intenance;
-Small overhead,jib,or A-frame type hoists in the machine shop
for handling material;and
A-frame or monorail hoists in other powerhouse areas for hand-
1ing small equipment.'
(f)E1ev ators
Access and service elevators will be provided for the power plant
as follows:
13-33
[iii]
- Access elevator from the control building to the powerhouse;
-Service elevator in the powerhouse service bay;and
-Inspection hoists in cable shafts.
(g)Power Plant Mechanical Service Systems
The power plant mechanical service systems for Devil Canyon will
be essentially the same as discussed in Section 12.17 for Watana,
except for the following:
- There will be no main generator breakers in the power pl ant;
therefore,circuit breaker air will not be required.The high-
pressure air system will be used only for governor as well as
instrument air.The operating pressure will be 600 to 1,000
psig depending on the governor system operating pressure.
-An air-conditioning system will be installed in the powerhouse
control room.
- Heating and ventilating will be required for the entrance build-
ing to the access shaft in the left abutment.
- For prel iminary design purposes,only one drainage and one de-
watering sump have been provided in the powerhouse.The de-
watering system will also be used to dewater the intake and dis-
charge lines for the compensation flow pumps.
(h)Surface Facilities Mechanical Service Systems
The entrance building above the power plant will have only a heat-
ing and ventilation system.The mechanical services in the stand-
by power building will include a heating and ventilation system, a
fuel oil system,and a fire protection system, as at Watana.
(i)Machine Shop Facilities
A machine shop and tool room will be located in the powerhouse
service bay area to take care of maintenance work at the pl ant.
-----lhef-ac-Hit-ies wi 11·not .be-as-extens-ive--as--at--Wat-ana~---Some of the
larger components will be transported to Watana for necessary
machinery work.
1J.17 - Accessory Electrical Equipment
(a) General
The accessory electrical equipment described below includes the
following main electrical equipment:
-Main generator step-up 15/345 kV transformers;
-Isolated phase bus connecting the generator and transformers;
-345 kV oil-filled cables from the transformer terminals to the
switchyard;
- Control systems;and
-Station service auxiliary ac and dc systems.
13-34
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Other equipment and systems described include grounding,lighting
system and communications.
The main equipment and connections in the power plant are shown in
the single line diagram,(Plate 70).The arrangement of equipment
in the powerhouse,transformer gallery,and cable shafts is shown
in Plates 65 to 67.
(b)General Design Considerations for
Transformers and HV Connections
)
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(i )General
Twelve single-phase transformers and one spare transformer
will be located in the transformer gallery.Each bank of
the three sing 1e-phase transformers wi 11 be connected to
one generator by isolated phase bus located in bus tunnels.
The HV terminal s of the transformer will be connected to
the 345 kV switchyard by 345 kV single-phase oil-filled
cables installed in 800-foot long vertical shafts.There
will be two sets of three single-phase 345 kV oil-filled
cables installed in each cable Shaft.One additional set
will be maintained as a spare three-phase cable circuit in
the second cable shaft.These cable shafts will also con-
tain the control and power cables between the powerhouse
and the surface control room, as well as emergency power
cables from the diesel generators at the surface to the
underground facilities.
As described in Section 12.18 for the Watana power plant,a
number of considerations led to the choice of the above
opt imum system of transformat ion and connect ions.Di f-
ferent alternative methods and equipment designs were also
considered.In summary,these are:
- One transformer per generator versus one transformer for
two generators;
-Underground transformers versus surface transformers;
-Direct transformation from generator voltage to 345 kV
versus intermediate step transformation to 230 kV or 161
kV, and thence to 345 kV;
- Si ngl e phase versus three-phase transformers for each
alternative method considered;and
-Oil-filled cable versus solid dielectric cable or SF6gas-insulated bus.
Reliability considerations are based on the general reli-
ability requirements for generation and transmission des-
cribed in Section 15 regarding the forced outage of a
single generator,transformer,bus or cable in addition to
planned or scheduled outages in a single contingency situa-
tion,or a subsequent outage of'equipment in the double
contingency situation.In the first case,the system
should be capable of readjustment after the outage for
13-35
(c)Main Transformers
loading within normal ratings and, in the second case,
within emergency ratings.
The transformers will be of the single phase, two-winding,oil-
immersed,forced-oil water-cooled (FOW)type.A total of twelve
single-phase transformers and one spare transformer will be pro-
vided,with rating and characteristics as follows:
Isolated phase bus connections will be located between the genera-
tor and the main transformer.The bus will be of the self-cooled,
welded aluminum tubular type with design and construction details
generally similar to the bus at the Watana power plant.The rat-
ing of the main bus is as follows:
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70 MVA
3454J3 kV,grounded Y
1300 kV
15 k V,Ue lta
..·15 percent .
For the same reasons as given in Section 12.18 for Watana,
surface transformers and the double-step transformation
scheme (15/161 kV generator-transformer,161 kV cable and
161/345 kV auto-transformer at the swi tchyard)were rul ed
out.The direct transformation (15/345 kV)scheme with 345
kV oil-filled cables is considered a better overall
scheme.
The one transformer per generator scheme was selected since
the operation of the Devil Canyon power plant will essen-
tially be a continuous base-load type operation;also the
smaller number of units at Devil Canyon compared to Watana
will allow a transformer gallery of reasonable length for a
unit generator-transformer scheme.
As at Watana,transport limitations for both dimensions and
weight will preclude the use of the larger size three-phase
transformers;hence,single-phase transformers will be
used.Une distinct advantage of single-phase transformers
is that a spare transformer can be provided at a fairly low
incremental cost.
Rated capac ity:
High Voltage Winding:
Basic Insulation Level
(BIL) of HV Winding:
Low Voltage Winding:
..-rr an sformel"'Impedan Ge·:
(d)Generator Isolated Phase Bus
Rated current:
Short circuit current momentary:
Short circuit current
symmetrical:
Basic Insul ation Level (BIL):
9,000 amps
240,000 amps
150,000 amps
150 kV
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(e)345 kV Oil-Filled Cable
The general design considerations leading to the choice of the 345
kV oil-filled cable for the connections between the transformer HV
terminals and the 345 kV switchyard at the surface are the same as
described in Section 12.18 for the Watana plant.
The cables will be rated for a continuous maximum current of 400
amps at 345 kV +5 percent.The cables will be of single-core con-
struction with oil flowing through a central oil duct within the
copper conductor.The cables will be installed in the 800-foot
cable shafts from the transformer gallery to the surface.No
cable jointing will be necessary for this installation length.
(f)Control Systems
(i)General
The Devil Canyon power plant will be designed to be oper-
ated as an unattended pl ant.The plant wi 11 be normally
contro 11 ed through superv i sory control from the Sus itna
Area Control Center at Watana.The plant will,however, be
provided with a control room with sufficient control,indi-
cation,and annunciation equipment to enable the plant to
be operated during emergencies by one operator in the con-
trol room.In addition,for the purpose of testing and
commissioning and maintenance of the plant,local control
boards wi 11 be mounted on the powerhouse floor near each
unit.
Automatic load-frequency control of the four units at Devil
Canyon will be accompl ished through the central computer-
aided contro 1 system located at the Watana Area Control
Center.
The power plant wi 11 be provided with "bl ack s t ar t"capa-
bility similar to that provided at Watana,to enable the
start of one unit without any power in the powerhouse or at
the switchyard,except that provided by one emergency die-
sel generator.After the start-up of one unit,auxiliary
station service power will be established in the power
plant and the switchyard;the remaining generators can then
be started one after the other tD bring the plant into full
output within the hour.
As at the Watana power pl ant,the control system will be
designed to permit local-manual or local-automatic start-
ing,voltage adjusting,synchronizing,and loading of the
unit from the powerhouse control room at Devil Canyon.
The protective relaying system is shown in the main single
line diagram (Plate 70)and is generally similar to that
provided for the Watana power plant.
13-37
(g)Station Service Auxiliary AC and DC Systems
(i)AC Auxiliary System
The station service system will be designed to acnieve a
reliable and economic distribution system for the power
plant and the switchyard and surface facilities.The aux-
iliary system will be similar to that in the Watana power
plant except that the switchyard and surface facilities
power will be obtained from a 4.16 kV system supplied by
two 5/7.5 MVA,OAlFA,oil-immersed transformers connected
to generators Nos.1 and 4,respectively.The 4.16 kV
double-ended switchgear will be located in the powerhouse.
It will have a normally-open tie breaker which will prevent
parallel operation of the two sections.The tie breaker
will close on failure of one or the other of the incoming
supplies.The 1400 hp compensation flow pumps will be sup-
pl ied with power directly from the 4.16 kV system.·Two
4.16 cables installed in the cable shafts will supply power
to the surface facilities.
The 480 V station service system will be exactly similar to
the Watana system described in Section 12.18,and will con-
sist of a main 480 V switchgear,separate auxiliary boards
for each unit,an essential auxiliaries board,and ~gener-
al auxiliaries board.The main 480 V switchgear will be
supplied by two 2000 kVA,15,000/480 V grounded wye sealed
gas dry-type transformers.A third 2000 kVA transformer
will be maintained as a spare.
Two emergency diesel generators,each rated 500 kW,will be
connected to the 480 V powerhouse main switchgear and 4.16
kV surface switchboard,respectively.Both diesel genera-
tors will be located at the surface.
An uninterruptible high-security power supply will be pro-
vided for the supervisory computer-aided plant control
systems.
(ii)DC Auxiliary Station Service System
The dc auxiliary system will be similar to that provided at
the Watana plant and will consist of two 125 Vdc lead-acid
batteries.Each battery system will be suppl ied by a
double rectifier charging system. A 48 Vdc battery system
will be provided for supplying the supervisory and communi-
cat ions systems.
(iii)Black Start Capability
As at the Watana power plant,the Devil Canyon power plant
will be provided with "black start"capability which will
enable the plant to start up in a completely "blacked out"
condition of the power plant and/or the power system.
13-38
11
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(h)Other Accessory Electrical Systems
The other accessory electrical systems including the grounding
system,lighting system,and powerhouse communications system will
be simil ar in general design and construction aspects to the
systems described in Section 12.18 for the Watana power plant.
13.18 -Switchyard Structures and Equipment
(a)Single Line Diagram
The electric system studies recommended a "breaker-and-a-hal t"
single line arrangement.This arrangement was recommended for
reliability and security of the power system.Plate 89 shows the
details of the switchyard single line diagram.
Devil Canyon will be the main switching station for the generation
and transmission system.Five lines will emanate from this
switchyard,with three going to Anchorage and two going to Fair-
banks.
(i)Control and Metering
All control and metering functions are handled by the
Watana control center.The Willow System Center can also
in it i ate a control funct ion through the Watan a control
center.
(ii)Relay Protection
Relay protection for transmission lines is similar to that
described in Section 14.5.Protection for 345 kV cable
from the powerhouse is described under Section 12.19.
(b)Switchyard Equipment
The number of 345 kV circuit breakers is determined by the number
of elements to be switched such as 1 ines or in-feeds from the
powerhouse.Each breaker will be equipped with two disconnect
switches to allow safe maintenance.
The auxiliary power for the switchyard will be obtained from the
generator bus via a 15 -4.16 kV transformer and 4.16 kV cable.
The voltage will then be stepped down to 480 V for local use.
(c)Switchyard Structures and Layout
The switchyard layout will be based on a convenFional outdoor type
design.The design adopted for this project will provide a two
level bus arrangement.This design is commonly known as a low
station profile.
13-39
The two-level bus arrangement is desirable because it is less
prone to extensive damage in case of an earthquake.Due to the
lower heights,it is also easier to maintain.
Although the present studies considered conventional switchyard
layouts,it is recommended that gas-insulated station equipment be
considered in the design stage.A more detailed discussion is
presented in Section 14.
13.19 -Project Lands
Project lands acquired for the project will be the mlnlmum necessary to
construct access and site facil ities,construct permanent facil ities,
to clear the reservoir,and to operate the project.
A large amount of public land in the Devil Canyon area is managed by
the Bureau 'of Land I~anagement.There are 1arge blocks of private
Native Village Corporation Lands along the river.Other private hold-
ings consist of widely scattered remote parcels.The state has select-
ed much of the federal 1 and in this area and is expected to receive a
patent.
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LIST OF REFERENCES
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Acres American Incorporated,Susitna Hydroelectric Project,1980-81
Geotechnical Report, prepared for the Alaska Power Authority,
February 1982.
1
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TABLE 13.1:WATANA PEAK WORK FORCE AND CAMP/VILLAGE DESIGN POPULATION
]
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Calendar Year
1992
1993
1994
1995
1996
1997
1998
1999
2000
Yearly Peak Force
180
730
1635
2455
3180
3180
2000
770
455
CamplVlllage Deslgn
200
800
1800
2700
3500
3500
2200
850
500
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TABLE 13.2:ARCH DAM EXPERIENCE
Dam Height Crest Length
(Year Completed)Location ft(m)ft(m)
Inguri Georgia,892 2,513 l(1985)USSR (272)(766)
Vaiont Veneto,858 624
(1961 )Italy (262)(190)
Mauvoisin Valais,777 1,706
(1957)Switzer land (237)(520)
Chirkei North Caucasas,764 1,109
\(1975)USSR (233)(338)
El Cajon Yoro/Cortes,741 1,253
(1964)Honduras (226)(382)
&'>1
Contra Ticino,722 1,246
(1965)Switzerland (220)(380)
Glen Canyon Arizona,710 1,560 J(1964)USA (216)(475)
Mohamed Reza Khouzestan,666 696
Shah Pahlav i Iran (203)(212)
.i(1963)
Almendra Salmanca,662 1,860
(1970)Spain (202)(567)
JVidraruArges,Rumania 549 1,000
(167)(305)
Gokcekaya Turkey 525 1,622
(160)(495)
lvbrrow Point Colorado 465 720
(141 )(218)
Pacoima California 372 589
(113)(180)
I
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TABLE 13.3:PRELIMINARY COMPENSATION FLOW PUMP DATA
Type •••••••••••••••••••••••••••••••••••••••••••••••••••••vertical,axial,or
mixed flow
Rated head (total dynamic level)•••••••••••••••••••••••••35 ft
Rated discharge •••••••••••••••••••••••••••.••••••••••••••115,000 gal/min
Pump input •••••••••••••••••••••••••••••••••••••••••••••••1,300 hp
Speed ••••••••••••••••••••••••••••••••••••••••••••••••••••400 rpm
Impeller diameter ••••••••••••••••••••••••••••••••••••••••51 in (approx.)
Motor
Type •••••••••••••••••••••••••••••••••••••••••••••••••••••vert ical induct ion
Rated power ••••••••••••••••••••••••••••••••••••••••••••••1,400 hp
Voltage ••••••••••••••••••••••••••••••••••••••••••••••••••4,160 VII
Speed 400 rpm
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No. phases ••.••.•••••••••••••••.•••••••••••••••••••••••••3
Frequency ••••.•••••••••••••••••••••••••••••••••••••••••••60 hz
TABLE 13.4:PRELIMINARY UNIT DATA
1 -GENERAL DATA
- Number of units ••••••••••••••••••••••••••••••••••••••••4
- Nominal un it out put ••••••••••••••••••••••••••••••••••••150 MW
-Headwater levels
-normal maximum El 1445
- minimum El 1395
-Tailwater levels
-minimum •..•...••....•...•....•••..••...•••..••.......E1 847
-normal ..•...•....•....•••...••.•.••...•.•....•••....•EL 849
-maximum ••••.•••••••••••••••.•••••••••••••••••••••••••E1 868
2 -TURBINE DATA
- Type •••••••••••••••••••••••••••••••••••••••••••••••••••vertical Francis
-Rated net head •••••••••••••••••••••••••••••••••••••••••575 ft
-Maximum head •••••••••••••••••••••••••••••••••••••••••••600 ft
- Minimum head •••••••••••••••••••••••••••••••••••••••••••542 ft
-Full gate output:
-at rated level 225,000 hp
-at maximum head ••••••••••••••••••••••••••••••••••••••240,000 hp
-at minimum head 205,000 hp
-Best gate output •••••••••••••••••••••••••••••••••••••••85%full gate output
-Full gate discharge at rated head ••••••••••••••••••••••3,790 cfs
-Speed ••••••••••••••••••••••••••••••••••••••••••••••••••225
-Specific speed •••••••••••••••••••••••••••••••••••••••••37.9
-Runner discharge diameter ••••••••••••••••••••••••••••••135 in
- Runaway speed ••••••••••••••••••••••••••••••••••••••••••405 rpm
-Centerline distributor •••••••••••••••••••••••••••••••••El.817
-Cavitation coefficient (sigma)•••••••••••••••••••••••••0.106
3 -GENERATOR DATA
1
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- Type ••I.'•••••••••••••••••••••••••••••••••••••••••••••••
- Rated output .................•..•..................•...
- Power factor •••••••••••••••••••••••••••••••••••••••••••
-Volt age ...............•..............•..............••.
-Inert ia const ant (H)*.
- Synchronous speed .:2 ••••••••••••••••••••••••••••••••••••
-Flywheel effect (WR )*•••••••••••••••••••••••••••••••••
___________________________-__~H~e.a••.viest lift ••••••••••••••••••••••••••••••••••••••.•••
*Including turbine
vert ical semi-
umbrella
180 MVA
0.9
15 kV
3.5 MW-sec/MVA
225 rpm
54 x 10 6 lb-ft 2
750,000 Ib
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115 CVa GENERATOR
RA ED POWER
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RESERVOIR EL. 1455 /----//
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BES GATE /
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BEST EFFIC ENCY7 FULL GATE
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RESER 'OIR IEL.1400 MINIMUM DEC EMBER HEAD
I --/
....-15 ) MW
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100 120 140 160
UNIT OUTPUT- MW
180 200 220
DEVIL CANYON - UNIT OUTPUT
FIGURE 13.2
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V v
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-:V
r-:
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40,000 80,000 120POO 160,000 200,000
TURBINE OUTPUT (HP)
DEVIL CANYON -TURBINE PERFORMANCE
(AT RATED HEAD)
240,000
4000
-(I)
lL.
30003
w
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1000
FIGURE 13.3
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14 -TRANSMISSION FACILITIES
The objective of this section is to describe the studies performed to
select a power delivery system from the Susitna River basin generating
plants to the major load centers in Anchorage and Fairbanks.This sys-
tem will be comprised of transmission lines,substations,a dispatch
center,and means of communications.
The major topics of the transmission studies include:
-Electric system studies;
-Transmission corridor selection;
-Transmission route selection;
-Transmission towers,hardware and conductors;
-Substations;and
- Dispatch center and communications.
Further discussion of the importance of these studies in determining
the method of operation of the Railbelt System is presented in Section
15.
In this section,each of the major topics will be discussed with re-
spect to previous studies,methodology,additional data obtained,and
conclusions arising from the studies.
14.1 -Electric System Studies
Transmission planning criteria were developed to ensure the design of a
reliable and economic electrical power system, with components rated to
allow a smooth transition through early project stages to the ultimate
developed potential.
Strict application of optimum,long-term criteria would require the
installation of equipment with ratings larger than necessary at exces-
sive cost.In the interest of economy and long-term system perfor-
mance,these criteria were temporarily relaxed during the early devel-
opment stages of the project.Although allowi ng for sat i sfactory
operation during early system development,final system parameters must
be based on the ultimate Susitna potential.
The criteria are intended to ensure maintenance of rated power flow to
Anchorage and Fairbanks during the outage of any single line or trans-
former element.The essential features of the criteria are:
- Total power output of Susitna to be delivered to one or two stations
at Anchorage and one at Fairbanks;
- "Breeker-and-a-hal f"switching station arrangements;
14-1
Overvoltages during line energizing not to exceed specified limits;
-System voltages to be within established limits during normal opera-
tion;
-Power delivered to the loads to be maintained and system voltages to
be kept within established limits for system operation under emer-
gency conditions;
-Transient stability during a 3-phase line fault cleared by breaker
action with no reclosing;and
-Where performance limits are exceeded, the most cost effective cor-
rective measures are to be taken.
(a)Existing System Data
Data compiled in a draft report by Commonwealth Associates Inc.,
(1)Has been used for preliminary transmission system analysis;
and (2) Other system data were obtained in the form of single-
line diagrams from the various utilities.
(b)Power Transfer Requirements
The Susitna transmission system must be designed to ensure the
reliable transmission of power and energy generated by the Susitna
Hydroelectric Project to the load centers in the Railbelt area.
The power transfer requi rements of thi s transmi ssi on s'ystem are
determined by the following factors:
-System demand at the various load centers;
- Generating capabilities at the Susitna project;and
- Other generation available in the Railbelt area system.
Most of the electric load demand in the Railbelt area is located
in and around two main centers:Anchorage and Fairbanks.The
largest load center is Anchorage,with most of its load concen-
---t rated in the An chorage urban area.The second largest load cen-
..t£L_Ls_Eaj_r.b_anks_.Iw.o_smaJJ_lo_ad_c_ent_e.Ls_CWJ_LLo_w_arld_I:l€_aJ.y-t-a r 8_
located along the Susitna transmission route.The only other sig-
nificant load centers in the Rai lbelt region are Glennallen and
Valdez,however,their combined demand is expected to be less than
2 percent of the total Railbelt demand in the foreseeable future.
A survey of past and present load demand levels as well as various
forecasts of future trends indicates these approximate load levels
at the various centers:
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14-3
The resulting power transfer requirements for the Susitna trans-
mission system are indicated in Table 14.1.
78
20
2
Percent of
Total
Rai lbelt LoadLoadArea
Anchorage -Cook Inlet
Fairbanks -Tanana Valley
Glennallen - Valdez
Development of other generation resources could alter the geo-
graphic load and generation sharing in the Railbelt,depending on
the location of this development.However,current studies indi-
cate that no other very large projects are likely to be developed
until the full potential of the Susitna project is utilized.The
proposed transmission configuration and design should,therefore,
be able to satisfy the bulk transmission requirements for at least
the next two decades.The next major generation development after
Susitna will then require a transmission system determined by its
own magnitude and location.
The potential of the Susitna Hydroelectric Project is expected to
be developed in three or four stages as the system load grows over
the next two decades.The transmission system must be designed to
serve the ultimate Susitna development,but staged to provide
reliable transmission at every intermediate stage.Present plans
call for three stages of Susitna development: 680 MW at Watana in
1993 followed by an additional 340 MW in 1997; and, 600 MW at
Devil Canyon in 2002.
Accordingly,it has been assumed for study purposes that approxi-
mately 80 percent of the generation at Susitna will be transmitted
to the Anchorage area and 20 percent to Fairbanks.To account for
the uncertainties in future local load growth and local generation
development,the Susitna transmission system was designed to be
able to transmit a maximum of 85 percent of Susitna generation to
Anchorage and a maximum of 25 percent to Fairbanks.
Considering the geographic location and the currently projected
magnitude of the total load in the area,transmission to Glenn-
allen-Valdez is not likely to be economical in the foreseeable
future.If it is ever to be economical at all,it would likely be
a direct radial extension,either from Susitna or from Anchorage.
In either case,its relative magnitude is too small to have
significant influence on either the viability or development
characteri st ics of the Susitna project or the transmi ssi on from
Susitna to the Anchorage and Fairbanks areas.
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(c) Transmission Alternatives
Having established the peak power to be delivered and the dis-
tances over which it is to be transmitted,transmission voltages
and number of circuits required were determined.To mai ntai n a
consistency with standard ANSI voltages used in other parts of the
United States,the following voltages were considered for Susitna
transmission:
Because of the geographic location of the various centers,trans-
mission from Susitna to Anchorage and Fairbanks will result in a
radial system configuration.This allows significant freedom in
the choice of transmission voltages,conductors,and other para-
meters for the two line sections,with only limited dependence
between them. In the end,the advantages of standardizati on for
the entire system will have to be compared to the benefits of
optimizing each section on its own merits.Transmission alterna-
tives were developed for each of the two system areas,including
voltage levels,number of circuits required,and other parameters,
to satisfy the necessary transmission requirements of each area.
500 kVor 345 kV
345 kV or 230 kV
Susitna to Anchorage
Susitna to Fairbanks
Transmission at either of two different voltage levels (345
kV or 500 kV)could reasonably provide the necessary power
transfer capabi1ity over the di stance of approximately 140
miles between Devil Canyon and Anchorage.The required,
transfer capability of 1,377 MW is 85 percent of the ulti-
mate generating capacity of 1,620 MW.At 500 kV,two cir-
cuits woul d provide more than adequate capacity.At 345
kV,either three circuits uncompensated or two circuits
with series compensation are required to provide the
necessary reliability for the single contingency outage
criterion.At lower voltages,an excessive number of
pi:!rcillel circuits are required,while above 500 kV,two
ctrcuitsare~sei-l-l-~rreErde-d-t~o··pro\;r;-ae--ser vic~e--in-ffj e-·eVe n'r .
of a line outage.
Applying the same reasoning used in choosing the transmis-
sion alternatives to Anchorage,two circuits of either 230
kV or 345 kV were chosen for the section from Devil Canyon
to Fairbanks.The 230 kV alternative requires series
compensation to satisfy the planning criteria in case of a
line outage.
(i)
(i i)
-Watana to Devil Canyon and on to Anchorage:
- Devil Canyon to Fairbanks:
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(iii)Total System Alternatives
The transmission section alternatives mentioned above were
combined into five realistic total system alternatives.
Three of the five alternatives have different voltages for
the two sections.The principal parameters of the five
transmission system alternatives analyzed in detai 1 are as
fo 11 ows:
Susitna to Anchorage Susitna to Fairbanks
Number of Number of
Alternative Circuits Voltage Circuits Vo ltage
(kV)(kV)
1 2 345 2 345
2 3 345 2 345
3 2 345 2 230
4 3 345 2 230
5 2 500 2 230
Electric system analyses,including simulations of line energiz-
ing,load flows of normal and emergency operating conditions,and
transient stability performance,were carried out to determine the
technical feasibility of the various alternatives.An economic
comparison of transmission system life cycle costs was carried out
to evaluate the relative economic merits of each alternative.All
five transmission alternatives were found to have acceptable per-
formance characteristics.The most significant difference was
that single-voltage systems (345 kV,Alternatives 1 and 2)and
systems wi thout seri es compensat i on (Alternat ive 2)offered re-
duced complexity of design and operation and therefore were likely
to be margi na lly more re1i ab 1e.The present-worth 1ife cyc1e
costs of Alternatives 1 through 4 were all within one percent of
each other.On ly the cost of the 500/230 kV scheme (Al ternat ive
5)was 14 percent above the others.A summary of the life cycle
cost analyses for the various alternatives is shown in Table 14.2.
Full details of the technical and economic comparisons are ex-
plained in a separate report (2).
A technical and economic comparison was also carried out to deter-
mine possible advantages and disadvantages of HVDC transmission,
as compared to an ac system,for transmi tt i ng Sus itna power to
Anchorage and Fairbanks.As outlined in (2),HVDC transmission
was found to be technically and operationally more complex as well
as having higher life cycle costs.
(d)Configuration at Generation and Load Centers
Interconnections between generation and load centers and the
transmission system were developed after reviewing the existing
14-5
system configurations at both Anchorage and Fairbanks as well as
the possibilities and current development plans in the Susitna,
Anchorage,Fairbanks,Willow, and Healy areas.
(i)Susitna Configuration
Preliminary development plans indicated that the first
project to be constructed would be Watana with an i niti al
installed capacity of 680 MW,to be increased to 1020 MW in
the second development stage.The next project,and the
last to be considered in this study,would be Devil Canyon,
with an installed capacity of 600 MW.
(ii)Switching at Willow
Transmiss i on from Susitna to Anchorage is faci 1itated by
the introduction of an intermediate switching station.
This has the effect of reducing line energizing overvolt-
ages and reducing the impact of line outages.on system
stability.Willow is a suitable location for this inter-
mediate switching station;in addition,it would make it
possible to supply local load when this is justified by
development in the area.This local load is expected to be
less than 10 percent of the total Railbelt area system
load,but the availability of an EHV line t ap vwoul d defi-
nitely facilitate future power supply.
(iii)Switching at Healy
A switching station at Healy was considered early in the
analysi s but was found to be unnecessary to sati sfy the
planning criteria.The predicted load at Healy is small
enough to be supplied by local generation and the existing
138 kV transmission from Fairbanks.
(iv)Anchorage Configuration
In its 1975 report on the Upper Susitna River Hydroelectric
---Stud+es(3);the eeE f avoreda--transmi-ss+on-Toute-termi-n-at-..
ing at Point MacKenzie.
A 1979 report for the Anchorage-Fairbanks Intertie by
International Engineering Company,Inc.(4)recommended one
circuit from Susitna terminating at Point MacKenzie and
another pass ing through Palmer and Ek 1utna substat ions to
Anchorage along the eastern side of Knik Arm.
Analysis of system configuration,distribution of loads,
and development in the Anchorage area led to the conclusion
that a transformer station near Palmer would be of little
benefit.Most of the major loads are concentrated in and
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around the urban Anchorage area at the mouth of Knik Arm.
In order to reduce the length of subtransmission feeders,
the transformer stations should be located as close to
Anchorage as possible.
The routing of transmission into Anchorage may be chosen
from the following three possible alternatives:
- Submarine Cable Crossing From Point MacKenzie
to Point Woronzof
This would require transmission through a very heavily
developed area.It would also expose the cables to
damage by sh i ps'anchors,which has been the experience
with existing cables,resulting in questionable transmis-
sion reliability.
Overland Route North of Knik Arm via Palmer
This may be most economical in terms of capital cost in
spite of the long distance involved.However,approval
for this route is unlikely since overhead transmission
through this developed area is considered environmentally
un accept ab 1e. A longer over1and route around the deve l-
oped area is considered unacceptable because of the
mountainous terrain.
- Submarine Cable Crossing of Knik Arm,In the Area of Lake
Lorraine and Six Mile Creek
This option,approximately parallel to the new 230 kV
cable under construction for Chugach Electric Association
(CEA),includes some 3 to 4 miles of submarine cable and
requires a high capital cost.Since the area is upstream
from the shipping lanes to the port of Anchorage,it will
result in a reliable transmission link,and one that does
not have to cross environmentally sensitive conservation
areas.
The third alternative is clearly the best of the three op-
tions.The details of this configuration are as follows:
-Submarine crossing with three cable circuits;
- Switching station at Knik Arm east terminal;
-Double-circuit,compact, overhead line at 345 kV into
Anchorage;
-Major transformer substation near University Substation;
14-7
- Routing approximately parallel to CEA's new 230 kV line.
An alternative routing may be possible near the Knik Arm
shoreline and into Anchorage from the north;
-Tap for supply to Matanuska Electric Association (MEA),
with transformation to 115 kV,at Knik Arm east terminal
or along transmission route,if preferred;and
-Tap for supply to Anchorage Municipal Light and Power
(AML&P),with transformation to 115 kV near AML&P's
Generating Station No.2 or at the transformer station
near University Substation.
With this configuration a different option is possible for
the submarine cable crossing.To reduce cable costs the
crossing could be constructed with two cable circuits plus
one spare phase. This option requires a switching station
at the west terminal of Knik Arm.A switching station at
the west terminal would clearly require increased costs and
complications for construction and operation as a result of
poor access.It would also require a separate location for
the tap to supply MEA.
Plans are presently underway for a bridge crossing at Knik
Arm for both railway and road traffic.If these plans
should be realized,transmission costs and complications
could be significantly reduced by routing the cables across
the bridge.
(v)Fairbanks Configuration
Susitna power for the Fairbanks area is recommended to be
delivered to a single EHV/138 kV transformer station lo-
cated at Ester.
(e)Recommended Transmission System
The confi gurat i on of the recommended transmi ssi on system,(Alter...
.-native2-)isshownon the si ng-le-lined-i-agr-am+~i-guY'e14.1).-The
main characteristics of the recommended system are summarized in
Table 14.3.
14.2 -Corridor Selection
(a)Methodology
Development of the proposed Susitna project will require a trans-
mission system to deliver e·lectric power to the Railbelt area.
The pre-building of the Intertie system will result in a corridor
and route for the Susitna transmission lines between Wi 11 ow and
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Healy.Therefore,three areas require study for corridor
selection:the northern area to connect Healy with Fairbanks;the
central area to connect the Watana and Devil Canyon damsites with
the Intertie;and the southern area to connect Willow with
Anchorage.
The corridor selection methodology followed the Susitna study plan
formulation and selection methodology.Previous studies,existing
data,aerial reconnaissance and limited field studies formed the
data base.Using the selection criteria discussed in paragraph
(c) below,corridors 3 to 5 miles wide which met these criteria
were se lected in each of the three study areas.These corri dors
were then evaluated to determine which ones met the more specific
screening criteria (see paragraph (d) below). This screening
process resulted in one corridor in each area being designated as
the recommended corridor for the transmission line.A more
detailed discussion of study methodology and the selection and
screening criteria is presented in a separate report (5).
(b)Previous Studies
The two reports reviewed which contained the most information
relevant to the transmission line studies were:
-The Upper Susitna River Basin Interim Feasibility Report,pre-
pared by the CaE (3),hereafter referred to as the CaE report;
and
-The Economic Feasibility Study for the Anchorage-Fairbanks
Intertie (4),hereafter referred to as the IECa/RWRA report.
The CaE report consisted primarily of an evaluation of alternative
corridor locations to aid in the selection of those which maxi-
mized reliability and minimized costs.Utilizing aerial photo-
graphs and existing maps,general corridors connecting the project
site with Anchorage and Fairbanks were selected.This study was
general in nature and was intended only to demonstrate project
feasibi 1i ty.
The IECa/RWRA report utilized the CaE report as background infor-
mation for both economic feasibility determination and route
selection.The corridor selected by IECa/RWRA was very similar to
that se1ected by the CaE with further defi nit ion.The route se-
lected was based on shortest length,accessibility and environmen-
tal compatibility.The report also presented a detailed economic
feasibility study for the Anchorage-Fairbanks transmission inter-
tie.
14-9
(c)Selectlon Crlterla and Selection Results
(1)Criteri a
The objectlve of the corrldor selectlon conducted by Acres
was to select feasible transmlsslon llne corrldors ln each
of the three study areas,1.e.,northern,central and
southern.Technlcal,economi c,and environmental criteria
were developed ln order to select the most optlmum corri-
dors withln each of the three areas.These criteri a are
listed in Table 14.4.
Environmental inventory tables were then compiled for each
corridor selected,l i st l nq length,number of road cross-
ings,number of r i ver and creek crosslngs,topography,
soils,land ownershlp/status,existing and proposed
development,existlng rights-of-way,scenlc quality/recrea-
tion,cultural resources,vegetatlon,f i sh, bi rds,fur-
bearers,and b i q game.These tables are i nc luded in the
Closeout Report.
(i 1)Results
Utllizing existlng lnformation,22 corridors were selected
based on the i r ability to meet technlcal,economic and
environmental criteria as listed ln Table 14.4 .•
Three of the corridors are in the southern study area,15
til the central area,and four in the northern study area.
Three of the corrldors ln the southern study area run in a
north-south directlon,whlle one runs northeast to Palmer,
then northwest to Wlll ow.Corrl dors 1n the central study
area are ln two general groups: those running from Watana
Dams ite west to the proposed Intert ie,and those runni ng
north across the Denali Highway and the Chulitna Rl ver.
Cort-i dors in the northern study area run ei ther west or
east to bypass the Al askan Range,then proceed north to
Fairbanks.
Flgures 14.2,14.3,and 14.4 show the Iocat i on of these
corridors.
(d) Screenlng Crlterla and Screening Results
(1)Criteri a
The object 1ve of the screen i ng process was to screen the
previously selected corrldors to determlne whlch ones best
meet the technical,economlc,and envlronmental criteria as
listed ln Table 14.5.The ratlonale for selection of these
crlteria is explained in (5).
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In addition to these criteria,each corridor was screened
for reliability.Six basic factors were considered:
-Elevation:Lines located at elevations below 4000 will
be less exposed to severe wind and ice condi-
tions which can interrupt service.
-Aircraft:Avoidance of areas near aircraft landing and
takeoff operations will minimize the risk of
power fai lures.
-Stability:Avoidance of areas susceptible to land,ice,
and snow slides will reduce the chance of
power failures.
-Topography:Lines located in areas with gentle relief
will be easier to construct,repair,and
maintain in operation.
A - recommended
C -acceptable but not preferred
F -unacceptable
The screening criteria and reliability factors for each
corridor were evaluated utilizing topographic maps,aerial
photos,aerial overflights,and published materials.Each
corridor was then assigned four ratings (one each for tech-
nical,economic and environmental considerations,and one
overall summary rating.)Ratings were defined as follows:
-Access:Lines located in reasonable proximity to
transportation corridors will be more quickly
accessible and,therefore,more quickly
repaired if any failures occur.
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From the technical point of view,reliability was the main
object i vee An envi ronmenta lly and economica lly sound cor-
ridor was rejected if it would be unreliable.Thus,any
line which received an F technical rating was assigned a
summary rating of F and eliminated from further
consideration.
Si mil arly,because of the crit ica1 importance of environ-
mental considerations,any corridor which received an F
rating for environmental impacts was assigned a summary
rating of F, and eliminated from consideration.
(i i)Results
Table 14.6 summarizes the comparison of the corridors
screened in the southern,central and northern study areas.
One corri dor in each of the three study areas received A
14-11
ratings for all three categories.These three corridors,
and the rationale for their A ratings,are discussed below.
A description of all 22 corridors and the rationale for
their ratings is given in (5).
-Southern Study Area
Corridor Two -Willow to Point MacKenzie via Red Shirt
Lake
Description
Corridor ADFC,consisting of Segments ADF and FC
(Figure 14.2),commences at the point of intersection
with the Intertie in the vicinity of Willow but imme-
di ate ly turns to the southwest,fi rst cross i ng the
rai lroad,then the Parks Hi ghway,then Wi llow Creek
just west of Willow.The land in the vicinity of this
part of the segment is very flat,with wetlands domi-
nat i ng the terrai n.
Southwest of Florence Lake,the proposed corridor
turns,crosses Rolly Creek,and heads nearly due
south,pass i ng through extensi ve wet1ands west and
south of Red Shirt Lake.The corridor in this area
parallels existing tractor trails and crosses very
flat lands with significant amounts of tall-growing
vegetation in the better drained locations.
Northwest of Yohn Lake, the corridor segment turns to
the southeast,pass i ng Yohn Lake and My Lake before
crossing the Little Susitna River.Just south of My
Lake, the corridor turns in a southern direction,
passing Middle Lake and east of Horseshoe Lake before
finally intersecting the existing Beluga 230 kV trans-
mission line at a spot just north of MacKenzie Point.
From here,the corridor parallels MacKenzie Point's
existing transmission facilities before crossing under
Armtoemerge-on-the--eastern·shore-·of~n+k Arm--i-n-
the vicinity of Anchorage,and then on to University
Substation.The land in the vicinity of this segment
is extremely fl at and wet.It supports stands of
tall-growing vegetation on the higher or better
drai ned areas.
Technical and Economical Rating
Corridor ADFC crosses the fewest number of rivers and
roads in the southern study area.It has the advan-
tage of paralleling an existing tractor trail for a
good portion of its length,thereby reducing the need
14-12
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for new access roads.Easy access will allow mainte-
nance and repairs to be carri ed out in mi nima1 ti me.
This corridor also occurs at low elevations and is
approximately one-half the length of Corridor One.
Environmental Rating
This corr idor cr os ses extens i ve wet1ands from Wi 11 ow
to Point MacKenzie. At higher elevations,or in the
better drained sites,extensive forest cover is
encountered.Good agri cultura 1 soil s have been i den-
tified in the vicinity of this corridor;the state
plans an Agricultural Lands Sale for areas to be
traversed by this corridor.The corridor also crosses
the Sus itna Fl ats Game Refuge.The presence of an
existing tractor trail near considerable portions of
this corridor diminishes the significance of some of
these constraints.Furthermore,its short length,and
the fact that it crosses only one ri ver and ei ght
creeks,increases its environmental acceptability.
-Central Study Area
Corridor One - Watana to Intertie via South Shore,
Susitna River
Descr i pt ion
This corridor,ABCD (Figure 14.3),originates at the
Watana Dam site and follows the southern boundary of
the river at an elevation of approximately 2,000 feet
from Watana to Devil Canyon.From Devil Canyon,the
corri dor conti nues along the southern shore of the
Susitna River at an elevation of about 1,400 feet to
where it connects with the Intertie,assuming the In-
tertie follows the railroad corridor.The land sur-
face in this area is relatively flat,though incised
at a number of locations by tributaries to the Susitna
River.The relatively flat hills are covered by dis-
continuous stands of dense,tall-growing vegetation.
Technical and Economical Rating
Corri dor One is one of the shortest corri dors con-
sidered.It is approximately 40 miles long,making it
economically favorable.No technical restrictions
were observed along the entire length of this corri-
dor.
14-13
Environmental Rating
Because of its short length,environmental disturbance
caused by transmission line construction would be
reduced.The more noteworthy constrai nts are those
identified under the categories of land use and vege-
tation.Corridor One would require the development of
a new right-of-way between Watana and Devi 1 Canyon,
but would utilize the COE-developed road for access
between the Intert ie and Devi 1 Canyon.Wet 1ands and
discontinuous forest cover occur in the corridor,
especially in the eastern third of the route.Access
road development and the associated vegetation clear-
ing present additional constraints to this corridor.
-Northern Study Area
Corridor One -Healy to Fairbanks via Parks Highway
Description
Corridor One (ABC),consisting of Segments AB and BC,
starts in the vicinity of the Healy Power Plant
(Figure 14.4).From here,the corridor heads north-
west,crossing the existing Golden Valley Electric
Association Transmission Line,the railroad,and the
Parks Highway before turning to the north'and paral-
leling this road to a point due west of Browne.Here,
as a result of terrain features,the corrigor turns
northeast,crossing the Parks Highway once again as
we 11 as the exi st ing transmi ss ion 1ine,the Nenana
River,and the railroad,and continues to a point
northeast of the Clear Missile Early Warning Station
(MEWS).
Continuing northward,the corridor eventually crosses
the Tanana River east of Nenana,then heads northeast,
fi rst crossi ng Litt 1e Go ldstream Creek,then the Parks
--H-i-ghwa-y-just-nor-th-of--the--Bonan-z-a-Gr-ee k-Exp er-ime nta-l-
Forest.Before reaching Ohio Creek,this corridor
turns back to the northeast,crossing the old Parks
Highway and heading into the Ester Substation west of
Fairbanks.
Terrain along this entire corridor segment is rela-
tively flat,with the exception of the foothills north
of the Tanana Ri ver.Much of the route,especi ally
that port i on between the Nenana and the Tanana Ri ver
crossings,is very broad and flat.It has standing
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water during the summer months and, in some places,is
overgrown by dense stands of tall-growing vegetation.
This corridor segment crosses the heavily wooded foot-
hills northeast of Nenana.
An option to the above, not shown in the figures,has
been considered,closely paralleling and sharing
rights-of-way with the existing Healy-Fairbanks trans-
mission line.While it is usually attractive to
parallel existing corridors wherever possible,this
opt ion necess i tates a great number of road cross ings
and results in an extended length of the corridor
paralleling the Parks Highway.A potentially
significant amount of highway-abutting land would be
usurped for containment of the right-of-way.The
combination of these features precludes this optional
corridor from further evaluation.
Technical and Economical Rating
This corridor crosses the fewest water courses in the
northern study area.Although it is approximately
four miles longer than Corridor Two,it is technically
favored because .of the exi stence of potent ia1 access
roads for almost the entire length.
Environmental Rating
Because it parallels an existing transportation corri-
dor for much of its length,this corridor would permit
line routing that would avoid most visually sensitive
areas.The three proposed road crossings for this
corridor (as opposed to the 19 road crossings of the
Healy-Fairbanks transmission line)could occur at
points where roadside development exists,in areas of
visual absorption capability,or in areas recommended
to be opened to long-distance views.
Four rivers and 40 creeks with potential for impacts
are crossed by th is corri dor,the fewest number of
water courses of any route under consideration in the
northern study area.The inactive nest site of a pair
of peregrine falcons occurs within this proposed cor-
ridor.
As with visual impacts,land use,wildlife,and fish-
ery resource impacts can be lessened through careful
route selection and utilization of existing access.
Impacts on forest clearing can be lessened through the
sharing of existing transmission line corridors.
14-15
(e) Concluslons
A revlew of prevlous reports,other ex i s t i nq lnformat i on ,and
aerlal overfllghts was used to select corrldors for conslderatlon
1n th 1s study.These corr i dors were screened agal nst certal n
technical,economic and envlronmental cr l t erla,resultlng ln one
recommended corrldor in each of the southern,central and northern
study areas.The corridors shown ln Figures 7.1 through 7.8 of
the screen 1ng are be11 eyed to best meet the techni cal,economi c
and envi ronment a1 cr i t.er t a;therefore,these corri dors are the
best locatlons in whlch to place the Susitna transmisslon lines.
14.3 - Route Selectlon
(a)Methodology
After ldentlfYlng the preferred transmisslon line corrldors,the
next step ln the route selection process lnvolved the analysis of
the data as gathered and presented on the base map.Overlays were
compiled so that various constralnts affectlng construction or
malntenance of a transmission facility could be vlewed on a single
map.The map is used to select posslble routes within each of the
three selected corridors.By placing all major constraints (e.g.,
area of high vi sual exposure,pr i vate lands,endangered species,
etc.)on one map,a route of least lmpact was selected.EXlsting
facilities,such as transmission lines and tractor trails within
the study area,were also considered dur i nq the selection of a
least lmpacted route.Whenever possible,the routes were selected
near eXlsting or proposed access roads,sharing whenever possible
existlng rights-of-way.
The data base used in thls analysis was obtained from the follow-
ing sources:
-An up-to-date land status study;
- EXlsting aerlal photos;
-New aerial photos conducted for selected sections of the pre-
viously recommended transmission line corridors;
-~----~--En-v-i-ronment alstudies-tnc.ludtnq.aestnet.tc.co ns.i.der;ations.;
-Climatological studies;
-Geotechnical exploration;
-Additional fleld studies;and
-Publlc opinlons.
(b)Selection Crlterla
The purpose of thls section is to identify three selected routes:
one from Healy to Falrbanks,the second from the Watana and Devll
Canyon damsites to the intertle,and the third from Wlllow to
Anchorage.
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(c)
The previ ously chosen corridors were subject to a process of
refining and evaluation based on the same technical,economic,
and environmental criteria used in corridor selection (see Table
14.5).In addition,special emphasis was concentrated on the
following points:
-Satisfy the regulatory and permit requirements;
-Selection of routing that provides for minimum visibility from
highways and homes;and
-Avoidance of developed agricultural lands and dwellings.
Environmental Analysis
The corridors selected were analyzed to arrive at the route width
which is the most compatible with the environment and also meet
the engineering and economic objectives.The environmental
analysis was conducted by the process described below:
(i)Literature Review
Data from vari ous 1i terature sources,agency communi ca-
tions,and site visits were reviewed to inventory existing
environmental variables.From such an inventory,it was
possible to identify environmental constraints in the
recommended corridor 1 ocat ions.Data sources were cata-
loged and filed for later retrieval.
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(i i)Avoidance Routing by Constraint Analysis
To establish the most appropriate location for a transmis-
sion line route,it was necessary to identify those en-
vi ronmenta 1 constraints that coul d be impedi ments to the
development of such a route.Many specific constraints
were identified during the preliminary screening;others
were determined during the 1981 field investigations.
By utilizing information on topography,existing and pur-
posed land use,aesthetics,ecological features,and cul-
tural resources as they exist within the corridors,and by
careful placement of the route with these considerations in
mind,impact on these various constraints was minimized.
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(iii)Base Maps and Overlays
Constraint analysis information was placed on base maps.
Constrai nts were i dent i fi ed and presented on overl ays to
the base maps.This mapping process involved using both
existing information and that acquired through Susitna
Project studies.This information was first categorized as
to its potential for constraining the development of a
14-17
transmission line route within the preferred corridor and
then placed on maps of the corridors.Environmental con-
straints were identified and recorded directly onto the
base maps.Overlays to the base maps were prepared indi-
cating the type and extent of the encountered constraints.
Three overlays were prepared for each map:one for visual
constraints,one for man-made,and one for biological con-
straints.These maps are presented as a separate document
(6) .
(d)Technical and Economic Analysis
Route location objectives are to obtain an optimum combination of
reliability and cost with the fewest e'nvironmental problems. In
many cases,these objectives are mutually compatible.
Throughout the evaluation,much emphasis was made to place the
route relatively close to existing surface transportation facili-
ties whenever possible.
The factors that contributed heavily in the technical and economic
analysis were:topography,climate and elevation,soils,length,
and access roads.Other factors of less importance were vegeta-
tion,and river and highway crossings.These factors are detailed
in Tables 14.4 and 14.5.
(i)Selection of Alternative Routes
The next step in the route selection process involved the
analysi s of the data gathered and presented on the base
maps.The data were used to select possible routes within
each corridor.By placing all major constraints on one
map,routes of smallest impacts were selected.Existing
facilities,such as transmission lines and tractor trails
within the study area,were al~o taken into consideration
during the selection of a least impact route.
The evaluation and selection of alternative routes to
arrive at a primary route involved a closer examination of
each of the possible routes using mapping process and data
previously described.Preliminary routes were compared to
determine the route of least impact within the primary cor-
ridors of each study area.For example, such variables as
number of stream and road crossings requi red were noted.
Then,following the field studies and through a comparison
of routing data,including the route1s total length and its
use of existing facilities,one route was designated the
14-18
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primary route.Land use,land ownership,and visual
impacts were key factors in the selection process.
(e) Route Soil Conditions
(i)Description
Baseline geological and geotechnical information has been
compiled through photointerpretation and terrain unit mapp-
ing (7).The general objective was to document the condi-
tions that would significantly affect the design and
construction of the transmission line towers.More specif-
ically,the conditions included the forms of various
origins,noting the occurrence and distribution of signifi-
cant geologic factors such as permafrost,potentially
unstable slopes,potentially erodible soils,possible
active fault traces,potential construction materials,
active floodplains,organic materials,etc.
Work on the ai rphoto i nterpretat ion consi sted of several
activities culminating in a set of terrain unit maps
showing surface materials and geologic features and
conditions in the project area.
The first activity consisted of a review of the literature
concerning the geology of the Intertie corridors and trans-
fer of the information gained to high-level photographs at
a scale of 1:63,000.Interpretation of the high-level
photos created a regional terrain framework which assisted
in interpretation of the low-level 1:30,000 project photos.
MajQr terrain divisions identified on the high-level
photos were then used as an aerial guide for delineation of
more detailed terrain units on the low-level photos.The
primary effort of the work was the interpretation of over
140 photos covering about 300 square miles of varied
terrain.The land area covered in the mapping exercise is
shown on map sheets and displayed in detail on photo
mo sai cs (7).
As part of the terrain analysis,the various bedrock units
and dominant lithologies were identified using published
U.S.Geological Survey reports.The extent of these units
was approximately shown on the photographs,and using
exposure patterns,shade,texture,and other features of
the rock unit as they appeared on the photographs,unit
boundaries were drawn.
Physical characteristics and typical engineering properties
of each terrain unit were considered and a chart for each
corridor was developed.The charts identify the terrain
units as they have been mapped and characterize their
14-19
properties in numerous categories.This allows an assess-
ment of each unit's influence on various project features.
(ii)Terrain Unit Analysis
The terrain unit is a special purpose term comprising the
land forms expected to occur from the ground surface to a
depth of about 25 feet.
The terrain unit maps for the proposed Anchorage to Fair-
banks transmission line show the aerial extent of the
specific terrain units which were identified during the air
photo invest igat i on and were corroborated in part by a
limited onsite surface investigation.The units document
the general geology and geotechnical characteristics of the
area.
The north and south corri dors are separated by several
hundred miles and not surprisingly encounter different
geomorphic provinces and climatic conditions.Hence,while
there are many landforms (or individual terrain units)that
are common to both corridors,there are also some landforms
mapped in just one corridor.The landforms or individual
terrain units mapped in both corridors were briefly
described.
Several of the landforms have not been mapped independently
but rather as compound or complex terrain units.Compound
terrain units result when one landform overlies a second
recognized unit at a shallow depth (less than 25 feet),
such as a thin deposit of glacial till overlying bedrock or
a mantle of lacustrine sediments overlying till.Complex
terrain units have been mapped where the surficial exposure
pattern of two landforms are so intricately related that
they must be mapped as a terrain unit complex, such as some
areas of bedrock and colluvium.The compound and complex
terrain units were described as a composite of individual
1andforms compri sing them.The stratigraphy,topographi c
pas-i-t-t 0 n,andaeri a l-extentef--a-l-1Amit-s-,--a-s th e;y .appear-i n
each corridor,were summarized on the terrain unit proper-
ties and engineering interpretations chart (7).
(f)Results and Conclusions
A study of existing information and aerial overflights,together
with additional aerial coverage,was used to locate the recommend-
ed route in each of the southern,central,and northern study
areas.
Additional environmental information and land status studies made
it possible to align the routes to avoid any restraints.
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Terrain unit maps describing the general material expected in the
area were prepared specifically for transmission line studies and
were used to locate the routes away from unfavorable soil
conditions whenever possible.
Figures 1 through 14 in (6)show the selected transmi ss ion 1ine
route for the three areas of study;namely,the southern study
area;the central study area;and the northern study area.As a
first step,the 3-to -5-mile-width corridor previously selected
for each of the three study areas was narrowed to a halfmile-width
corridor based on the previous criteria.The preliminary center-
line of the right-of-way is shown in the figures.This centerline
represents a right-of-way width of 400 feet.This width is ade-
quate for three,single-circuit,parallel lines with tower struc-
tures having horizontal phase spacing of 33 feet.However,
between the Devi 1 Canyon damsite and the intertie,the width of
the right-of-way is 700 feet which is needed to accommodate five
single-circuit lines.Environmental constraint analysis informa-
tion was placed on base maps and overlays (6).
14.4 - Towers,Foundations and Conductors
A transmission line intertie between Anchorage and Fairbanks is planned
by the Power Authority.The intertie will consist of existing lines
and a new section between Willow and Healy.The new section will be
built to 345 kV standards and will be fully compatible with Susitna
requirements.
(a)Transmission Line Towers
(i)Selection of Tower Type
Because of unique soil conditions in Alaska, with extensive
regions of muskeg and permafrost,conventional self-sup-
porting or rigid towers will not provide a satisfactory
solution for the proposed transmission line.
Permafrost and seasonal changes in the soi 1 are known to
cause large earth movements at some locations,requiring
towers with a high degree of flexibility and capability for
handling relatively large foundation movements without
appreciable loss of structural integrity.
The guyed tower is well suited to these conditions.The
recommended type of structure for this study is therefore
the hinged-guyed steel x-tower (Figure 14.6).
The design features include hinged connections between the
leg members and the foundations which,together with the
longitudinal guy system,provide for large flexibility
combined with excellent stability in the direction of the
14-21
line.Transverse stability is provided by the wide leg
base which also accounts for relatively sm-Tl and
manageable footing reactions.
The selected tower is rated very favorably concerning reli-
ability,maintenance,construction,economy,and aesthe-
tics.
(ii)Climatic Studies and Loadings
Climatic studies for transmission lines were performed to
determine likely wind and ice loads based on historical
data.A more detailed study incorporating additional
climatic data was performed to confirm or modify the
obtai ned data.
Details of the climatic studies for transmission lines may
be found in Appendix A.
The design loads acting on wires and structures ar~mainly
based upon weather conditions.Four cases of loadings were
established for the tower design.
(b)Tower Foundations
(i)Geological Conditions
The generalized terrain analysis (7)was conducted to col-
lect geologic and geotechnical data for the transmission
line corridors,a relatively large area.The engineering
characteristics of the terrain units have been generalized
and described qualitatively.When evaluating the suitabil-
ityof a terrain unit for a specific use,the actual prop-
erties of that unit must be verified by onsite subsurface
investigation,sampling,and laboratory testing.
The three main types of foundation materials along the
transmission line are:
-Good material,which is defined as overburden which
permits augered excavation and allows installation of
concrete without special form work;
Wetland and permafrost materi al which requires speci al
design details;and
Rock material defined as material in which drilled-in
anchors and concrete footings can be used.
Based on aeri a1,topographi c,and terrai n unit maps,the
following was noted:
14-22
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-For the southern study area:Wet 1and and permafrost
materials constitute the major part of this area.Some
rock and good foundation materials are present in this
area in a very small proportion.
-For the central study area:Rock foundation and good
materials were observed in most of this study area.
-For the northern study area:The major part of this area
is wetland and permafrost materials.Some parts have
rock materials.
(ii)Types of Foundations
The recommended two-legged x-frame tower is hinged at the
foundation attachment connection for longitudinal freedom
and restrained by fore and aft guying to an equalizing
yoke. This arrangement will result in relatively smaller
loads on the foundations.The recommended types of founda-
tions are shown in Figure 14.7.These are the rock anchor
and the pile foundation.
(iii)Design Criteria
The greater part of the combined maximum reactions on a
transmission tower footing is usually from temporary loads
such as broken wire,wind,and ice.With the exception of
heavy-angle,dead-end,or terminal structures,only a part
of the total reaction is of a permanent nature.As a
consequence,the permissible soil pressure,as used in the
design of building foundations,may be considerably
exceeded for footing for transmission structures.
The permissible values of soil pressure used in the footing
des i gn wi 11 depend on the structure and the support i ng
soil.The basic criterion is that displacement of the
footing is not restricted because of the flexibility of the
selected x-frame tower and its hinged connection to the
footing.The shape and configuration of the selected tower
are important factors in foundation considerations.
Loads on the tower consist of vertical and horizontal loads
and are transmitted down to the foundation and then distri-
buted to the soil.In a tower placed at an angle or used
as a dead-end in the line,the horizontal loads are respon-
sible for a large portion of the loads on the foundation.
In addition to the horizontal shear,a moment is also
present at the top of the foundation,creating vertical
download and uplift force~on the footing.
To select and design the most economical type of foundation
for a specific tower location,soil conditions at the site
14-23
must be known.Soil investigation will furnish this needed
information.
(c) Conductor Requirements
Based on the transmission and power transfer requirements at the
various stages of the Susitna development,economic conductor
sizes were determined.
The methodology used to obtain the economic conductor size and the
results obtained are described elsewhere (8).
When determining appropriate conductor size,the economic conduc-
tor is checked for radio interfere~ce (RI)and corona performance.
If RI and corona performance are within acceptable limits,then
the economic conductor size is used.However,where the RI and
corona performance are found to be limiting,the conductor selec-
tion is based on these requirements.
14.5 -Substations
(a)Recommended System Configurations
In order to ensure the design of a reliable and economic electri-
cal power system for the Railbelt,the electric system studies
resulted in a system configuration which is shown in Figure 14.1.
The recommended configuration has stations at several locations.
The main function of each station is listed below.
-Wi 11 ow
Intermedi ate swi tch i ng of 345 kV transmi ssi on to nn m mi ze the
impact of line outages and facilitate operation;local load can
be provided by transformation to 138 kV.
-Knik Arm
Switching of 345 kV transmission from 3 circuits to 2 circuits
into-An-chorage;locallo ad-can be-provided by-transformat i onto
115 kV;terminal for submarine cable.
-University
Terminal station for Anchorage,transformation from 345 kV to
230/115 kV.
-Ester
Terminal station for Fairbanks,transformation from 345 kV to
138 kV.
14-24
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(b)Single Line Diagrams
The electric system studies recommended a IIbreaker-and-a-half ll
singl eli ne arrangement.Th is arrangement was recommended for
re 1iabi1i ty and secur i ty of the system.Fi gure 14.1 shows the
single line diagram of the 345 kV transmission system with station
configurations at each location.
For further information on single line diagram details see Plates
32, 33, 70,and 71.
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Control and Metering
It is proposed to remotely operate all the stations listed
above.The control functions,such as closing and opening
of circuit breakers,will be initiated from the system con-
trol center at Willow.The metering functions will be
telemetered to the control center.The system center will
monitor equipment status for each station.
The communication medium between the master station and the
remote stations will be a microwave system.Enough redun-
dancy will be included in the system to provide highly re-
liable service.The microwave system will also be used for
relay protection.
345 kV Relay Protection
The re 1ayi ng protect ive schemes proposed for the 345 kV
power system are generally in accordance with conventional
practices.It is not anticipated,presently,that this
project will require any special relaying equipment.
Future protective schemes could make use of digital compu-
ters.These schemes would be part of an overall computer-
ized system which would involve control,monitoring and
protection of the power system.If an integrated system is
commercially available at the time of detailed design,it
is recommended that such a system should be evaluated for
the Susitna project.
The protection philosophy is generally based on dual relay-
ing and the local backup principle.To ensure sound relay-
i ng protect ion,the proposed schemes wi 11 provi de fault
clearance for either of the following contingencies:
-Failure of either the primary or backup relays to oper-
ate,or a failure in their secondary and control cir-
cuits;or
-Failure of a circuit breaker to interrupt,including a
faulted circuit breaker.
14-25
For two winding transformers and autotransformers without a
delta tertiary winding,it is proposed to provide a two-winding
biased differential relay having a second harmonic restraint.
As backup,an overall differential relay is provided.Gas pres-
sure,oil level,winding temperature,and overvoltage protec-
~---_.----------t-ions are -al so--proposed-.---~----
(c)
A brief description of the proposed protection schemes for various
equipment is outlined below.
- Line Protection
For the 345 kV overhead transmission lines,dual primary multi-
zone high speed distance protection relays for phase and ground
faults are proposed.Microwave wi 11 be used for protection
signalling between the two ends of a line.It is not proposed
to provide high speed single pole automatic reclosing,but
delayed three pole auto-reclosing should be considered as an
operator's aid to restore a faulted line quickly.
Each section of line from Willow to Knik Arm consists of 36
miles of overhead conductor and 4 miles of submarine cable.It
is proposed to protect the cable as part of the overall line
distance protection scheme without any provisions for special
relays for cable protection.
- Shunt Reactor Protection
Where 1ines are equipped with shunt reactors,separate protec-
t i on is provided for the reactors.The protect ive schemes
consist of primary differential relays,backu~overcurrent phase
fault and neutral ground fault protection,gas pressure,oil
level,winding temperature,and overvoltage protection .•
-Bus Protection
Differential protection will be provided for each 345 kV bus.
- Transformer Protection
For the autotransformer equipped with a loaded tertiary winding,
a three-winding biased differential relay is proposed.
Additional backup overcurrent relays will also be provided for
the tertiary winding.
Station Equipment
The station equipment requirements were determined by the load
flow studies and reliability requirements.The breaker-and-a-half
arrangement will require 1-1/2 breakers for every element (line or
transformer circuit).Thi s wi 11 determine the number of breakers
required for each station.
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(e)
The transformer capacities are also determined by the load
requirements at each substation shown in Figure 14.1.
Station Layouts
The switchyard layouts are based on a conventional outdoor type
design.Figures 14.8,14.9 and 14.10 indicate the physical layout
of the stations.These layouts show the extent of land area re-
quired for each station.They also indicate the area required by
each voltage level and their location relative to each other.The
station geographical orientation was determined by the line entry
requirements.
In an area where visual considerations are important,it is essen-
tial to maintain a low station profile.The layout adopted for
this project will provide a two level bus arrangement.The maxi-
mum structure height for 345 kV which only occurs at the line
entries will be 75 feet.The bus levels will be at 20 and 35 feet
respectively from grade.Figure 14.11 shows a typical elevation
of one diameter consisting of three breakers and associated dis-
connect switches.The tower and bus heights for 230, 138 and 115
kV will be lower; hence,their profile will not be the major fac-
tor at any of the stations.
The low profile station is easier to maintain,because crews do
not need 1arge cranes or other equi pment to deal wi th extreme
heights.
A two level bus arrangement has an added feature which is advanta-
geous in an area prone to earthquakes.The bus structures are
lower in height and, hence,less susceptible to damage during an
earthquake.A larger station area also permits more space between
the major equipment components,thus minimizing the possibility of
damage affecting adjacent equipment.
Station Facilities
Although the stations are remotely controlled,each one will be
provided with a control building.In some cases,where the land
area is large,an additional relay building will be provided.The
control bui lding wi 11 normally contain all the local control,
communication and relaying equipment.Each station will be
provided with auxiliary power at 480 V and proper distribution
boards.The 480 V ac power will be supplied from the tertiaries
on the autotransformers or the local utility.
It should be noted that storage or service bui ldings wi 11 be
provided for maintenance purposes.
In the case of Willow,it is recommended that the Energy Manage-
ment Center be located within the station compound.The service
building shown on the same grounds could also be the headquarters
14-27
for the maintenance group.This location is close to the major
1and center at Anchorage and centrally located for the southern
area transmission system.
(f)Alternate Station Layout
Although all the studies have been carried out on conventional
outdoor stations,there has been considerable development in the
last few years in SF6 gas-insulated equipment.This equipment
has been used extensively in substations in urban areas.A gas-
insul ated substat ion requi res 10 to 15 percent of the area of a
conventional substation.The development in this field has been
carried up to 800 kV,and hence the Susitna 345 kV is well within
the range of experience.
Because of the limited land area required,a gas-insulated station
can be conveniently housed in a building.This is an advantage in
Al aska where the weather can be severe.Furthermore,enclosing
the station will probably create less impact on the environment
and visual considerations.Maintenance and equipment repairs will
be simpler and faster indoors where the staff wi 11 be protected
against the weather.
A recent comparison of cost estimates indicated that the capital
expenditure for either a conventional or a gas-insulated substa-
tion is comparable.It is recommended that SF6 station equip-
ment should be considered in the detail design phase for Susitna.
14.6 -Dispatch Center and Communications
(a) 1993 Rai lbelt Power System
The introduction of Susitna hydroelectric power in the Railbelt
area will require several hundred miles of transmission lines from
the Susitna River basin to Anchorage and Fairbanks.In fact,the
ultimate development will require approximately 850 miles of
transmission,5 switchyards and 2 hydro generating stations,one
at Watana and one at Devi 1 Canyon. Thermal generation at Fair-
banks and~~Anch'dr'a'gewillrelfl aiff ilioper-arron:-~-T~t0 ta:rilfSt a:nea'~.
generation capacity will be over 2,000 MW.
To operate such an enlarged Ra i 1be It system,a control system or
energy management system (EMS)will be required.This system will
insure security of the 345 kV transmission lines and switchyards/
substations operations.The system will also exercise remote con-
trol and efficient dispatching of the generating units in the
Rai lbelt.
(b) Energy Management System Requirements
To provide an efficient and secure dispatching system for the
Railbelt,the following subsystems are proposed:
14-28
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-Supervisory Control and Data Acquisition (SCADA)Subsystem;
-Generation Control Subsystem;
-Power Scheduling and Load Forecasting Subsystem;
-Energy Accounting Subsystem;
-System Security Subsystem;and
-System Support Subsystem.
A detailed description of the functional requirements for each of
the above is given in a separate report (8).
(c) Energy Management System Alternatives
An evaluation of alternative system configurations showed that two
different approaches to generation control are possible:
-Alternative I provides indirect control of generating units;
and
-Alternative II provides direct control of generating units.
To formulate and evaluate these two alternatives,the following
criteria were used:
-Configurations must fulfill functional requirements discussed
above in paragraph (c);
-Configurations must be technically,economically,and operation-
ally maintainable through the life of the systems (10 to 15
years);and
-Configuration must be technically feasible,as well as proven.
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( i )Alternative I System Configuration
The Alternative I system configuration is typical of the
present offeri ngs of several EMS equipment manufacturers
(see Figure 14.12,EMS Alternative I System Configuration).
The configuration is based on the assumptions that:
-An in-plant,computer-based control system,located at
Susitna Hydroelectric Control Center,will be provided;
-The Susitna in-plant control system will directly control
all hydro generating units and the switching stations at
Watana and Devil Canyon.EMS will determine generation
participation requirements on the unit level,but the
units wi 11 be pulsed by the in-plant system.The super-
vi sory contro 1 act ions for Watana and Devi 1 Canyon
generating stations will be initiated at EMS level,but
the control functions will be implemented by the in-plant
contro 1 system;
14-29
-The northern and southern computer-based systems will
receive generation participation requirements from the
EMS,but participation allocation and direct unit pulsing
will be accomplished by these systems;and
-EMS will directly monitor and control the following 345 kV
substat ions:
Ester;
Wi 11 ow;
Kn i k Arm;
Un i vers ity;and
Others,as required.
(ii)Alternative II System Configuration
The Alternative II system configuration is also typical of
present offeri ngs of several EMS equi pment manufacturers
(see Figure 14.13,EMS Alternative II System Configuration).
The configuration is based on the assumptions that:
-An in-plant,computer-based control system,located at
Watana,will be provided to monitor generating units
performance and control the units;
- All Watana and Devil Canyon generating units will be con-
trolled (raise and lower)directly by EMS from'system
control center at Willow;
- All northern and southern area generating units will be
directly controlled (raise and lower) by EMS,Willow
Control Center;and
-The switching stations at Watana and Devil Canyon and the
other four 345 kV substations will be directly monitored
and controlled by the EMS Control Center.
(d)irements
Effective operation of EMS is very dependent on transfer of data
and immediate response of supervisory functions such as control
and telemeterihg.Various communication systems to determine the
most reliable and cost-effective communication media were
eva1uated.
Microwave systems are line-of-sight propagation and have an aver-
age standard transmission path of approximately 35 to 40 miles in
an area of flat terrain.The cost was estimated for approximately
17 towers and repeater stat ions.A mi crowave system is recom-
mended for this application.
14-30
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(e) Control Center Facility
The faci1i ty wi 11 be the nerve center of the APA power system
operations of 345 kV transmission network and the electric power
generation.All decisions concerning the operation and mainte-
nance of the power system wi 11 be imp 1emented through th is com-
plex.The importance of this facility dictates that its location
be selected with a great deal of care.
(i)Location of Site
The control center must be located on a site that provides
high security against disruption of power system operations
by human intervention or by acts of God.
Other factors that have a bearing on the suitability of a
site are the availabi lity of land,housing,power and educa-
tional facilities.These factors together with transporta-
tion accessibility,climatic conditions,centralized
location in the power system,and the fact that a major
switchyard is already located in the area make it appropri-
ate to recommend Willow as the location for the EMS center.
Willow has additional qualifications as a possible capital
site.The Willow center could also be the headquarters for
the maintenance staff for the transmission network between
Susitna and Anchorage.The Willow site also has flat lands
between it and Anchorage which also reinforces the recommen-
dation to use microwave as the communication media.
(ii)Control Center Building
The EMS control center buildin9 can be located on the same
site as the Wi 11 ow switchyard.The construction of this
building will require special facilities.This is all
described in the "Energy Management System (EMS)- System
Requirements"report.
Figure 14.14 provides a conceptual layout of the Wi 11 ow
Control Center.This layout is based on a single story
building having a total space of 14,500 ft 2.
(f)Budgetary Cost Estimates
Overall budgetary cost estimates for the development,procurement,
system testing,and installation of EMS Alternatives I and II are
compared in Table 14.7.Costs for the EMS Control Center and
Microwave System are also provided.These costs are representa-
tive of what Energy and Control Consultants estimate as the middle
price bids for such a project and are given in January,1982
doll ars.
14-31
(g)Recommendations
Alternative I,shown in Figure 14.15,is recommended for the Rail-
belt Energy Management System as the most cost-effective and
desirable system approach. Unlike Alternative II,Alternative I
system approach allows generation control of the southern (Anchor-
age)and northern (Fairbanks)areas to remain under their respec-
tive utilities.Alternative I also encourages the formation of
regional control centers for each area.This is in accordance
with the present trend in power system control to decentralize in
large geographical areas.
Alternative I is also marginally less costly than Alternative II.
Microwave is recommended as a communicating medium.Once pro-
vided,this system will perform the following additional func-
tions:
-Provide a transmission media for protective line relaying;and
-Provide reliable voice communications between the various sta-
tions.This is very important in power system operations.
It is recommended that the EMS Control Center be located at Willow
within the Willow Switching Station compound.This location has
many advantages and is centrally located in the southern Railbelt
power system.It would also be reasonable to designate this loca-
tion as a maintenance center for the transmission system.This
area also has room for future expansion.There also appear to be
some plans to provide a highway crossing at Kn i k Arm.If these
plans materialize,Willow would only be one hour away by highway
from Anchorage.
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LIST OF REFERENCES
(1)Commonwealth Associates Inc.,Anchorage-Fairbanks
Intertie -Transmission System Data (Draft).
the Alaska Power Authority.November 1980.
Transmi ssion
Prepared for
(2)Acres Ameri can Incorporated,
Planning Memorandum Subtask
Sus itna Hydroe1ectr ic Project
8.02 -Preliminary Transmission
Prepared for the Alaska Power
I 1LJ
I)lJ
System Analysis (Draft).
Authority.November 1981.
(3) U.S. Corps of Engineers,Alaska District.Southcentral Railbelt
Area,Alaska - Upper Susitna River Basin -Interim Feasibil-
ity Report - Appendix 1,Part 2.December 1975.
(4)International Engineering Company,Inc.,Robert Retherford Associ-
ates,Economic Feasibility Study.Prepared for the Alaska
Power Authority.December 1979.
(5) Acres American Incorporated,Susitna Hydroelectric Report -Trans-
mission Line Corridor Screening Closeout Report.Prepared
for the Alaska Power Authority.September 1981.
(6) Acres American Incorporated/Terrestrial Environmental Specialists
Inc.Transmission Line Selected Route.Prepared for the
Alaska Power Authority.March 1982.
(7)R&M Consultants Inc.,Terrain Analysis of the North and South
Intertie Power Transmi ssion Corridors.Prepared for Acres
American Incorporated.November 1981.
(8) Acres American Incorporated,Susitna Hydroelectric Project Elec-
tric System Studies.Prepared for the Alaska Power Author-
ity.February 1982.
TABLE 14.1:POWER TRANSFER REQUIREMENTS (MW)
INSTALLED CAPACITY TRANSFER REQUIREMENT
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Susitna to Susitna to
Year Watana Devil Canyon Total Susitna Anchoraae Fairbanks
1993 680 --680 578 170
1997 1020 --1020 867 255
2002 1020 600 1620 1377 405
TABLE 14.2:SUMMARY OF LIFE CYCLE COSTS
TRANSMISSION ALTERNATIVE 2 3 4 5
Transmission Lines 1981 $ x 10
6
Capital $156.70 $159.51 $133.96 $140.94 $159.27
Land Acquisition 18.73 20. 79 18.07 20.13 18.65
Capitalized Annual Charges 127.34 130.14 107.43 112.83 126.91
Capitalized Line Losses 53.07 54.50 64.51 65.82 42.82------
Total Transmission Line Cost $355.84 $364.94 $323.97 $339.72 $347.65
Switchina Stations
Capital $114.09 $106.40 $128.32 $120.64 $154.75
Capitalized Annual Charges 121.02 113.30 135.94 128.22 165.02------
Total Switching Station Cost 235.11 219.70 264.26 248.86 319.77------
TOTAL $590.95 $584.64 $588.23 $588.58 $667.42
I ---------
TABLE 14.3:TRANSMISSION SYSTEM CHARACTERISTICS
Number of Number &Slze
Line Section Len~th Circuits Voltage of Conductors
(ml)(kv)(kcmll)
Watana to Devil Canyon 27 2 345 2 by 954
Devil Canyon to Fairbanks 189 2 345 2 by 795
Devil Canyon to Willow 90 3 345 2 by 954
Willow to Knik Arm 38 3 345 2 by 954
Knik Arm Crossing*4 3 345
Knik Arm to University
Substation 18 2 345 2 by 1351
*Submarine Cable ,.1
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TABLE 14.4:TECHNICAL,ECONOMIC,AND ENVIRONMENTAL CRITERIA
USED IN CORRIDOR SELECTION
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Type
1.Technical
- Primary
- Secondary
2.Economical
- Primary
- Secondary
3.Environmental
-Primary
-Secondary
Criteria
General Location
Elevation
Relief
Access
River Crossings
Elevation
Access
River Crossings
Timbered Areas
Wetlands
Development
Existing Transmission
Right-of-Way
Land Status
Topography
Vegetation
Selection
Connect with Intertie near Gold Creek,Willow,
and Healy. Connect Healy to Fairbanks.Con-
nect Willow to Anchorage.
Avoid mountainous areas.
Select gentle relief.
Locate in proximity to existing transportation
corridors to facilitate maintenance and repairs.
Minimize wide crossings.
Avoid mountainous areas.
Locate in proximity to existing transportation
corridors to reduce construction costs.
Minimize wide crossings.
Minimize such areas to reduce clearing costs.
Minimize crossings which require special designs.
Avoid existing or proposed developed areas.
Parallel.
Avoid private lands,wildlife refuges,parks.
Select gentle relief.
Avoid heavily timbered areas.
Technical
TABLE 14.5:TECHNICAL,ECONOMIC AND ENVIRONMENTAL CRITERIA
USED IN CORRIDOR SCREENING
Primary
Secondary
Economic
Primary
Secondary
Topography
Climate and Elevation
Soils
Length
Vegetation and Clearing
Highway and River Crossings
Length
Presence of Right-of-Way
Presence of Access Roads
Topography
Stream Crossings
Highway and Railroad Crossings
;,;.:)--
Environmental
Primary
Aesthetic and Visual
Land Use
Presence of Existing Right-oF-Way
Existing and Proposed Development
Secondary
Length
Topography
Soils
Cultural Reservoir
Vegetation
Fishery Resources
Wildlife Resources
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TABLE 14.6:SUMMARY OF SCREENING RESULTS
RAT I N GS
Corridor Env.Econ. fech.Summary
- Southern Study Area
(1)ABC'C C C C
*(2)ADfC A A A A
(3)AEFC F C A F
- Cental Study Area
*(1)ABCD A A A A
(2)ABECD F C C F
(3)AJCF C C C C
(4)ABCJHI F F F F
(5)ABECJHI F F F F
(6)CBAHI F C F F
(7)CEBAHI F F C F
(8)CBAG F F C F
(9)CEBAG F F C F
(10)CJAG F F C F
(11)CJAHI F C C F
(12)JACJHI F F C F
(13)ABCF A C A C
(14)AJCD C A A C
(15)ABECF F C C F
- Northern Study Area
*(1)ABC A A A A
(2)ABDC C A C C
(3)AEDC F C F F
(4)AEF F C F F
A =recommended
C =acceptable but not preferred
F =unacceptable
*Indicates selected corridor.
TABLE 14.7:EMS ALTERNATIVES 1 AND 11
COMPARATIVE COST ESTIMATES
AIternabve I AIternabve II
,I
EMS Project
1Hardware$2,942,000 $3,072,000
Software 3,956,000 4,200,000
Auxiliary 1,210,000 1,350,000 I
1
Internal (APA costs)3,416,000 3,606,000
$11,524,000 $12,228,000
Susitna In-Plant Control System
1Hardware$1,131,000 $1,094,000 ,
Software 1,200,000 1,200,000
Auxiliary 750,000 700,000 '1Internal(APA costs)1,770,000 1,875,000
$4,851,000 $4,869,000
Microwave System $4,920,000 $5,100,000
_1EMSControlCenterBuilding$3,853,140 $3,853,140
TOTAL $25,148,140 $26,050,140
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ELECTRIC
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150 MVA STATIC VAR
345 -COMPENSATOR
138113.8 KV
1lf--::---
,111~
ESTER
( FAIRBANKS)
SHUNT
REACTOR
195 MI.
84 MI.
-----------..,
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75MVA
345-138 KV
--if--D--
",..,.,- ....rT"f ~'j ...to-• I ..I "
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KNIK ARM
40MI.
75 MVAr345-115KV
,---------..,
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:UNOERKNIK ARM'I
A IIII-'~L _
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RAILBELT 345 KV TRANSMISSION SYSTEM SINGLE LINE DIAGRAM [Ii]FIGURE 14.1
STAGING LEGEND
---1993
----2002
DEVIL CANYON
WATANA
26 MI.
\I I I
6 x 170 MW UNITS
UNIVERSITY
(ANCHORAGE)--,
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'T''T-
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LIGHT a POWER
18MI.
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~~~;'3.8KV Tl ~001[1"'(r'
II STATICVARICOMPENSATOR
\ I l'I
CHUGACH ELECTRIC ASSOCIATION
FAIRBANKS
LOCATION MAP
lEGEND
---STUDY CORRIDOR
..............INTERTIE
(APPROXIMATE)
o 5 10I!
SCALE IN MilES
ALTERNATIVE TRANSMISSION LINE CORRIDORS
SOUTH ERN STUDY AREA FIGURE 14.2
LOCATION MAP
FAIRBANKS
10
!
FIGURE 14.3
5
SCALE IN MILES
o
i
LEGEND
------STUDY CORRIDOR
..............INTERTIE
(APPROXIMATE)
ALTERNATIVE TRANSMISSION LINE CORRIDORS
CENTRAL STUDY AREA
.X.i'+
LOCATION MAP
LEGEND
----STUDY CORRIDOR
••••••••••••••I NTERTIE
(APPROXIMATE)
ALTERNATIVE TRANSMISSION LINE CORRIDORS
NORTHERN STUDY AREA
o 5
i
SCALE IN MILES
10
!
FIGURE 14.4
[.r=J L-...-~'--''--------'
,
'-------i ----J ~~--.J ---1
TALKEETNA MOUNTAINS
DEVIL CANYON
WATANA
"j
t)'tt ANCHORAGE (\~\~~'-.1-'..[]
T:ELA 41'01(G \......::::!,
3 "'-=t -».D. GOLD CREEK WILLOW .-'1~~./'~.._.-._.,//
..~~./TAt::KEETNA,~...~_.,
DENALI ~._.-~~C<S'/rj,iA~"'\I STATE ~~R/VcRL1PARKI'"
I 3
L----1 i "'"l __J\
MEWS
ALASKA RANGE
rt/!
HIGHWAY
RAILROAO
TRANSMISSION LINE ROUTE
PROPOSED SWITCHING STATioNo
®
-0-
LEGEND
T( ER..~v
~\
•FIGURE 14.5
12SCALEO~==5;;==iil
ANCHORAGE TO FAIRBANKS
PROPOSED TRANSMISSION LINE ROUTE
THE PROPOSED INTERTIE FROM WILLOW TO HEALY WILL BE CONSTRUCTED
FOR 345 KV CAPABILITY AND INITIALLY OPERATED AT 13B KV.
IF SUSITNA IS PROVED FEASIBLE,THE FULL 345 KV CAPACITY WILL BE UTILIZED.
---I l-.J 1--,---
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RECOMMENDED 345 KV TANGENT TOWER
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:ACCEPT HEAVY DUTY
GUY-THIMBLE WITH
'I GUY- WIRE,a PREFORMED
GUY ATTACHMENT
I
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TOWER LEG
CLEARANCE TO PILE
II
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II
PILE
DETAIL B
x-FRAME GUYED STEEL TOWER
9
SECTION A-A
CHAMBER HOLE TO
ACCEPT HEAVY DUTY
GUY THIMBLE WITH
GUY WIRE a PRE-
FORMED 'GUY ATTACH-
MENT
FIGURE 14.6 11~~m I
2 EACH,
I ANCHOR,II REBAR
IN 4"12l X a-o"HOLES
2 EACH,
MULTI-HELIX ANCHORS
15~0"LONG
ROCK FOUNDATION
5'-0"
STANDARD FOUNDATION
2 EACH, 12"STEEL
H-PILES,25'-0"LONG
2 EACH,3 CU.YD.CONCRETE
2 ANCHORS, II REBAR
IN 4"12l X s-o"HOLES
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2 EACH,
MULTI-HELIX ANCHORS
301-0"LONG
2 EACH,12"STEEL
H-PILES,50'LONG
WET LAND FOUNDATION
TRANSMISSION TOWER FOUNDATION CONCEPTS
FIGURE 14.7
1_-1 _I 1 __-.J __---I ~,~__.-1
II II -.ft,II _
LW
I 1050'-0"~--~I
~SERVICE ROAD -I r-F .1[ 1[ 1r,11 I
A
If
R
LK I
1:[tJ
LW 2 f-TO DEVIL
CANYON
I
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"0,
"0
0
I =
I
II I 0
345 KV
I II II I I L-l r-LL.':l-I-'-
n
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RELAY BUILDING
175 MVA
---if-+--<l "-------J I I I I I I I / 3 PHASE
I I I I I I ,r I I rflt-r---------
LK 2TO KNIK ARM
JL 138 KV
rtfr-
II I 0
I II II I I l-d L....l..J..jp-
LK 3
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--V---L
---------~~~t~Ir--{lp---i=I I
I---<ll>--;:j '~.=-..:I I----l+--__+I_.J---<Lb--*-i...J
)
SERVICE ROAD
N
MICROWAVE TOWER ~ENERGY
MANAGEMENT
CENTER
CONTR
SLOG.
o 100
FEET
200
II
WILLOW SWITCHING STATION - GENERAL LAYOUT
FIGURE 14.8 m
L-,_:_-'----~-'
•FIGURE 14.9
TO KNIK ARM
LU2
LUI
-0
oo
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UNIVERSITY SUBSTATION-GENERAL LAYOUT
200100
FEET
-----lSERVICE ROAD
~;"ci~
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r-=t..----...I r-i.-'--_----------r----------......J I ~=--_----..,f}---r-f------,
I f--'..............::;..__---dl>---l I II-------------r-....I ,.;~-15KV----y-
I
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l =Fo jE
0 I.,;;E;"
I 230KV ~M 0 D
.",;;=:Jt=345 KV~!~tl
3--,
~=15KV .n,.n,
I 1:~f-e::::---------=---tE n
250MVA ~~I I I ill
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3-SINGLE PHASE 4#ITRANSFORMERS -
SERVICE ROAD
:Je-t I I
-,_I
,
-~'"',."
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I.500'-0"
I I I 15KV STATIC VAR COMPENSATOR
I I IROOM
I I I
I ~MICROWAVE I I I
ITOWERIIII----"WULtlJlI.Ll r-n n h n
SERVICE 'TT1rL[-'T'rT ~~r'~
ANO I L I 250 MVA
I STORAGE L - ,r J 1n 3 -SINGLE PHASE
BUILDING ~II TRANSFORMERS
r''r I
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l r I I
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o
'-"--L-
ESTER SUBSTATION
-----
--+,r Z
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138 KV
=0,
-0
"'....
STATIC VAR
COMPENSATOR
-
SERVICE ROAD
J
--
TOWER
----
I
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,..I "00"0'"I
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F 2
TO
DEVIL
CANYON
LFI
FIGURE 14.10 181m I
=0
I
~I KNIK ARM SWITCHING STATION
"'
ESTER AND KNIK ARM STATIONS - GENERAL LAYOUT
1':1 MVA
3 PHASE
TRANSFORMER'=*-n n---E:j rl I--'-I 115KV-----I:i-0 0 l345KV
0 Ei=H],
If o TO UNIVERSITY
IE :::JOE Fe",P JF1tlUSTOR
BLDG.'-------'r )2t-MICROWAVE
TOWER--
LKI
LK3
1050'-0"I~-I
,-SERVICE ROAD -~tNI~1r 1r 1r 11 lr I
TO WILLOW -1 LK 2
100
!!!!!!!!!!!!!SO
FEET
o
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.......---HO.lIMS
.103NNOOSIC
.......---ll3>tV3ll8
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......----HO.lIMS
.103NNOOSIC
.......---!l11l---SO8 NI V ~
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r 1
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L---'--'~--
I ICOMPUTERI1 COMPUTER
PERIPHERALS
MAN/MACHINE
INTERFACE
COMMUNICATION SUBSYSTEM
NORTHERN AREA
SOUTHERN AREA SUSITNA HYDROELECTRIC
CONTROL SYSTEM CONTROL SYSTEM CONTROL CENTER
_L..-------FT~l-,...-L..-
G ------RTU G G ------RTU RTU -------RTU
-'---
SUBSTATION
RTU s
ENERGY MANAGEMENT SYSTEM,ALTERNATIVE I,SYSTEM CONFIGURATION FIGURE 14.121 ~~~I~I
"--~L..-_....
COMPUTER 1
I
PERIPHERALS
MAN/MACHINE
INTERFACE
COMMUNICATION SUBSYSTEM
~
COMPUTER
-----'
G
NORTHERN AREA
CONTROL SYSTEM
-----fb G
SOUTHERN AREA
CONTROL SYSTEM
------RTU
SUSITNA HYDROELECTRIC
CONTROL CENTER
G
RTU L........IRTU
....--1--
~------lRTUsl-8------IR~Ul
WATANA/DEVIL CANYON SUBSTATION RTU
SUBSTATIONS
ENERGY MANAGEMENT SYSTEM,ALTERNATIVE IT,SYSTEM CONFIGURATION FIGURE 14.131 ~~I!~I
~L-._l--__~...--J
,..170'--I
Iii Iii i-
MECHANICAL AND
FACILITY SUPPORT
COMMUNICATION I STORAGE
ROOM I 300
600 SQ. FT.I SQ. FT.
BATTERY ROOM
350 SQ. FT.
UPS ROOM
350 SQ. FT.
LAV.8
KITCHEN
350 SQ.FT.DISPATCHING
1200 SQ. FT.
CONFER.I TRAIN /PROG.
EMS EQUIR
MAINT.ROOM
EMS EQUIPMENT
ROOM
DISPATCH
AREA
ARENA
1500 SQ. FT.
400 SQ. FT.1400 SQ. FT.
ROOM ROOM
900 SQ. FT.
HALL 7.5 FT. WIDE
1500 SQ.FT.650 SQ.FT.
LOBBY
00
~
00
MANAGEMENTOFFICE AREA
1500 SQ. FT.
ENG.
SUPPORT
KITCHEN 8
LOUNGE
MEN
LAV.
450
WOMEN
LAV.
450
450 SQ. FT.
AREA
600 SQ. FT.900 SQ. FT. SQ. FT.I SQ. FT.637 SQ.FT.
o 20
FEET
40
..........'-
ENTRANCE
TOTAL:14,500 SQ. FT.
WI LLOW SYSTEM CONTROL CENTER,
FUNCTIONAL LAYOUT FIGURE 14.14 I ~~Il~,I
r 1!j
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...
TO
GENERATORS
NORTHERN AREA
CONTROL SYSTEM-1----------.
FAIRBANKS
ESTER
SUBSTATION
WILLOW
SUBSTATION
ENERGY MANAGEMENT
SYSTEM
WILLOW CONTROL
CENTER
KNIK ARM
SUBSTATION
WATANA
SWITCHING
STATION
TO GENERATORS
j""j I'JI'jI'JI\
SUSITNA
HYDROELECTRIC
CONTROL CENTER
lit ,,,,It lit
TO GENERATORS
DEVIL CANYON
SWITCHING
STATION
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GENERATORS
UNIVERSITY
SUBSTATION
ENERGY MANAGEMENT SYSTEM, ALTERNATIVE I,!IPO[P I
CONFIGURATION BLOCK DIAGRAM FIGURE 14.15 "UOlO
15 -PROJECT OPERATION
This section describes the operation of the Watana and Devil Canyon
power plants in the Railbelt electrical system.Under current condi-
tions in the Railbelt,a total of nine utilities share responsibility
for generation and distribution of electric power,with limited inter-
connections.The proposed arrangements for optimization and control of
the dispatch of Susitna power to Railbelt load centers is based on the
assumption that a single entity would eventually be set up for this
purpose.In the year 2010 the projected Ra t lbe l t system,with Susitna
on line,will comprise:
Coal-fired Steam:
Natural Gas GT:
Diesel:
Natural Gas CC:
Hydropower:
Total
13 IVJW
326 MW
6 MW
317 MW
1440 MW
2102 IVIW
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It is important to note that the Susitna project will be the single
most significant power source in the system.The dispatch and distri-
bution of power from all sources by the most economical and reliable
means is therefore essential.The general principles of reliability of
plant and system operation,reservoir regulation,stationary and spin-
ning reserve requirements,and maintenance programming are discussed in
this section.Estimates of dependable capacity and annual energy
production for both Watana and Devil Canyon are presented.Operating
and maintenance procedures are described,and the proposed performance
monitoring system for the two projects is also outlined.
15.1 -Plant and System Operation Requirements
The main function of system planning and operation control is the allo-
cation of generating plant on a short-term operational basis so that
the total system demand is met by the available generation at minimum
cost consistent with the security of supply.The objectives are gener-
a lly the same for long-term pl anning or short-term operat ional load
dispatching,but with important differences in the latter case.In the
short-term case,the actual state of the system dictates system relia-
bility requirements,overriding economic considerations in load dis-
patching.An"important factor arising from economic and rel iabil ity
considerations in system planning and operation is the provision of
stationary reserve and spinning reserve capacity.Figure 15.1 shows
the daily variation in demand for the Railbelt system during typical
winter and summer weekdays and the seasonal variation in monthly peak
demands for estimated loads in a typical year (the year 2000).
15.2 -General Power Plant and System Railbelt Criteria
The following are basic rel iabil ity standards and criteria generally
adopted in the industry for power systems.
15-1
(a)Installed Generating Capacity
Sufficient generating capacity is installed in the system to in-
sure that the probabil ity of occurrence of load exceedi ng the
available generating capacity shall not be greater than one day in
ten years (LOLP of 0.1).
(b) Transmission System Capability
The high-voltage transmission system should be operable at all
load levels to meet the foll owtnq unscheduled single or double
contingencies without instability,cascading or interruption of
load:
-The single contingency situation is the loss of any single gen-
erating unit,transmission line,transformer,or bus (in addi-
tion to normal scheduled or maintenance outages)without exceed-
ing the applicable emergency rating of any facility.
-The double contingency situation is the subsequent o~tage of any
remaini ng equi pment,1 ine or subsystem without exceedi ng·the
short time emergency rating of any facility.
In the single contingency situation,the power system must be cap-
able of readjustment so that all equipment will be loaded within
normal ratings,and in the double contingency situa'tion,within
emergency ratings for the probable duration of the outage.
Our i ng any conti ngency :
-Sufficient reactive power (MVAR)capacity with adequate controls
are installed to maintain acceptable transmission voltage pro-
fil es,
-The stability of the power system is maintained without loss of
load or generation during and after a three-phase fault,cleared
in normal time,at the most critical locatio~.
--(-c-)'SUllimary
Operational reliability criteria thus fall into four main cate-
gories:
(i)Loss-of-load probability (LOLP)of 0.1,or one day in ten
years,is maintained for the recommended plan of operation
through the year 2010 (Section 6).
(ii)The single and double contingency requirements are main-
tained for any of the more probable outages in the plant or
transmission system.
(iii)System stability and voltage regulation are assured from
the electrical system studies (Section 14).Detailed
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studies for load frequency control have not been performed,
but it is expected that the stipulated criteria will be met
with the more than adequate spinning reserve capacity with
six units at Watana and four units at Devil Canyon.
(iv)The loss of'all Susitna transmission lines on a single
right-of-way has a low level of probability as described in
Section 18 under Risk Analysis.In the event of the loss
of all 1i nes,the hydro pl ants at Watana and Devil Canyon
are best suited to restore power supply quickly after the
first line is restored since they are designed for "bl ack
st ar t "operation.In this respect,hydro plants are super-
ior to thermal plants because of their inherent black start
capability for restoration of supply to a large system.
15.3 -Economic Operation of Units
The Central Dispatch Control Engineer decides which generating units
should be operated at any given time.Decisions are made on the basis
of known information,including an "or dervof-mer t t "schedule,short-
term demand forecasts,limits of operation of units,and unit mainten-
ance schedules.
(a)Merit-Order Schedule
In order to decide which generating unit should run to meet the
system demand in the most economic manner,the Control engineer is
provided with information of the running cost of each unit in the
form of an "crder vof-mer t t "schedule.The schedule gives the cap-
acity and fuel costs for thermal units,and reservoir regulation
limits for hydro plants.
(b)Optimum Load Dispatching
One of the most important functions of the Control Center is the
accurate forecasting of the load demands in the various areas of
the system.
Based on the anticipated demand,basic power transfers between
areas and an allowance for reserve,the planned generating capa-
city to be used is determined,taking into consideration the
reservoir regulation plans of the hydro plants.The type and size
of the units should also be taken into consideration for effective
load dispatching.
In a hydro-domi nated power system, such as the Ra il belt system
would be if Susitna is developed,the hydro unit will take up a
much greater part of base load operation than in a thermal dom-
inated power system.The planned hydro units at Watana typically
are well suited to load following and frequency regulation of the
system and providi ng spi nni ng reserve.Greater fl exi bil ity of
operation was a significant factor in the selection of six units
of 170 MW capacity at Watana,rather than fewer,larger size
units.
15-3
(c)Operating Limits of Units
There are strict constraints on the mlnlmum load and the loading
rates of machines,and to dispatch load to these machines requires
a system wide dispatch program taki~g these constraints into con-
sideration.In general,hydro units have excellent startup and
load following characteristics;thermal units have good part-
loading characteristics.
Typical plant loading limitations are given below:
(i )Hydr0 Unit s
Reservoir regul ati on constrai nts resulting in not-to-
exceed maximum and minimum reservoir levels,daily or
seasonally.
-Part loading of units is impo~Jible in the zone of rough
turbine operation (typically from above speed-no-load to
50 percent load)due to vibrat40ns arising from hydraulic
surges.
(ii)Steam Units
-Loading rates are slow (10 percent per minute).
-The units may not be able to meet a sudden steep rate of
rise of load demand.
Usually have a minimum economic shutdown period (about 3
hours) •
The total cost of using conventional units include bank-
ing,raising pressure and part-load operations prior to
maximum economic operation.
(iii)Gas Turbines
..Cannot be used as spinning.reser.ve.because·of-ver-y poor
efficiency and reduced service life.
- Require 8 to 10 minutes for normal start-up from cold.
Emergency start up times are of the order of 5 to 7
mi nutes,
(d)Optimum Maintenance Program
An important part of operational planning which can have a signif-
icant effect on operati ng costs is mai ntenance programmi ng.The
program specifies the times in the year and the sequence in which
plant is released for maintenance.Further details of Watana and
Devil Canyon power plant maintenance programs are given in Sec-
tion 15.8.
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15.4 -Unit Operation Reliability Criteria
During the operational load dispatching conditions of the power system,
the reliability criteria often override economic considerations in
scheduling of various units in the system.Also important in consider-
ing operational reliability are system response,load-frequency con-
trol,and spinning reserve capabilities.
(a)Power System Analyses
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Load-frequency response studies determine the dynamic stability of
the system due to the sudden forced outage of the largest unit (or
generat i on block) in the system.The generat i on and load are not
balanced,and if the pick-up rate of new generation is not ade-
quate,loss of load will eventually result from under-voltage and
under-frequency relay operation,or load-shedding.The aim of a
well-designed high security system is to avoid load-shedding by
maintaining frequency and voltage within the specified statutory
limits.
System Response and Load-Frequency Control
To meet the statutory frequency requirements,it is necessary that
the effective capacity of generating plant supplying the system at
any given instant should be in excess of the load demand.In the
absence of detailed studies,an empirical factor of 5/3 times the
capacity of the largest unit in the system is normally taken as a
design criterion to maintain system frequency within acceptable
limits in the event of the instantaneous loss of the largest unit.
It is recommended that a factor of 1-1/2 times the largest unit
size be considered as a minimum for the Alaska Railbelt system,
with 2 times the largest unit size as a fairly conservative value
(i .e.,300 to 340 MW).
The qui ckest response in system generat i on wi 11 come from the
hydro units.The large hydro units at Watana and Devil Canyon on
spinning reserve can respond in the turbining mode within 30 sec-
onds. This is one of the particularly important advantages of the
Susitna hydro units.Gas turbines can only respond in a second
stage operation within 5 to 10 minutes and would not strictly
qualify as spinning reserve.If thermal units are run part-loaded
(example,75 percent),th i s would be another source of spinning
reserve.Ideally,it would be advantageous to provide spinning
reserve in the thermal generation as well,in order to spread
spinning reserves evenly in the system, with a compromise to eco-
nomic loading resulting from such an_operation.
(c)Protective Relaying System and Devices
The primary protect i ve re1ayi ng systems provi ded for the gener-
ators and transmission system of the Susitna project are designed
15-5
to disconnect the faulty equipment from the system in the fastest
possible time. Independent protective systems are installed to
the extent necessary to provide a fast-clearing backup for the
primary protecti ve system so as to 1imit equi pment damage,to
limit the shock to the system and to speed restoration of service.
The relaying systems are designed so as not to restrict the normal
or necessary network transfer capabilities of the power system.
15.5 -Dispatch Control Centers
The operation of the Watana and Devil Canyon power plant in relation to
the Central Dispatch Center can be considered to be the second tier of
a three-tier control structure as follows:
- Central Dispatch Control Center (345 kV network)at Willow:manages
the main system energy transfers,advises system confi gurati on and
checks overall security.
-Area Control Center (Generation connected to 345 kV system, for ex-
ample,Watana and Devil Canyon):deals with the loading of genera-
tors connected directly to the 345 kV network, sWitching and safety
precautions of local systems, checks security of interconnections to
mai n system.
-District or Load Centers (138 kV and lower voltage networks): gener-
ation and distribution at lower voltage levels.
For the Anchorage and Fairbanks areas,the district center functions
are incorporated in the respective area control centers.
The details of the Central Dispatch Control Center and of the Watana
Area Control Center are given in Section 14.Each generating unit at
Watana and Devil Canyon is started up, loaded and operated and shut
down from the Area Control Center at Watana according to the loading
demands from the Central Dispatch Control Center with due consideration
to:
-Watana reservoir regulation criteria;
---.--Bevil Canyon reservoir regulation cr-i-t-eria;.-...----
- Turbine loading and de-loading rates;
-Part loading and maximum loading characteristics of turbines and gen-
erators;
- Hydraulic transient characteristics of waterways and turbines
- Load-frequency control of demands of the system; and
- Voltage regulation requirements of the system.
The Watana Area Control Center is equipped with a computer-aided con-
trol system to efficiently carry out these functions.The computer-
aided control system allows a minimum of highly trained and skilled
operators to perform the control and supervi sion of Watana and Devil
Canyon plants from a single control room.The data information and
retrieval system will enable the performance and alarm monitoring of
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each unit individually as well as the plant/reservoir and project oper-
ation as a whole.
15.6 -Susitna Project Operation
A reservoir simulation model was used to evaluate the optimum method of
operation of the Susitna reservoirs and power plants at Watana and
Devil Canyon.
Substantial seasonal as well as over-the-year regulation of the river
flow is achieved with the two reservoirs.The simulation of the reser-
voirs and the power facilities at the two developments was carried out
on a monthly basis to assess the energy potential of the schemes,river
flows downstream and flood control possibilities with the reservoirs.
Details of the computer model are described in Appendix B.The follow-
ing paragraphs summarize the main features of reservoir operation.
(a)Reservoir Operation
Gross storage volume of the Watana reservoir at its normal maximum
operating level of 2185 feet is 9.47 million ac/ft,which is about
1.6 times the mean annual flow (MAF)at the damsite.Live storage
in the reservoir is about 4.3 million ac/ft (75 percent of MAF).
Devi 1 Canyon reservoi r has a gross storage of about 1.1 mill i on
ac/ft and live storage of 0.34 million ac/ft.
(b)System Demand and Reservoir Operating Rules
An optimum reservoir operation was established by an iterative
process to minimize net system operating costs while maximizing
firm and usable energy production.Four a lternat ive operati ng
cases for the Watana reservoir (A,B,C,and D)were selected for
study,to define the possible range of operation.Case A repre-
sents an optimum power and energy scenario,while Case D reflects
a case of II no impact on downstream fisheries ll or lI avoidance
f l ows",Cases Band C are intermediate levels of power operation
and downstream impact.These essentially define monthly minimum
flows at Gold Creek that must be maintained while providing energy
consistent with other project constraints.For feasibility report
pur poses,operation model II All was adopted for project design.
Studies with appropriate fisheries mitigation measures were
developed based on Case A f l ows at Gold Creek.Details of the com-
puter simulation runs for energy potential and their impact on
project economics may be found in Appendix B. Table 15.1 presents
a summary of potential energy generation with different operating
rules for Watana and Devil Canyon developments.
(c)Energy Potential of the Watana-Devil Canyon Developments
Average annual energy potential of Watana development is 3460 GWh,
and that of Devil Canyon development is 3340 GWh.A frequency
15-7
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analysis of the river hydrology was made to derive the firm annual
energy potential (or the dependable capacity)of the hydro devel-
opment.
The Federal Energy Regul atory Commi ssion (FERC)defi nes the
dependab 1e capacity of hydroe 1ectri c pl ants as:lithe capacity
which,under the most adverse flow conditions of record can be
relied upon to carry system load,provide dependable reserve capa-
city,and meet firm power obligations taking into account seasonal
variations and other characteristics of the load to be supplied"
(1).Based on the Railbelt system studies and previous experience
on large hydroelectric projects,it was assumed that a dry hydro-
logical sequence with a recurrence period of the order of 1:50
years would constitute an adequate reliability for the Railbelt
electrical system.
An analysis of annual energy potential of the reservoirs showed
that the lowest annual energy generation has a recurrence fre-
quency of 1 in 300 years (see Fi gure 15.2).The second lowest
annua 1 energy of 5400 GWh has a recurrence frequency of 1 in 70
years.Th is 1atter fi gure has been adopted as the firm energy
from the development.
Expressed another way,the firm energy,as defined,may fall short
of its value by about 5 percent once in 300 years.This is,
again,a conservative interpretation of the FERC definition.
The monthly distribution of firm annual energy as simulated in the
reservoir simulation has been used in system generation planning
studies.Average monthly energy based on the recorded sequence
hydrology is used in the economic analysis.
(d)Reservoir Filling Seguence
Given the rel ati ve si zes of the Watana and Devil Canyon reser-
voirs,it is apparent that the most significant impact on the
downstream flow regime will occur during filling of the Watana
reservoir.Since this will be the first reservoir filled,careful
(i)Watana Reservoir Impoundment
Minimum monthly flows that must be maintained in the river
below the dam during filling were established in consulta-
tion with fisheries and other environmental study groups
and agencies.Table 15.2 presents the minimum monthly flow
that is considered acceptable for ri ver mai ntenance and
fisheries requirements during the filling period.With the
above mi nimum flow requirement,it would take at 1east
2-1/2 years of average stream flow to fill the reservoir.
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It may be noted that the construction of the dam critically
controls the reservoir filling in average streamflow years
and restricts earlier filling should wet years be experi-
enced.The driest recorded streamflow sequence would ex-
tend the filling period by one year (see Figure 12.2).
The fi 11 ing sequence in the years of average streamflow
would allow first power on line by July,1993.The units
coul d be tested and commi ssi oned pri or to th is date.A
bonus in power and energy coul d be gai ned with one or two
units installed by July 1992 when the power intake will be
submerged sufficiently to allow power generation utilizing
the minimum downstream flow requirements.
(t t )Devil Canyon Reservoir
With Watana Reservoir in operation,the filling of the
Devil Canyon Reservoir is relatively easily accomplished •
Average monthly power flows from Watana between the months
October through December ina single year will fi 11 the
reservoir while maintaining the minimum downstream flow re-
quirements.
(e)Operating Capabilities of Susitna Units
(i)Turbine Performance
The reservoir operati on studi es descri bed above show that
the Watana plant output may vary anywhere from zero,with
the unit at standstill or spinning reserve,to 1,200 MW
when the six units are operating under maximum output at
maximum head.(Note that there is a limitation in loading
of a single unit in the zone of turbine operation from
above speed-no-load operati on to about 50 percent load).
The four units at Devil Canyon have a maximum total output
of 700 MW at maximum head.
The operating conditions of the turbines are summarized in
Table 15.3.
The turbine design head corresponds to the weighted average
head.Based on the predicted daily load curves through the
year 2010 and expected reservoir operation,it is expected
that each unit at Watana is to supply a load averaging be-
tween 196 MW and 100 MW.This is the load which corres-
ponds most closely to the best efficiency operation of the
turbine.
Similarly,the Devil Canyon units will supply a load be-
tween 174 MW and 100 MW.
15-9
(ii)Expected Unit Performance Characteristics
The rated output of the turbi ne corresponds to full gate
operat i on at the rated head.Each turbi ne should operate
satisfactorily at the maximum head.The output of the gen-
erator is'limited by its continuous maximum rat ingof 115
percent with a maximum temperature rise of BO°C.The con-
tinuous maximum rating of the generator determines the max-
imum output of the unit,and it will be necessary to limit
the turbine output to this value at the higher heads.
The plant efficiency with different numbers of units in
operation is shown in Figures 15.3 and 15.4.In practice,
the load following requirements of the plant results in
widely varying loading,however,because of the multiple
unit installation,the efficiency is relatively constant.
(iii)Stability and Governing of Units
Electrical transient stability studies of the Railbelt sys-
tem indicate that the "natural"inertia of 3.2 to'3.5 kW-
sec/KVA for the Watana and Devil Canyon generators is ade~
quate for electrical stability of the system.
The pertinent plant data for stability and governing are
given in Sections 12 and 13 for Watana and Devjl Canyon
plant,respectively.
Pressure rise and speed rise are within normally acceptable
1imits of about 40 to 50 percent.A ow ratio of the
starting time of the water masses to the mechanical start-
ing time of the unit is an indication of the hydraulic sta-
bility and acceptable response (promptitude time constant)
of the governor.Good governing response and stability are
indicated for the Watana and Devil Canyon units and are
important from the overall considerations of system load
following and load-frequency response of the units.
-~-tf-Y--Watana--P-}ant-D-a-ily-~S-imu-lat10 n-Studf-es-
The objective of the plant daily simulation studies is to present
performance studies of the selected 6-170MW'unit plant at Watana.
The studies demonstrate its improved performance in comparison
with a 4-250 MW plant.The simulation program was arranged to:
-Study the operation and load following characteristics of the
Watana powerplant with different number and rating of units;
-Determine the effect of minimum and maximum loading constraints
of the units;
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- Determine the effect of critical single or double contingency
outages of units on the amount and type of spi nni ng reserves
available in the system;
-Study the effects of maintenance outages and its impact on gen-
eration scheduling and system reliability;and
-Check the operation of gas turbines as peaking plant.
(i)Computer Simulation Model
To achieve the stated objectives,a computer simulation
program was used to simulate Watana power plant and system
operation.The Watana turbines and reservoir were modeled
in detail to simulate closely the reservoir regulation and
load following characteristics of the turbines.
The model included the following principal features:
- Turbine characteristics as a function of head,gate open-
ing (flow),and efficiency.
-Minimum loading limitations of the turbine due to opera-
tion in the zone of rough operation up to 50 percent of
the gate openings were constraints for turbine loading
and operation.
-Maximum continuous rating (MCR)of the generators con-
stituted the maximum loading of the units.
-Predicted daily system load demand curves were used for
two typical load shapes for winter and summer,respec-
tively.Monthly peak load variation of the load was
taken into account.
-Reservoir characteristics as a function of level and
storage.
- Unit by unit loading and de-loading of Watana generators
according to load demand (load-following)was done taking
into account all constrai nts mentioned above.The pro-
gram loads the units equally for maximum efficiency of
operation.
-Loading steam plants as base-load plants,and gas tur-
bines as peaking plants.
-Maintenance scheduling of the generating units.
15-11
(i i)Results of the Simulation Studies
Printouts of the results of the simulations are included in
Appendix B.For each run,printouts are presented for the
following outputs in a typical day for each month of the
year 2000 (January to December):
-Watana plant kW output;
-Watana turbine kW output,with flow and efficiency for
each uni t;
-Watana turbine utilization,showing number of units
loaded;
-Watana reservoir level;
- Peaking plant kW output;
- Total system load kW demand;
- Total system reserve,including maintenance outage;
-Watana reserve capacity;and
-Annual energy output of Watana,thermal plant,small
hydro, gas turbine plants,and overall annual system
energy•
Simulation results of a typical December,2000 day is shown
in Figure 15.5.The simulation indicates that the six unit
Watana plant (6-170 MW)has superior overall performance in
terms of load followi ng,improved overall efficiency and
minimum loading constraints over the four unit plant (4-250
MW)•
The overall rel i abil ity of the six unit Watana plant is
also better than that of the four unit plant.During main-
..tenance-the .six'unit pl-ant-has-ap'l-anned'ou"t'ageof170 MW,
as opposed to 250 MW for the four unit plant.During peak
December loading,a double contingency outage of two units
brings down system reserve to 107 MW for the 6-170 MW unit
plant and to less than zero for the 4-250 MW unit plant.
The simulations indicate that sufficient spinning reserve
comprising a minimum of one Watana unit is available for
all peak day loadings for the six unit Watana plant for the
year 2000 study.
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[~)15.7 -Performance Monitoring
(a)Watana Dam
Instrumentation is installed to enable the performance of the dam
to be monitored to ensure that its behavior is within the limits
assumed in the design,and to enable any variations beyond those
1 imits to be recogni zed qui ck ly so that remedi a 1 acti on can be
taken without delay.
The most important aspects of the monitoring program and likely
maintenance requirements are outlined below:
(i)Foundation Abutment Pore Pressures and
Discharge From Pressure Relief System
Si nce secti ons of the foundation are frozen,the grouted
cut-off may not be fully effecti ve,and 1eakage may i n-
crease as the rock temperature increases.
This condition would be indicated by increased discharge
from the drainage system and would be remedied byaddi-
tional grouting from the grouting gallery,possibly com-
bined with additional drainage holes.
(ii)Quality of Discharge from Pressure Relief System
Any discoloration of the drainage system discharge would
indicate the leaching of fine material either from the rock
foundation or from the core.The problem area would be
located and additional grouting carried out.Water quality
should also be monitored for any change in mineral con-
tent.
(iii)Deformation of the Structure
Most deformation of the structure as observed by settle-
ments and lateral movements is expected to occur soon after
construction and under initial filling of the reservoir.
Any excessive settlement would be made good to maintain
freeboard.Deformation records would be correlated with
such data as reservoir 1evel,heavy storms and sei smic
activity.
(iv)Routine Observations
An essential part of any monitoring program is a regular
routine visual inspection of all exposed parts of the
structure and the area downstream of the dam for any un-
usual features such as local settlement or other movement,
zones of seepage discharge,wet areas,and changes in vege-
tation.All exposed concrete surfaces would also be in-
spected and records kept of any signs of distress,cracking
or deterioration.
15-13
-Corrective maintenance,to restore lost efficiency of plant;and
-Emergency maintenance,arising from plant failure.
(v)Relict Channel
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Access and Maintenance in the Powerhouse
Techniques developed both in the design and the operation of con-
ventional underground hydroelectric power plants have resulted in
Frequency of Inspections and Maintenance
Experience records from machines similar to the Watana and Devil
Canyon machines indicate that a minimum maintenance period of 5 to
6 days are required for each machine,resulting in an outage of
150 to 170 MW capacity for an average period of 50 to 60 days in
the year.In exceptional cases,certain machines may be down for
greater maintenance periods.It is therefore reasonable to allow
a total of 2-1/2 to 3 months planned outage as a conservative ap-
proach to system generati on and mai ntenance--pl ennt ng for the
S_usitoa_units.In prjn!::iJ)JE!,:t:IlE!~E!~!ages are schedule~during
the months of June to August when'the Tower-summerT6ad demands
make it possible to release the units for maintenance.The actual
outages will be coordinated on a week-to-week basis with the
planned maintenance of the units in the rest of the system,and
will take into consideration emergency shutdowns,breakdowns,de-
lays in construction and maintenance and other unforeseen contin-
gencies.
(b)
(a)
Particular attention must be paid to monitoring the entire
area of the relict channel,including regular readings of
piezometers and thermistors,of surface elevation,survey
monitoring and inspections of the discharge zone for
changes in seepage flows and any signs of piping failure.
Notwithstanding this,generating plant must undergo periodic mainten-
ance for various reasons:
-Preventive maintenance, to ensure safe and reliable operation (per~
formed either on load or shut down);
15.8 -Plant Operation and Maintenance
The system demand varies throughout the year from a winter (December/
January)peak to a summer (July/August)trough,and from hour-to-hour
throughout the day.The Central Dispatch Center operates with the ob-
ject of ensuring that sufficient plant is available at all times to
meet the varying load in accordance with a merit-order schedule with
due consideration to reliability.
underground facilities which are not significantly more difficult
to maintain than surface plants.Isolation of underground instal-
lations from both penstock water and from tailrace water is a vi-
tally important factor.Downstream water conduits with manifolds
require draft tube isolating devices of appropriate design.
Drainage and dewatering facilities must be highly reliable and of
adequate capacity.
There will be situations where a decision must be made as to
whether to carry out maintenance and repair work on components un-
derground or on the surface.Many items are 1arge and heavy and
therefore are best handl ed by the powerhouse crane.Suffi cient
erection bay space and laydown area between the generating units
are provided for all normal maintenance and overhaul needs.
Transformers wi 11 be moved withi n the access tunnel andtransfor-
mer gallery by means of wheels mounted on the transformer base.
The greatest demand in laydown space within the powerhouse cavern
is likely to occur during the initial equipment installation pro-
cess and the 10 to 15 year major disassembly/maintenance proce-
dure.The working area will be sized to allow the simultaneous
placing of turbine and generator components.
(c)Major Overall Activities
The major activities which require special space and handling con-
siderations in the plants include:
- Replacing generator stator winding coils;
- Rotor inspection;
-Replacement of thrust-bearing assemblies;
-Replacement of runner seals;
-Cavitation damage repair to runner;
- Repair and refinishing of waterpassage steel and concrete sur-
faces;
- Generator circuit breaker repair;and
- Transformer maintenance.
(d)Maintenance Workshops
The Watana and Devi 1 Canyon power pl ants are each provided with
workshops to faci 1Hate the normal mai ntenance needs of each
plant.The workshop block includes operations for fitting and
macht nt nq, welding,electrical,and relay instrumentation,with
adequate stores for tools and spare parts.The Watana power plant
will be provided additionally with surface maintenance and central
storage facilities to cater to the needs of both plants.
Maintenance operation plannings of both plants are centralized at
Watana.Staff will be normally located at Watana and housed at
the operqtors village at Watana.With centralized control of the
15-15
Susitna project located at Watana,the Devil Canyon plant will not
have a resident operating and maintenance staff.Proper road and
transport facilities should be maintained between Watana and Devil
Canyon to facil itate movement of personnel and/or equipment be-
tween the plants.
15-
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LIST OF REFERENCES
1.U.S.Department of Energy, Federal Energy Regulatory Commission,
Hydroelectric Power Evaluation,DOE/FERC-0031,August 1979.
r )
11
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TABLE 15.1:ENERGY POTENTIAL OF WATANA -DEVIL CANYON DEVELOPMENTS
FOR DIFFERENT RESERVOIR OPERATING RULES
ENE R G Y POT E N T I A L GWH
WA TAN A U N L WA TAN A &D E V I C A N YON
tlt M t.Nt.HlY tor ~HliY t HM t.Nt.~iY t.Nt HliY
MONTH CASE A C D A C D A C D A C D
OCT 234 200 172 2B1 214 17B 437 399 334 511 422 346
NOV 270 235 201 34B 331 271 502 463 3BB 543 625 506
DEC 322 276 236 445 397 364 59B 547 45B B17 751 6B3
JAN 2B3 242 20B 3B3 357 325 590 4BO 403 715 677 61B
FEB 22B 202 173 31B 335 293 452 395 330 599 632 561
MAR 235 201 173 276 330 277 470 39B 335 532 629 536
APR 199 165 142 203 214 197 460 332 2BO 451 419 3B7
MAY 1BO 152 131 1BO 247 174 462 304 2B6 465 536 399
JUN 170 135 111 175 212 191 492 323 27B 478 4B5 460
JUL 1B2 209 345 25B 267 374 3B7 471 755 521 579 7B4
AUG 170 311 531 344 327 545 321 659 1095 59B 679 1095
SEP 15B 151 155 249 15B 166 293 326 390 463 346 395
•TOTAL 2632 2479 257B 3459 33B9 3354 5394 5099 5332 6793 67B1 676B
NOTE:Cases Band C were similar and only Case C was analyzed in detail.
TABLE 15.2:MINIMUM ACCEPTABLE FLOWS BELOW
WATANA DAM DURING RESERVOIR FILLING
MONTH MINIMUM ACCEPTABLE FLOW CFS
OCT 2050
NOV 900
DEC 900
JAN 900
FEB 900
MAR 900
APR 900
MAY 4000
JUN 4000
JUL 6000
AUG 6000
SEP 4600
)
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TABLE 15.3:TURBINE OPERATING CONDITIONS
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Maximum net head
Minimum net head
Design head
Rated head
Turbine flow at rated head
Turbine efficiency at design head
Turbine-generating rating at rated head
Watana Devil Canyon
728 feet 597 feet
576 feet 238 feet
680 feet 575 feet
680 feet 575 feet
3550 feet 3800 feet
91%9U~
181,500 kW 164,000 kW
i _i --'--!-::::"_-.-J
-./-...."-
I -,
/\
"-......V
FMAMJJASOND
MONTH
LOAD VARIATION
IN YEAR 2000
/
<,/
-,/
<,/-
I I I
500
100
o
800
900
1000
1100
'"<{
~400
300
200
~~700
~600
o..J
242016812
HOURS
SUMMER WEEKDAY
HOURLY LOAD VARIATIOti
4
/--....."'"-1/-,
J-,/......-.../
o o
100
90
o 80<{
0
..J 70
'"<{60
llJ
0.
...50
0
I-40
z
~30
a:
~20
10
242016812
HOURS
WINTER WEEKDAY
HOURLY LOAD VARIATION
4
o
o
100
90
o 80
<{3 70
~60
llJ
0.50u,
0
40I-
~30o
a:
llJ 200.
10
NOTE: PEAK MW DECEMBER 2000 AD =1084 MW NOTE: PEAK MW JULY 2000 AD =658 MW
TYPICAL LOAD VARIATION
IN ALASKA RAILBELT SYSTEM
FIGURE 15.1
r---',
L-._-......
15 I I I I I I I
1.11
RETURN PERIOD IN YEARS
1.25 2 5 10
.-,I
rt WATANA PLUS
DEVIL CANYON
100 1000
,--"I 1_
"r""""'t _
I II II I I
1 I
I,-WATANA ONLY
, I I I I I I I I LOWEST ANNUAL
_-+_--t-_-+_--t-__t---'==_.....I=::=:---t----+--JI---t---".-E'='N'-'-=ERGY SIMULATED
I I 1 1 I 1 1 1 1 'Ii I
II I1I11 1----+0--
r-I L I I I I I I FIRM ENERGY-,
I I ,___
, ,Tr-+--l-
I I I I
I I I
f FIRM ENERGY
""'"'I
i-I-_
LOWEST ANNUAL.:
ENERGY SIMULATED
99.8 99.99899959020304050607080
PERCENT EXCEEDENCE PROBABILITY
105_2 0.5 I 2
I I I I I I I!I 1 I I I I 1 I I I I I I I I !
0.01 0.05 0.1 C
FREQUENCY ANALYSIS OF
AVERAGE ANNUAL ENERGY FOR SUSITNA DEVELOPMENTS
FIGURE 15.2
I~~~m
!\
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I
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94 r---.,------.,.-----r-------,---------r-----.-----,
r
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90
i)
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86
1\~
I.)~
>-u
I 1 Z
i I w
(3 82IIi:i:u,w
11
78
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74
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II
100 300 500 700
PLANT OUTPUT (MW)
900 1100
Ll
i IiJ
WATANA-UNIT EFFICIENCY
(AT RATED HEAD)
FIGURE IJIII I
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11
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94
90
86
>-ozw
§82u,
u,w
78
74
I Ij\NIT ~~IT/LI..3 UNITS ~4 UNITS
V V .........~
(\1/V ~
!II
I I
100 200 300 400
PLANT OUTPUT (MW)
500 600
I 1
1.1
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DEVIL CANYON -UNIT EFFICIENCY
(AT RATED HEAD)
FIGURE IJ ~~I!~I
SUSITI~A F'ROJECT SI~ULmO/j :2000(f,ElI.LOAII):UATAIlII 6-170 Page
Hinir,ufii l.:ATflNh verses TIME lio:-:iruur.,Minin,ufu RESEF:V verses TIME Ha}:ilbuDI
1.0321Ef05 3.0339Et05 4.4711Ef05 1.1428Et06
TIME UATA:lA ::II GEtJKU EFF RESERV :.INSTAL KULOAO UATRES.
1;0~25E+01 6.4956Et05 ------------------------------+4-:-0000EtOO 1.6239Et05 9.1580£-01 6.0144Et05 -----t I.531 OEt06 9.2956Et05 4.2646Et05
~16 HRS,1.0667EfOI 6.8468Ef05 ----------------------~----t 4.0000E+00 1.7117Et05 9.0705£-01 5.6632£t05 -------+I.5310Et06 9.646BEt05 3.9129Et05
Cl I.070llEfOl 7:1935Et05 ------------------------------+5.0000EtOO 1.4387H05 9.1747E-Ol 5:3165Et05 -----+1.5310Et06 9.9935Et05 3.5656Et05...I _18__1.0750EtOI 7.0940£+05 -----------------------------------------t MOOOEtOO 1.7735Et05 8.9966E-Ol 5.4160E+05 ------t 1.5310Et06 9.8940Et05 3.6645Ef05<to:uw 1.0792EtOI 6.960BEt05 -----------------------------------------f MOOOE fOO 1.7152Et05 9.0661£-01 5.6492Et05 -------t 1.5310£+06 9.660BE+05 3.8971E+05-aJ ~0..:;;1.0833EtOI.0,6276£+05 ---------------------------------------f 4.0000EtOO 1.6569Et05 9.1455E-OI 5.8B24E+05 ---------+1.5310Et06 9.4276Ef05 4.I 29BEt05>-w1->1.0875E+01 6.3935£+05
_______________________________c ______+
4.0000E+00 I.5994Et05 9.1651£-01 6.1165Et05 -----"----+I.5310Et06 9.1935Et05 4.3634E+05
0 ~1.0917£+01 5,7272E+05 --------------------------------f 4.0000E+00 1.431BEt05 9.16BB£-01 6.7B28Et05 ----------------t 1.5310Ef06 B.5272Et05 5.0292E+05z
1.0950EtOI 5.0609[f05 ----------------------------f 3.0000EtOO 1.6B70E+05 9.1049E-OI 7.4491E+05 --------------------f 1.5310Et06 7.8609Et05 5.6951Et05241.1000EtOl 4.8959Ef05 I 3.0000EtOO 1.6320£+05 9.1560E-01 7.6141Et05 1 .1.5310£+06 7.6959Et05 5.B598Et05
OHRS,1.1042E+01 4.6429E+05 ------------------------f 3.0000E+00 1.5476Et05 9,1789£-01 7.B671E+05 ------------------------f 1.5310Et06 7.4429Et05 6.1123Et0521.1033£+01 4.3900Et05 -----------------------f 3.0000EtOO 1.4633Et05 9.1944£-01 8.1200Et05 -------------------------t 1.5310£+06 7.1900£+05 6.3649E f05
1.1125EtOI 4.I38IEf05 ---------------------t 3.0000EtOO 1.3794Et05 9.l258E-01 B.3719Et05 ----------------------------t 1.5310£+06 6.9381E+05 6.6165Et05_4__
1.1167£+01 4,3549£+05 -----------------------+3.0000E+00 1.4516Ef05 9.1847£-01 8.1551Et05 .--------------------------+1.5310Et06 7.1549£+05 6.3994E+05,
1.120BEfOl 4.5717£+05 -------------------------f 3.0000EtOO 1.5239Et05 9.1854£-01 7.9383£+05 --------------------t 1.5310Et06 7.3717Et05 6.IB22Et05_6__1.1250£+01 4.7397E+05 --------------------------f 3.0000EtOO 1.5966Et05 9.1657£-01 7.7203Et05 ..;----------------------+1.5310Et06 7.5B97Et05 5.9638Ef05
1.1292EtOl 5,5847£+05 --------------------------------f 4.0000HOO 1.3962E+05 9.1393E-OI 6.9253Et05 ----------------f 1.5310Et06 8.3B47£+05 5.16B4Et058__
1.I 333EtOI 6.3796E+05 -------------------------------------f 4.0000HOO 1i5949Et05 9.1662£-01 ·6.1304Et05 -----------t 1.5310Et06 9.1796£+05 4.3730£+05
~1.1375EtOl 7.I72BEt05 ---------~---------------------------------t 5.0000£+00 I.4346Et05 9.1706£-01 5.3372[+05 ------+I.5310Ef06 9.9728Et05 3.5792Ef05
Cl 10 1.1417EtOl 7.1728Ef05 -------------------------------------------f 5.0000EtOO 1.4346£+05 9.1705E-Ol 5.3372Et05 ------+1.5310Et06 9.9728£+05 3.57B6£+05...I --
<t 0:1.1458EtOl 7.1728Et05 ------------------------------------------f 5.0000EfOO 1.4346E+05 9.1704£-01 5.3372£+05 -----t 1.5310£+06 9.9728£+05 3.57BOEf05UWNOON1.1500EtOl 7.1729El05 -------------------------------------------f 5.0000E+00 1.4346£+05 9.1704£-01 5.3371£+05 ------f 1.5310£t06 9.9729Et05 3.5773Et05-aJ0..:;;1.1542EfOI 7.2090E+05 ~------------------------------------------+5,0000£tOO 1.4418£+05 9,1762E-OI 5.3010Et05 -----+1.5310E+06 1.0009£+06 3.5405Et05>-wI-u _14__1.1533E+01 7,2451£~·O5 --------------------------------------------f 5,000mOo 1.4490Et05 9.1S20E-Ol 5.2649£+05 -----f '1.5310£+06 1.0045Etol>3,5038Et05uro1.1biSEfOl 7.2321Et05 --------------------------------------------f 5.0000EtOO I.4564£t05 9,1880£-01 5,2279£+05 -----t 1.5310£+06 I.00B2Et06 3.4662Et051_6__1.16/,7EfOI I.U30E105 -----------------------------------------------f 5.0000£fo<)1,5326E+05 9,1833E-Ol 4.B470£+05 --+I.5310Et06 1.0463E+06 3.0B47Et05
1.1708EtOl B.0389Et05 -------------------------------------------------+5.0000£+00 I.6078Ef05 9.1629£-01 4.4711Et05 t 1,5310Et06 1.0839Et06 2.708IE+051_8__1.1750[{01 7.9310Et05 -------------------------------------------------+5.0000EtOO I.5862£+05 9,1688£-01 4.5790Et05 t 1.5310Et06 1.0731Ef06 2.8153Et05
I.1792E+01 7,6781E+05 -----------------------------------------------f 5.0000£fOO 1.5356Et05 9.1826£-01 4.8319E+05 --f 1.5310Et06 1.047B£+06 3,0675Et05
20 LIB33E+01 7,~252[~O5 ----._----------------------------------------+5.0000Et00 1.4850Et05 9.1963E-01 5.0B4BEt05 ----+1.5310£+06 r'.0225Et06 3,319BEt05
1.1S7SaOl 7.l7Im05 -------------------------------------------f 5.0000EtOO 1.~342E+05 9.1695Hl 5.3389£+05 ------t 1.5310Et06 9.9711£+05 3.5732Ef05~1.l917E101 C.44CS[105 --------------------------------------1 4.0000£+00 1.6121Ef05 9.1619£-01 6.0615E+05 -----------+1.5310£+06 9.24B5Et05 4.2953Et05
24 HRS,
1.195BEtOl 5,725fJEtOS ---------------------------------t 4.0000£tOO 1.4315Et05 9.167IE-01 6.7B42Et05 ---------------+1.5310£+06 B.5258£+05 5.0174Et05
Ez<t z 0:::>ClzoO:I:<t-!;tu >-W W
!;t!;t ...Io:<t t.)>~...I~t-~t-:=0:wW z 0::=~:=...J
z~w ur ~:.:~z:=<t:=l1..0..z~o~(1)'::-<t:.:w:.:ui ->o~...I:.:0 0 (!>~i:L:t-0:>-Z t-:=c[~o..~->-o:~l1..Z :.:<t w<tl-<tl-ww :;;!:::::;;t-:;;~
z::>W z::>o Wt.)Wo w z6:
~:=aJ(I)~:=t-O:~lt ~lt t-Cl ~w:;;!::::_w (I)<t <t(l)~5 ::>z ~5 zo..>-<t >-<t >-0 :=~z::>::>~(l)t.)(l)t.)(1)..:.1
WATANA PLANT SIMULATION
DECEMBER 2000
FIGURE 15,5
fl
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16 -ESTIMATES OF COST
This section presents estimates of capital and operating costs for the
Susitna Hydroelectric Project,comprising the Watana and Devil Canyon
developments and associated transmission and access facilities.The
costs of design features and facilities incorporated into the project
to mitigate environmental impacts during construction and operation are
identified.A cash flow schedules,outlining capital requirements
during planning,construction,and start-up are presented.The
approach to the deriv~tion of the capital and operating costs estimates
is descri bed.
The total cost of the Watana and Devil Canyon projects is summarized in
Table 16.1.A more detailed breakdown of cost for each development is
presented in Tables 16.2 and 16.3.
16.1 -Construction Costs
This section describes the process used for deri·vation of cons~ruction
costs and discusses the Code of Accounts established,the basis for the
estimates and the various assumptions made in arriving at the esti-
mates. For general consistency with planning studies,all costs devel-
oped for the project are in January,1982 dollars.
(a)Code of Accounts
Estimates of construction costs were developed using the FERC for-
mat as outlined in the Federal Code of Regulations,Title 18 (1).
The estimates have been subdivided into the following main cost
groupings:
11
lJ
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Group
Production Plant
Transmission Plant
General Plant
16-1
Description
Costs for structures,equip-
ment,and facilities necessary
to produce power.
Costs for structures,equip-
ment,and facilities necessary
to transmit power from the
sites to load centers.
Costs for equipment and facili-
ties required for the operation
and mai ntenance of the produc-
tion and transmission plant.
(b)Approach to Cost Estlmatlng
The detalled schedule of account Hems is presented i n Appendix
C.
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Production Plant
Reservoir,Dam,and Waterways
Main Dam
Main Dam Structure
Excavation
Rock
Costs for englneering and
admlnlstratlon.
Costs that are common to a
number of construct 1on act 1vi-
t i es. For th i s estlmate only
camps and electric power costs
have been lncluded in this
group.Ot her 1nd i rect cost s
have been included in the
costs under product 1on,trans-
mission,and general plant
costs.
Descrlption
Determlnatlon of direct unlt costs for each major type of work
by development of labor,material,and equipment requlrements;
development of other costs by use of estlmating guides,quota-
tions from vendors,and other lnformatlon as approprlate;
The estlmating process used generally lncluded the following
steps:
Overhead Construction Costs
-Revi ew of engineeri ng drawl ngs and techni ca1 i nformatl on wi th
regard to construction methodology and feasibility;
- Productlon of detailed quantity takeoffs from drawings in accor-
dance wi th the prevlously developed Code of Accounts and Hem
listlng;
-Group:
-Account 332:
-Maln Structure 332.3:
-Element 332.31:
-Work Item 332.311:
-Type of Work:
-Collection and assembly of detailed cost data for labor,mater-
ial,and equipment as well as information on product i vi t y,cli-
matic cond i t lons,and other relatedri t ems;
Indi rect Costs
Further subdlvlslon Wlthin these groupings was made on the basis
of the various types of work involved,as t yp i cal Iy shown in the
following example:
Group
r~
I I.
i I
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11II
11I )
Development of construction indirect costs by review of labor,
material equipment,supporting facilities,and overheads;and
-Development of construct i on camp si ze and support requi rements
from the labor demand generated by the construction direct and
indirect costs.
The above steps are discussed in detail in the following:
(c) Cost Data
Cost information was obtained from standard estimating sources,
from sources in Alaska, from quotes by major equipment suppliers
and vendors,and from represent at ive recent hydroe 1ectr ic pro-
jects.Labor and equipment costs for 1982 were developed from a
number of sources (2,3)and from an analysi s of costs for recent
projects performed in the Alaska environment.
It has been assumed that contractors wi 11 work an average of two
9-hour shifts per day, 6 days per week,with an expected range as
fo 11 ows:
Mechanical/Electrical Work
Formwork/Concrete Work
Excavation/Fill Work
8-hour shifts
9-hour shifts
10-hour shifts
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These assumptions provide for high utilization of construction
equipment and reasonable levels of overtime earnings to attract
workers.The two-shift basis generally achieves the most
economical balance between labor and camp costs.
Construction equipment costs were obtained from vendors o~an FOB
Anchorage basis with an appropriate allowance included for trans-
portation to site.A representative list of construction equip-
ment requi red for the project was assembled as a basis for the
est imate.It has been assumed that most equipment would be fully
depreciated over the life of the project.For some activities
such as construction of the Watana main dam,an allowance for
major overhaul was included rather than fleet replacement.Equip-
ment operat i ng costs were est imated from ;ndustry source data,
wi th appropri ate mod ifi cat ions for the remote nature and extreme
climatic environment of the site.Fuel and oil prices have also
been included based upon FOB site prices.
Information for permanent mechanical and electrical equipment was
obt ained from vendors and manufacturers who provi ded guide 1ine
costs on major power plant equipment.
The costs of materials required for site construction were esti-
mated on the basis of suppliers·quotations,adjusted for Alaskan
conditions.
16-3
(d)Seasonal Influences on Productlvlty
A revlew of climat lc conditions,together with an ana lys i s of
experlence ln Alaska and in Northern Canada on large constructlon
projects was undertaken to determine the average duration for var-
i ous key act i v i t i es .It has been assumed for current study pur-
poses that most aboveground actlvltles wlll elther stop or be cur-
tal led dur i nq the per i od of December and January because of the
extreme cold weather and the assoclated lower product i v i ty.For
the main dam construction act lv i t i es ,the followlng assumptlons
have been used:
- Watana dam fill - 6-month season;and
-Devll Canyon arch dam - 8-month season.
Other aboveground actlvlties are assumed to extend up to 11 months
dependlng on the type of work and the crlticallty of the schedule.
Underground actlvities are generally not affected by climate and
should contlnue throughout the year.
Studies by others (4) have indicated a 60 percent or greater
decrease 1n effi c t ency 1n construct 1on operat ions under adverse
wl nter condit 1ons.Therefore,it is expected that most contrac-
tors would attempt to schedule outslde work over a perlod of be-
tween 6 to 10 months.
Studles performed as part of thls work program lndlcate that the
general constructlon act i v t ty at the Susitna damsite durlng the
months of Apri l through September would be comparable with that tn
the northern sect i ons of the western Un ited St ates.Rai nfa 11 1n
the general regi on of the site 1s moderate between mi d-Apri 1 and
ml d-Oc tober ranglng from a low of 0.75 Inches precipitatlon in
Apri l to a h i qh of 5.33 inches in August.Temperatures in t h i s
perlod range from 33°to 66°for a twenty-year average.In the
flve-month per i od from November through March,the temperature
ranges from 9.4°F to 20.3°F with snowfall of 10 lnches per month.
(e)Constructlon Methods
The constructlon methods assumed for development of the estlmate
and constructlon schedule,are generally consldered as "normal",
ln llne wlth the avallable level of technlcal information.A con-
servatlve approach has been taken ln those areas where more
detalled lnformatlon wlll be developed durlng subsequent investl-
gatlon and englneerlng programs.For example,normal dr i l l i nq,
bl ast i nq, and mucklng methods have been assumed for all under-
ground excavatlon.Also conventlonal equipment has been con-
s 1dered for major fi 11 and concrete work. Various construct 1on
methods were cons 1dered for several of the major work items to
determlne the most economlcally practlcal method. For example,a
comprehensive evaluatlon was made of the means of excavatlng
materl a 1 from Borrow SHe E and the downstream rlver for the
j
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(f)
Watana dam shells.A comparison of excavation by dragline,
dredge,backhoe,and scraper bucket methods was made,with consid-
eration given to the quantity of material available,distance from
the dam,and location in the river or adjacent terraces.
Quantity Takeoffs
11I ]
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Det ai 1ed quant i ty takeoffs were produced from the engi neeri ng
drawings using methods normal to the industry.The quantities
developed are those listed in the detailed summary estimates in
Appendix C.
(g)Indirect Construction Costs
Indirect construction costs were estimated in detail for the civil
construction activities.A more general evaluation was used for
the mechanical and electrical work.
Indirect costs included the following:
-Mobilization;
Technical and supervisory personnel above the level of trades
foremen;
- All vehicle costs for supervisory personnel;
- Fixed offices,mobile offices,workshops,storage facilities,
and laydown areas,including all services;
- General transportation for workmen on site and off site;
-Yard cranes and floats;
-Utilities including electrical power,heat,water,and com-
pressed air;
-Small tools;
-Safety program and equipment
-Financing;
-Bonds and securities;
-Insurance;
- Taxes;
-Permits;
-Head office overhead;
- Contingency allowance;and
-Profit.
In developing contractor's indirect costs,the following assump-
tions have been made:
-Mobilization costs have generally been spread over construction
items;
-No escalation allowances have been made,and therefore any risks
associated with escalation are not included;
16-5
- Financing of progress payments has been estimated for 45 days,
the average time between expenditure and reimbursement;
-Holdback would be limited to a nominal amount;
-Project all-risk insurance has been estimated as a contractor's
indirect cost for this estimate,but it is expected that this
insurance would be carried by the owner;and
Contract packaging would provide for the supply of major mater-
ials to contractors at site at cost.These include fuel,elec-
tric power,cement,and reinforcing steel.
16.2 -Mitigation Costs
As discussed in previous sections,the project arrangement includes a
number of features designed to mitigate potential impacts on the natur-
al environment and on residents and communities in the vicinity of the
project.In addition,a number of measures are planned during con-
struct i on of the project to mit i gate simi1ar impacts caused 'by con-
struction activities.The measures and facilities represent additional
costs to the project than would be normally required for safe and effi-
cient operation of a hydroelectric development.These mitigation costs
have been estimated at $149 million and have been summarized in Table
16.4.In addition,the costs of full reservoir clearing at both sites
has been estimated at $85 million.Although full clearl nq t i s con-
sidered good engineering practice,it is not essential to the operation
of the power facilities.These costs include direct and indirect
costs,engineering,administration,and contingencies\
A number of mitigation costs are associated with facilities,improve-
ments or other programs not directly related to the project or located
outside the project boundaries.These would include the following
items:
- Caribou barriers;
- Fish channels;
ish hatcheri es;
.-~St-l"eam-i·mpI"0vementst-.~-~~-~~_._~....._~_._-_..._._..
-Salt licks;
-Recreational facilities;
-Habitat management for moose;
Fish stocking program in reservoirs;and
-Land acquistion cost for recreation.
It is anticipated that some of these features or programs will not be
required during or after construction of the project.In this regard a
probabi 1ity factor has been assi gned to each of the above items,and
the estimated cost of each reduced accordingly.The estimated cost of
these measures, based on this procedure,is approximately $9 million.
These costs have been assumed to be covered by the construction contin-
gency.
..16-6
IJ
L]
A number of studi es and programs wi 11 be requi red to moni tor the
impacts of the project on the environment and to develop and record
various data during project construction and operation.These include'
the following:
-Archaeological studies;
-Fisheries and wildlife studies;
- Right-of-way studies;and
-Socioeconomic planning studies.
The costs for the above work have been estimated to be included in the
owner's costs under project overheads.
16.3 -Operation,Maintenance,and Replacement Costs
The facilities and procedures for operation and maintenance of the pro-
ject are described in Section 15.Assumptions for the size and extent
of these facilities have been conservatively made on the basis of
experience at large hydroelectric developments in northern climates,
noteably Canada.The annual cost s for operat ion,mai ntenance,and
interim repl acement for the Watana development have been est imated at
$10 million.When Devil Canyon is brought on line these costs increase
to $15.2 million per annum.
16.4 -Engineering and Administration Costs
Engineering has been subdivided into the following accounts for the
purposes of the cost estimates:
-Account 71
. Engineering and Project Management
Construction Management
.Procurement
-Account 76
Owner's Costs
The total cost of engineering and administrative activities has been
estimated at 12.5 percent of the total construction costs,including
conti ngenc i es.Th is is in general agreement with experi ence on pro-
jects similar in scope and complexity.A detailed breakdown of these
costs is dependent on the organizational structur-e established to
undertake design and management of the project,as well as more defini-
tive data relating to the scope and nature of the various project com-
ponents.However,the main elements of cost included are as follows:
(a) Engineering and Project Management Costs
These costs include allowances for:
16-7
-Fe as tbt l t ty stud i es,lncluding sl t e surveys and lnvestigations
and logistlcs support;
-Preparation of a llcense application to the FERC;
- Technlcal and admlnistratlve i nput for other federal,state and
local permit and license applicatlons;
- Overall coordlnation and administratlon of englneerlng,con-
structlon management,and procurement activitles;
- Overall plannlng,coordinatlon,and monltorlng activities
related to cost and schedule of the project;
-Coordlnation with and reportlng to the Power Authority regarding
all aspects of the project;
-Prellmlnary and detailed design;
Technlcal input to procurement of construction services,support
servlces,and equlpment;
- Monltoring of constructlon to ensure conformance to design
requirements;
-Preparatlon of start-up and acceptance test procedures;and
-Preparatlon of project operating and maintenance manuals.
(b)Construction Management Costs
Constructlon management costs have been assumed/to lnclude:
-Initlal plannlng and schedullng and establlshment of project
procedures and organlzatlon;
-Co ordi nat i on of ons i t e contractors and constructlon management
act 1vH 1es;
-Administratlon of onsite contractors to ensure harmony of
trades,comp l i ance wlth appllcable regylatlons,and maintenance
of adequate slte security and safety requirements;
-Development,coordinatlon,and monitorlng of constructlon
schedules;
-Constructlon cost control;
-Materlal,equlpment and drawing control;
-Inspectlon of constructlon and survey control;
-Measurement for payment;
-Start-up and acceptance test for equipment and systems;
- Compilation of as-constructed records;and
(c)Procurement Costs
Procurement costs have been assumed to include:
-Establlshment of project procurement procedures;
-Preparatlon 0+non-technical procurement documents;
-Sollcltatlon and revlew of bids for constructlon servlces,sup-
port services,permanent equlpment,and other items required to
complete the project;
- Cost admlnlstratlon and control for procurement contracts;and
-Quality assurance services durlng fabricatlon or manufacture of
equlpment and other purchased items.
16-8
1
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j
(d)Owner's Costs
Owner's costs have been assumed to include the following:
Administration and coordination of project management and
engineering organizations;
-Coordination with other state,local,and federal agencies and
groups having jurisdiction or interest in the project;
-Coordination with interested public groups and individuals;
- Reporting to legislature and the public on the progress of the
project;and
-Legal costs (Account 72).
16.5 -Allowance for Funds Used During Construction
At current high levels of interest rates in the financial market-place,
AFDC will amount to a significant element of financing cost for the
lengthy periods required for construction of the Watana and Devil Can-
yon projects.However,in economic evaluations of the Susitna project,
the low real rates of interest assumed would have a much reduced impact
on assumed project deve1opment costs.Furthermore, as discussed in
Section 18,direct state involvement in financing of the Susitna pro-
ject will also have a significant impact on the amount,if any, of
AFDC.For purposes of the current feas i bi1i ty study,therefore,the
conventional practice of calculating AFDC as a separate line item for
inclusion as part of project construction cost,has not been followed.
Provisions for AFDC at appropri ate rates of interest are made in the
economic and financial analyses described in Section 18.
16.6 -Escalation
As noted,all costs presented in this Section are at January,1982
levels,and consequently include no allowance for future cost escala-
tion.Thus,these costs would not be truly representative of construc-
tion and procurement bid prices.This is because provision must be
made in such bids for continuing escalation of costs,and the extent
and variation of escalation which might take place over the lengthy
construction periods involved.Economic and financial evaluations dis-
cussed in Section 18 take full account of such escalation at appropri-
ately assumed rates.
16.7 -Cash Flow and Manpower Loading Requirements
The cash flow requirements for construction of Watana and Devil Canyon
are an essential input to economic and financial planning studies dis-
cussed in Section 18.The basis for the cash flow are the construction
cost estimates in January,1982 dollars and the construction schedules
presented in Section 17,with no provision being made as such for esca-
lation.The cash flow estimates were computed on an annual basis and
do not include adjustments for advanced payments for mobilization or
for holdbacks on construction contracts.The results are presented in
Figures 16.1 through 16.3.The manpower loading requirements,which
16-9
are included in Appendix C, were developed from cash flow projections.
These curves were used as the basis for camp loading and associated
socioeconomic impact studies.
16.8 -Contingency
A contingency allowance of 17.5 percent of construction costs has been
inc 1uded in the cost est i mates.The cont i ngency is est imated to
include cost increases which may occur in the detailed engineering
phase of the project after more comprehensive site investigations and
final designs have been completed and after the requirements of various
concerned agenc i es have been accounted for.The cont i ngency est i mate
also includes allowances for inherent uncertainties in costs of labor,
equipment and materi als,and for unforeseen conditions which may be
encountered during construction.Escalation in costs due to inflation
is not included.No allowance has been included for costs associated
with significant delays in project implementation.
16=10
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LIST OF REFERENCES
1.Code of Federal Regulations,Title 18,Conservation of Power and
Water Resources,Parts 1 and 2,Washington,D.C.,Government
Printing Office,1981.
2.Alaska Agreements of Wages and Benefits for Constructi on Trades.
In effect January 1982.
3.Caterpill ar Performance Handbook,Caterpi 11 ar Tr actor Co.,Peori a,
Illinois,October 1981.
4.Roberts,William S.,Regionalized Feasibility Study of Cold Weather
Earthwork,Cold Regions Research and Engineering Laboratory,
July 1976,Special Report 76-2.
IlII( j
11
ij
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TABLE 16.1:SUMMARY OF COST ESTIMATE
January 1982 Dollars $ X 106
Category Watana Devil Canyon Total
Production Plant $1,986 $835 $2,821
Transmission Plant 391 91 482
General Plant 5 5 10
Indirect 378 188 566
Subtotal $2,760 $1,119 $3,879
Contingency 17.5~~482 196 678---
Total Construction $3,242 $1-+315 $4,557
Overhead Construction 405 165 570------
TOTAL PROJECT $3,647 $1,480 $5,127
P5700.00
P5700.14.09
OF __5
DATE _
DATE 2/82
JOB NUMBER
FILE NUMBER
SHEET----1
BY _
CHKD JRP
Feasibility
•JDL
TYPE OF ESTI MATE
APPROVED Bv ~~__
TABLE 16.2
WATANA
I
C-1IC-TnIA HYDROELECTRIC PROJECT
[
ALASKA POWER AUTHORITY
PROJECT JUJ,!,11m II
CLIENT
ESTIMATE SUM~ARY
•
No.DESCRIPTIONI
AMOUNT TOTALS REMARKS
(x 10 6)(x 106)
PRODUCTION PLANT
Land &Land Rights •••••••••••••••
Power plant Structures &Improvement~
$51
73
Reservoir,Dams &Waterways 1,532
33l
33~
Waterwheels,Turbines &Generators .1 •••••••••••••••••••••••••••••••••••
Accessory Electrical Equipment •••••~•••••••••••••••••••••••••••••••••••
Miscellaneous Powerplant Equipment (i1-":"':IIi:III.1.l:d.l.J •••••••••••••••••••••••
Roads &Railroads •••••••••••••••••••••••••••••••••••••••••••••••••••••
65
21
14
230
TOTAL PRODUCTION PLANT ••••••••••••$1,986
~'_-_._-
L--'L--L.-.L_-J
---
--~
DESCRIPTION
PROJECT ....u .....L "m
ESTIMATE SUMMARY
Bla
No.
CLIENT ALASKA POWER AUTHORITY
TABLE 16.2 I JOB NUMBER
P5700.00
WATANA FILE NUMBER P5700.14.09
TYPE OF ESTI MATE Feasibility-SHEET 2 OF -5
BY DATE
APPROVED BY JDL JRP 2/82CHKDDATE
AMOUNT TOTALS REMARKS
(x 10
6)(x 10 6 )
TOTAL TRANSMISSION PLANT ••••••••••••••••••••••••••••••••••.••••••••••••
359 I Roads &Trails ••••••••••••••••••••••••••••••••••••••••••••••••••••••••
354 I Steel Towers &Fixtures •••••••••••••••••••••••••••••••••••••••••••••••
353 I Substation &Switching Station Equipment ••••••••••••••••••••••••••••••
$1,986
I
$8
12
129
130
99
13
I
$391
.................................................TOTAL BROUGHT FORWARD
TRANSMISSION PLANT
356 I Overhead Conductors &Devices •••••••••••••••••••••••••••••••••••••••••
352 I Substation &Switching Station Structures &Improvements ••••••••••••••
350 I Land &Land Rights ••••••••••••••••••••••••••••••••••••••••••••••••••••
$2,377
P5700.00
P5700.14.09
OF __5
DATE __
DATE 2/82JRP
JOB NUMBER
FILE NUMBER ----'-..::....:....;:...;:
SHEET__3
BY _
CHKD
JDL
_FeasibilityTYPEOFESTIMATe'_--=--===='-'--
APPROVED Bv -=~__
WATANA
TABLE 16.2
AI ASKA POWEELllliIHOIUIY
_.._~~...HYDROELECTRIC PROJECTPROJECT:JIm!II~tI HIUrsLJt.Lt.LpU Frs >It.
CLIENT
ESTIMATE SUMMARY
I
IIII
No.DESCRIFJTION AMOUNT TOTALS REMARKS
(x 106 )(x 106 )
TOTAL BROUGHT FORWARD
INDIRECT COSTS
$2,382
61
62
63
64
65
66
Temporary Construction Facilities •
Construction Equipment
Camp &Commissary •••••••••••••••••
Labor Expense •••••••••••••••••••••
Superintendence •••••••••••••••••••
Insurance •••••••••••••••••_••••••••
$
378
See Note
See Note
See Note
See Note
69 Fees ••••••••••••••••••••••••••••••See Note
Note: Costs under accounts 61,62,164,65, 66, and 69
are included in the appropri~te direct costs
listed above.
TOTAL INDIRECT COSTS $378
$2,760
------.J
L-1--L _L.-J ~-~'l '....1 ...I ,---'
TABLE 16.2 JOB NUMBER
P5700.00ESTIMATESUMMARYWATANAFILENUMBERP5700.14.09
III CLIENT ALASKA POWER AUTHORITY TYPE OF ESTI MATE Feasibility SHEET 4 OF 5-
JDL BY DATE
PROJECT SUSITNA HYDROELECTRIC PROJECT APPROVED BY JRP 2/82CHKDDATE
No.DESCRIPTION AMOUNT TOTALS REMARKS
(x 10 6)(x 10
6)
71
72
75
76
77
80
TOTAL BROUGHT FORWARD (Construction Costs)••••••••••••••••••••••••••••
Contingency 17.5~~•••••••••••••••••••••••••••••••••••••••••••••••••••••
TOTAL CONSTRUCTION COSTS ••••••••••••••••••••••,•••••••••••••••,•••••••
OVERHEAD CONSTRUCTION COSTS (PROJECT INDIRECTS)
Engineering/Administration •••••••••••••••••••••••••••••••••••••••••••1 $
Legal Expenses ••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Taxes •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Administrative &General Expenses •••••••••••••••••••••••••••••••••••••
Interest ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Earnings/Expenses During Construction •••••••••••••••••••••••••••••••••
Total Overhead ••••••••••••••••••••••••••••••••••••••••••••••••••••••••
TOTAL PROJECT COST ••.•••••••••••.•..••••••••••••••••••••••••••••••••••
$2,760
482
$3,242
405
-I Included in 71
-Not applicable
-. .Included in 71
-. .Not included
-----J Not included
405
$3,647
ESTIMATE SUM~ARY P5700.00
P5700.14.09
OF __5
DATE _--:-__
DATE 2/82JRP
BY --::-:-_
CHKD
JOB NUMBER
FILE NUMBER _
SHEET ~
JDL
...FeasibilityTYPEOFESTIMATI:"_--"'''':'':''-=-':':'--<-'
APPROVED BY _
TABLE 16.2
WATANA
I
~IKTTNA HYDROELECJRIC PROJECT
ALASKA POWER AUTHbRITY
PROJECT -.,...
CLIENTiii]
No.DESCRI~TION AMOUNT TOTALS REMARKS
(x 106)(x 10
6 )
TOTAL BROUGHT FORWARD
GENERAL PLANT
$2,377
389
390
39,1
,
392
39'3
394
N5
Land &Land Rights
Structures &Improvements •••••••••
Office Furniture/Equipment ••••••••
Transportation Equipment ••••••••••
Stores Equipment ••••••••••••••••••
Tools Shop &Garage Equipment •••••
Laboratory Equipment ••••••••••••••i•••••• ••• ••• •• •••• •••••••••• •••••• ••
Power-Operated Equipment
Communications Equipment
Miscellaneous Equipment
$Included under 330
Included under 331
Included under 399
""
" "
""
II II
""
""
" "
other Tangible Property 5
TOTAL GENERAL PLANT •••••••••••••••$5
$2,382
----,
_1__
r-;
l-l-
r--
l-
,---,L __'_1___1__,I ;!;-'--".--i :i .I .]---,
----.J .I :=J ---.J
DATE ---
DATE 2/82
P5700.14.09
OF 2.
P5700.00
BY ------
CHKD JRP
JOB NUMBER
FILE NUMBER
SHEET 1Feasibility
,JDLAPPROVEDBv~~_
TABLE 16.3
DEVIL CANYON
TYPE OF ESTIMATE
CIICTT..n HYDROELECTRIC PROJECT
ALASKA POWER AUTHORITY
PROJECT ...u ......"m
CLIENT
ESTIMATE SUMMARY[Ii]
No.DESCRIPTION AMOUNT TOTALS REMARKS
(x 10 6)(x 10 6)
330
331
332
333
334
335
336
PRODUCTION PLANT
Land &Land Rights •••••••••••••••••••••••••••••••••••••••••••••••••••.1 $
Powerplant Structures &Improvements ••••••••••••••••••••••••••••••••••
Reservoir,Dams &Waterways •••••••••••••••••••••••••••••••••••••••••••
Waterwheels,Turbines &Generators ••••••••••••••••••••••••••••••••••••
Accessory Electrical Equipment ••••••••••••••••••••••••••••••••••••••••
Miscellaneous Powerplant Equipment (Mechanical)•••••••••••••••••••••••
Roads &Railroads •••••••••••••••.•••••••••••••••••••••••••••••••••••••
22
71
635
42
14
12
39
TOTAL PRODUCTION PLANT ••••••••.••••••••••••••••••••••••••••••••••••••••$835
P5700.00
P5700.14.09
OF __5
DATE _---,-_
DATE 2/82JRP
JOB NUMBER
FILE NUMBER _
SHEET__2
By _
CHKD
JDL
~Feasibility
APPROVED BY __PROJECT ----",..
I
ESTIMATE SUM~ARY
CLIENT ALASKA POWER AUT~ORITY
C:IIC:TTMLI HYDROELEOTRIC PROJECTIlllU
No.DESCRI~TION AMOUNT TOTALS REMARKS
TOTAL BROUGHT FORWARD
TRANSMISSION PLANT
(x 106 )(x 106)
$835
Land &Land Rights $Included in Watana Estimate
Substation &Switching Station Str~ctures &Improvements ••••••••••••••
Substation &Switching Station Equ~pment
Steel Towers &Fixtures ••••••••••
Overhead Conductors &Devices ••••
7
21
29
34
Roads &Trails •••••••••••••••••••Included in Watana Estimate
TOTAL TRANSMISSION PLANT •••••••••$91
$926
>_1_-'---
~'--I c:=J [-
I..--~L...-._1_-~~!_~___I •I ~-~!
392 I Transportation Equipment ••••••••••••••••••••••••••••••••••••••••••••••
390 I Structu~es &Improvements •••••••••••••••••••••••••••••••••••••••••••••
391 I Office Furniture/Equipment ••••••••••••••••••••••••••••••••••••••••••••
393 I Stores Equipment ••••••••••••••••••••••••••••••••••••••••••••••••••••••
394 I Tools Shop &Garage Equipment ••.••••••••••••••••••••••••••••••••••••••
395 I Laboratory Equipment ••••••••••••••••••••••••••••••••••••••••••••••••••
Other Tangible Property •••••••••••••••••••••••••••••••••••••••••••••••
JOB NUMBER
P5700.00
FILE NUMBER P5700.14.09
Feas.i.bi.Lit v _I SHEET 3 OF -5
BY DATE
'1"'11 2/82CHKDJRPDATE
TOTALS
1
REMARKS
(x 10
6)
$926
I
Included under 330
Included under 331
Included under 399
""
""
""
""
""
" "
""
5
A PPROVED BY uv~
(x 106)
AMOUNT
$
TABLE 16.3
DEVIL CANYON
TYPE OF ESTI MATE ._
(','('Tn,.HYDROELECTRIC PROJECT
ALASKA POWER AUTHORITY
PROJECT ;;JU;;JJ.I "M I
DESCRIPTION
CLIENT
ESTIMATE SUMMARY
Miscellaneous Equipment
Communications Equipment
Land &Land Rights
Power Operated Equipment
TOTAL BROUGHT FORWARD
GENERAL PLANT
396
397
398
399
AlIa
No.
389
TOTAL GENERAL PLANT ••••••••••••••••••••••••.••••••••••••••••••••••••••$5
$931
Temporary Construction Facilities .i ••••••••••••••••••••••••••••••••••••
JOB NUMBER P5700.00
FILE NUMBER P5700.14.09
Feas Ibi l Lt v _I SHEET 4 OF 5-
lnl BY DATE
CHKD JRP DATE 2/82
TOTALS I REMARKS--
(x 10 6)
$931
I
See Note
See Note
$
AMOUNT
(x 10 6 )
APPROVED BY ---
TABLE 16.3
DEVIL CANYON
TYPE OF ESTIMATE .-----
CIICTT.,A HYDROELEOTRIC PROJECTPROJECT-.JU-.JJ.'''''
DESCRIIFION
I
ESTIMATE SUMIYIARY
I
i
CLIENT ALASKA POWER AUTHORITY
Construction Equipment
TOTAL BROUGHT FORWARD
INDIRECT COSTS
No.
1110
6
6,
Camp &Commissary •••••••••••••••••'••••••••••••••••••••••••••••••••••••188
Labor Expense •••••••••••••••••••••i ••••••••••••••••••••••••••••••••••••See Note
6~
6f
6~
Super intendence •••••••••••••••••••'••••••••••••••••••••••••••••••••••••
Insurance •••••••••••••••••••••••••1 ••••••••••••••••••••••••••••••••••••
Fees ••••••••••••••••••••••••••••'••••••••••••••••••••••••••••••••••••••
See Note
See Note
See Note
Note:Costs under accounts 61,62,'64,65,66,and 69
are included in the appropriate direct costs
listed above.
TOTAL INDIRECT COSTS •••••••••••••$188
$1,119
'---'-'-'-'
I .
~L.--.-J
--~.:'__..J
--~,.--~,
'_.~.J
DATE ---
DATE 2/82
P5700.00
P5700.14.09
OF 2.
JOB NUMBER
FILE NUMBER ---'--"-'-'--
SHEET 2.
BY -----
CHKD JRP
Feasibility
.JDLAPPROVEDBv-=~_
TABLE 16.3
DEVIL CANYON
TYPE OF ESTI MATEALASKAPOWERAUTHORITY
_.._~~...HYDROELECTRIC PROJECTPROJECTJlJJl!!VI nwn
CLIENT
ESTIMATE SUMMARY
•
No.DESCRIPTION AMOUNT TOTALS REMARKS
(x 10
6 )(x 10 6)
71
72
75
76
77
80
TOTAL BROUGHT FORWARD (Construction Costs)••••••••••••••••••••••••••••
Contingency 17.5%•••••••••••••••••••••••••••••••••••••••••••••••••••••
TOTAL CONSTRUCTION COSTS ••••••••••••••••••••••••••••••••••••••••••••••
OVERHEAD CONSTRUCTION COSTS (PROJECT INDIRECTS)
Engineering ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Legal Expenses •••••••••••••••••••••••••••••••••••••••••••••••••••••••
Taxes ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Administrative &General Expenses ••••••••••••••••••••••••••••••••••••
Interest .
Earnings/Expenses During Construction ••••••••••••••••••••••••••••••••
Total Overhead Costs •••••••••••••••••••••••••••••••••••••••••••••••••
TOTAL PROJECT COST •••••••••••••••••••••••••••••••••••••••••••••••••••
$1,119
196
1,315
$165
-I Included in 71
-Not Applicable
-. .Included in 71
-Not Included
-----J Not Included
165
$1,480
TABLE 16.4:MITIGATION MEASURES -SUMMARY OF COSTS INCORPORATED
IN CONSTRUCTION COST ESTIMATES
, 1
COSTS INCORPORATED IN CONSTRUCTION ESTIMATES
Outlet Facilities
Main Dam at Devil Canyon
Tunnel Spillway at Watana
Restoration of Borrow Area D
Restoration of Borrow Area F
Restoration of Camp and Village
Restoration of Construction Sites
Fencing around Camp
Fencing around Garbage Disposal Area
Multilevel Intake Structure
Camp Facilities Associated with trying
to Keep Workers out of Local Communities
Restoration of Haul Roads
SUBTOTAL
Contingency 17.5%
TOTAL CONSTRUCTION
Engineering 12.5%
TOTAL PROJECT
WATAN~
$X 10
47,050
1,617
551
2,260
4,050
350
125
18,400
10,156
756
85,315
14,930
100,245
12,530
112,775
DEVIL C~NYON
lLlQ._-
14,610
NA
NA
990
2,016
217
125
NA
9,000
505
27,463
4,806
32,269
4,034
36,303 149,078
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WATANA DEVELOPMENT
CUMULATIVE AND ANNUAL CASH FLOW
JANUARY,1982 DOLLARS
19B2 19B3 19B4 19B5 19B6 19B7 19BB 19B9
YEARS
1990 1991 f992 1993 1994 f995 1996 1997
FIGURE, 16.•
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YEARS
SUSITNA HYDROELECTRIC PROJECT
CUMULATIVE a ANNUAL CASH FLOW ENTIRE PROJECT
JANUARY t 1982 DOLLARS
FIGURE 16.3
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17 -DEVELOPMENT SCHEDULES
This section describes the development schedules prepared for both
Watana and Devil Canyon to meet the on-line power requirements of 1993
and 2002,respectively.These schedules span the period from 1983
unti 1 2004.Schedules for the development of both Watana and Devi 1
Canyon are shown on Plates 75 and 76.The main elements of the project
have been shown on these schedules,as well as some key interrelation-
ships.
17.1 -Preparation of Schedules
Preliminary schedules were first developed by estimating the durations
of the main construction activities and arranging these in logical se-
quence.Some activity adjustments were then made to reduce excessive
demands on resources,such as underground excavation or concrete plac-
ing.The preliminary schedules were then used as a basis for the prep-
aration of cost estimates.The schedules were also reviewed for over-
all compatability with major constraints such as licensing,on-line
power requirements,and reservoir filling.
At both sites it became apparent that the period for construction of
the main dam would be critical and that other activities should be
fitted to the main dam work.A study was made of the front end
requirements at Watana,and it was concluded that a pioneer road would
have to be completed before 1985 to permit a sufficiently rapid build-
up of manpower and equipment after licensing to meet the construction
requirements for the main dam.
During development of the final project arrangement and preparation of
the cost estimates (Section 16),the preliminary schedules were modi-
fied and refined.As estimating data were developed, the production
rates and construction durations were calculated.Networks were
developed for the main construction activities and the durations and
sequences of activities determined.The overall schedules were
modified to suit.
17.2 -Watana Schedul e
The Watana schedules were developed to meet two overall project con-
strai nts:
-FERC license would be issued by December 31, 1984;and
- Four units would be on-line by the end of 1993.
The critical path of activities to meet the overall constraints was
determined to be through site access,site facilities,diversion and
main dam construction.These are highlighted as follows:
17-1
(i)Access
Road access to slte is requlred by January 1, 1985. A ploneer
road from Gold Creek lS requlred to moblllze labor,equipment,
and materlals ln the flrst part of 1985 for the following major
constructlon activities:
-Main access road/rallhead;
-Slte facilitles;
-Diversion;and
-Mal n dam.
(il)Slte Facllltles
Slte facilltles must be developed ln a very short time to sup-
port the ma in constructlon activities.A camp to house more
than 1,000 men must be constructed during the flrst year.Site
constructlon roads and contractors'work area have to be start-
ed.An aggregate processlng plant and concrete batching plant
must be operatlonal to start diversion tunnel concrete work by
January 1986.Constructlon power supply must also be started'ln
1985 for completlon by mld-1987.One clrcult of the permanent
transmission line should be built from the proposed intertle at
Gold Creek to Watana.
(ill)Diversion
Construction of diverslon and dewaterlng faclllties,the first
major act ivi t y,should start by mLd-1985.Excavation of the
portals and tunnels requlres a concentrated effort to allow
completion of the lower tunnel for river ~iverslon by August
1986.The upper tunnel i s needed to handle the spring runoff
by 1987.The upstream cofferdam must be placed to divert
rlverflows i n August 1986 and raised sufflclently to avoid
overtopping by the followlng sprlng.
(iv)Maln Dam
····Theprogress of work -in the main dam is er-l-t-l-e a1 throughout··the
peri od 1986 through 1992.Mobil izat 1on of equi pment and start
of site work must begln in 1985. Excavatlon on the right abut-
ment proceeds ln 1986, as well as rlver alluvium under the dam
core.During 1987 and 1988,dewatering,excavatlon and founda-
t i on treatment must be completed i n the riverbed area and a
substantlal start made on placlng f i ll,The construction
schedule lS based on the followlng program:
17-2
[J
Acc umu 1ated
Quant itt¥Quantity
Year (cy x 10 ) (cy x 10
6)
1987 3
1988 6 9
1989 12 21
1990 13 34
1991 13 47
1992 12 59
1993 3 62
Fi 11
Elevation
October 15
(feet)
1660
1810
1950
2130
2210
Reservoir
Elevation
(feet)
1460
1865
2050
2185
f]
\
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(v)
The program for fill placing has been based on an average six
months season.It has been developed to provide high utiliza-
tion of construction equipment required to handle and process
fill materia 1s.
Spillways and Intakes
These structures have been scheduled for completion one season
in advance of the requirement to handle flows.In general,
excavation for these structures does not have to begin until
most of the excavation work has been completed for the main
dam.
(vi)Powerhouse and Other Underground Works
The first four units are scheduled to be on line by late 1993
and the remaining two units in early 1994. Excavation of the
access tunnel into the powerhouse complex has been scheduled to
start in 1987. Stage I concrete begins in 1989 wi th start of
installation of major mechanical and electrical work in 1991.
In general,the underground works have been scheduled to level
resource demands as much .as possible.
r IU
(vi 1)Transmission Lines/Switchyards
An initial line from Gold Creek is scheduled for completion by
mi d-1987.Construct i on of the remai n i ng 1i nes has been sched-
uled to begin in 1989 and be completed before commissioning of
the fi rst uni t.
(J
i 1I'U
(vi i 1)General
The Watana schedule requires that extensive planning,bid sel-
ection and commitments are made before the end of 1984 to per-
mit work to progress on schedule during 1985 and 1986.The
rapid development of site activities requires commitments par-
ticularly in the areas of access and site facilities in order
that construction operations have the needed support.
17-3
17-4
Excavation of access into the powerhouse cavern is scheduled to
begin in 1996. Stage I concrete begins in 1998 with start of
installation of major mechanical and electrical work in 2000.
The spillway and intake are scheduled for completion by the end
of 2000 to permit reservoir filling the next year.
(vi)Powerhouse and Other Underground Works
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schedule was developed to meet the on-line power
four units in 2002.The critical path of activities
follow through site facilities,diversion and mai n
It has been planned that site facilities should
the main construction activities starting in 1995.
Arch Dam
Spillways and Intake
Excavation and concreting of the single diversion tunnel should
begin in 1995. River closure and cofferdam construction will
take place to permit start of dam construction in 1997.
The construction of the arch dam will be the most critical con-
struction activity from start of excavation in 1996 until top-
pi ng out in 2001.The concrete prograrrihas been based on an
"average 8=m6nlhpl at ings-eason-fm"---4-;;;112~ye-ar"s-=~-rh-e-workhas
been scheduled to maintain a fairly constant effort during this
period to make best use of equipment and manpower.
(v)
(i v)
It has been assumed that site access facilities built for
Watana exist at the start of construction.The bridge crossing
upstream of Devil Canyon will be replaced by a temporary cross-
ing downstream when reservoir impoundment takes place,and will
finally be across the completed dam.
(ii)Site Facilities
Camp facilities should be started in 1994.It has been assumed
that buildings can be salvaged from Watana.Site roads and
power could also be started at this time.
(ft t)Diversion
(i)Access
The Devi 1 Canyon
requirement of all
was determi ned to
dam construction.
start in 1994 with
The schedule has also been developed to take advantage of pos-
sible early reservoir filling to the minimum operating level by
October 1992.Should this occur,power could possibly be
generated by the end of 1992.
17.3 - Devil Canyon Schedule
(1
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(vii)Transmission Lines/Switchyards
The additional transmission facilities needed for Devil Canyon
have been scheduled for completion by the time the final unit
is ready for commissioning in late 2001.
(vi i i )General
The development of site facilities at Devil Canyon begins slow-
ly in 1994 with a rapid acceleration in 1995 through 1997.
Within a short period of time,construction begins on most
major civil structures.This rapid development is dependent on
the provision of support site facilities which should be com-
pleted in advance of the main construction work.
17-5
II
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18 -ECONOMIC,MARKETING AND FINANCIAL EVALUATION
18.1 -Economic Evaluation
This section provides a discussion of the key economic parameters used
in the study and develops the net economic benefits stemming from the
Susitna Hydroelectric Project.Section 18.1 (a)deals with those eco-
nomic principles relevant to the analysis of net economic benefits and
develops inflation and discount rates and the Alaskan opportunity val-
ues (shadow prices)of oil,natural gas and coal.In particular the
analysis is focused on the longer-term prospects for coal markets and
prices.This follows from the evaluation that in the absence of
Susitna,the next best thermal generation plan would rely on exploita-
tion of Alaskan coal.The future coal price is therefore considered in
detail to provide rigorous estimates of prices in the most likely al-
ternative markets and hence the market price of coal at the mine-head
within the state.
Section 18.1 (c)presents the net economic benefits of the proposed
hydroelectric power investments compared with this thermal alternative.
These are measured in terms of present valued differences between bene-
fits and costs.Recognizing that even the most careful estimates will
be surrounded by a degree of uncertainty,the benefit-cost assessments
are also carried out in a probabil istic framework as shown in Section
18.2.The analysis therefore provides both a most likely estimate of
net economic benefits accruing to the state and a range of net economic
benefits that can be expected with a 1ikel ihood (confidence level)of
95 percent or more.
(a)Economic Principles and Parameters
I )
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( i )tconomic Principles -Concept of Net Economic Benefits
A necessary condition for maximizing the increase in state
income and economic growth is the selection of public or
private investments with the highest present val ued net
benefits to the state.In the context of Al askan electric
power investments,the net benefits are defined as the dif-
ference between the costs of optimal Susitna-inclusive and
Susitna-exclusive (all thermal)generation plans.
The energy costs of power generation are initially measured
in terms of opportunity values or shadow prices which may
differ from accounting or market prices currently prevail-
ing in the state.The concept and use of opportunity val-
ues is fundamental to the opt imal allocat ion of scarce re-
sources.Energy investment decisions should not be made
solely on the basis of accounting prices in the state if
the internat iona1 value of traded energy commod it ies such
as coal and gas diverge from local market prices.
18-1
The choice of a time horizon is also crucial.If a short-
term planning period is selected,the investment rankings
and choices will differ markedly from those obtained
through a long-term perspective.In other words,the
benet i t-co st analysis would point to different generation
expansion plans depending on the selected planning period.
A short-run optimization of state income WOuld,at best,
allow only a moderate growth in fixed capital investment;
at worst,it would lead to under investment in not only the
energy sector but also in other infrastructure facilities
such as roads,airports,hospitals,schools,and communica-
tions.
It therefore follows that the Sus itna Project,as other
Alaskan investments,should be appraised on the basis of
long-run optimization,where the long-run is defined as the
expected economic 1 ife of the facil ity.For hydroelectric
projects,this service life is typically 50 years or more.
The costs of a Susitna-inclusive generation plan have
therefore been compared with the costs of the next-best al-
ternative which is the all-thermal generation plan -and
assessed over a pl anning period extending from 1982 to
2040,using internally consistent sets of economic scenar-
ios and appropriate opportunity values of Alaskan energy.
Throughout the analysis,all costs and prices are expressed
in real (inflation-adjusted)terms using January 19~2 dol-
l ars. Hence,the results of the economic calc;ul ations are
not sensitive to modified assumptions.concerning the rates
of general price inflation.In contrast,the financial and
market analyses,conducted in nominal (inflation-inclusive)
terms,will be influenced by the rate of general price in-
flation from 1982 to 2051.
(ii)Price Inflation and Discount Rates
General Price Inflation
Despite the fact that price levels are generally higher
in Alaska than in the Lower 48,there is little differ-
ence in the comparative rates 'of price changes;i.e.,
price inflation.Between 1970 and 1978,for example,the
U.S. and Anchorage consumer price indexes rose at annual
rates of 6.9 and 7.1 percent,respectively.From 1977 to
1978,the differential was even smaller:the consumer
pr ices increased by 8.8 percent and 8.7 percent in the
U.S.and Anchorage (1).
Forecasts of Al askan prices extend only to 1986 (2).
These indicates an average rate of intrease of 8.7 per-
cent from 1980 to 1986.For the longer period between
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1986 and 2010,it is assumed that Al askan prices wi 11 es-
calate at the overall U.S.rate,or at 5 to 7 percent
compounded annually.The average annual rate of price
i nfl at ion is therefore about 7 percent between 191)2 and
2010.As this ..is consistent with long-term forecasts of
the CPI advanced by leading economic consulting organiza-
t ions,7 percent has been adopted as the study val ue
(3,4).
-Discount Rates
Discount rates are required to compare and aggregate cash
flows occurring in different time periods of the planning
horizon.In essence,the discount rate is a weighting
factor reflecting that a dollar received tomorrow is
worth less than,a doll ar received today.This holds even
in an inflation-free economy as long as the productivity
of capital is positive.In other words,the value of a
dollar received in the future must be deflated to reflect
its earn ing power foregone by not receiv inq it today.
The use of discount rate's extends to both real dollar
(economic)and escalated dollar (financial)evaluations,
with corresponding inflation-adjusted (real)and
inflation-inclusive (nominal)values.
Real Discount and Interest Rates
Severa 1 approaches have been suggested for est imat ing
the real discount rate appl icable to publ ic projects
(or to private projects from the publ ic perspective).
Three common alternatives include:.
the social opportunity cost (SOC)rate;
the social time preference (STP)rate;and
the government's real borrowing rate or the real
cost of debt capital (5,6,7).
The SOC rate measures the real social return (before
taxes and subsidies)that capital funds could earn in
alternative investments.If,for example,the marginal
capital investment in Alaska has an estimated social
yield of X percent,the Susitna Hydroelectric Project
should be appraised using the X percent measure of
"foregone returns"or opportunity costs.A shortcoming
for this concept is the difficulty inherent in deter-
mining the nature and yeilds of the foregone invest-
ments.
The STP rate measures society's preferences for allo-
cating resources between investment and consumption.
This approach is also fraught with practical measure-
ment difficulties since a wide range of STP rates may
18-3
be inferred from market interest rates and socially-
desirable rates of investment.
A sub-set of STP rates used in project evaluations is
the owner's real cost of borrowing;that is,the real
cost of debt capital.This industrial or government
borrowing rate may be read i ly measured and provides a
starting point for determining project-specific dis-
count rates.For example,long-term industrial bond
rates have averaged about 2 to 3 percent in the U.S.in
real (inflation-adjusted)terms (3,8).Forecasts of
real interest rates show average values of about 3 per-
cent and 2 percent in the periods of 1985 to 1990 and
1990 to 2000,respectively.The U.S.Nuclear Regula-
tory Commission has also analyzed the choice of dis-
count rates for investment appraisal in the electric
ut i 1 ity industry and has recommended a 3 percent real
rate (24).Therefore,a real rate of 3 percent has been
adopted as the base case discount and interest rate for
the period 1982 to 2040.
Nominal Discount and Interest Rates
The nominal discount and interest rates are derived
from the real values and the anticipated rate of gen-
eral price inflation.Given a 3 percent real discount
rate and a 7 percent rate of price inflation,the nomi-
nal discount rate is determined as 10.2 percent or
about 10 percent*.
(i i i)0 il and Gas Prices
-Oil Prices
In the base period (January 1982),the Al askan 1982
dollar price of No.2 fuel oil is estimated at $6.50/
MMBtu.
Long-term trends in oil prices will be infl uenced by
events that are economic,pol itical and technological in
nature,and are therefore estimated within a probabil is-
tic fr amework.
As shown in Table 18.1,the base case (most 1ikely es-
calation rate)is estimated to be 2 percent to 2000'and 1
percent from 2000 to 2040.To be consistent with
* (1 +the nominal rate)=(1 +the real rate)x (1 +the inflation
rate)=1.03 x 1.07,or 1.102
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Battelle forecasts,a 2 percent rate was used throughout
the OGP planning period 1982 to 2010 and 0 percent there-
after.In the low and high scenarios the growth rates
were estimated at 0 percent from 1982-2051,and at 4 per-
cent to 2000, and 2 percent beyond 2000,respectively.
These projections are also consistent with those recently
advanced by such organizations as ORI (9),World Hank
(LO}, U.S.DOE (LL),and Canadian National Energy Bo aro
(l2).
- Gas Prices
Al askan gas prices have been forecast using both export
opportunity values (netting back elF prices from Japan to
Cook Inlet)and domestic market prices as likely to be
faced in the future by Alaskan electric utilities.The
OGP analysis used market prices as estimated by tlattelle,
since there are indications that Cook Inlet reserves may
remain insufficient to serve new export markets.
Uomestic Market Prices
Table 18.2 depicts the low,medium and high domestic
market prices used in the OGP5 analysis.In the medium
(most likely)case,prices escalate at real rates of
2.5 percent from 1982 to 200U and 2 percent beyond
2000. In the low case,there is zero escalation and in
the high case,gas prices grow at 4 percent 1982 to
2000 and 2 percent beyond 2000.
.Export Opportunity Values
Table 18.2 also shows the current and projected oppor-
tunity value of Cook Inlet gas in a scenario where the
Japanese export market for LNG continues to be the al-
ternative to domestic demand.From a base period plant
gate price of $4.69 MMBtu (CIF Japan),low,medium and
high price escalation rates have been estimated for the
interval s 1982 to 2000 and 2000 to 2040.The cost of
1 iquefaction and shipping (assumed to be constant in
real terms)was subtracted from the escalated CIF
prices to derive the Cook Inlet plant-gate prices and
their growth rates.These Alaskan opportunity values
are proj ected to esc alate at 2.7 percent and 1.2 per-
cent in the medium (most likely)case.Note that the
export opportunity values consistently exceed the
domestic prices.In the year 2000,for example,the
opportunity value is nearly double the domestic price
estimated by tlattelle.
18-5
(iv)Coal Prices
The shadow price or opportunity value of Beluga and Healy
coal is the delivered price in alternative markets less the
cost of transportation to those markets.The most likely
alternative demand for thermal coal is the East Asian
market,principally Japan,South Korea,and Taiwan.The
development of 60-year forecasts of coal prices in these
markets is conditional on the procurement po l tc ies i of the
importing nations.These factors,in turn,are influenced
to a large extent by the price movements of crude oil.
-Historical Trends
Examination of historical coal price trends reveals that
FOB and CIF prices have escalated at annual real rates of
1.5 percent to 6.3 percent as shown below:
.Coal prices (bituminous,export unit value,FOB U.S.
ports)grew at real annual rates of 1.5 percent (1950
to 1979)and 2.8 percent (1972 to 1979)(11).
In Alaska, the price of thermal coal sold to the GVEA
utility advanced at real rates of 2.2 percent (1965 to
1978)and 2.3 percent (1970 to 1978).
In Japan, the average CIF prices of steam coal experi-
enced real escalation rates of 6.3 percent per year in
the period 1977 to 1981 (20,21).TlifiS represents an
increase in the average price from approximately $35.22
per metric ton (mt)in 1977 to about $76.63/mt in 1981.
As shown below, export prices of coal are highly correl-
ated with oil prices,and an analysis of production costs
has not predicted accurately the level of coal prices.
Even if the production cost forecast itself is accurate,
it wi 11 estab 1ish a min imum coal pr ice,rather than the
..mar-.ketcleadng--.:pl"ice set.b",-both-suppJ~..and~.demand con,.,
ditions.
In real terms export prices of U.S. coal showed a 94
percent and 92 percent correlation with oil prices
(1950 to 1979 and 1972 to 1979).*
. Supply function (production cost)analysis,has esti-
mated Canadian coal at a price of $23.70 (1980 U.S.
* Analysis is based on data from the World Bank.
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$/ton)for S.E.British Columbia (B.C.)coking coal,
FOB Roberts Bank,B.C.,Canada (18,23).In fact,
Kaiser Resources (now B.C.Coal Ltd.)has signed agree-
ments with .Japan at an FOB Price of about $47.5u (198U
U.S.$/ton)(19).This is 1UO percent more than the
price estimate based on production costs.
The same comparison for Canadian B.C.thermal coal in-
dicates that the expected price of $5ti.OU (19~1
Canadian ~)per MT (2200 pounds) or about $37.0U (19~0
U.S.$)per ton woul d be 60 percent above est imates
founded on production costs (18,19,23).
In longer-term coal export contracts,there has been
provision for reviewing the base price (regardless of
escalation clauses)if significant developments occur
in pricing or markets.That is,prices may respond to
market conditions even before the expiration of the
contract .**
Energy-importing nations in Asia,especially Japan,
have a stated pol icy of diversified procurement for
their coal supplies.They will not buy only from the
lowest-cost suppl ier (as would be the case in a per-
fectly compet it ive model of coal trade)but instead
will pay a risk premium to ensure security of supply
(see Battelle 18,23).
-Survey of Forecasts
Data Resources Incorporated is projecting an average
annual real growth rate of 2.6 percent for U.S.coal
prices in the period 1981 to 20UO (9).The World Bank has
forecast that the real price of steam coal would advance
at approximately the same rate as oil prices (3
percent/a)in the period 1980 to 1990 (10).Canadian
Resourcecon Limited has recently forecast growth rates of
2 percent to 4 percent (19~0 to 2010)for subbituminous
and bituminous steam coal (22).
-Opportunity Value of Alaskan Coal
Delivered Prices,CIF Japan
Based on these consideration,the shadow price of coal
(CIF price in Japan)was forecast using conditional
**Th is clause forms part of the recently cone 1uded agreement between
Denison Mines and Teck Corporation and Japanese steel makers.
18-7
probabilities glven low,medlum,and hlgh 011 pr i ce
scenarios.Table 18.3 deplcts the estlmated coal price
growth rates and thelr assoclated probabllitles,glven
the three sets of 011 pr i ces.Comb i ni ng these proba-
b i l i t les wlth those attached to the 011 pr i ce cases
ylelds the followlng coal prlce scenarlos,CIF Japan.
Scenari 0 Probabi 1ity Real Prlce Growth
Medlum 49 percent 2 percent (1982-2000)
(mo st 1ike 1y)1 percent (2000-2040)
Low 24 percent 0 percent (1982-2040)
High 27 percent 4 percent (1982-2000)
2 percent (2000-2040)
The 1982 base per i od price was i nl t i al ly estlmated
us i nq the data from the Battelle Beluga Market Study
(18).Based on th i s study,a sample of 1980 spot
prices (averaging $1.66/MMBtu)w~s escalated to January
1982 to prov i de a startlng value of $1.95/MMBtu in
January 1982 dollars.*
As more recent and more complete coal lmport prlce sta-
tlstlcs became avallable,thls extrapolatlon of the 19
sample was found to glve a slgnificant underestlmate of
actual CIF pr ices ,By late 1981,Japan's average lm-
port price of steam coal reached $2.96/MMBtu.**An lm~
portant sens t t i vi t y case was therefore developed re-
flectlng these updated actual CIF pr i ces .The updated
base perlod value of $2.96 was reduced by 10 percent to
$2.66 to recognize the prlce dlscount dlctated by qual-
ity differentlals between Alaskan coal and other sour-
ces of Japanese coal imports,as estimated by Battelle
(18) . Tables 18.2 and 18.3 111 ustrate the range of
recent CIF and FOB pr i ces of steam coal imports to
Japan.
*The escalatlon factor was 1.03 x 1.14,where 3 percent is the fore-
cast real growth i n prices (mld-1980 to January 1982)at an annual
rate of 2 percent,and 14 percent lS the 18-month increase if the CPI
is used to convert from mld-1980 dollars to January 1982 dollars.
**As reported by Coal Week Internatlonal ln October 1981,the average
CIF value of steam coal was $75.50 per MT.At an average heat value
of 11,500 Btu/lb,this lS equivalent to $2.96/MBtu.
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Opportunity Values in Alaska
Base Case -Battelle-based CIF Prices,
No Export Potential for Healy Coal
Transportation costs of $0.52/MMBtu were subtracted
from the initially estimated CIF price of $1.95 to
determine the opportunity value of Beluga coal at
Anchorage.In January 1982 dollars,this base
period net-back price is therefore $1.43.In subse-
quent years,the opportunity value is derived as the
difference between the escalated CIF price and the
transport cost (est imated to be constant in real
terms).The real growth rate in these FOB prices is
determined residually from the forecast opportunity
values.In the medium (most likely)case,the
Beluga opportunity values escalate at annual rates
of 2.6 percent and 1.2 percent during the intervals
1982 to 2000 and 2000 to 2040,respectively.
For Healy coal,it was est imat eo that the base
period price of $1.75/MI~Btu (at Healy)would also
escalate at 2.6 percent (to 2000)and 1.2 percent
(2000 to 2040).Adding the escalated cost of trans-
portation from Healy to Nenana results in a January
1~82 price of $1.75/MMBtu.*In subsequent years,
the cost of transportation of Which 30 percent is
represented by fuel cost (which escalates at 2 per-
cent)is added to the Healy price resulting in
Nenana prices that grow at real rates of 2.3 percent
(1982 to 2000)and 1.1 percent (2000 to 2040).
Table 18.3 summarizes the real escalation rates ap-
plicable to Nenana and Beluga coal in the low,
medium, and high price scenarios.
Sensitivity Case -Updated CIF Prices,
Export Potential for Healy Coal
The updated CIF price of steam coal ($2.66/MMBtu
after adjusting for quality differentials)was re-
duced by shipping costs from Healy and Beluga to
Japan to yield Alaskan opportunity values.In
January 1982,prices are $2.08 and $1.74 at
Anchorage and Nenana,respectively.The differences
between escalated CIF prices and shipping costs re-
sult in FOB prices that have real growth rates of
*Transportation costs are based on Battelle (18,23).
18-9
(b)Analysis of Net Economic Benefits
2.5 percent and 1.2 percent for Beluga coal and 2.7
percent and 1.2 percent for Healy coal (at Nenana).
Table 18.3 shows escalation rates for the opportun-
ity value of Alaskan coal in the low,medium,and
high price scenarios,using updated base period
values.
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Modeling Approach
Using the economic parameters discussed in the previous
section and data relating to the electrical energy genera-
tion alternatives available for the Ra i lbel t ,an analysis
was made comparing the costs of electrical energy produc-
t ion with and without the Sus itna project.The primary
foo-r for ffieanalysTs ·was-agenerarfbnpraniling ·m6del
(OGP5)which simulates production costs over a planning
period extending from 19B2 to 2010.
The method of compar ing the "with"and "without"Sus itna
alternative generation scenarios is based on the long-term
present worth (PW)or total system costs.The planning
model determines the total production costs of alternative
plans on a year-by-year basis.These total costs for the
period of modeling include all costs of fuel and operation
and maintenance (O&lvJ)for all generating units included as
part of the system,and the annualized investment costs of
any generating and system transmission plants added during
the period of 1993 to 2010.Factors which contribute to
(i)
(v)Generation Planning Analysis -Hase Case Study Values
Based on the considerations presented in Sections (i)
through (iv)above, a consistent set of fuel prices was
assembled for the base case pr-ob atril i s t ic generation plan-
ning (OGP5)analysis,as shown in Table 18.4.The study
values include probabilities for the low,medium and high
fuel price scenarios.The probabilities are common for the
three fuels (oil,gas and coal)within each scenario in
order to keep the number of generation planning runs to
manageable size.In the case of the natural gas prices,
domestic market prices were selected for the base case
analysis with the export opportunity values used in
sensitivity runs.The base period value of $3 was derived
by deflating the 1996 Battelle prices to 19B2 by 2.5
percent per year.Coal prices were also selected from the
base case using Battelle's 1980 sample of prices as the
starting point,with the updated CIF prices of coal
reserved for sensitivity runs.Oil prices 'have been
escalated by 2 percent (1982 to 2040).
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the ultimate consumer cost of power but which are not in-
cluded as input to this model are investment costs for all
generation plants in service prior to 19Y3 investment,cost
of the transmission and distribution facilities already in
service,and administrative costs of utilities.These
costs are common to all scenarios and therefore have been
omitted from the study.
In order to aggregate and compare costs on a significantly
long-term basis,annual costs have been aggregated for the
period of 1993 to 2051.Costs have been computed as the
sum of two components and converted to a 1982 PW.The
first component is the 1982 PW of cost output from the
first 18 years of model simul ation from 1993 to 2010.The
second component is the est imated PW of long-term system
costs from 2011 to 2051.
For an assumed set of economic parameters on a particul ar
generation alternative,the first element of the PW_value
represents the amount of cash (not including those costs
noted above) needed in 1982 to meet electrical production
needs in the Railbelt for the period 1993 to 2010.The
second element of the aggregated PW value is the long-term
(2011 to 2051)PW estimate of production costs.In consid-
ering the value to the system of the addition of a hydro-
electric power pl ant,which has a useful 1 ife of approxi-
mately 50 years,the shorter study period would be inade-
quate.A hydroelectric plant added in 1993 or 2002 would
accrue PW benefits for only 17 or 9 years,respectively,
using an investment horizon that extends to 201U.However,
to model the system for an additional 40 years it would be
necessary to develop future load forecasts and generation
alternatives which are beyond the realm of any prudent pro-
jections.For this reason,it has been assumed that the
production costs for the final study year l20lU) would
simply reoccur for an additional 41 years,and the PW of
these was added to the 18-year PW (19%to 2010)to estab-
lish the long-term cost differences between alternative
methods of power generation.
(ii)i)ase Case Analysis
-Pattern of Investments IIWith ll and IIWithout
ll Susitna
The base case comparison of the "wi tn"and "wf thout"
Susitna plans is based on an assessment of the PW produc-
tion costs as outlined in 18 (c)(i)for the period 1993
to 2051,using mid-range values for the energy demand and
load forecast,fuel prices,fuel price escalation rates,
capital costs,and capital cost escalation rates.Load
forec asts,fuel pr ices and construct ion costs are
18-11
analyzed in Sections 5,18.1 (b) and 16,respectively.
As discussed in Section 18.1 (b),a real interest and
discount rate of 3 percent is used.
The with-Susitna plan calls for 680 MW of generating ca-
pacity at Watana to be available to the system in 1993.
Although the project may come on-line in stages during
that year,for model ing purposes full-load generating
capability is assumed to be available for the entire
year.The second stage of Sus itna,the Dev il Canyon
project,is scheduled to come on-line in 2002.The opti-
mum timing for the addition of Devil Canyon was tested
for earlier and later dates.Addition in the year 2002
was found to result in the lowest long-term cost.Devil
Canyon will have 600 MW of installed capacity.
The without-Susitna plan is discussed in Section 6.7.It
includes 3200 MW coal-fired plants added at Beluga in
1993,1994,and 2007.A 200 MW unit is added at Nenana
in 1996.In addition,nine 70 jVjW gas-fired combustion
turbines (GTs)are added during the 1997 to 2010 period.
-Base Case Net Economic Benefits
The economic comparison of these plans is shown in Table
18.5.During the 1993 to 2010 study period,the 1982 PW
cost for the Susitna plan is $3.119 million.The annual
production cost in 2010 is $0.385 billion.The PW of
this level cost,which remains virtually constant for a
per ion extending to the end of the life of the Devil
Canyon plant (2051),is $3.943 billion.The resulting
total cost of the with-Susitna plan is $7.06 billion in
1982 dollars,presently valued to 19~2.
The non-Susitna plan which was modeled has a 1982 PW cost
of $3.213 b ill ion for the 1993 to 2010 per iods with a
2010 annual cost of $0.491 bill ion.The total long-term
cost has a PW of $8.24 billion.erefore,the net eco-
.fj·5mTc 5erleriT··of·aao-plTn~rlhe-··Susrt na ·pTan -is··$T:T8·on:·
lion.In other words,the present valued cost difference
between the Susitna pl an and the expansion pl an based on
thermal plant addition is $1.18 billion in 1982 dollars.
This is equivalent to a 1982 per capita net economic
benefit of $2,700 per capita for the 1982 population of
the State of Alaska.Expressed in 1993 dollars (at the
on-l ine date of Watana) ,the net benefits would have a
levelized value of $2.48 billion.*
*$1.18 billion times 2.105,where 2.105 is the general price inflation
index for the period 1982 to 1993.
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It is noted that the magni tude of net economi c benefi ts
($1.18 billion)is not particularly sensitive to alterna-
tive assumptions concerning the overall rate of price in-
flation as measured by the CPI. The analysis has been
carried out in real (inflation-adjusted)terms.There-
fore,the present valued cost savings wi 11 remain close
to $1.18 billion regardless of CPI movements, as long as
the real (inflation-adjusted)discount and interest rates
are maintained at 3 percent.
The Susitna project's internal rate of return (IRR),
i.e.,the real (inflation-adjusted)discount rate at
which the with-Susitna plan has zero net economic bene-
fits,or the discount rate at whi ch the costs of the
with-Susitna and the "alternate"plans have equal costs,
has also been determined.The IRR is about 4.1 percent
in real terms,and 11.4 percent in nominal (inflation-
inclusive)terms.Therefore,the investment in Susitna
would significantly exceed the 5 percent nominal rate of
return "test"proposed by the State of Al aska in cases
where state appropriations may be involved.*
It is emphasized that these net economic benefits and the
rate of return stemming from the Susitna project are in-
herent ly conservat ive estimates due to several assump-
tions made in the OGP5 analysis.
Zero Growth in Long-term Costs
From 2010 to 2051,the OGP5 analysi s assumed constant
annual production costs in both the Susitna and non-
Susitna plans.This has the effect of excluding real
esca 1at ion in fuel pri ces and the capital costs of
therma 1 plant replacements,and thereby understating
the long-term PW costs of thermal generation plans.
Loss of Load Probabilities
The loss of load probability in the non-Susitna plan is
calculated at 0.099 in the year 2010.This means that
the system in 2010 is on the verge of adding an addi-
tional plant,and would do so in 2011. These costs are,
however, not included in the analysis,which is cut off
at 2010.On the other hand,the Susitna pl an has a
loss of load probability of 0.025,and may not require
additional capacity for several years beyond 2010.
* See State of Alaska's SB-25,Section 44.83.670.
18-13
.Long-term Energy From Susitna
Some of the Susitna energy output (about 350 GWh)is
st ill not used by 2010.Th is energy output would be
available to meet future increases in projected demand
in the summer months.No benefit is attributed to this
energy in the analysis.
Equal Environmental Costs
The OGP5 analysis has implicitly assumed equal environ-
mental costs for both the Susitna and the non-Susitna
plans.To the extent that the thermal generation ex-
pansion plan is expected to carry greater environmental
costs than the Susitna plan,the economic cost savings
from the Susitna project are understated.It is con-
ceivable that these so-called negative externalities
from coal-fired electricity generation will have been
mitigated by 1993 and beyond as a result of the enact-
ment of new environmental legislation.However,such
government action would simply internal ize the ex ter-
nality by forcing up the production and market costs of
thermal power.
(iii)Sensitivity Analysis
Rather than rely on a single point comparison to assess the
net benefit of the Susitna project,a sensitivity analysis
was carried out to identify the impa(t of modified assump-
tions on the results.The analysis was directed at the
following variables:
- Load forecast;
- Real interest and discount rate;
-Construction period;
-Period of analysis;
-Capital costs;
. Sus itna
erm ves
-O&M costs;
Base period fuel price;
- Real escalation in capital costs,U&M costs,and fuel
pr ices;
-System reliability;and
Chackachamna.
Tables 18.6 to 18.14 depict the results of the sensitivity
analysis.In particular,Table 18.14 summarizes the net
economic benefits of the Sus itna Project assoc i ated with
each sensitivity test.The net benefits have been compared
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using indexes relative to the base case value ($1.176
billion)which is set to 100.
The greatest variability in results occurs in sensitivity
tests pertaining to fuel escalation rates,discount rates,
and base period coal prices.For example,a scenario with
high fuel price escalation results in net benefits that
have a value of 253 relative to the base case.In other
words,the high case provides 253 percent of the base case
net benefits.In general,the Susitna plan maintains its
positive net benefits over a reasonably wide range of
values assigned to the key variables.
A multivariate analysis in the form of probability trees
has been undertaken to test the joint effects of varying
several assumptions in combination rather than individual-
ly.This probabilistic analysis reported in Section 18.2
provides a range of expected net economic benefits and
probability distributions that identify the chance~of ex-
ceeding particular values of net benefits at given levels
of confidence.
18.2 -Probability Assessment and Risk Analysis
(a)Introduction to Multivariate Sensitivity Analysis
The feasibil ity study of the Susitna Hydroelectric Project in-
cluded an economic analysis based on a comparison of generation
system product ion costs with and without the proposed project
using a computerized model of the Railbelt generation system.In
order to carry out this analysis,numerous projections and fore-
casts of future conditions were made.These forecasts of uncer-
tain conditions include future electrical demand,costs,and esca-
lation.In order to address these uncertain conditions,a sensi-
tivity analysis on key factors was carried out.This analysis
focused on the variance of each of a number of forecast conditions
and determined the impact of variance on the economic feasibility
of the project.Each factor was variea singularly with all other
variables held constant to determine clearly its importance.
The purpose of this multivariable analysis was to select the most
critical and sensitive variables in the economic analysis and to
test the economic feasibility of the Susitna Project in each pos-
sible combination of the selected variables.
While a number of variables were identified and tested in the
single variable sensitivity analysis for the Susitna economic
feasibility study,the variables which were chosen for the multi-
variate sensitivity analysis represent the key issues such as load
forecasts,capital cost of alternatives,fuel escalation and
Susitna capital cost.
18-15
The methodology for the multivariate analysis was implemented by
constructing probability trees of future conditions for the Alaska
Railbelt electrical system,with and without the Susitna Project.
Each branching of the tree represents three values for a given
variable.These were assigned a high,medium,and low value as
well as a corresponding probability of occurrence.The three
values represent the expected range and mid-point for a given
variable.In some cases,the mid-point represents the most likely
value which would be expected to occur.End limbs of the proba-
bility tree represent scenarios of mixed variable conditions and a
probability of occurrence of the scenario.
The OGP5 production cost model was then used to determine the PW
(in 1982 dollars)of the long-term cost of the electric generation
related to each variable.The PW of the long-term costs for each
"w i th"and "without"Sus itna scenario in terms of cumul at ive pro-
bability of occurrence were determined and plotted.Net benefits
of the project have also been calculated and analyzed in a proba-
bilistic manner.
Figures 18.1 and 18.2 present the non-Susitna and Susitna proba-
bility trees with resultant long-term costs.
(b) Comparison of Long-term Costs
Figure 18.3 presents the two histograms of long-term costs for the
"w i th''and "w l thout " Sus itna cases plotted on the same axes.From
these plots it is seen that the non-Susitna plan costs could be
expected to be significantly less than the Susitna plan costs for
about 6 percent of the time,approximately equal to the Susitna
costs 16 percent of the time,and significantly greater for 78
percent of the time.
A comparison of the expected val ue of long-term costs of the
"w i th"and "wi thout "Susitna cases yields an expected value net
benefit of $1.45 billion.This value represents the difference
between the non-Susitna LTC of $8.48 billion and the Susitna'LTC
(c) Net Benefit Comparison
A second method of comparing the "wi th"and "wi t hout"Susitna pro-
bability trees is by making a direct comparison of similar scen-
arios and c al cul at tnq Ltne net benefit which applies.As jn the
case of the individual tree cases,the net benefits were ranked
from low to high and plotted against cumul ative probabil ity.This
graph has been represented as a single line due to the number of
points on the curve.It,however,would be most accurately por-
trayed as a histogram in the manner of Figure 18.3.The net bene-
fits vary from a negative $2.92 billion with an associated pr oba-
bilityof .0015 to a high of $4.80 billion with an associated
18-16
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probability of .018.The single comparison with the highest pro-
bability of occurrence of .108 has a net benefit of $2.0~billion.
Figure 18.4 plots the net benefit with the cross-over between the
"wi th"and "without"Sus itna costs occurring at about 23 percent.
This is consistent with the previous comparison and with the ex-
pected value net benefit calculated by this method of $1.45 bil-
l ion.
(d)Sensitivity of Results to Probabilities
In assigning the probabilities of occurrence for each set of vari-
ables,a number of subjective assumptions were made.An exception
was the Susitna capital cost probabil ity distribut ion which was
supported by a probabilistic risk assessment of construction cost.
The probabilities for load forecast of 0.2,0.6 and 0.2 for the
low,medium and high cases respectively,reflect the analysis by
Battelle and the probability of exceedence of approximately 10
percent for the high level of demand.
Capital costs,for alternative generation modes as estimated by
EBASCO for Battelle reflect a 0.20,0.60 and 0.20 distribution,
again within a range of a 90 percent chance of exceedence of the
low and 10 percent exceedence of the high level.
The single variable to which the results are most sensitive is the
rate of real fuel escalation adopted.(This conclusion is sup-
ported by the single variable analysis as well.)The distribution
of probabilities was 0.25,0.50 and 0.25 for low,medium and high
fuel cost escalation scenarios.A case can be made for the agree-
ment that some of the combined events,for example high fuel cost
escalation,load and capital cost are not (as our results assume)
independent of each other.Hi gh fuel pr ices,it may be argued,
would result in lower load and increased capital cost.It is pro-
bable,however,that the greater revenues consequent on higher
fuel prices would result in greater economic activity in Alaska
thus increasing demand for energy.This and other considerations
led to the conclusion that the results would be relatively insen-
sitive to probable ranges of interdependence.
(e)Approach to Risk Analysis
A separate risk analysis was undertaken to provide a basis for de-
termining the extent to which perceived risks are likely to influ-
ence capital costs and schedule.In addition,because Susitna
Project when operating would represent a major portion of the to-
tal generation system, a further risk analysis was made to assess
the probability and consequences of a long-term outage of the pro-
posed transmission system.Paragraphs (e) to (h)summarize both
risk analyses.A more detailed treatment is included in the ref-
erence report "Economic,Marketing on Financial Ev aluat i on "(20).
18-17
Any major construction effort is inevitably exposed to a large
number of risks.Low probabil ity magnitude floods may occur at
critical periods of construction:accidents may happen:sub-sur-
face investigations,no matter how thorough,cannot always predict
actual conditions uncovered when the major excavations are under-
taken:the normal estimating process implicity assumes a set of
reasonably "normal"expectations as direct costs are developed,
adding a contingency to the directly computed total on the grounds
that problems usually do occur even though their specific nature
may not be accurately foreseen at the outset.
The Susitna risk analysis took explicit account of 21 different
risks,applying them, as appropriate,to each major construction
activity.The effort involved combining reasonably precise data
(e.g.,the probability that a particular flood crest will occur in
any given year can be determined from analysis of hydrologic
records)with numerous subjective judgments (e.g.,until a parti-
cul ar flood crest does occur,it cannot be known with any degree
of certainty what damage it will cause).The overall methodology
is illustrated in Figure 18.5.
(f)Elements of the Risk Analysis
Figure 18.6 depicts graphically important questions which were
addressed at the start and relates them to elements of the analy-
sis.Each element is further subdivided as follows:
(i)Configurations
Three primary configurations were considered:
-The Watana hydroelectric project (with transmission);
-The Dev il Canyon hydroe 1ectr ic project (with transmi s-
sion);and
-The Susitna transmission system alone.
Separate risk studies of these configurations permitted the
.·pr 6a-uct,on·.of daTa:·wnicficanoeagg reg area-in··\far-To us···ways
to accommodate alternative IIpower-on-linell dates which
differ according to the various demand forecasts.
(ii)Configuration States
Two configuration states were considered:
-Construction Period - appl icable to Watana and Devil
Canyon
-Operation Period -applied only in this analysis,to the
transmission system configuration.
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(iii)Risks
Twenty-one risks were identified for consideration in the
analysis and were grouped as follows:
Natural Risks - 7 risks including flood,ice,seismic
effects,geologic conditions,etc.
Design Controlled Risks -2 risks,seepage piping erosion
and ground water.
-Construction Risks -6 risks including availability of
equipment,labor and material and weather.
-Human Risks -4 risks including accidents,sabotage and
factors relating to contract~r capability.
-Special Risks -2 risks,regulatory delay and estimating
variance.
(iv)Activities
For each configuration state involving construction,up to
22 activities were considered.For Watana,for example,
these included facilities ranging from the main dam to
transmission lines and major key events such as impoundment
and start-up.
(v)Damage Scenarios
Up to ten different damage scenarios were associated with
each logical risk-activity combination.While these varied
significantly from one risk-activity combination to
another,they generally described a range of possibilities
wh ich accounted for discrete increments extend ing from "no
d amaqe"to "c at as tr oph tc loss".
(vi)Criteria
The consequences of realizing particular risk magnitudes
for each activity were measured in terms of cost and sche-
dule implication and manpower requirement.
(vii)Boundary Conditions
The following assumptions and limitations were established
to permit a reasonable and consistent analysis of the pro-
blem:
-All cost est imates were made in terms of January 1982
dollars.Thus,results are presented in this report in
18-19
terms only of real potential cost variations,exclusive
of inflation.
-The analysis was limited only to the construction periods
for Watana and Devil Canyon since the greatest potential
cost and schedule variance would be possible during these
periods.The risk analysis for the operating period was
associated solely with the transmission system since that
configuration represents the most 1 ikely source of a
major system outage during the project operation.
-The risk analysis was accomplished concurrently with
finalization of the total project cost estimate and was
necessarily associated with the feasibility level design.
There is clearly some potential for design change as the
project proceeds;a further risk analysis should be
undertaken coincident with completion of final detailed
des ign and pr ior to commitment to major construct ion
activities.Even so,the "e stimating variance"risk
takes into account the fact that'some design changes are
likely to appear as detailed design effort proceeds.
(g)Risk Assessments
For each of the risks identified in paragraph 18.2 (f)(iii)
above,the assessment commenced with detailed definition of credi-
ble events.Where flood was identified as a risk,for example,
the potential magnitudes and associated probabilities of the
floods were estimated.Data sources ranged from reasonably accur-
ate scientific data (particularly applicable to the natural risk
category),historical experience on water resources projects,to
subjective group judgments where data gaps existed.
In each case,the maximum credible event was first establ ished.
This choice set an upper limit on a scale of possible events
starting at "no damage"situation.Continuing with flood as an
example,the maximum credible event was considered to be the pro-
hab1e maximum flood .whic h hadbeencomputedjn ..theh,ydroJog ic
studies (corresponding to a return period of more than 10,000
years and an annual probability of occurrence of less than .0001).
Once risks were defined and logical risk-activity combinations
were reviewed,the consequences of realizing each selected risk
magnitude were considered (if this risk magnitude is realized,
will a partially completed structure be damaged? Will it fail?
If it fails,is some other work in progress disrupted?).Because
of the uncertainties associated with these projections,a range of
damage scenarios and associated probabilities of them occurring
was establ ished.
Even if a particul ar risk level is real ized and a particul ar
damage is suffered,the cost and schedule of restoring the
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activity are difficult to precisely establish.Each of the risk
analysts therefore provided three values for each criterion:
- a minimum value corresponding to the one time in twenty that the
weather is particularly good,materials are readily available,
no accidents occur,etc.;
- a modal value associated with the most likely expectation of the
anal yst;
- a maximum value corresponding to the one time in twenty that
everything is more difficult than expected.
In the computerized calculation process,the three criterion
values supplied by the risk analyst were fitted to a triangular
distribution,which approximated the beta distribution illustrated
at the bottom of Figure 18.7.
In effect,then,designation of the three conceptual criterion
values led to generation of a histogram with relatively narrow in-
tervals and a nearly continuous range of possible values over a
relatively wide spectrum.
Figure 18.7 illustrates the structural relationship for handling
risk-activity combinations,damage scenarios,and criterion
values.
(h)Interpretation of Results
(i)Presentation of Data
Minor variations in activity costs were generated by the
estimating team concurrent with development of the risk
analysis.In addition,account was taken of the expecta-
tion that construction costs will escalate at a faster rate
than normal infl ation -both in the economic analyses and
the risk analyses.To avoid confusion regarding absolute
cost values,the results of the risk analysis are presented
in th is sect ion as percentages of the est imated proj ect
cost or as ratios between actual costs and estimated
costs.
(ii)Watana Cost-Probability Distribution
Figure 18.8 illustrates the cumulative distribution of
total direct costs and their rel ated non-exceedance proba-
bilities as determined in the risk analysis.Certain im-
portant points noted on the figure are interpreted as
follows:
18-21
- The project direct cost estimate,including contingen-
cies,was presented in Chapter 16.Point II All on Figure
18.8 corresponds to this project estimate:the analysis
suggests that the probabil ity of completing Watana for
less than the project estimate which includes a 17.5
percent contingency allowance is 73 percent.
-Point IIB II corresponds to the "Tow"cost estimate which
was tested for sensitivity in the OGP5 system cost analy-
sis.The probability that Watana will be completed for
less than this cost estimate is about 46 percent.
-Point "C"on Figure 18.8 corresponds to a cost equal to
the "h i qh"estimate tested in the OGP5 analysis to deter-
mine the effect of such a cost on total project econom-
ics.The risk analysis suggests that there is a 90 per-
cent probability that this cost will not be exceeded.
-As will be noted from Figure 18.8,there remains a small
but measurable possibility that the project costs will
exceed even the "hiqh"estimate value at Point IIC II ..It
can be argued that the degree of conservatism which was
used in the analysis has overstated the possibility of
extreme upper 1 imits on total cost.Paragraph (v) below
addresses this issue,comparing these results with his-
tor ica 1 data.
The expected value of the actual cost is 9U.25 percent of
the project estimate.
(iii)Devil Canyon -Probability Distributions
Figure 18 e ,9 provides the cumul at ive probabil ity distribu-
tion for Uevil Canyon costs.Points A,B, and C on the
curve correspond to those discussed above for Watana and
are associated with probabilities of 74 percent,47 per-
cent,and 90 percent,respectively,for actual percentages
.....__.....Qf ..t b~J>Y'Qj~fJ .~stjrn_~t~_Q~il}g_._l§_~j:_t!.~n_j nd i c~ted .._v Cllll~?·
Once again,a not insignificant long "t a i l" in the extreme
upper righthand portion of the distribution provides a
measure of the potent ial exposure to 1 arge overruns.The
expected val ue of the actual cost is 91.5 percent of the
project estimate.
(iv)Total Project Distribution
Figure 18.10 combines the separate Watana and Devil Canyon
projects,providing a cumulative distribution for the
Susitna Hydroelectric Project as a whole.Points A,B, and
C now have associated probabilities of non-exceedance of 73
percent,47 percent and 90 percent,respectively,suggest-
ing that a broad range of total project cost ratios are
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possible.In the 10 percent range and 90 percent probabil-
ity interval,the cost range spans nearly $3 billion.If
the project follows historical patterns,it may be expected
that this range will narrow over time as detailed design
and construction proceed.Note that the cost distributions
are in every case based upon January 1982 dollars and do
not account for the effects of inflation.Interest during
construction and finance charges are not incl uded.Only
the potential for extraordinary construction cost escala-
tion (over and above inflation)has been taken into ac-
count.It follows that if the project is completed in the
next several decades,the final "actual"cost will have to
be adjusted to equivalent 1982 dollars if it is to be com-
pared with risk analysis results presented herein.
(v)Comparison with Available Uata
During the assessment of the important "est imat ing vari-
ance"risk,historical data for 4~federal water resources
projects completed prior to passage of NEPA was considered.
Figure 18.11 offers a cumul ative probabil ity historical
program for various cost ratios.In each case,the cost
rat io refl ects the actual project cost (after adjustment
for inflation)divided by the "{n i t i al "estimated cost.It
will be seen that relatively large overruns have occurred
in the past,while there is also evidence that a substan-
t ial number of water resources projects have been accom-
plished for less than the originally estimated costs.
In order to compare this information with the Susitna risk
analysis results,it is necessary to determine the meaning
of the "f n i t i a l"estimate in terms of the historical data.
In each case,the "{n i t i al "estimate is the estimate pre-
sented to the Congress at the time that a request was made
for project authorization.Thus,it would be inappropriate
to regard the current Susitna estimate (as discussed in
Chapter 16)as an "fn it t e l"estimate in the federal sense.
Fortunately,however,the Susitna Project does have a long
history of federal involvement.Indeed,the Corps of Engi~
neers provided a detailed "f n i t i al "estimate in 1975 as the
basis for seeking authorization for important design activ-
ities.This "fn it t al "estimate was further updated by a
second "{n i t i al "estimate in 1979 after some additional ex-
ploratory work and further analysis were requested by the
Office of Management and Budget.Incl us ive of cont ingen-
cies and excluding lands,the direct cost "In i t t al "Corps
of Engineers'estimate (from the 1979 report)in January
1982 dollars for the Watana/Devil Canyon (thin arch dam)
Project was used as the denominator for display of possible
Susitna cost ratios.
18-23
Figure 18.12 overlays the results of the Susitna risk
analysis on the historical data.Note that the cost ratios
differ on this display from those on Figure 18.10 because
of the necessity to use the "{n i t i al "estimate for compari-
son purposes.
As may be seen from Figure 18.12,the Susitna risk analysis
results reflect a more pessimistic expectation at low cost
levels than the historical data would appear to indicate is
appropriate.
(vi)Schedule Risks
At the same time that minimum,modal,and maximum cost
values were estimated for each damage scenario in each
risk-activity set,estimates were also made of similar
values for potential schedule changes.As a result,sche-
dule probability distributions were generated for each
major activity.However,these individual distributions
could not be combined in the same manner in which the cost
data were hand 1ed.
A critical path network was prepared for the entire set of
activities for each configuration.Individual probability
distributions for critical activities were then combined to
yield a distribution for the total project schedule.
Several crit ical paths were ident ified in the process,
since a long delay on a non-critical activity can,of
course,place that activity on a new critical path.The
"r aw"schedule delay distribution was then considered in
the context of a one-year schedul e contingency which had
been built into the original estimate and in light of regu-
latory delay risks.The resulting distributions are dis-
cussed and interpreted as follows:
-Figure 18.13 provides a cumulative probability distribu-
tion·in months from the scheduled compl.et-ton-dat.a for the
Watana Project.It reflects all risk contributions ex-
cept those posed by regulatory requirements.It is based
upon a critical path through the main dam construction
and takes into account the one-year schedule contingency.
The indicated probability of completing the project ahead
of schedule or on time is about 65 percent.There is
only a 17-percent chance of completing the proJect a year
early (i .e . , in 1992).
-Figure 18.14 provides a similar distribution after regu-
1 ator y risks are accounted for.Two components are
included:(1)prior to the start of construction,a
1 icense must be issued by the Federal Energy Regul atory
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Commission.There is a small chance (estimated to be 25
percent)that the 1 icense will be issued a year earl ier
than the current 30-month licensing schedule anticipates.
The probability of meeting or improving upon the 30-month
est imate is about 72 percent and there is a 90 percent
probabil ity that not more than 38 months wi 11 be re-
quired;(2)during the construction period,regulatory
del ays may be imposed as a resul t of various permitt ing
requirements,injunctions,etc.These delays yield only
increases in schedule and range from a 50 percent proba-
bility of delays of a month or less to a 95 percent pro-
bability that regulatory delays during construction will
not exceed 12 months.
As may be seen from Figure 18.14,the net effect of the
regulatory risks is to broaden the range of possible
values.At the lower end of the distribution,it will be
noted that the chances of completing at least a year early
will have increased to nearly 40 percent -primarily be-
cause of the chance of getting a 1 icense early and there-
fore,starting early.No significant change appears for
the probability of meeting or improving upon the schedule.
A substantial effect is evident in the upper portion of the
curve where the chances of long regul atory del ays have
pushed out the 95 percent confidence level to an expecta-
t ion of no more than three months attributable to risks
other than regulatory,as may be seen on Figure 18.13.
While similar distributions can be plotted for Devil
Canyon,they are less meaningful since there is flexibility
associated with its starting date.
(vii)Transmission Line Risks
The separate risk analysis of the Susitna transmission sys-
tem (which is described in detail in Section 14)was con-
ducted to determine the probability of significant power
supply interruptions at the two major load centers in
Anchorage and Fairbanks.The methodology was generally
similar to that described in preceding paragraphs.Recog-
nizing that the system is assumed to be in an operating
mode,those risks which had appl ied only for construction
in the preceding analysis (e.g.,contractor capability)
were eliminated from the risk list.Additions to the list
were made to account for the potential effects of lighting,
aircraft,collisions,and anchor-dragging in Knik Arm
(appl icable to the submarine cable segment).Account was
taken of redundancies designed into the system (e.g.,a
loss of one line in the three-line system extending south
toward Anchorage can be tolerated with no loss of energy
delivery capability).
18-25
In addition,special attention was given to dependencies
(e.g.,an earthquake which causes the loss of two lines
will very likely knock out the third.On the other hand,
vandalism which causes an outage on one line is only infre-
quently expected to extend to all 1 ines).Important
assumptions included the availability of well-trained
repair crews and equipment,and a reasonable supply of
spare components.
The results of the analysis provide the cumulative proba-
bil ity of not exceeding a given number of days of reduced
energy del ivery capabil ity.Figures 18.15 and 18.16"dis-
play this information for Anchorage and Fairbanks,respec-
tively.Interpretations are as follows:
- In the particular case of Anchorage (Figure 18.15),it
will first be noted that the probability scale includes
only the extreme upper range of non-exceedance probabili-
ties.The intersection of the distribution curves on the
probabil ity axis indicates that the probabil ity of no
lost energy delivery capability in a given year is 0.95$
and of not having 50 percent reduction of 0.955.Beyond
these points the curves rise sharply,indicating that
outages beyond five days are extremely unlikely.The
"expected"annual value of 0.06961 days for a total de-
livery loss may be compared with the "Ioss of load pro-
babil i ty"of 0.1 (one day in ten years)which had been
used in the generation planning efforts in the economic
studies.In short,the risk analysis confirms that the
reliability of the transmission system for energy deliv-
ery to Anchorage is consistent with the requirements of
the overall Railbelt generation system.The "expected"
annual value of 0.09171 days for a 50 percent reduction
in energy delivery appears to be similarly acceptable
when compared to assumed loss of load probability.
-The cumulative probability distribution for Fairbanks
.."."(Figure Is.16)"hasasl fght r.y"cfrrrere"rir···i nterce pt·Onffi"e
probability axis and its shape is also slightly different
from those for Anchorage. These differences stem from
the fact that del ivery to Fairbanks requires no submerged
crossing and certain other risks (e.g.,flood,tempera-
ture extremes)would be expected to have different proba-
bil ities for northern and southern segments of the sys-
tem. In spite of the absolute differences,it may be
seen from the d ispl ay that "expec ted"annual value of
.08116 does not exceed the loss of load probability cri-
terion of 0.1 days per year.No 50 percent loss for
Fairbanks is shown since the loss of one of two lines
causes no reduction in del ivery capabil ity.Two 1 ines
lost is,of course,a 100 percent loss.
18-26
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(1)
In sp i t e of the apparent r-e t t ab i l t ty of the transmlssion
system,It 15 nonetheless true that a small but f i nl t e
chance of relatlvely long-term outages does ex i st .It i s
also unfortunately true that cer t ain extreme risk magnl-
tudes (e.g.,comblnatlon of extreme loss temperature,wind,
and lce)whlch could lead to an outage also tend to cOln-
clde wlth hlgh demands by users on the generatlng system.
The "response"i n t hi s case i s extremely lmportant.The
sectlon deallng wlth rlsk analysls,in the Reference Report
"Economic,Marketlng and Flnanclal Evaluatlon"(25) pro-
v i des such a response i n the form of a prellmlnary emer-
gency plan wh i ch Inc ludes such measures as sheddlng non-
essentlal loads,puttlng reserve capaclty on-Ll ne,and
energy transfers from ml l i tary generat 1on systems.Pr 1or
to the t ime that the Susltna Hydroelectrlc Project comes
into operatlon,thls plan should be updated and occaslonal
tests should be made.
Concluslons
The central concluslons of the Probablllty Assessment are that the
expected value of the PW net beneflt from Susitna is $1.45 blllion
and that th i s value has a 0.5 probablllty of being exceeded.
There lS also only a 0.36 probabillty of the net benefit falling
below $0.5 bi ll i cn.
Based upon the Rlsk Analysls,it is concluded that:
-The prob ab t l i t i es that actual costs will not exceed values
subjected to sens it iv i ty tests in the economic analys i s are as
follows:
Value
Probablllty That Value
Will Not Be Exceeded
18-27
-The annual probablllty that no lnterruptlon ln energy dellvery
to major load centers wlll occur as a result of tr ansml ss ton
line fallures lS ln excess of 95 percent.
- Exposure to potent ial costs above the project est irnat es does
eXlst and there lS about a 1 percent chance that an overrun of
40 percent or more (in 1982 dollars)will occur.
73%
47%
90%
Project Estimate
Low Capltal Cost Tested ln the
Economlc Analysls
Hlgh Capltal Cost Tested ln the
Economlc Analysis
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- Expected values of energy delivery interruptions are less than
one day in ten years and are consl stent with loss of load
probabilities assumed in the generation planning efforts.
- There is a 65 percent probability that the Watana Project will
be completed prior to the scheduled time in 1993. Exposure to
schedule delays is heavily influenced by regulatory requirements
and there is a 10 percent pr-ob abi ll ty that the Watana Project
will not be completed until 1995 or later.
18.3 - Marketing
This section presents an assessment of the market in the Ra i lbel t
Region for the energy and capacity of the Susitna development. A range
of rates at which this power could be priced is presented together with
a proposed basis for contracting for the supply of Susitna energy.
(a)The Railbelt Power System
Susl tna capac i ty and energy will be deli vered to the "Ra i lbeIt
Regi on Interconnected Syst em"wh i ch will result from the 11 nkage
of the Anchorage and Fairbanks systems by an intertie to be com-
pleted in the mid-1980s.
The Railbelt Region covers the Anchorage-Cook Inlet area,the
Fairbanks-Tanana Valley area,and the Glennallen-Valdez area
(Figure 18.17).The utilities,military installations and uni-
versities within this Region which own electric generating facil-
ities are listed in Table 18.15.The service areas of these util-
ities are shown in Figure 18.18 and the generat ng p s serving
the region are listed in Table 18.16.
The Railbelt Region is currently served by nine major utility sys-
tems;five are rural electric cooperatives,three are municipally
owned and operated,and one is a federal wholesaler.The relative
mix of electric generating technologies and types of fuel used by
the Railbelt utilities in 1980 is summarized in Figure 18.19.
~Tn .1980,the Anchor.aqe-Cook In]et~ace~had~8L_peLcent,the
Fairbanks-Tanana Valley area 17 percent,and the Glennallen-Valdez
area 2 percent of the total energy sales in the Railbelt Region.
If the recommendations of the May 1981 Gilbert/Commonwealth Report
are implemented,the Anchorage and Fairbanks power systems will be
intertied before the Susi tna Project comes into operat i on .The
proposed intertie will allow a capacity transfer of up to 70 MW in
either direction.The proposed plan of interconnection envisages
initial operation at 138 kV with subsequent uprating to 345 kV
allowing the line to be integrated into the Susitna transmission
f aci lit ies.
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(c)
Regional Electric Power Demand and Supply
A review of the socioeconomic scenarios upon which forecasts of
electric power demand were based is presented in Section 5 of this
report.The forecasts adopted here are the mid-range levels pre-
sented by Battelle Northwest in December 1981.Subsequent fore-
casts which introduce price/demand elasticity considerations have
not been used at this stage.The results of studies presented in
Section 5 call for Watana to come into operation in 1993 and to
del iver a full year ' s energy generation in 1994. Devil Canyon
will come into operation in 2002 and deliver a full year's energy
in 2003. Energy demand in the Railbelt Region and the del iveries
from Susitna are shown in Figure 18.20.
Market and Price for Watana Output in 1994
It has been assumed that Watana energy will be suppl ied at a
single wholesale rate on a free market basis.This requires,in
effect,that Susitna energy be priced so that it is attractive
even to ut i 1 it ies with the lowest cost alternat ive source of
energy.On th is bas is it is est imated that for the 3315 GWh of
energy generated by Watana in 1994 to be attractive,a price of
145 mills per kWh in 1994 dollars is required.Justification for
this price is illustrated in Figure 18.21.Note that the assump-
tion is made that the only capital costs which would be avoided in
the early 1990s would be those due to the addition of new coal-
fired generating plants (i.e.,the 2 x 200 MW coal-fired Beluga
station).The Susitna energy price of 145 mills/kWh suggested
here matches closely the value determined from OGP5 analysis in
the financial evaluation (18.4).
The financing considerations under which it would be appropriate
for Watana energy to be sold at approximately 145 mills kWh price
are considered in Section 18.4 of this report;however,it should
be noted that some of the energy which would be displaced by
Watana IS 3387 GWh woul d have been generated at a lower cost than
145 mills,and util ities might wish to delay accepting it at this
price until the escalating cost of natural gas or other fuels made
it more attractive.A number of approaches to the resolution of
this problem can be postulated including pre-contract arrangements
considered in (c)(i)below.
(i)Contractual Preconditions for Susitna Energy Sale
It will be necessary to contract with Railbelt Utilities
for the purchase of Susitna capacity and energy on a basis
appropriate to support financing of the project.This
should be a precondition for the actual commencement of
project construction.Delay in contract negotiations until
after the project was truly committed would be undesirable
as the project would then represent a trapped resource with
no alternative markets.
18-29
Pricing policies for Susitna output are assumed to be con-
strained by both cost (as defined by Senate Bill 25)and by
the price of energy from the best thermal option.
Marketing Susitna's output within these twin constraints
would ensure that all state support for Susitna flowed
through to consumers and under no circumstances were prices
to consumers higher than they would have been under the
best thermal option.In addition,consumers would also
obtain the long-term economic benefits of Susitna's low
cost energy.
(d) Market Price for Watana Output 1995-2001
After its initial entry into the system in 1994,the price and
market for the 3387 MWh of Watana output is consistently upheld
over the years to 2001 by the projected 20 percent increase in
total demand over this period.
There would, as a result,be a 70 percent increase in cost savings
compared with the best thermal alternative:the increasing cost
per unit of output from a system without Susitna is illustrated in
Figure 18.22.
(e) Market and Price for Watana and Devil Canyon Output in 2003
A diagramatic analysis of the total cost savings which the com-
bined Watana and Devil Canyon output will confer on the system
compared with the present thermal option in the year 2003 is shown
in Figure 18.23.These total savings are divided by the energy
contributed by Susitna to indicate a price of 250 mills per kWh as
the maximum price which can be charged for Susitna output.Here
again,the problem of competing with lower cost combined cycle,
gas turbines,etc.,will have to be addressed;however,this pro-
blem is likely to be short term in nature,as by this time period
.t.hese thermal power facilities will be appro!'lGhillg retirement.
~-~-~---~~
Only about 90 percent of the-total Susltna'ouTputwrnbe-absorbed
by the system in 2002,the bal ance of the output being progres-
sively absorbed over the following decade.This will provide in-
creasing total savings to the system from Susitna,with no associ-
ated increase in costs.
(f)Potential Impact of State Appropriations
In the preceding paragraphs the maximum price at which Susitna
energy could be sold has been identified.Sale of the energy at
these prices will depend upon the magnitude of any proposed state
appropriation designed to reduce the cost of Susitna energy in the
earl ier years.At significantly lower prices it is 1 ikely that
the total system demand will be higher than assumed.This,
18-30
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comb ined with a state appropr i at ion to reduce the energy cost of
Watana energy,would make it correspondingly easier to market the
output from the Susitna development;however,as the preceding
analysis shows,a viable and strengthening market exists for the
energy from the development that would make it possible to price
the output up to the cost of the best thermal alternative.
Conclusions
Hased on the assessment of the market for power and energy output
from the Susitna Hydroelectric Project it has been concluded that,
with the appropriate level of state appropriation and with pricing
as defined in Senate Bill 25,an attractive basis exists,particu-
larly in the long term,for the Railbelt utilities to derive bene-
fit from the Project.It should be recognized that contractual
arrangements covering purchase of Susitna output will be an essen-
tial precondition for the actual commencement of project construc-
tion.
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18.4 -Financial Evaluation
(a)Forecast Financial Parameters
The financial,economic,and engineering estimates used in the
financial analysis are summarized in Table 18.17.The interest
rates and forecast rates of inflation (in the Consumer Price Index
- CPI)are of special importance.They have been based on the
forecast inflation rates and the forecast of interest rates on
industrial bonds as given by Data Resources Incorporated,and con-
form to a range of other authoritative forecasts.To allow for
the factors which have brought about a narrowing of the differen-
t i al between tax-exempt and non-taxexempt secur it i es,it has been
assumed that any tax-exempt financing would be at a rate of 80
percent rather than the historical 75 percent or so of the non-
tax-exempt interest rate.Th i s ident ifies the forecast interest
rates in the financing periods from 1985 in successive five-year
periods as being of the order of 8.6 percent,7.8 percent,and 7
percent.The accompanying rate of infl at ion would be about 7
percent.In view of the uncertainty attaching to such forecasts
and in the interest of conservatism,the financial projections
which follow have been based upon the assumpt ion of a 10 percent
rate of interest for tax-exempt bonds and an ongoinginfl at ion
rate of 7 percent.
(b)The Inflationary Financing Deficit
The basic financing problem of Susitna is the magnitude of its
"inflationary financing deficits".Under inflationary conditions
these defic its (ear ly year losses)are an inherent characteri st ic
of almost all debt f in anced ,long life,tapital intensive projects
(see Figure 18.24).As such,they are entirely compatible (as in
the Susitna case)with a project showing a good economic rate of
18-31
return.However,unless specific measures are taken to meet this
"inflationary financing deficit"the project may be unable to pro-
ceed without imposing a substantial and possibly unacceptable bur-
den of high early-year costs on consumers.
(c)The Basic Financial Options
A range of financing options compatible with the conditions laid
down in Senate Bill 25 have been considered as a means of meeting
the inflationary financing deficit.The options basically consist
of a range of appropriations by the State of Alaska with the bal-
ance of the project fi nancing made up by either 35-year tax-
exempt revenue bonds or by a combination of General Obl igation
(G.O.)bonds and 35-year revenue bonds, with the G.O.bonds re-
financed into revenue bonds at the earliest opportunity.Through-
out central estimates of capital costs,revenues,etc.,are used.
(i)1UO Percent State Appropriation of Total
Capital Cost ($5.1 billion in 1982 dollars)
This conforms to the possible outco~e of Senate ~ill 25 and
represents the simplest financing option.It could take
the form of the State of Alaska appropriating funds to meet
capita1 costs as incurred over the 15-year construct ion
schedule detailed in Table 18.18.
On the basis of the present wholesale energy rate setting
requirement incorporated in Senate Bill 25,the APA would,
however, not be able to charge more than the actual costs
incurred.Given that in this case the only costs would be
the very small year-to-year operating costs,this option
would involve the output from Susitna being suppl ied at
only a fraction of the price of electricity from the best
thermal option.
(ii)State Appropriation of $3 Billion (in
1982 dollars)with Residual Bond Financing
The outcome for this option is summarized in Figure 18.25
and Table 18.19.It would still enable Susitna energy to
be produced at a price 46 percent less than that of the
best thermal option.It would also enable the project to
be completed with only $0.9 billion (in 1982 dollars)of
revenue bonds or G.O.bonds over the period 1991-93.The
Devil Canyon stage could then be completed with a 'further
$2.3 billion (in 1982 dollars)of revenue bonds over the
period 1994 to 2002.
This level of appropriation would enable Susitna energy
prices to be held virtually constant at their initial level
for nearly a decade.A temporary "step-up"in price of
Susitna output to the cost of the electricity from the best
thermal option Would be required when Devil Canyon was
18-32
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completed on the basis of its IOU percent revenue bond
financing.Thereafter,however,the cost of the Susitna
energy would again stabil ize and give ever-increasing sav-
ings compared with cost of the best thermal option.
(iii)"Ni n trmm"State Appropriation of $2.3 ~illion
(in 1~82 dollars)with Residual ~ond Financing
The "m in lmtm''state appropriation is taken as the mm imum
amount required to meet a debt service cover of 1.25 on the
residual debt financing by revenue bonds and makes
Susitna's wholesale energy price competitive with the best
thermal option in its first normal cost year (1994).This
level of appropriation would require $1.7 billion (in 1982
doll ars)of bond financ ing in 1990-93 and a further $2.1
bill ion (in 1982 doll ars) over the period 1994 to 2002 to
complete Devil Canyon (see Figure 1H.26 and Table 18.2U).
These levels of state appropriation would all therefore eliminate
Susitna's "{nf l at ionar y financing cef ic i t".
(d)Issues Arising from the Basic Financing Uptions
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Need for Financial Restructuring
Irrespective of Susitna being chosen as the best means of
meeting the Ra i lbel t energy needs,significant financial
restructuring of some Railbelt utilities will be required
to enable them to offer adequate financial security in
their power contracts and debt financing to meet generation
expansion.It is assumed that this restructuring will take
place.
Tax-exempt Bond Financing
In the $2.3 billion state appropriation case interest cost,
on the basis of tax-exempt financing,accounts for 90 per-
cent of the unit price of Susitna output in 1994.Failure
to obtain tax-exempt bond financing would increase these
interest costs by approximately one-quarter.Ensuring
tax-exempt status for the Susitna bond issues is therefore
of fundamental importance to the economics of the project
under these options.
This issue has been extensively reviewed by tax advisers
and consultants and it has been concluded that at the stage
at which bond financing is required in the early 19~Os,
tax-exempt financing should be possible in compl iance with
Section 103 of the IRS code.
18-33
(iii)Options for Residual Financing
Tables 18.21 and 18.22 set out the estimated requirements
for bond financing with State Appropriations of $3 billion
and $2.3 billion respectively.Several options are avail-
able to meet these financing needs and these are summarized
below.
-Revenue ~onds with a Completion Guarantee
A completion guarantee must be assumed to be a precondi-
tion of bond financing at the watana stage (up to 1~~3).
A State of Alaska guarantee of project completion would
probably enable all residual financing to be met by rev-
enue bonds.(The completion guarantee may of necessity
have to take the form of a G.O.bond authorization of an
amount to be determined prior to the timing of the
issuance of revenue bonds).
- Guaranteed Revenue Bonds with Post-Completion
Refinancing
If the revenue bonds were guaranteed by the State of
Alaska they could be issued without the provision of a
completion guarantee.
-G.O.Bonds with Post-Completion Refinancing
G.O.Bonds on the "full faith and credit"of the State of
Al aska are effectively identical to guaranteed revenue
bonds and would also avoid the necessity of a completion
guarantee.
In this case,as with that of guaranteed revenue bonds,
the burden on the credit of the state could be minimized
by making the bonds subject to "c all"after a few years
(when project viabil ity was establ ished)and refinancing
ihtonoh"'guaranteed revenue bonds.
(iv)Refinancing Watana and the Financing of Devil Canyon
Early refinanc ing of any guaranteed or G.O.bonds used to
finance Watana,and the ongoing financing of Devil Canyon
entirely by revenue bonds is taken to be an important
financing objective.The main factor determining the date
at which such refinancing will be possible is the magnitude
of the initial state appropriation.This is dealt with in
terms of the risk analysis in 18.5 below.
The basic conclusion from the analysis is that,with a
state appropriation of $2.3 billion (in 1982 dollars),
there is a very high degree of certainty that refinancing
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into non-guaranteed revenue bonds could occur within a few
years of project completion.
(v)Importance of Adequate State Appropriation
The principal effect of appropriations significantly less
than $2.3 bill iqn would be a possible need for additional
guaranteed or G.O.bond financing for Devil Canyon. This
is because the impact of lesser appropriations would (as
illustrated in Figure 18.27)give rise to inadequate earn-
ings coverage in the early years of Watana,and subsequent-
ly Devil Canyon, so that the raising of revenue bonds re-
quiring such cover would have to be delayed.In addition,
such inadequate funding would force the Susitna price to
"tr ack"the cost of energy from the best thermal option
unt i1 adequate revenue had been bui It up to all ow such re-
financing.
(vi)Impact on State Credit Rating of
Guaranteed or G.O.Bond Financing
The impact on state credit rating of guaranteed or G.O.
bond financing of the order of $1.7 billion in the $2.3
billion (both in 1982 dollars)state appropriation case has
been assessed by the Al askan Power Author ity's investment
banking and financial advisers First Boston Corporation
and First Southwest Company.They have concurred in the
following statement.
IIWe are only able to render a conditional estimate of the
possible impact on the credit of the State of Alaska as a
result of the contemplated general obligation bond finan-
cing of $1.7 billion for the Watana stage of the Susitna
hydroelectric project.Alaska's presently favorable rat-
ings are greatly influenced by it's low debt to assessed
value ratio which helps to overcome the unusually high
per capita debt statistics.Given the dramatic growth of
assessed valuation and the fact that interest expense
through start-up of Watana is to be capitalized from bond
proceeds the envisaged financing should not significantly
impair the cred it of the state.Even if the State of
Alaska's general obligation bond rating were reduced one
full letter grade,the cost in terms of interest rates on
future bond issues would likely be in the approximate
range of 1/4 percent to 1/2 percent per annum.II
Financing Options Under Senate Bill 646 and House Bill 655
As proposed these bills would permit financing of approved energy
developments by state funding to be repaid at the rate of 3 per-
cent per annum with an "upl if t"reflecting past inflation.
18-35
(i)100 Percent State Appropriation
The outcome in this case is illustrated in Figure 18.28 and
would differ from that covered by the outrightappropria-
tion (c)(i)above in that the resulting charge for Susitna
energy to cover the repayment of state funding would be 81
mills/kWh in 1994 compared with 19 mills/kWh in the (c)(i)
case.
(ii)"Minimum"State Appropriation of $3 Hillion
(in 1982 dollars)
The outcome of a state appropriation of $3 billion (in 1982
dollars)is shown in Figure 18.29.This also would differ
from the $3 billion outright appropriation dealt with in
(c)(ii)in representing the minimum compatible with resid-
ual financing by revenue bonds,since the increasing pay-
ments to the state create an earnings cover shortfall in
2003.It would al so result in a consequent higher charge
for Susitna energy.In this case it would be 120 mills/kWh
in 1994 compared with 80 mills/kWh under (c)(ii).
In both (i)and (ii)Susitna energy would still be produced at a price
competitive with the best thermal option.These scenarios would also
be compatible (subject to certain legislative requirements)with resid-
ual financing by revenue bonds.
(f)Future Development and Resolution of Uncertainties
Prior to the decision to proceed with actual construction of
Susitna,several significant uncertainties affecting the project
will have been reduced.Demand forecasts will be more certain and
the impact of the electrical intertie between Anchorage and Fair-
banks will be known.Fuel cost trends and energy prices from al-
ternative generation sources will be more precisely known.More
advanced engineering work and definition of the basis for con-
struct ion contracts will have firmed up requirements for capital
_f und ~,_~~JlJ_C!(:tgjt iQYlLtb e _Ra ss ag~.J)fJ~jrnj~wLlL1La ve.C!.ll owe<Lbetterr-
definition of the level of state appropriation required and the
ability of the state to provide the necessary financial support.
The development of the institutional structure of the Railbelt
utilities by this date should also permit power contracts and
legislative proposals to be drawn up which would equitably share
these then more clearly del ineated risks between the util ities,
the Power Authority and the State of Alaska.The key requirements
for state guarantees and financing could then be more precisely
defined in an appropriately limited form which would be acceptable
to the state and adequate for project financing.
18;;;36
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(g) Conclusion
The principal conclusion of the financial evaluation is that with
a state appropriation of not less than $2.3 billion (in 19S2 dol-
lars)and consent for guaranteed or G.O.bond financing of $1.7
billion (in 1982 dollars),Susitna would be financially viable.
It would also be able to market its output at an initial price
competitive with the most efficient thermal option and produce
substantial long-term savings compared with this option.
The evaluation,however,stressed the importance of establ ishing
the project on a strong financial basis that would enable it to
secure conversion of the guaranteed or G.O.bonds issued for the
construction of Watana into non-guaranteed revenue bonds and ob-
tain a highly competitive rate of interest.These objectives (to-
gether with the marketing of the Watana output in 19Y4 and a price
46 percent below that of the most efficient thermal option),could
be secured by state appropriation of $3.0 billion (in 1982 dol-
lars).
It should also be noted that the cost benefit analysis shows that
full recovery long-term of any state appropriation would be pos-
sible with a better than 10 percent rate of return.IVleeting the
Susitna "inflationary financing deficit"by such appropriations
can therefore be co~sidered as a separate issue from subsidization
of electricity prices by foregoing recovery of all or part of the
state appropriation designed to meet this deficit.
lS.5 -Financial Risk
The financial risks considered are those arising to the State of Alaska
and to Alaskan consumers.The analysis of these risks is restricted to
the period up to 2001 covering the completion of Watana and its first
eight years of operation.
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t a)Pre-completion Risk
The major pre-completion risk is simply the risk that the project
will not be completed.The possibility of this arising owing to
natural hazard is dealt with in Sections 9 and 10,and on the
basis of this analysis this outcome has a negligibly small proba-
bility of occurrence.
The risk of non-completion owing to capital overrun is also ass-
essed to have negligible probability.This is on the grounds that
the project only involves well-established technology,has been
extensively evaluated by Acres and wholly independent consultants
and shown by formal probability analysis to have only a 27 to 20
percent probability of any real capital overrun.
18-37
(b)Post-completion Kisks
(i)The Generation of Post-completion Risks
A probabilistic financial model was developed taking into
account the probab i1 ity d istr ibut ions of the major eng i-
neering and financial variables on which the financial out-
come for Susitna depends.This madel,the basic parameters
of wh ich are given in Tab1e 18.23,was then used to con-
sider in detail critical specific and aggregative risks
posed by the project.
(ii)Specific Risks
-Specific Risk I;Risk of Hand
Requirement Overrun (Figure 18.30)
Extensive analysis was undertaken to assess the probabil-
ity that the bond financing requirements would overrun
the forecast val ues as a result of capital costs,infl a-
tion,interest rates,etc.,being less favorable than
forecast.In the $2.3 billion state appropriation case
it was found that the probabil ity of the bond financing
requirement exceeding the forecast of $1.7 billion (in
1982 dollars)by more than 50 percent was only 0.12.
There is also a significant probability (0.71)that the
bond financing requirements will be less than the fore-
cast $1.7 billion.
-Specific Risk II;Inadequate Debt
Service Cover (Figure 18.31)
Adverse impact on state credit rating might occur if the
project failed to earn adequate debt service and cover
and consequently conversion into non-guaranteed revenue
bonds was delayed.The analysis showed that in the $2.3
billion state appropriation case .
....~~~-_..•~.._.~._---_._----_...~.._--_.__..•..~..----~----_.....--~-~._----_..~-_._----~~---~_.._...._..._.....•_~--_....•.
The probabil ity of forecast coverage being less than
adequate (1.25 coverage)in 1994 (first normal year of
Watana)is 0.22.
Given that the probabil ity of coverage shortfall dimin-
ishes with time (due to increased cost of alternative
fuels),the risk of delayed conversion due to inadequate
cover is minimal.
-Specific Risk III;Early Year
Non-viability (Figure 18.32)
The measure of financial non-viability in the early years
is taken as the ratio of Watana's unit cost to the costs
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of the best thermal option in Watana's third year (19~ti).
(For comparab il ity excess debt serv ice cover was ex-
cluded.)If this ratio is less than forecast it would
reflect "non-viability"in the sense of the project not
real izing its forecast savings in these important early
years.This analysis indicates that in the $2.3 billion
appropriation case there is only a 0.29 chance of the
Susitna costs exceeding their forecast value (51 percent
of the best thermal).
(iii)The Aggregate Risk
While specific risks of the type considered above are of
importance basic concern must center on the aggregate risk.
In long-term economics this is measured by the risk attach-
ing to the rate of return.For the purpose of the finan-
cial risk,however,it is taken as represented by accumula-
tive net operating earnings at the end of the first eight
years of operation of Watana.Since this statistic is net
of interest and debt repayment,it effectively subsumes all
the risks involved in capital expenditure,inflation,in-
terest rates,revenue,etc.,deviating from their forecast
values.This statistic was also adjusted to allow the
pricing up of Watana energy to the cost of the best thermal
option so that the statistic reflects the "upside"risk as
well as the "downside."
On this basis in the $2.3 billion state appropriation case
the statistic (see Figure 18.33)was found to have only a
0.27 chance of being below forecast level of $0.8 billion
(in 1982 dollars)by more than $0.2 billion.There is also
a 0.73 probability of the statistic exceeding $0.8 billion
and thus creating greater savings for the Alaskan·comsumer.
Conclusions
The analysis shows the exposure of the project,either to critical
specific risks or to aggregative risk,at the Watana stage is rel-
atively 1 imited.The qual ification attaching to this analysis is
that the est imates and probabil it ies used are free from any sys-
tematic biases.The structure of the plan of the overall plan of
study for Sus itna and analys i s of its alternat ives has however
been specifically designed to take every reasonable precaution
against this possibil ity by seeking extensive independent verifi-
cation of the key variables by Batelle and Ebasco operating wholly
as independent consultants.
18-39
I)
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LIST OF REFERENCES
(1) u.S.Department of Labor,Monthly Labor Review,various issues.
(2) Alaska Uepartment of Commerce and Economic Development,The Alaska
Economic Information and Reporting System,July 19~0.
(3) Data Resources Inc.,U.S.Long-Term Review,Fall 1980, Lexington,
MA,1980.
(4)Wharton Econometric Forecasting Associates,Fall 19~1,Philadel-
phia,PA,(reported in Economic Council of Canada CANuIDE
Model 2-0 Run,dated December 1~,lY~I.)
(5)Baumo l, W.J.,"On the Social Rate of Dt scourrt",American Economic
Review,Vol. 58,September 1968.
(6)Mishan,E.J.,Cost-Benefit Analysis,George Allen and Unwin,
London,1975.
(7)Prest,A.R.and R.Turvey,"Co s t-Benef i t Analysis:A Survey",
Economic Journal,Vol. 75, 1965.
(8)U.S.Department of Commerce,Survey of Current Business,various
issues.
(9) Data Resources,Inc.,personal communication,November 1981.
(10)World Bank,personal communication,January 1981.
(11) U.S.Department of Energy,Energy Information Administration,
Annual Report to Congress,Washington,D.C.,1980.
(12) National Energy Board of Canada,Ottawa,Canada,personal communi-
cation,October 1981.
(13)Noroil,"Natur-al Gas and International LNG Trade";Vol.9, October
1981.
(14)Segal,J. "Slower Growth for the 19(50'sll,Petroleum Economist,
December 1980.
(15)Segal,J.and F.Niering,"Spec i al Report on World Natural Gas
Pricing ll,Petroleum Economist,September 1980.
(16)SRI International,personal communication,October 1981.
(17)World Bank,Commodity Trade and Price Trends,Washington 1980.
LIST UF REFERENCES (Cont'd)
(18)Battelle Pacific Northwest Laboratories,Beluga Coal Market Study,
Final Report, Richland,Washington,198U.
(19)B.C.Business,August 1981.
(20)Coal Week International,various issues.
(21) Japanese Ministry of International Trade and Industry,personal
communication,January 1982.
(22)Canadian Resourcecon Limited,Industrial Thermal Coal Use in
Canada,1980 to 2010,May 1980.
(23)Battelle Pacific Northwest Laboratories,Alaska Coal Future Avail-
ability and Price Forecast,May 1981.
(24)Roberts,J.O.et al,Treatment of Inflation in the Development of
Discount Rates and Level ized Costs in NEPA Analyses for the
Electric Util ity Industry,U.S.Nuclear Regul atory Commis-
sion,Washington,D.C., January 19~0.
(25)Acres American Incorporated.Report on "Economic,Marketing and
Financial Evaluation"for Susitna Hydroelectric Project.
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TABLE 18.1:REAL (INFLATION-ADJUSTED)ANNUAL
GROWTH IN OIL PRICES
Growth Rates (Percent)
11 Low Case
Medium (most likely case)
High Case
1982-2000
a
2.0
4.0
2000-2040
a
1.0
2.0
Probability
0.3
0.5
0.2
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Base Period
(January 1982)
Price of No.2 Fuel Oil -$6.50/MMBtu.
TABLE 18.2:DOMESTIC MARKET PRICES AND EXPORT
OPPORTUNITY VALUES OF NATURAL GAS
Domestic Market Price 1 Export OPaortunit~Value
Low Medlum Hlgh
Probability of ---Low Me lum 19h
Occurrence N.A.N.A. N.A.279~469~279~
Base Period Value $3.00/MMBtu -$4.65/MMBtu 2 -
Real Escalat~on CIF
Pr ice,Japan
1982 - 2000 N.A.a·'2·'4·''.-c '.
2000 - 2040 m6 1·'2%.c
Real Escalatton
Alaska Price
1982 - 2000 a·'2.59~5.09~a·'2.7%5.29~-c '.
2000 - 2040 0%2.09~2.09~a·'1.29~2.29~'.
OGP5 analysis used domestic market prices with zero escalation beyond 2010.
(Source:Battelle)
2 Based on CIF price in Japan ($6.75)less estimated cost of liquefaction and
shipping ($2.10).(Source:13,14,15).
3 Source:(9),(16) •
4 Alaska opportunity value escalates more rapidly than CIF prices as lique-
faction and shipping costs are estimated to remain constant in real terms.
TABLE 18.3:SUMMARY OF COAL OPPORTUNITY VALUES
Base Period Annual Real
Growth Rate Probabilit y
:'\(Jan.1982)of
Value 1980 - 2000 2000 - 2040 Occurrence .
($/MMBtu)(~O (~O 0''0
Base Case
'1BattelleBase,
Period CIF Price
Med ium Scenar io I- CIF Japan 1.95 2.0 1.0 49
-FOB Beluga 1.43 2.6 1.2 49
- Nenana
1.75 2.3 1.1 49 +~l
Low Scenario
- CIF Japan 1.95 0 0 24 ,I-FOB Beluga 1.43 0 0 24
- Nenana 1.75 0.1 0.1 24
High Scenar io
.1- CIF Japan 1.95 4.0 2.0 27
-FOB Beluga 1.43 5.0 2.2 27
- Nenana
1.75 4.5 1.9 27
Sensitivity Case
Updated Base
Period CIF Price1
Medium Scenario
- CIF Japan 2.66 2.0 1.0 49
-FOB Beluga 2.08 2.5 1.2 49
-FOB Nenana 1.74 2.7 1.2 49
Low Scenario
- CIF Japan 2.66 0 0 24
-FOB Beluga 2.08 0 0 24
-..FOB-Nenana-1.74 -0.2 -0.1 24
High Scenario -\
I- CIF Japan 2.66 4.0 2.0 27
-TOB Beluga 2.08 4.8 2.2 27
-FOB Nenana 1.74 5.3 2.3 27
J
Assuming a 10 percent discount for Alaskan coal due to quality differen-
tials,and export potential for Healy coal.
rJ
TABLE 18.4:SUMMARY OF FUEL PRICES USED IN THE
OGP5 PROBABILITY TREE ANALYSIS
Fuel Price Scenario
Low Medium High
I ]
Probability of occurrence 25~~5m~25~~
Base period January 1982 prices
(1982$/MMBt u)
()
Fuel Oil 6.50 6.50 6.50II
Natural Gas 3.00 3.00 3.00
Coal
-Beluga 1.43 1.43 1.43
- Nenana 1.75 1.75 1.75
Real escatation rates per year
(percent)
Fuel Oil
- 1982 - 2000 0 2.0 4.0
- 2000 - 2040 0 2.0 2.0
Natural Gas
- 1982 - 2000 0 2.5 5.0
- 2000 - 2040 0 2.0 2.0
Beluga Coal
- 1982 - 2000 0 2.6 5.0
- 2000 - 2040 0 1.2 2.2
Nenana Coal
- 1982 - 2000 0.1 2.3 4.5
- 2000 - 2040 0.1 1.1 1.9
Beyond 2010,the OGP analysls has used zero real escalation in
all cases.
LJ
u
]
Net Economic Benefit
of Susitna Plan
Plan ID
Non Susitna A
Susitna C
TABLE 18.5:ECONOMIC ANALYSIS JSUSITNAPROJECT-BASE PLAN
1982 Present Worth gf System Costs
$x 10
1993-Estimated 1993-
Components 2010 2010 2011-2051 2051
600 MW Coal-Beluga 3,213 491 5,025 8,238
200 MW Coal-Nenana
630 MW GT
680 MW Watana 3,119 385 3,943 7,062 ~1
600 MW Devil Canyon
180 MW GT J
1,176
TABLE 18.6:SUMMARY OF LOAD FORECASTS
USED FOR SENSITIVITY ANALYSIS
Medium Low High
MW GWh MW GWh MW GWh---
___________1.9.9.0..892 4,456 802 3,9.99___..j.,.o98 __...._...5,203.
2000 1,084 5,469 921 4,641 1,439 7,457
2010 1,537 7,791
1,245 6,303 2,165 11,435
I.1
i]
I I
TABLE 18.7:LOAD FORECAST SENSITIVITY ANALYSIS
1982 Present Worth of System Costs ($x 10
6)
Ii
1
)
Plan ID Components
Non-Susitna K1 400 MW Coal-Beluga
with
Low Forecast 200 MW Coal-Nenana
560 MW GT
Susitna K2 680 MW Watana (1995)
with
Low Forecast 600 MW Devil Canyon (2004)
Non-Susitna J 1 800 MW Coal-Beluga
with
High Forecast 200 MW Coal-Nenana
700 MW GT
430 MW Pre-1993
Susitna J2 680 MW Watana (1993)
with
High Forecast 600 MW Devil Canyon (1997)
350 MW GT
430 MW Pre-1993
1 From 1993 to 2040
1993-
2010
2,640
2,882
4,176
3,867
2010
404
360
700
564
Estimated
2011-2051
4,238
3,768
6,683
5,380
1993-
2051
6,878
6,650
10,8591 1
Net
Economic
Benefit
228
1,612
TABLE 18.8:DISCOUNT RATE SENSITIVITY ANALYSIS
1982 Present Worth of System Costs ($x 10
6)
Real Net
I .
Discount Rate 1993-Estimated 1993- Economic
I I Plan ID (Percent)2010 2010 2011-2051 2051 BenefitLJ
Non-Susitna Q1 2 3,701 465 7,766 11,167
U Susitna Q2 2 3,156 323 5,394 8,550 2,617
Non-Susitna A 3 3,213 491 5,025 8,328
..'
lJ Susitna C 3 3,119 385 3,943 7,062 1,176
Non-Susitna S1 4 2,791 517 3,444 6,235
Susitna S2 4 3,080 457 3,046 6,126 109
Non-Susitna P1 5 2,468 550 2,478 4,946
Susitna P2 5 3,032 539 2,426 5,459 (513)
TABLE 18.9:CAPITAL COST SENSITIVITY ANALYSIS
1982 Present Worth of System Costs ($ x 1061-
Net
1993-Estimated 1993-Economic
Plan ID 2010 2010 2011-2051 2051 Benefit
Non-Susitna Capital
1CostsUp20Percent
Non-Susitna G 3,460 528 5,398 8,858
Susitna C1 3,119 385 3,943 7,062 '1,976 ,I
Non-Susitna Capital
Costs Down 10 Percent ~JNon-Susitna G 3,084 472 4,831 7,915
Susitna C1 3,119 385 3,943 7,062 853
Susitna Capital Costs
Less Contingency
Non-Susitna A 3,213 491 5,025 8,238 ~)Susitna X2 2,710 336 3,441 6,151 2,087
Susitna Capital Costs
Plus Doubled Contingency
Non-Susitna A 3,213 491 5,025 8,238
Susitna Y2 3,529 434 4,445 7,974 264
An adjustment calculation was made regarding the +capital costs of
the 3GT ~nits added in 2007-2010 since the difference was less than
$10 xl0.Beyond 2010,this effect was not included.
TABLE 18.10:SENSITIVITY ANALYSIS -UPDATED BASE PLAN
(JANUARY 1982)COAL PRICES
1982 Present Worth of System Costs ($x 10
6)
Base
Period Beluga Costs of Costs of Net
Coal Price Non-Susitna Susitna Economic
(1982 $/MMBtu)Plan Plan Benefits
Base Case 1.43 8,238 7,062 1,176
Sensitivity
(Updated)Case 2.08 9,030 7,062 1,968
,.j
I'
I J
[1
\J
11I'~.J
I]
L-l
LJ
u
TABLE 18.11:SENSITIVITY ANALYSIS -REAL COST ESCALATION
1982 Present Worth gf System CostsrsX10 )
1993-Estimated 1993-Net
Plan ID 2010 2010 2011-2051 2051 Benefit
Zero-Escalation in
Capital and O&M Costs
•Non-Susitna 01 2,838 422 4,319 7,157
•Susitna O2 2,525 299 3,060 5,585 1,572
Escalation in Capital 1
Costs and O&M (Battelle)
•Non-Susitna X1 3,142 477 4,881 8,023
•Susitna X2 2,988 366 3,745 6,737 1,286
Double Escalation
Capital and O&M Costs
•Non-Susitna P1 3,650 602 6,161 9,811
•Susitna P2 3,881 503 5,148 9,029 782
Zero-Escalation
in Fuel Prices
•Non-Susitna V1 2,233 335 3,427 5,660
•Susitna V2 3,002 365 3,736 6,738 (1,078)
High Escalation
in Fuel Prices
•Non-Susitna W1 4,063 643 6,574 10,367
•Susitna W2 3,267 403 4,121 7,388 2,979
1capital and O&M costs assumed to escalate at 1.4 percent 1982 to 2010
TABLE 18.12:SENSITIVITY ANALYSIS -NON-SUSITNA
PLAN WITH CHAKACHAMNA
1982 Present Worth gf System Costs
($X 10 )
1993 Estimated 1993-Net
Plan ID Components 2010 2010 2011-2051 2051 Benefit----
•Non-Susitna with B 330 MW Chakachamna 2,038 475 4,861
7,899
Chakachamna 400 MW Coal-Beluga
200 MW Coal-Nenana
440 MW GT
•Susitna C 680 MW Watana 3,119 385 3,943
7,062 837
600 MW Devil Canyon
180 MW GT
TABLE 18.13:SENSITIVITY ANALYSIS -
SUSITNA PROJECT DELAY
l
ID
$X 106
1982 Present Worth
of System Costs
$x 106
Net Economic Benefit
Susitna Base Case C 7,062 1,176
One-year delay for
Watana (1994)C3 7,105 1,133
One-year delay for
Devil Caryon (2003)C4 7,165 1,134
One-year delay for
Watana and Devil
Canyon (1994, 2003)C5 7,230 1,138 1
-J
1
-/
I
J
TABLE 18.14:SUMMARY OF SENSITIVITY ANALYSIS INDEXES
OF NET ECONOMIC BENEFITS
Index Values
(1,J
[\
\.J
, 1
LJ
u
11
BASE CASE ($1,176 MILLION)
Fuel Escalation
- High
-Low
Discount Rates
- High-High (5%)
-High (4%)
-Low (2%)
Susitna Capital Cost
- High
-Low
Load Forecast
- High
-Low
Non-Susitna (Thermal)
Capital Costs
- High
-Low
Capital and O&M
Cost Escalation
- High
-Intermediate (Battelle)
-Low
Chakachamna (included in
Non-Susitna Plan)
Updated Base Coal Price
Planned Delay in Susitna
Project
- One-year delay,Watana
- One-year delay,Watana and Devil Canyon
- Two-year delay,Watana and Devil Canyon
100
-44
9
223
23
178
137
19
168
73
67
109
134
71
167
96
96
97
1 High fuel escalation case provides net benefits equal to 253 percent of the
base value,2.53 x $1,176,or $2,975.
2 Low fuel escalation case provides minus 92 percent of the base case net
benefits,-.92 x $1,176,or -$1,082.
!
Generating Purchases Utility Annual
Capacity 1981 Predominant Tax Status Wholesale Provides Energy Demand
MW at oaF Type of Re: IRS Electrical Wholesale 1980
UTILITY
i
Rating Generation Section 103 Energy Supply GWh
IN ANCHORAGE-COOK INLET
Anchorage Municipal Light and Power 221.6 SCCT Exempt *-585.8
Chugach Electric Association 395.1 SCCT Non-Exempt **941.3
Matanuska Electric Association 0.9 Diesel Non-Exempt *-268.0
Homer Electric Association 2.6 Diesel Non-Exempt *-284.8
Seward Electric System 5.5 Diesel Non-Exempt *-26.4
Alaska Power Administration 30.0 Hydro Non-Exempt -*-
National Defense 58.8 ST Non-Exempt ---
Industrial - Kenai 25.0 SCCT Non-Exempt ---
IN FAIRBANKS -TANANA VALLEY,
Fairbanks Municipal Utility System 1 68.5 ST/Diesel Exempt --116.7
Golden Valley Electric Association 1 221.6 SCCT/Diesel Non-Exempt --316.7
University of Alaska 18.6 ST Non-Exempt ---
National Defense1
46.5 ST Non-Exempt ---
IN GLENALLENIVALDEZ AREA
Copper Valley Electric Association 19.6 SCCT Non-Exempt --37.4
TOTAL 1114.3 2577.1
1Pooling Arrangements in Force
,TABLE 18.15 - RAILBELT UTILITIES PROVIDING MARKET POTENTIAL
[Ii
'--~-
1I
I
[]
11
']I,
[J
u
u
IJ
PLANT LIST
PLANT TYPE OF
No.NAMEOF PLANT UTILITY
OWNERSHIP
2 Anchorage No. 1 Anchorage Municipal Light and Power Municipal
3 Anchorage Anchorage Municipal Light and Power Municipal
6 Eklutna Alaska Power Administration Federal
7 Chena Fairbanks Municipal Utilities System Municipal
10 Knik Arm
Chugach Electric Association, Inc.Cooperative
22 Elmendorf-West United States Air Force
Federal
23 Fairbanks Golden Valley Electric Association, Inc.
Cooperative
32 Cooper Lake Chugach Electric Association, Inc.
Cooperative
34 Elmendorf-East United States Air Force Federal
35 Ft. Richardson United States Army Federal
36 Ft. Wainright United States Air Force Federal
37 Eilson United States Air Force Federal
38 Ft. Greeley United States Army Federal
47 Bernice Lake Chugach Electric Association,Inc.Cooperative
55 International Station Chugach Electric Association,Inc.Cooperative
58 Healy Golden Valley Electric Association,Inc.Cooperative
59 Beluga Chugach Electric Association,Inc.Cooperative
75 Clear AFB United States Air Force Federal
80 Collier-Kenai Collier-Kenai Municipal
81 Eyak Cordova Public Utilities Municipal
82 North Pole Golden Valley Electric Association,Inc.Cooperative
83 Valdez Golden Valley Electric Association,Inc.Cooperative
84 Glennallen Golden Valley Electric Association,Inc.Cooperative
TABLE 18.16 - LIST OF GENERATING PLANTS SUPPLYING RAILBELT REGION
TABLE 18.17:FORECAST FINANCIAL PARAMETERS
$3.647 $1.470
billion billion
$10.0 $5.42
million million
$10.94 $4.41
15 percent of Operating Costs
10 percent of Revenue
Project Completion - Year
Energy Level - 1993
- 2002
- 2010
Costs in January '1982 Dollars
Capital Costs
Operating Costs - per
annum
Provision for Capital
Renewals - per annum
(0.3 percent of Capital Costs)
Operating Working Capital
Watana
1993
Devil
Canyon
2002
Total
3 387 GWh 15 223 "6 616 "
$5.117
billion
$15.42
million
$15.35
Reserve and Contingency Fund
Interest Rate
Debt Repayment Period
Inflation Rate
Real Rate of Increase in Operating Costs
- 1982 to 1987
- 1988 on
100 percent of Operating Costs
100 percent of Provision for Capital
Renewals
10 percent per annum
35 years
7 percent per annum
1.7 percent per annum
2.0 percent per annum
Real Rate of Increase in Capital Costs
- 1982 to 1985
-1986 to 1992
1.1 percent
1.0 percent
annum
annum
I
I
i~I .,~:---
l.-........~_,;L---i ~-~
*************************************~.~~.~~~~~~~.~~~~~~~~~~~~~~~~*******~*****************************************************DATA10K WATANA-DC (ON LINE 1993-2002)-INFLATION 7%-INTEREST 10%-CAP COST $5.117 BN 23-FEB-82
*********************r.:****************~¥¥~~~¥~~~~~~*~~** * ******** ********* ************ ****** ***** ******* *** *** ****** ***********
1987 1983 1989
CASH FLOW SUMMARY
===($MILLION)====
000
0.00 U.OO 0.00
14S.08 155.24 166.10
0.00 0.00 0000
73
521
466
520
51&
110
517
214
550
391
ENERGY GWH
REAL PRICE-MILLS
INFLATION INOEX
PR ICE-MILLS
-----INCQM~-----------------REVENUE
LESS OPERATING COSTS
OPtRATING INCOME
ADD INTEREST EARNED 8N FUNDS
LESS INT2REST ON SHORT T=RM DEBT
LESS INTEREST ON LONG TERM D~BT
1935
o
0.00
120.72
0.00
0.0
0.0
0.0
0.0
0.0
0.0
1986
o
0.00
135.59
0.00
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
O.f)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1990
o0.00
177.73
0.00
0.0
0.0
0.0
0.0
0.0
0.0
1991
a
0.00
190.17
0.00
0.0
0.0
0.0
0.0
0.0
0.0
1992
a0.00
203.48
0.00
0.0
0.0
0.0
0.0
O.C
0.0
1993
3387
3.65
217.73
1.94
26.9
26.9
0.0
0.0
0.0
0.0
1994
3387
7.98
232.91
18.59
63.0
29.3
33.6
5.6
9.6
0.0
54U ~ET EARNINGS FRO~OPERS
-----CASH SOURCE AND USE----
54g CASH INCOME FRCM OP~RS
446 STATE CONTRIBUTION
143 LONG TERM DEBT DRAWDOWNS
243 WORCAP DEBT ORAWDOWNS
54q TOTAL SOURCES OF FUNDS
320 LeSS CAPITAL EXPENDITURE
44ti LESS WQRCAP AND FUNDS
260 LESS DEBT REPAYMENTS
141 CASH SURPLUS(DEFICIT)
24q SHORT TfRM DEBT
444 CASH RECOVERED
-----BALANCE SHEET----------
22~RESERVE AND CONT.FUND
371 OTHER WORKING CAPITAL
454 CASH SURPLUS RETAINED
370 CUM.CAPITAL EXPENDITURE
405 CAPITAL EMPLOYED
401 STATE CONTRIBUTION
462 ~EIAINED EARNINGS
555 DEBT OUTSTANDING-SHORT TERM
554 DEBT OUTSTANDING-LONG TERM
542 ANNUAL DEBT DRAWWDOWN$1962
543 CUM.DE8T DRAWWDOWN 11982
51~DEBT SERVICE COVER
0.0
0.0
403.7
0.0
0.0
403.7
403.7
0.0
0.0
0.0
0.0
0.0
0.00.0
0.0
403.7
========403.7
403.7
0.0
0.0
0.0
0.0
0.0
0.00
0.0
0.0472.7
0.0
0.0
472.7
472.7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
876.4----------------876.4
876.4
0.0
0.0
0.0
0.0
0.0
0.00
0.0
0.0479.7
0.0
0.0
479.7
479.7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1356.1========1356.1
========
1356.1
0.0
0.0
0.0
O.C
0.0
0.00
0.0
0.0499.5
0.0
000
499.5
499.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
185506========1355.0========135506
0.0
0.0
0"".0
0.0
0.0
0.00
0.0
0.0
938.3
0.0
0.0
938.3
938.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
2794.0===..:====2794.0========2794.0
0.0
0.0
0.0
0.0
0.0
0.00
0.0
0.0
1550.4
0.0
0.0
1550.4
1550.4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
4344.3
========4344.3========4344.3
0.0
0.0
0.0
0.0
0.0
0.00
0.0
0.0
1247.1
0.0
0.0
1247.1
1247.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
5591.4----------------5591.4========5591.4
0.0
0.0
0.0
0.0
0.0
0.00
0.0
0.0b7604
0.0
0.0
676.4
67b.4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
6267.8
========6267.8========6267.8
0.0
0.0
0.0
0.0
0.0
0.00
0.0
0.0
333.1
0.0
98.0
431.1
333.1
98.0
0.0
0.0
0.0
0.0
56.5
41.5
0.0
6600.9========b698.9
========6600.9
0.0
98.0
0.0
0.0
0.0
0.00
29.5
29.5
229.1
0.0
17.7
276.9
259.2
17.70.0
0.0
0.0
0.0
61.6
54.1
0.0
6860.1----------------b975.8----------------6830.6
29.5
115.1
0.0
0.0
0.0
0.00
Sheet 1 of 3
1
100%STATE APPROPRIATION OF TOTAL CAPITAL COST ($5.1 BILLION IN 1982 DOLLARS)I IIPorn
TABLE 18.18 nUOld
,
*************************************~_~~~~_~_~__h~~~_~~~b~~__~******************************************** **************** *DATA10K WATA~A-DC (ON LINE 1993-2002)-INFLATION 7%-INTEREST 10%-CAP COST $50117 BN 23-FEB-82***************************************r~¥**~~~*~~~~****~~******~~*******************************************************~*****
1995 1996 1997 1~98 1~99 2000 2001 2002 2003 2004
CASH FLOw SUMMARY
===($MILLION)====
73 tNERGY GftH 3367 3387 3387 3387 3387 3387 3387 5223 5414 5605
521 REAL PRICE-MILLS 8024 B038 8.74 8038 9.04 9.17 9.3Q 7066 8.84 8068
466 !NFLATION INDEX 249.28 266073 2B5.40 305.38 326075 349.62 374010 400.29 428.31 45B029
~2J PRICE-MILLS l0055 22036 24.93 27013 29.53 32006 34079 30.64 37.86 390BO
-----INCOME-----------------'16 REVENU~69 06 75.7 84.4 91 09 100.0 108.6 11708 160.0 204.9 22301
170 LESS OPERATING COSTS 32.0 35.0 3801 4106 45.4 49.6 54.1 91.1 9904 10B.5--------------------------------------------------------------------------------517 OPERATING INCOME 37.6 4008 4603 50.2 5406 5900 63.7 69.0 105.5 114.621~ADD INTEREST EARN~D ON FUNDS 602 6.7 7.3 B.O 807 9.5 10.4 1104 19.1 20.9
550 LESS INTEREST ON SHORT TERM DEBT 11.6 1204 15.3 1604 1707 IB.7 i9.B 21.0 33.8 36.3
391 LESS INTEREST ON LONG TERM DE8T 0.0 000 0.0 0.&0.0 0.0 0.0 0.0 0.0 000------------------------------------------------ --------------------------------54g NET EARNINGS FROM OPERS 32.2 35.1 33.3 41.B 45.6 49.8 54.4 59.3 90.9 99.2
-----CASH SOuRCE AND USE----
54i;CASH INCOME FROM OPERS 3202 35.1 3B.3 41.B 45.6 49.8 5404 59.3 9009 99.2~46 STATE CONTRIBUTION 363.1 362.1 30308 I02e03 117705 12040B 913.1 303.0 000 0.0
143 LONG TERM DEBT ORAWDOWNS 0.0 0.0 0.0 0.0 000 Oou 0.0 000 0.0 0.0
249 WORCAP DEBT DRAWDOwNS 8.1 29.3 11.2 12.2 1006 1004 1203 12B.0 24.7 42.8-------- -------------------------------------------------------- ----------------54~TOTAL SOuRCES OF FUNDS 403.4 446.5 353.3 1082.4 123307 12650~979.8 490.3 115.6 142.0
320 lESS CA~ITAL EXPENOITURC 395.3 41102 342.1 1070.1 1223.2 1254.6 967.5 362.3 90.9 99.2
448 LESS HORCAP AND FUNDS Bo1 29.3 11.2 12.2 1006 1004 12.3 12B.0 24.7 42.8
?'60 LESS DEBT REPAYMENTS 0.0 0.0 OoG 0.0 000 000 0.0 ·0.0 0.0 0.0------------------------------------------------ -------- ------------------------141 CASH SURPLUS(DEFICIT.0.0 000 0.0 000 0.0 000 0.0 000 0.0 0.0
249 SHORT TERM DEBT 0.0 0.0 0.0 0.0 0.0 000 0.0 0.0 0.0 000444CASHRECOVERED0.0 0.0 0.0 000 0.0 000 0.0 0.0 0.0 0.0
-----BALANCE SHEET----------22~RESERVE AND CONT.FUND 67.2 73.4 8001 67.4 9504 104.1 113.7 19103 208.8 22708
371 OTHER WOKKING CAPITAL 56.6 7907 84.2 89.1 91.7 93.4 96.2 14606 153 08 177.6
454 CASH SuRPLUS RETAINED 0.0 0.0 0.0 0.0 0.0 000 000 0.0 0.0 0.0370CUM.CAPITAL EXPENDITURE i7255.4 7072.6 8014.7 90840B 10308.0 1156206 12530.1 12892.5 12983.3 13082.5
~65 CAPITAL EMPLOYED =~131~:~==7;~5:1 ==8i1~:O ==~~~l:~=iO~~5:i =li7~o:2 =12140:0 =13230:3 =i3345:~=i3:81:~===============================================:======== =================:======461 STATE CONTRIBUTION 7193.7 757508 7879.6 3907.9 10085.4 11290.3 12203.4 12506.4 12506.4 12500.4
462 RETAINED E4RNINGS .61.6 96.8 135.1 17609 222.6 272.4 326.7 386.1 ~77.0 516.1
555 DE8T OUTSTANDING-SHORT TERM 123.9 153.1 10403 176.0 187.1 197.6 209.9 337.8 30206 405.4
554 ~EBT OUTSTANDING-LONG TERM 000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 000 0.0
542 ANNUAL DEBT DRAWWOOWN $1982 0.0 0.0 0.0 O.C 0.0 0.0 0.0 0.0 0.0 0.0
543 CUM.DEBT URAWWDOWN $1982 0.0 000 0.0 0.0 0.0 0.0 0.0 0.0 000 000
519 DEBT SERVICE COVER 0000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
.Sheet 2 of 3
100%STATE APPROFrRIATION OF TOTAL CAPITAL COST ($5.1 BILLION IN 1982 DOLLARS)
TABLE 18.18 [UJ
i 1-,--,----
L_'LH__'~-~'~----I ----.J ~,I
*************************************~~-~~~-•••~--~~.~~--~~~~~~~-**************************************************************OATAI0K WATANA-DC ION LINE 1993-2002)-INFLATION 1%-INTEREST lot-CAP COST $5.111 BN 23-FEB-82
*************************************~~¥~~~~¥~~~¥¥~~~¥~~~~~~*******************************************************************
2007 2003 2009
CASH FLOW SUMMARY
===($MILLION)====
6250 6472 6544
8.33 9.24 8.30
561.42 600.72 642.77
46.75 49.49 53.35
13 ~NERGY GWH
521 REAL PRICE-MILLS
466 INFLATION INDEX
52U PRICE-MILLS
-----INCOME-----------------
51~REVENUE
170 LESS OPERATING CaSTS
517 OPERATING INCOME
214 ADD INTEREST EARNED ON FUNDS
55J LESS INTEREST ON SHORT TERM DEBT
391 LESS INTEREST ON LONG TERM DEBT
540 NET EA~NlNGS FROM JPERS
-----CASH SOURCE AND USE----
548 CASH INCOME FROM OPERS
44b STATE CONTRIBUTION
143 LONG TERM DEBT DRAWOOWNS
24a WORCAP DEBT DRAWDOWNS
549 TOTAL SOURCES OF FUNDS
320 LESS CAPITAL EXPENDITURE
44d LESS WORCAP AND FUNDS26GLESSDEBTREPAYMENTS
141 CASH SURPlUSIDEFICIT)249 SHORT TERM DEBT
444 CASH RECOVERED
-----BALANCE SHEET----------
225 RESERVE AND CONT.FUND371OTHERWORKINGCAPITAL
454 CASH SURPLUS RETAINED370CUM.CAPITAL EXPENDITURE
405 CAPITAL EMPLOYED
461 STATE CONTRIBUTION
462 RETAINED EARNINGS
555 OF.BT OUTSTAN~ING-SHORT TERM
554 DEBT OUTSTANDING-LONG TERM
542 ANNUAL DEBT DRAftWuOW~$1982
543 CUM.DEBT DRAWWDOWN $1982
?1~DfBT SERVICe COVER
2005
6092
8.18
490.31
40.12
244.4
113.4
120.1)
22.8
40.50.0
108.2
108.2
0.0
0.0
36.4
144.7
108.2
36.4
0.0
0.0
0.0
0.0
248.1
193.2
0.013190..7========13032.0========12506.4
684.4
441.8
0.0
0.1)
0.0
0.00
2006
0141
8.27
524.69
43.39
266.'1
129.2
137.4
24.9
44.2
0.0
118.1
118.1
0.0
0.0
51.3
169.4
11a.1
51.30.0
0.0
0.0
0.0
271.4221.7
0.013308.9========13801.9======:::=12506.4
802.5
4'}3.1
0.0
0.0
0.0
0.00
292.1
141.0
151.1
27.1
49.30.1)
128.9
128.9
0.0
0.0
59.3
188.2
128.959.3
0.0
0.0
0.0
0.0
296.2256..2
0.013437.8========13990.2
=======::
12506.4
931.4
552.4
0.0
1).0
0.0
0.00
320.3
153.9
166.3
29.6
55.2
0.0
140.1
140.7o.c
0..0
45.8
186.5
140.1
45.8
0.0
0.00.0
0.0
323.3274.9
0.013518.5
========
14176.1========12506.4
1072.1
598.2
0.0
0.0
0.0
0.00
349.1
168.0
181.1
32.3
59.80.0
153.6
153.6
0.0
0.0
45.9
199.4
153.0
45.90.0
0.0
0.0
0.0
352.8291.2
0.0
13732.1========14316.1========12<;06.4
1225.7
644.0
0.0
0.0
0.0
0.00
2010
6616
8.35687.17
57.45
380.1
183.4--------196.7
35.3
64.40.0
167.6
167.6
0.0
0.0
52.0
219.6
167 ..6
52.0
0.0
0.0
0.0
0.0
385.1310.9
0.013899.7========14595.7========12506.4
1393 ..3
696.0
0.0
0.0
0.0
0.00
2011
6638
8.48
735.91
62.39
414.1
200.1--------214.0
33.5
69 ..60.0
182.9
182.9
0.0
0.0
37.1
220.6
182.9
37.7
0.0
0.0
0.0
0.0
420.3
313.4
0.014082.6========1411UI.3========12506.4
1570.3
733.1
0.0
0.0
0.0
0.00
2012
6660
8.57
787.42
67.48
449.4
218.4
231.0
42.0
73.40.0
199.7
199.7
0.0
0.0
41.2
240.8
199.7
41.2
0.0
0.0
0.0
0.0
458.7316.2
0.014282..3========15057.1========12506.4
1775..9
774.8
0.0
0.0
0.0
0.00
2013
6682
8.67
842.54
13.02
487.9
238.4
249.5
45.9
71.50.0
211.9
217.9
0.0
0.0
44.9
262.8
211.9
44.9
0.0
0.0
0.00.0
500.6319.2
0.014500.2========15319.9========12506 ..41993·.8
819.7
0.0
0.0
0.0
0.00
TOTAL
104826
0.00
0.00
0.00
4530.0
2202.0--------2328.0
412.4
746.60.0
1993.8
1993.8
12506.4
0.0
819.7
15319.9
14500.2
819.7
0.0
0.0
0.0
0.0
500.6319.2
0.014500.2========15319.9========12506.4
1993.8
819.7
0.0
0.0
0.0
0.00
Sheet 3 of 3
100%STATE APPROPRIATION OF TOTAL CAPITAL COST ($5.1 BILLION IN 1982 DOLLARS)
TABLE 18.18 •
I***********************************~**b********************~*******************************************************************DATAI0K WATANA-DC (ON LINE 1993-2002)-1$3.0 BN(SI982)STATE FUNDS-INFLATION 7t-INTEREST 10%-CAPCOST S5.117 BN 23-FEB-82
**************************************~****************************************************************************************
1
I 1985 1986 :1987 1988 1989 1990 1991 1992 1993 1994
CASH FLOW SUMMARY
===(SMILLIONJ====
73 ENERGY GWH 0 0 0 a 0 0 a 0 3387 3381521REALPRICE-MILLS 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 29.74 34.38466INflATIONINDEX126.72 135.59 145.08 155.24 166.10 111.73 190017 203.48 217.73 232.97520 PR ICE-MILLS 0000 0000 0000 0000 0.00 0000 0.00 0.00 64.76 80.08
-----INCOME-----------------
516 REVENUE 0.0 000 000 0.0 0.0 0.0 0.0 000 219.3 271.2170lESSOPERATINGCOSTS0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 26.9 29.3
~-~----------------------------- -------------------------------- ----------------517 OPERATING INCOME 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 192.4 241.9zi»ADO INT£REST EARNED ON FUNDS 0.0 0.0 000 0.0 0.0 0.0 0.0 0.0 0.0 5..6
550 LESS INTEREST ON SHORT TERM DEBT 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.8391lESSINTERESTONLONGTERMDEBT0.0 0.0 000 000 000 0.0 0.0 0.0 154.0 183.4---------------------------------------- ----------------------------------------548 NET EARNINGS FROM OPERS 0.0 0.0 000 0.0 000 0.0 000 0.0 3805 54.3
-----tASH SOURCE AND US(----
5403548CASHINCOMEFROMOPERS0.0 0.0 0.0 0.0 000 000 000 000 38.5446STATECONTRIBUTION403.1 47201 479.1 499.5 938.3 1550.4 462.4 0.0 0.0 0.0
143 LONG TERM DEBT DRAWDOWNS 0.0 0.0 0.0 0.0 000 0.0 784.1 75409 294.6 211.6248WORCAPDEBTDRAWOOWNS0.0 0.0 000 0.0 0.0 0.0 000 0.0 9800 17.7------------------------ ------------------------ --------------------------------!j4~TOTAL SOURCES OF FUNDS 403.7 472.1 419.7 499 ..5 93803 1550.4 124701 154.9 431.1 283.7
320 LESS CAPITAL EXPENDITURE 403.1 412.7 419.1 499.5 93803 1550.4 124101 15409 33301 259.2448lESSWORCAPANDFUNDS0.0 (l00 0.0 000 0.0 000 0.0 0.0 98.0 17.7260LESSDEBTREPAYMENTS0.0 0.0 0.0 0.0 0.0 000 0.0 000 0.0 6-.8---------------------------------------------------------------- ----------------141 :ASH SURPlUS(DEFICITJ 0.0 000 000 0.0 000 0..0 0.0 0.0 000 000249SHORTTERMDEBT000 000 0.0 0.0 0.0 0.0 000 0.0 0..0 0.0444CASHRECOVERED0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
-----BALANCE SHEET----------
61.6225~ESERVE AND CONTo fUND 0.0 0.0 0.0 000 0.0 0.0 0.0 0.0 56.5371aTHERWORKINGCAPITAL0000.0 0.0 C.O 000 0.0 0.0 000 41.5 5401
454 CASH SURPLUS RETAINED 000 0.0 0.0 000 0.0 0.0 0.0 0.0 0.0 0.0310CUM.CAPITAL EXPENDITURE 403.7 876.4 1356.1 1855.6 2794.0 4344.3 559104 6346.3 6679.4 6938.6
~=============== ================================================ =============:==465 CAPIrAL EMPLOYED 403.7 876.4 1356.1 1855.6 2194.0 434403 5591.4 6346.3 6111.4 7054.3:============::=======================================================:======:==461 STATE CONTRIBUTION .403.7 876.4 1356.1 1855.b 2194.0 434"'.3 4806.7 4806.7 480607 4806.7462RETAINEDEARNINGS0.0 0.0 0.0 000 0.0 000 0.0 0.0 38.5 92.8555DEBTOUTSTANDING-SHORT TERM 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 98.0 115.7554DEBTOUTSTANDING-LONG TERM 0.0 0.0 0.0 0.0 0.0 0.0 784.1 1539.5 1834.2 2039.0
542 ANNUAL DEBT DRAWWDOWN 51982 0.0 0.0 0.0 0.0 0.0 0.0 41206 31100 f 135.3 90.8543CUM.DEBT DRAWWDOWN 51982 0.0 0.0 000 0.0 0.0 0.0 1t1206 783.6 918.9 100901519DEBTSERVICECOVER0.00 0.00 0.00 0.00 0.00 0000 0000 0.00 1.25 1.25
I,
Sh:eet 1 of 3
$3 BILLION (1982 DOLLARS);STATE APPROPRIATION SCENARIO
i 7%INFLATiON AND 10%INTEREST
,
I
-'--~
TABLE 18.19 •
~c:::=1--L _'--~i-.i
********************~*****************************************************************************************~****************DATA10K WATANA-DC (ON LINE 1993-2002)-$3.0 ~M(i1982t STATE FUNDS-INfLATION 1%-INTEREST 10%-CAPCOST S5.111 aN 23-FEa-82*******************************************************************************************************************************
J 1991 1998 1999
CASH FLOW SUMMARY
===(SMILlIONJ====
3387 3381 3387
29.31 21.83 26.39
285.40 305.38 326.15
83.81 84.97 86.24
73
521466
:>20
516
170
511214
55?
391
548
ENERGY .GWH
REAL PRICE-MIllS
INfLATION INDEX
PRICE-MillS
-----INCOME-----------------REVENUE
lESS OPERATING COSTS
OPERATING INCOME
ADD INTEREST EARNED ON FUNDS
LESS INTEREST ON SHORT TERM DEBT
LESS INTEREST ON LONG TERM DEBT
NET EARNINGS FROM OPERS
1995'
3381
32.59
249.28
31.25
215.2
32.0
243.16.2
11.6
182.7
55.0
1996
333.7
30.81
266.73
li2.18
278.3
35.0
243.4
6.7
12.4
182.0--------55.1
283.8
38.1
245.7
1.3
15.3
181.2
56.6
287.8
41.6
246.2
8.0
16.4
1'30.3
57.5
292.1
45.4
246.6
8.1
11.7
119.3
58.4
2000
3387·25.04
349.62
87.54
296.5
49.6
246.99.5
18.1
178.2
59.5
2001
3387
23.79
314.10
89.00
301.4
54.1
241.3
10.4
20.0
171.0
60.7
2002
.5223
58.55
400.29
234.36
1224.0
91.1
1132.9
11.4
21.9
883.'"
239.0
2003
5414
55.54
428.31
237.89
1287.8
99.4
1188.4
19.1
34.7
895.7
271.2
2004
-5l:D 550.49·
458.29
231.37
1296.7
108.5
1188.2
20.9
36.3
891.5
281.4
-----CASH SOURCE A~D USE----
548 CASH INCOME FROM OPERS446STATECONTRIBUTION
143 LONG TERM DEBT DRAWDOWNS
-243 WORCAP DEBT DRAWOOWNS
549 TOTAL SOURCeS OF FUNDS
320 LESS CAPITAL EXPENDITURE
448 LESS WORCAP AND fUNDS
260 lESS DEBT REPAYMENTS
141 CASH SURPlUSlOEFICITt
249 SHORT TERM DEBT
444 CASH RECOVERED
-----BAlANCE SHEET----------225 RESERVE AND CONT.FUND
311 OTHER WORKING CAPITAL
454 CASH SURPLUS RETAINED
370 CUM.CAPITAL EXPENDITURE
465 CAPITAL EHPlaYED
461 STATE CONTRIBUTION
462 RETAINED EARNINGS
555 0EBT OUTSTANDING-SHORT TERM
554 DEBT OUTSTANDING-LONG TERM
542 ANNUAL DE8T DRAWWDOWN S1982
543 CUM.DEBT DRAWWDOWN S1982
519 DEBT StRVICE COVER
55.0
0.0
368.9
8.1
432.0
416.4
8.17.4
0.0
0.0
0.0
61.2
56.6
0.0
7355.0========7418.8==:=====4806.7
147.8
123.9
2400.5
148.0
1157.7
1.25
55.7
0.0
427.7
29.3
512.8
475.3
29.3
8.2
0.0
0.0
0.0
73.4
79.7
0.0
1830.3========7983.4----------------4806.7
203.5
153.1
2820.0
160.4
1318.0
1.25
56.6
0.0
395.4
11.2--------463.1
442.9
11.29.0
0.0
0.0
0.0
aO.1
84.2
0.0
8273.2========8431.5----------------4806.7
260.1
1b4.3
3206.4
138.5
1456.6
1.25
57.5
0.0
1163.0
12.2
1232.7
1210.5
12.2
9.9
0.0
0.0
0.0
8104
89.1
0.0
9483.1========9660.3========4806.7
317.5
176.6
4359.4
380.8
1831.4
1.25
58.1t
0.0
1432.3
10.6
1501.3
1419.8
10.6
10.9
0.0
0.0
0.0
95.4
91.1
0.0
10963.5----------------11150.6========4806.1
376.0
187.1
5780.8
438.3
2275.7
1..25
59.50.0
1604.7
10.4
1614.7
1654.5
10.4
12.0
-2.3
2.3
0.0
104.1
93.4
0.0
12618.0----------------12815.6----------------4806.7
435.5
199.8
7373.5
459.0
2734.7
1.25
60.7
0.0
1473.5
1203
1546.5
1527.9
1203
13.2
-6.8
6.8
0.0
113.1
96.2
0.0
14145.9
========14355.8=======:4806.7
496.2
219.0
8833.8
393.9
3128.6
1.25
239.0
0.0
131.8
128.0--------504.8
362.3
128.0
14.5
0.0
0.0
0.0
191.3
146.6
000
14508.2
========14846.1==::=::z==
4806.7
135.2
346.9
8957.1
34.4
3163.0
1.25
277.20.0
0.0
24.7
301.9
90.9
24.1
42.6
143.7
-9.1
134.6
208.8
153.8
0.0
14599.1===::===14961.1
::======
4806.7
871.8
362.6
891.,..6
0.0
3163.0
1.25
281.4
0.0
0.0
42.8
324.3
99.2
42.846.8
135.4
0.0
135.4
221.8
177.6
0.0
14698.3
========15103.7
========4806.7
1023.8
405.4
8861 ..1
0.0
3163.0
1.25
$3 BILLION (1982 DOLLARS)STATE APPROPRIATION SCENARIO
7%INFLATION AND 10%INTEREST
Sheet 2 of 3
TABLE 18.19 I u_,,__!
1
I
:***************************************~******************~:*****************************************************~~***~*********~ATAI0~WATANA-DC (ON LINE 1993-20021-$3.0 8N(S1982)STATE FUNDS-INFLATION 7%-INTEREST 10%-CAPCOST $5.117 BN 23-FEB-82*******************************************************************************************************************************
I 2005 2006 2007 2008 2009 2010 2011 2012 2013 TOTAL
CASH FLOW SUMMARY
===($MILLION)====
73 ENERGY GWH 60'12 6147 6250 6412 6544 6616 6638 6660 6682 104826
521 KEAl PRICE-MILLS 43.82 40.97 38.08 34.79 32.53 30.45 28.74 27.13 25.63 0.00
466 INFLATION INDEX 490.37 524.69 561.42 600.72 642.77 687.77 735.91 787.42 842.54 0.00
520 PRICE-MILLS 214.89 214.98 213.79 208.98 209.12 209 ..41 211.54 213.62 215.95 0.00
-----INCOME-----------------
516 ~EVENlJE 1309.0 1321.4 1336.1 1352.4 1368.4 1385.3 1404.1 1422.6 1442.9 18656.4
170 LESS OPERATING COSTS 118.4 129.2 141.0 153.9 168.0 183.4 200.1 218.4 238.'"2202.0---------------- ---------------- ----------------------------------------517 OPERATING INCOME 1190.6 1192.2 1195.0 1198.5 1200.4 1202.0 1204.0 1204.2 1204.5 16454.4
214 ADD l"TEREST EARNED ON FUNDS 22.8 24.9 2701 29.6 32.3 35.3 38.5 42.0 45.9 412.4
550 LESS INTEREST ON SHORT TERM DFBT 40.5 44.2 49.3 55.2 59 ..8 64.4 69.6 73.4 77.5 148.6
391 LESS INTEREST ON LONG TERM DEBT 886.8 881 ..6 816.0 869.7 862.9 855.3 847 ..0 837.9 821.9 12013.6---------------- ---------------- -------- -------- ------------------------548 ~ET EARNINGS FROM OPERS 286.1 291.2 296.9 303.1 310 ..0 317.5 325.8 335.0 345 ..0 4104.6
-----C~SH SOURCE AND USE----
543 CASH INCOME FROM OPERS 286.1 291.2 296.9 303.1 310.0 317.5 325.8 335.0 345.0 4104.6
446 STATE CONTRIBUTION 0.0 0.0 0..0 0.0 0.0 0.0 0.0 0.0 0.0 4806.7
143 LONG TERM DEaT DRAWOOWNS 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9049.0243WORCAPDEBTORAWD014NS36.4 51.3 59 ..3 45.8 45.9 52.0 31.7 41.2 44.9 819.1-------------------- -------- ---------------------------------------- --------549 TOTAL SOU~CES QF FUNDS 322.5 342.5 356.2 349.0 355.9 369.5 363.6 376.1 389.9 18180.1
320 LESS CAPITAL EXPENDITURE 108.2 118.1 128.9 140.7 153.6 167 ..6 182.9 199.7 211 ..9 16115 ..9441LESSHORCAPANDFUNDS36.4 51.3 59.3
45.13 45.9 52.0 37.7 41.2 44.9 819.1
260 LESS DEBT REPAYMENTS 51.5 56.7 62.3 68.6 75.4 83.0 91.3 100.4 110.4 880.9------------------------------------ ----------------------------------------141 CASH SURPLUS(OEFICIT)126.3 116.4 105.6 93.9 81.0 67.0 51.6 34.9 16.7 963.5249SHORTTERMO:BT 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0444CASHRECOVERED126.3 116.4 105.6 93.9 81.0 67.0 51.6 34.9 16.7 963.5
-----BALANCE SHEET----------225 RESERVE ANO CONT.FUND 249.7 271.4 296.2 323.3 352.8 385.1 420.3 1t58.7 500.6 500.6371OTHERWORKINGCAPITAL193.2 221.7 256.2 274.9 291.2 310.9 313.4 316.2 319.2 319.2
454 CASH SURPLUS RETAINED 0.0 0.0 0..0 0.0 0.0 0.0 0.0 0.0 0..0 0..0370CUM.CAPITAL EXPENDITURE 14306.5 14924.6 15053.6 15194.3 15347.9 15515.5 15698.4 15898.1 16116.0 16116.0
=~=:============:==:==::========================================================465 CAPITAL EMPLOYED 15248.3 15411.7 15605.9 15792.4 15991.9 16211.4 16432.1 16612.9 16935.7 16935.1
461 STATE CONTRI~UTION =f==============================================================================:4806.1 4806.7 4806.7 4806.7 4806.7 4806.7 4806.1 4806.7 4806.7 4806 ..7
462 RETAINED EARNINGS !1183.5 1358.3 1549.b 1758.9 1987.9 2238.5 2512.7 2812.8 3141.1 3141.1555DEBTOUTSTANDING-SHORT TERM 441.3 493.1 552.4 598.2 644.0 696 ..0 733 ..7 174.8 819.7 819.7554DiBTOUTSTANDING-LONG TERM ,8816.2 8759.5 8697.2 13628.6 8553.2 8410.2 8378.9 8278.6 8168.1 8168.•1
542 ANNuAL DEBT ORAWWDOWN $1982 f).0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0 3163.0'543 CUM.aEBT DRAWWDOWN $1982 3163.0 3163.0 3163.0 3163.0 3163.0 3163.0 3163.0 3163.0 3163.0 3163.0519DEBTSERVICECOVER1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 0.00
~heet 3 of 3
$3 BILWION (1982 DOLLARS)STATE APPROPRIATION SCENARIO
.7%INFLATIONiAND 10%INTEREST
._::_1_.
TABLE ia.t •
,
,~--L.-L--L -'-_.
---,.L--J --~'
.--,
'-----.J ~.....-J
*******************************************************************************************************************************DATA10K WATANA-DC (ON LINE 1993-2002)-$2.3 BN (S1982)STATE FUNDS-INFLATION7%-INTEREST 10%-CAP COST $5.117 8N 23-FEB-82*******************************************************************************************************************************
1985 1986 1987 1988 1989 1990 1991 1992 1993 199~
CASH FLOW SUMMARY
===(SMILLION)====
73 ENERGY GWH 0 0 0 0 0 a 0 0 3387 3387521REALPRICE-MILLS 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50.85 58.76466INFLATIONINDEX126.72 135.59 145.08 155~24 166.10 177.73 190.17 203.48 217.73 232.97
520 PRICE-HILLS 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 110.73 136.90
-----INCOME-----------------516 REVENU~0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 375.0 463.6
170 LESS OPERATING C~STS 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 26..29.3---------------- -------- ---------------------------------------- ----------------517 OPERATING INCOME 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 348.1 43~.3214ADOINTERESTEARNEDONFUNDS0.0 0.0 000 000 000 000 0.0 0.0 0.0 5.6
550 LE:SS INTEREST ON SHORT TERM DEBT 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.8
391 LESS INTEREST ON LONG TERM DEBT 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 303.1 331.9------------------------ ---------------- -------------------------------- --------548 NET EARNINGS FROM OPERS 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 45.0 98.3
-----CASH SOURCE AND USE----548 CASH INCOME fROM OPERS 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 45~0 98.3446STATECONTRIBUTION403.7 472.7 47907 49905 938.3 138.4 0.0 000 0.0 0.0
143 LONG TERM DEBT DRAWDOWNS 0.0 0.0 0.0 000 0.0 812.0 1328.3 890.4 288.1 113.2248WORCAPDEBTDRAWDDWNS0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 98.0 17.7------------------------ -------- ---------------- -------- ------------------------549 TOTAL SOURCES OF fUNDS 403.7 472.7 479.7 499.5 938.3 1550.4 132803 890.4 431.1 289.2
320 LESS CAPITAL EXPENDITURE 403.7 472.7 479.7 499.5 938.3 1550.4 1328.3 890.4 33301 259.2448lESSWORCAPANDFUNDS0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 98.0 17.7260LESSDEBTREPAYMENTSn.o 000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 12.2------------------------ -------- ---------------------------------------- --------141 CASH SURPLUS(DEFICIT)0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
249 SHORT TERM DE8T 0.0 0.0 0.0 0.0 0.0 0.0 000 0.0 0.0 0.0
444 CASH RECOVERED 0.0 000 0.0 0.0 0.0 0.0 0.0 000 0.0 0.0
-----BALANCE SHEET----------225 RESERVE AND CONT.FUND 000 0.0 0.0 0.0 0.0 0.0 0.0 000 56.5 61.63713THERWORKINGCAPITAL0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 41.5 54.1
454 CASH SURPLUS RETAINeD 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0370CUM.CAPITAL EXPENDITURE 403.7 876.4 1356.1 1855.6 2794.0 4344.3 5672.6 6563.0 6896.1 1155.3
======== ================================ =========~==============================465 CAPITAL EMPLOYED 403.7 876.4 1356.1 1855.6 2794.0 4344.3 5672.6 6563.0 6994.1 1271.0================================================================================461 STATE CONTRIBUTION 403.7 876.4 135601 1855.6 2794.0 3532.4 3532.4 3532.4 3532.4 3532.4
462 RETAINfD EARNINGS 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 45.0 143.3
555 DEBT OUTSTANDING-SHORT TERM 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 98.0 115.7
554 DEBT OUTSTANDING-LONG TERM 0.0 0.0 0.0 0.0 0.0 812.0 2140.2 3030.7 3318.7 3~19.6
542 A~NUAL DEBT DRAWWDOWN $1982 0.0 0.0 0.0 0.0 0.0 456.8 698.4 437.6 132.3 74.3
543 CUM.DEBT DRAWWDOWN S1982 0.0 0.0 0.0 0.0 0.0 456.8 1155.3 1592.9 1725.2 1799.5
519 DEBT SERVICE COVER 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.15 1.25
$2.3 BILLION (1982 DOLLARS)MINIMUM STATE APPROPRIATION SCENARIO
7%INFLATION AND 10%INTEREST
Sheet 1 of 3
TABLE 18.20
I
5605
55.83
458.29
255.86
0.0
3827.2
1.25
5414
59.90
428.31
256.58
0.0
3827.2
1.22
5223
63.57
400.29
254.47
35.1
3821.2
1.Z2
3387
38.96
374.10
145.75
375.7
3191.5
1.25
3387
41.29
349.62
144.36
440.1
3415.8
1.25
419.4
2975.7
1.25
362.4
2556.3
1.25
120.6
2194.0
1.25
33fl7
52.11266.73
139.00
142.9
2073.4
1.25
3387
55.38249.28
138.06
i 131.0
'1930.5
1.25
467.6 470.8 476.3 480.2 484.5 488.9 493.6 1329.0 1389.0 1434.0
32.0 35.0 38.1 41.6 45.4 49.6 54.1 91.1 99.4 108.5-------------------------------------------------------- -------- ----------------435.6 435.8 438.1 438.6 439.1 439.3 439.5 1237.9 1289.6 1325.56.2 6.7 7.3 8.0 8.7 9.5 10.4 11.4 19.1 20.9
11.6 12.4 15.3 16.4 17.7 18.1 19.8 21.0 33.8 36.3
330.6 329.3 327.8 326.2 324.4 322.4 320.3 982.5 994 ..1 988.8---------------- -------- ------------------------ -------- -------- ----------------99.5 100.8 102.3 104.0 105.8 107.7 109.9 245.8 280.8 321.3
99.5 100.8 102.3 104.0 105.8 107.1 109.9 245.8 280.8 321.30.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
326.5 381.2 344.2 1106.6 1310.3 1538.8 1405.6 142.8 0.0 0.0
3.1 29.3 11.2 12.2 10.6 10.4 12.3 128.0 24.7 42.8
-~-------------------------------------- -------- --------------------------------434.2 511.3 457.7 1222.11 1486.6 1651.0 1527.8 516.5 305.5 364.2
412.6 467.2 430.2 1192.1 1456.3 1624.8 1491.6 362.3 90.9 99.28.1 29.3 11.2 12.2 10.6 10.4 12.3 128.0 24.7 42.813.5 14.8 16.3 17.9 19.7 21.7 23.9 26.2 53.9 59.3
-~---------------------- ---------------------------------------- ----------------0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 136.0 162.80.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 136.0 162.8
67.2 73.4 60.1 87.4 95.4 104.1 113.1 191.3 208.8 227.85b.6 79.7 84.2 89.1 91.1 93.4 96.2 146.6 153.8 171.6
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
17567.9 8035.1 8465.3 9657.9 11114.2 12739.1 14230.7 14593.0 14683.8 14783.0
=';;;i:;==;i;;:;==;~;;::==;;;::;=ii;~i::=i;;;~:~=i:;;;:;=i:;;;:;=i;~;~::=i;i;;:;
='3532::=:3532::==3532::==3532:4 ================ ============:::========-=-===========3532.4 3532.4 3532.4 3532 ..4 3532.4 3532.4
i 242.8 343.7 446.0 550.0 655.7 763.4 873.3 1119.1 1263.9 1422.4
!123.9 153.1 16tt.3 116.6 181.1 197.6 209.9 331.8 362.6 405.it3792.1 4159.0 4486.9 5575.6 6926.2 8443.3 9825.0 9941.5 9887.6 9826.2
ENERGY GWH
REAL PRICE-I'll llS
INflATION INDEX
PRICE-MIllS
-----INCOME-----------------
itEVENUE
LESS OPERATING COSTS
,JPERAT IlliG INCOME
ADD INTEREST EARNED ON FUNDS
LESS INTEREST ON SHORT TERM DEBT
LESS INTEREST ON LONG TERM DE8T
NET EARNINGS FROM OPERS
13
521466
520
516
170
517
214
550
HI
::i4tl
-----CASH SOURCE AND US(----
~43 CASH INCOME FROM OPERS446STATECONTRIBUTION
143 LONG TERM DEBT ~RAWDOWNS
243 WORCAP DEBT DRAWDOWNS
549 TOTAL SOURCES OF FUNDS
320 LESS CAPITAL EXPENDITURE448LESSWORCAPANDFUNDS
260 lESS DEaT REPAYMENTS
141 CASH SURPlUS(DEFICITJ
249 SHORT TERM DEBT
444 CASH RECOVERED
-----BALANCE SHEET----------225 RESERVE AND CONT.FUNO
371 JTHER WORKING CAPITAL
454 CASH SURPLUS RETAINED
370 CUM.CAPITAL EXPENDITURE
465 CAPITAL EMPLOYED
461 STATE 'CONTRIBUTION
462 RETAINED EARNINGS
555 DEBT OUTSTANDING-SHORT TERM
554 DEBT OUTSTANDING-LONG TERM
542 ANNUAL OEaT DRAWWDOWN $1982
543 CUM.DEBT DRAWWDOWN £1982
513 DEBT SERVICE COVER
,.I******************************************************************************************~************************************DATAIJK WATANA-DC (ON LINE 1993-2002)-$2.3 BN(£19S2)STATE fUNDS-INFLATION 7~-INTEREST 10~-CAP COST £5.117 BN 23-FEB-82*******************************************************************************************************************************
I
I 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
CASH FLOW SUMMARY
===(~MILLION)====
3387 3387 3387
49.27 46.43 43.78
285.40 305.38 326.75
140.63 141.79 143.06
SHeet 2 of 3
$2.3 BILLION (1982 DOLLARS)MINIMUM STATE APPROPRIATION SCENARIO
I 7%INFLATION !AND 10%INTEREST
TABLE lB.20.
~~
L-L-L-r-L_~·L--:___,~:=J ___.J
*~:*********************************************************~*******************************************************************DATAI0K WATANA-DC (ON LINE 1993-2002)-$2.3 SN (S1932)STATE FUNDS-INFLATION 1%-INTEREST lOt-CAP COST $5.111 BN 23-FEB-82*******************************************************************************************************************************
104826
0 0 00
0.00
0000
496504
TOTAL
21929.6
2202.0
lt965.4
353204
10107.8
819.7
1972706
412.4
146.614428.0
3532.4
3126.1
819.1
8942.2
3821.2
3821.2
0.00
50006319.2
0.0
16200.7========17020.5==::==;;::=:
19lt2503
16200.7
819.11165.5--------123903
0.01239.3
ltOl.9
000
0.0
44.9
0.0
3827.2
1025
446.8
211.9
44.9
139.9
44.1
000
44.1
1341.1
45.9
11.5908.2
2013
401.9
1580.1
23804
6682
28.07
842054
236049
500.6319.2
000
16200.7
========17020.5========3532.lt
3126.1
819.1
8942.2
62.4
0.06204
1341.4
4200
13.4920.9
389.2
0.0
0.0
4102
430.3
19907
41.2
12701
1559.8
218.4
389.2
2012
666029.15
181042
234.23
3532.4
336803
114.8
9082.1
0.0
3821.2
1.25
========
lt58.1
316.2
000
1598208======:c=16751.6
1541.3
200.1
377.6
31106000
0.0
3107
415.3
182.9
37.7
115.6
79.1
000
19.1
134102
3805
69.6
932.5
2011
6638
31055
735.91
232.21
3532.4
3041.5
733.7
920902
0.0
3827.2
1.25
========
420.3
313.4
000
15783.2========1651608
3532.4
2143.0
69600
9324.8
36701
419.0
167.6
5200105.1
36101
000
000
52.0
661633.46
681.77
230.15
2010
9404
0.094.4
0.0
3821.2
1025
16296.2
385.1310.9
0.0·
15600.2
.152206
183.4--------1339.2
35.3
64.4
94300
----------------
========
108.4
0.0
108.4
403.4
153.6
45.9
95.5
1505.6
168.0
351.5
357 0 5
0.0
0.0
4509
1337.6
3203
59.·8
95205
353204
2410 03644.0
9429.9
0.0
3821.2
1025
352.8
291.2
0.0
151t32.6========16016.6========
348.9
0.0
0.0
45·.8
34809
394.1
140.1
45.886.8
3532.4
2221.2
598.2
9525.4
0.0
3827.2
1.25
121.3
0.0
121.3
323.3274.9
0.015219.0
15811.2
1489.6
1'53.9--------1335.1
29.6
5502961.2
========
========
341.0
2907 200B 2009
CASH FLOW SUMMARY
===($MIlLION)====
6250 6412 6544
41099 38.32 35.80
561.42 600.72 642011
235075 230.18 230.09
1413.3
141.0
341.0
000
0.0
59.3
133.1
0.0
133.1
400.2
128.q
59.378.9
1332.3
27.1
49.3
969.1
3532.4
1993.7
,552.4
9612.3
000
3827.2
1.25
296.2
25602
0.0
15138.3
15690.1========
========
1458.6
129.2
333.8
0.0
0.0
5103
6141
45.23524.69
237.31
2006
143.9
0.0
14309
1329.4
24.9
44.2
916.3
385.0
11801
51.311.8
333.8
3532.4
1785.8
493.1
9691.2
0.0
3827.2
1.25
271.4
221.7
0.0
1500904
15502.5========
=====::=
1446.3
11804
321.3
0.0
0.0
36.4
1327.8
22.8
4005
982.8
153.8
0.0
153.8
363.1
10802
36.465.2
32103
2005
6092
48.42
490.31
237.42
0.0
3827.2
1.25
353204
1595 09
441.8
9163.0
248.7
19302
0.0
14891.3========15333.1==:=====
ENERGY GWH
REAL ?RICE-MIlLS
INflATION INDEX
PR ICE-MILLS
-----INCOME-----------------
REVENUE
LESS OPERATING COSTS
OPERATING INCOME
ADO INTEREST EARNED ON FUNDS
LESS INTEREST ON SHOKT TERM DEBT
lESS INTEREST ON LONG TERM DEBT
N~T EARNINGS FROM QPERS
-----CASH SOURCE AND USE----
CASH INCOME FROM OPERS
STATE CONTRI3UTION
LuNG TERM DEBT.DRAWDOWNS
WORCAP DEBT ORAWDOWNS
TOTAL SOURCES OF FUNDS
13521
466
520
516
110
517
21ft
550
391
543
543
446
143
248
549
320 LESS CAPITAL EXPENDITURE
448 lESS WORCAP AND FUNDS260lESSDEBTREPAYMENTS
141 CASH SURPLUS«DEFICIT)
249 SHORT TERM DEBT
44~CASH RECOVERED
-----BAlANCE SHEET----------
RESERVE AND CONT.FUND
OTHER WORKING CAPITAL
CASH SURPLUS RETAINED
CUM.CAPITAL EXPENDITURE
CAPITAL EMPLOYED
STATE CONTRIBUTION
~ETAINED EARNINGS
DEBT OUTSTANDING-SHORT TERM
DEBT OUTSTANDING-lONG TERM
ANNUAL DEBT DRAwwDOWN $1982
CUM.DEBT DRAWWOOWN $1932
DEBT SERVICE COVER
461
462
555
554
225
371
454
310
465
542
'543
51CJ
Sheet 3 of 3
$2.3 BILLION (1982 DOLLARS)MINIMUM STATE APPROPRIATION SCENARIO
7%INFLATION AND 10%INTEREST
TABLEIS.20 [iii
TABLE 18.21:FINANCING REQUIREMENTS - $BILLION
For $3.0 billion State Appropriation Scenario
Interest Rate 10%
In flation Rate 7~~
1982
Actual Purchasing
Power
--rbillion
1985 State Appropr iat ion 0.4 0.3
86 "0.5 0.4
87 "0.5 0.3
88 "0.5 0.3
89 "0.9 0.6
90 "0.5 0.9
91 "1.5 0.2
Total State Appropriation 4.8 3.0
1990 Guaranteed or G.O Bonds
1 " "
0.8 0.4
2 ""0.7 0.4
3 ""0.3 0.1
Total Watana Bonds 1.8 0.9
1994 Revenue Bonds 0.2 0.1
5 ""0.4 0.1
6 ""0.4 0.2
7 ""0.4 0.1
8 ""1.2 0.4
9 ""1.4 0.4
2000 ""1.6 0.5
1 ""1.5 0.4
2 ""0.1 0.1
.J
],
1
;)
J
Total Susitna Bonds 9.0 3.2
11
I )
rl
lJ
TABLE 18.22:FINANCING REQUIREMENTS - $BILLION
For $2.3 billion State Appropriation Scenario
Interest Rate 10%
Inflation Rate 7~~
1982
Actual Purchasing
Power
--rbillion
(]1985 State Appropriation 0.4 0.3
86 "0.5 0.4
87 "0.5 0.3
88 "0.5 0.3r~l 89 "0.9 0.6
90 "0.7 0.4
Total State Appropriation 3.5 2.3
1990 Guaranteed or G.O Bonds 0.8 0.5
1 ""1.3 0.7
[2 ""0.9 0.4
3 ""0.3 0.1
Total Watana Bonds 3.3 1.7
--------------------------------------------------------
1994 Revenue Bonds 0.2 0.1
5 ""0.3 0.1l16""0.4 0.2
7 ""0.3 0.1
8 ""1.1 0.4
9 ""1.4 0.4
2000 ""1.5 0.4
1 ""1.4 0.4
2 ""0.2
Total Devil Canyon Bonds 6.8 2.1
(1_J
u
u
u
Total Susitna Bonds 10.1 3.8
BASIC PARAMETERS OF RISK GENERATION MODEL
.CAPITAL COSTS (REAL 1982 $billion)
Below 3.1 Below 3.6 Below 4.3 Below 5.1
COAL PRICE ESCALATION (%REAL)
)
I
),
J
)
)
~)
)
r
)
)
I
)
)
)
J
)
l
'fA8LE-,8;23-_I .
.15
1.00
.33
11 - 13
-4%
.25
5.0 to 2000
2.2 thereafter
.90
.43
.
9 -11
.34
-3%
.32
.73
7-9
.50
2.6 to 2000
INTEREST RATES %
1.2 thereafter
.33
-2%
.46
INFLATION'RATE
DIFFERENCE FROM INTEREST RATE
.10
o
.25
5-7
PROBABILITY
PROBABIL1TY
PROBABI L1TY
PROBABIL1TY
i,..__'L __L __',--.
i~__=::J
LOAD
FORECAST
ALTERNATIVE
CAPITAL COST
PUEL COST
ESCALATION
RESULT
10 PROBAB I L1TY
LONG-TERM COST
PRESENT WORTH
.09 5,661
.03 10.321
.03 5.991
.01 8,492
.03 4.590
.03 8,746
.01 4.856
.02 7,460
.01 9,253
.06 6.878
.18 8.238
.06 8,858
.09 10.637
.01 7.184 _
.03 11.272
~3 1~194
.01 13.742
.06 10.859
.01 7.624
.02 10.503
.01 $15.058
.02 1Ui69
.03 7.313
~c 1.00
T26 .02 6.101
.01 4,412
B-~~06 7.915
.03 5,489
.t HIGH TOIHIGH.04 MEDIUM Ib2~LOW I03%I04HIGH.20 .60 MEDIUM .12 /<.<,T05
T06
T07LOW.04 /
<,TOBT09
TlOr&HIGH .12 /-,III%TI2
TI360MEDIUM.60 .60 MEDIUM .36 /Tl4~<,TI5
Tl6"b LOW .12 /
-,B~
HIGH .04 /Tl9
T20<,I21IxLOW.20 .60 MEDIUM .12 /T22
"<.-,T23
T24
","HIGH T25LOW.04 ~o MEDIUM T26,<'1t LOW T27
FIGURE rs.t -PROBAB' L1TY TREE - SYSTEM WITH ALTERNAT,VES TO SUSITNA 11~lm I
1
I
),
],
)
)
j
1
j
)
r-~-L_L __-,--
502 .0025 10,683
532 .Q150 "1,062
5IT6 .0120 8,390
507 H_H .0016~8,961 _
508 .0025 8,050
509 .0060 7.161
510 .0045 11,6.!!~_
5 II .0075 10,868
512 .0180 9.758
513 .0090 10,1~L _~__H _
514 .0150 ---!!..247 ~u__
5 15 .0360 8,347.~~_
516 .0046 8;908 _
5 17 .0.(176 8,008
518 .0180 7,108
519 .0015 11,414
522 .0030 10,126
503 .0060 ...,9"',7""8=4 _
504 .0030 _--',10"",1=-:9"==0,---_
505 .00fiO 9,290
537 .0075 7,884
520 .0025 10,614
521 .00609.614
533 _.1800___6.161
529 .0375 7,388
538 .0125 6,99153903006097 -----
540 .0150 _7,543
541 .0250 _6,650
528 .0226 8,371
542 .0600 5.757
531 .0460 7,974
524 .Q120 8.326
525 .0015 8,886
526 .0026 7,986
523 .0050 9,221
530 .0000 6,477
527 .0060_'_7.081
534 .0226 7,660
535 .0376 6,738S36..!IBOfi...-_~8-=-27=--------
RESULT LONG-TERM COSTm..PROBABILITY PRESENT WORTH
501 .0015 $11,684
543 .0075 7.331
544 .0125_u__~,437 _
545 .0300 5.543, _
L =1.000
FIGURE 18.2 -PROBABILITY TREE -SYSTEMWITH SUSITNA I~~Im I
SUSITNA
CAPITAL
COST
FUEL COST
ESCALATION
ALTERNATIVE
CAPITAL
COST
LOAD
FORECAST
HI(.;H -
HIGH .QI ~MEDIUM,25
"-lOb LOW.~
HIGH 04 ,50 MEDIUM m /-,"<,LOW ,01 /
-,
0 HIGH ,03 /rv -,~HIGH 20 .60 MEDIUM 12 _50 MEDIUM OF /
~-,
'rJ
0 LOW ,03 /-,
HIGH ,01 /
"%LOW ,04 ,SO MEDIUM ,02 /
!""-/.~,
LOW ,01 /
cl <,
'Vi
i HIGH 15 /-,I I~/
, 60 MEDIUM 60 1.0
MEDIUM ,60 ,50 MEDIUM ,30 /
"<.<,
'b
LOW -'5 /
"-
HIGH oe /-,%LOW .20 10 MEDIUM 20 50 MEDIUM .10 /
~-,
HIGH
LOW ,05 %5 MEDIUM
""0 LOW
t
J
.~
)
)
J
1
.J
.J
~
!
I
1
L-I~_-L...--_--,
14
12
10
e
°....
x
°8°o.....
~
en...en
0
(J
E 6a-
ll)
l-
e"c
0
..I
4
2
r
.J
...--r
r--r-/
Non-Susitna Plan-\r ~/~
r J
I ,.r ~.......r-
~.
.tIr
................
Susitna Plan J---,!il~~~~~~~111~~~11j1
o .1 .i .3 .4 .5 .6 .7 .8
.9 1.0
Cumulative Probability
FIGURE 18.3 -SUSITNA MULTIVARIATE SENSITIVITY ANALYSIS - LONG-TERM COSTS VS CUMULATIVE PROBABILITY
L-i _
'---
1.0
.9
.8
.7
>~:c .6
III.cea.
Q).5
.::...III
"3 .4E
:lo
.3
.2
.1
->-
/
/
/
/
/
./V
//'
/
,
..../V
(4500) (3500) (2500)
(1500) (500) 0 500
Net Benefit -$x 106 (1982 $)
1500 2500
3500 4500 5500
FIGURE 1B.4- SUSITNA MULTIVARIATE SENSITIVITY ANALYSIS -CUMULATIVE PROBABILITY VS NET BENEFITS 11~lm I
_!_-
r----l __
~~-311
VI.
SOFTWARE
REVISIONS
X.
TRANSMISSION
SYSTEM
AND
EMERGENCY
GENERATION
START
I
I
I
SUMMARY
NOTES
I
I,~
dJ
v.
TR ANSFORMATION
ASSESSMENTS
JI't1t
IX.
INITIAL
COMPUTATION
AND
INTERPRETATION
~
~
XI.
UPDATE
AND
FEEDBACK
\I;
-JJ
II.
RISK
LIST
DEVELOPMENT
-.
RISK
LISTS
~
IV.
RISK
ASSESSMENTS
.-
ASSESSMENT
DOCUMENTS
-311
VII.
CONSEQUENCE
IRESPONSE
CRITERION
ASSESSMENTS
I
DOCUMENTATION
-31
VIII.
REVIEW
AND
REVISE
XII.
FINAL
COMPUTATION ~
AND
INTERPRETATION
I
RISK
ANALYSIS
REPORT
"RISK ANALYSIS STUDY METHODOLOGY
FIGURE 18.5
lJ
[I..J
QUESTION:
WHAT MAJOR CONSTRUCTION
PROJECTS ARE INVOLVED?
WHAT KIND OF WORK is GOiNG ON
FOR A GIVEN CONFIGURATION '?
WHAT ARE THE POSSIBLE INITIATING
MECHANISMS WHICH COULD INFLUENCE
ESTIMATED COSTS OR COMPLETION TIMES?
WHAT MAJOR PORTIONS OF ANY GIVEN
CONFIGURATION ARE SUBJECT TO
RISK REALIZATION 1
IF A PARTICULAR RISK MAGNITUDE IS
REALIZED.WHAT POSSI BLE
CONSEQUENCES CAN OCCUR?
HOW CAN THESE CONSEQUENCES
BE MEASURED?
WHAT IMPORTANT ASSUMPTIONS AND
LI MITATIONS MUST BE ESTABLISHED
TO PERMIT A REASONABLE ANALYSIS
AND TO DRAW IMPORTANT
CONCLUSIONS?
STUDY ELEMENT:
ELEMENTS OF THE RISK ANALYSIS
FIGURE 18.6
@FOR ANY GIVEN DAMAGE
LEVEL,THREE CRITERION
VALVES ARE ESTIMATED
AND FIT TO A MODIFI ED
BETA DISTRIBUTION.
®IF A RISK EVENT OCCURS,
IT CAN CAUSE A NUMBER
OF POSSIBLE DAMAGE
LEVELS,EACH WITH A
PARTICULAR PROBABI L1TY
OF OCCURENCE.IF
RISK MAGNITUDE ®
OCCURS, THE PROBABIL1TY
IT WILL CAUSE MODERATE
DAMAGE IS THE VALUE OF®ON THE DIAGRAM.
CD A SERIES OF DISCRETE
RISK PROBABILITY LEVELS
EXISTS FOR EACH RISK-
ACTIVITY COMBINATION.
THE ANNUAL PROBABILITY
OF EACH IS DETERMINED.
MAXMINMODE
INCREASING
OF RISK
t
PROBABI L1TY
OF A
PARTICULAR
RISK
MAGNITUDE
t ®
PROBABI L1TY
OF A
PARTICULAR
CRITERION
RISK
PROBABIL1TY
OF A
PARTICULAR
DAMAGE LEVEL
IF A PARTICULAR
RISK
MAGNITUDE
IS REALIZED
fj
1/
i )
lJ
il
L]
INCREASING CRITERION
VALVE
\)(J STRUCTURAL RELATIONSHIP FOR HANDLING
RISK ACTIVITY COMBINATIONS,DAMAGE SCENARIOS
AND CRITERION VALUES
FIGURE 18.7
,~_.L-L _
----'
1.0
0
W
I.LW .9
OUX
WW .8
<.!)I-~O .7
ZZ
W...J~...J .6
W-CL~
I-W .5
e:(I-W::r:e:(:::>.4I-~...J
>-I-~1-(1).3
...JW O
-I-W
~U~.2
m~u00-
0::0::0 .1
CLCL Z
0
I
IEXPECTEDVALUE ~.C=IIHIGHII ESTIMATE90.25%~I
~I
f"1 ~~ROJECT ESTIMATE)
I
..>-:-r
I
~8=IIL6~1I ESTIMATE
/
I
I
I
/I
I-:I
I
ILI
I
-'1
70 80 90 100 110 120 130 140
PERCENTAGE OF FINAL DIRECT COST ESTIMATE WITH CONTINGENCIES
CUMULATIVE PROBABILITY DISTRIBUTION
FOR WATANA PROJECT COST
FIGURE 18.8
II
L-_L-.....i.,_~.l..-.-_~
ATE
I I --I ~.----EXPECTED VALUE ~~..C= HIGH ESTIM)91.5°/c;.~~
I ~PROJECT ESTIMATE)I
V
_/I
I
l}!JS =IILOW"IESTIMATE
-:I
I
/'I
/I
/'I
I
V I".~I
II
..J..J 1.0
3:W .9I-C)(1)~Oz .8
Uw
U
..JO::.7
<X:W
::,:)Q.
I-.6
UO
<X:WI-.5~~z-
1-0 .4z
>-0 .3I-W
..J W
-Umx .2
<X:Wm
01-.1
0::0
Q.Z
60 70 80 90 100 110 120 130
PERCENTAGE OF PROJECT ESTI MATE
CUMULATIVE DISTRIBUTION
OF DEVIL CANYON COSTS
FIGURE 18.9
rr:::L__
1.0
.9
oz .8-CI
1LI
.71LI
~1LI
1LI :::>.6
b ~.5z
CI
I.L.1LIot-09-«>-u
.3t-CI
-'Z
rn .2«m
0 .10::
0...
0
I I ~ESTIM~TEEXPECTED VALUE ~
9.06%
H ~
:lV
:/A =(PROJECT ESTIMATE)
/~
I
fts=IILOW;"ESTIMATE
/'I
I
V I
I
/'II
I
/II
I
4'I
70 80 90 100 110 120 130 140
PERCENTAGE OF FINAL DIRECT COST ESTIMATE WITH CONTINGENCIES
CUMULATIVE PROBABILITY DISTRIBUTION
FOR SUSITNA HYDROELECTRIC PROJECT
FIGURE 18.10
[i]
i_,__'_L-__•L__l"..-.--'
,,
~--,
,
--.......-'---"
1.0
.90
IJ...80
0
>-U .70zw:::)w
OU .60WZ
a::w
IJ..O::
0::
W:::).50
>8-0~.40
...J
:::)
~
:::).30'
U
.20
.10
0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3
RATIO OF ACTUAL COST TO IINITIAL"ESTI MATE
2.5 2.7 2.9 3.1
HISTORICAL WATER RESOURCES
PROJECT COST PERFORMANCE (48 PROJECTS)
FIGURE 18.11
L..._-__I .IL_~L_".--.l.~~""';~---<__:~i
1.0
.90
I.L..80
0
>-U .70zw
wu
::::>z
Ow .60Wo::
0::::::>
I.L.U
U .50wO>
~.40
..J
::::>
:E .30::::>
U
.20
.10
FIGURE 18.12
0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3
RATIO OF ACTUAL COST TO IIINITIALII ESTIMATE
COMPARISON OF SUSITNA RISK RESULTS WITH
HISTORICAL WATER RESOURCES PROJECT
COST PERFORMANCE (48 PROJECT )
2.5 2.7 2.9 3.1
r-r-r-r-r-:
,----:---
'--~~_1__1 _:__i ~--j J
"
~~
I V,/
/
)~= SCHEDULE ESTIMATE
,/INCLUDING A ONE YEAR
CONTINGENCY
/V
/
_/V
~B=SCHEDULE ESTIMATE
WITHOUT CONTINGENCY»>I
.9
1.0
.1
o
(!)
.z 8is.,
ww~.7
ww:::>b.J .6
Z::J
I.L.0 .5
Ow
~~.4_0.J-_0
~Z .3
moa::.2
c,
-15 -10 -5 0 5 10
MONTHS FROM SCHEDULED COMPLETION
15 20
WATANA SCHEDULE DISTRIBUTION
EXCLUSIVE OF REGULATORY RISKS
FIGURE 18.13
_1_-I I •L·I
~'__'~~_-.-1 __~I
.1
.6
.7
1.0
.9
.8
(!)
Z
ow
~
X
LLl W....3 .5
~~
u,0 .4
Ow
>-~.3t-u
::JOiiiz .2«-rno
0::a.
o
-
--------»>I---"""
/I-'"
..J:·~SCHEDULE ESTIMATE
/INCLUDING A ONE YEAR
CONTINGENCY
JV
./B= SCHEDULE ESTIMATE
WITHOUT CONTINGENCY
/V
/
--'V
-30 -20 -10 o 10 20 30 40
MONTHS FROM SCHEDULED COMPLET ION
WATANA SCHEDULE DISTRIBUTION
INCLUDING THE EFFECT OF REGULATORY RISKS
FIGURE 18.14
[L-I .'L,__i ~'--'i
l..---...J
_,__I -j '.I ,
--~'_---i
1.0
oz
.99-0wo::
We:::{OwX>-w
.980::....WOn..z
IJ..OOO~.970>-
....0
...JW-....me:::{
.96e:::{om_
OoO::zn.._
----~-"~......
......~",......
sS'"~
\.-0",.",-'(,.\oy
~~v·r",0 ,/~EXPECTED VALUES:/0\0
/v.:,0 TOTAL LOSS 0.06961
I /50%REDUCTION 0.09171//
/f I I
ANCHORAGE
/
f
o 2 3 4 5 6 7 8
DAYS PER YEAR OF REDUCED ENERGY DELIVERY
CUMULATIVE PROBABILITY
DISTRIBUTION FOR DAYS OF REDUCED
ENERGY DELIVERY TO ANCHORAGE
FIGURE 18.15
'---L-I 1--
'----L.-........:.--i --~'~'_~I :.--i __~I ~~..--J
--~___I
1.0
(!)z
0
UJUJO:::.99O<{
XUJ
UJ>-
1-0:::
oUJzo..98
lL.cn
O~
>-0
1-0 .97
...JUJ
(DI-
<{<{
(DO
0-
0:::0 .96o.~
/'~
/
,/
/EXPECTED VALUE: .08116
/I IFAIRBANKS
I
f
o 2 :3 4 5 6 7 8
DAYS PER YEAR WITH NO ENERGY DELIVERY
CUMULATIVE PROBABILITY DISTRIBUTION
FOR DAYS PER YEAR WITH NO SUSITNA
ENERGY DELIVERY TO FAIRBANKS
FIGURE 18.16
\
\
\
Tanana
[J
(]
0 65 130 KILOMETERS
IJ I I I
0 65 ''''M''''.[J
I
FIGURE 18.17 .
lJ
lJ
lJ
lJ
lJ
u
FIGURE 18.18 - SERVICE AREAS OF RAI LBELT UTILITIES 111m I
(J
lJ
u
u
(]
LOCATION MAP
l,EGEND
\1 PROPOSED
DAM SITES
----PROPOSED 1:38 KV WNE
--EXISTING l.INES
20 0
1J';1lti;\i it!"_Ii ('I:if
SCAl.E IN MILES
20 60
11::l%:l:,i":=::3C..,~!':~jl'C,':I
u.s.Government
Alaska Power
Administration -Eklutna
University of
Alaska
Alaska Power
Administration -Eklutna
1. Does Not Include Self Supplied Energy from
Military Installations and The University of
Alaska
11
\.J A ENERGY SUPPLY
(Based on Net Generation 1980)
B GENERATING FACILITIES
(Based on Nameplate Generating Capacity 1980)
o RELATIVE MIX OF ELECTRICAL GENERATING
TECHNOLOGY -RAILBELT UTILITIES -1980
FIGURE 18.19 [iii
Regenerative
Cycle
Combustion
Turbine
(111 MW-
12%)
Diesel
(60.6 MW - 6%)
Combined Cycle
Combustion Turbine
(139 MW - 14%)
1. Does Not Include Generation by Military
Installations and The University of Alaska
C NET GENERATION BY TYPES OF FUEL
(Based on Net Generation 1980)
Oil
2%
u
u
11u
IJ
(J
[-1
10,000
rI J
9,000
I)
\ I 8,000
1
7,000
6,000
11 :e-II $:
C)
;:5,000
~.,
c
W
Ir-----..
I
1iIIIII'I1II'lIIII'I-__J
Note: OGP·5 Program Increases Usable
Output at Two Year Intervals
(J 4,000
Energy Deliveries
From Susitna.>
3,000
....II....~-------Watana Alone ---------<+01-------Watana And Devil Canyon ------..
2,000
I)u
u 1,000
u
IJ
1992 1995 2000
Years
2005 2010
FIGURE 1020 - ENERGYDEMAND AND DELIVERI'S FROM 'USITNA IA~lm I
L __L--...--~.
'~I_-L._L..--
I WATANA ONLY IN
1994 1
LEGEND
300 Energy Cost of Best Thermal Option
250
-.
•
Energy Cost of Susitna Option
Operating Costs of Thermal Plant in Use
in 1993 Extended to 1994
Shaded Area Represents Plant Operating
in 1992 Displaced by Watana
•
1 Growth System Energy
it for 1994;4,829 GWh
5,000
FIGURE 18.21 -ENERGY PRICING COMPARISONS -1994
4,000
Area Represents Annual ODE
from Existing Genera
-Common to Both Su
3,0002,000
Annual Energy Output GWh
1,000
jjjj\Area Under This Line is Annual Cost of Best Thermal Option
F::[(Including Investment Costs)
1111------------------------1
dtt:I [Area Under This Line is Annual Cost of Susitna Option
1~~~~ttt -l ~Area Under This Line is Annual
............:Operating Cost of Existing Capacity 1993/4
(Avoided Costs of Fuel and O&MOnly)
. ,rating Costs
ting Plant
sitna and
mal Options
MediulT
Forecai
o I .:.-.:.:.:.-....•:'1'••••••·············································1········;.;.;.;.;.;.;.;.;.1".;.;.;.;.;·;·;·:,.;·····························t.·.·.
50
200
..cs:.:.:~
:E
en...150en
0o
>-'"..
'"cw
100
SYSTEM COSTS AVOIDED BY DEVELOPING SUSITNA
COMPARED WITH BEST THERMAL OPTION IN MILLS PER UNIT
OF SUSITNA OUTPUT IN CURRENT DOLLARS
Rev. 1
380
360
340
320
300
:c
~280.....
~
~260
'"Q)
C,)
';:
0..240'tlc
III
'"....
'"2200
(J
>Cl...
Q)200cw
180
160
140
120
L _
~.
It~
~lr#II#I COST SAVINGS FROM SUSITNA INCREASING
~OVER WHOLE LI FE OF PROJECT
.l
ll#
,...l1li"
Increasing Thermal Fuel i~
Cost Avoided S .#
~#
-lIfIlIIIIl ••-....II1IIII1IIl1liII1II,~.-~~~~~~-#.~
-#~,~
J
J
/..-Avoids Cost of a Further 200 MW Coal Fired Generating Unit
I/II•~l1II."""'"Avoids Cost of 2 x 200 MW Coal Fired Generating Units
Watana on Stream in 1993100
94 5 6 7 8 9 2000 01 02 03
Years
Devil Canyon on Stream in 2002
04 05 06 07 08 09 2010 11 12 13
FIGURE 18.22 - SYSTEM COSTS AVOIDED BY DEVELOPING SUSITNA
[i]
~'--
rWATANA &DEVIL CANYON IN 2003
400
300
.c
$:
~
~
~
t!200o
(,J
~
Q)ew
100
i,
,LEGENDI'I Area Under This Line isAnnual Cost of Best Thermal OptionI-'(Including Investment Cost)l1li '"Energy Cost of Best Thermal Option
:'\.• Energy Cost of Susitna Option:.....I11III __..
::..-Operating Costs of Thermal Plant in Use
::::.in 1993 Extended to 1994
Ill,............i riWWI f:;:'.;.;",;.~::::.~.:,'"::::::m'Operati..
[:[~[t[l[~[t[l~t~t[~[l[l[~[~[~~t~t Im __,r Area Under This Line isAnnual Cost of Susitna Option
::i:~·~:~'~:i;.A.f;i:_1.11111110•••1 •••1111 •••811.111111181111 ••11 DluaD.IID.IIDI 1111.1 ••DB ••••I.DID D1.1 a I.D.D.I.I.D.1.DII 111.108.101 Dill•••BI.I 1.111l1
!!:!!
1,000 '2,000 3,000 4,000 5,000 6,000.
Annual Energy Output GWh
FIGURE 18.23 - ENERGY PRICING COMPARISONS- 2003 1~1(1
1_'__L__L--'----
200
Mill Rate Cost
Best Thermal Option
0%Inflation,3%Interest
----------------
COST SAVINGS
NO STATE APPROPRIATION SCENARIO
100%DEBT FINANCING
-----------_..._-
,/
/#f
I COST SAVINGS GROWING OVERIWHOLE OF SUSITNA LIFE
7%Infl.don,\'nte.."I AJ.mrJ 1 ..
__~~~fjji!:i.~."~''''''''~''''!~
.~'
260
160
140
120
380
320
180
360
340
.c
~280
';;;
~
en
Q)
.2..
0-
"C 240c
C'Cl
:l
8
>-E'
ell
C
W
Rev. 1
;.;.;.;.;.;::::::::::::;
100 f::::'~:::::::l
iliL&Negligible Financing Deficit with Zero Inflat
FIGURE 18.24 -ENERGY COSTCOMPARISON - 100%DEBT FINANCING 0 AND 7%INFLATION
Years
94 5 6 7 8 9 2000 01 02 03 04 05 06 07 08 09 2010 11 12 13
[i]
L...-...-
COSTSAVINGS GROWING OVER
WHOLE OF SUSITNA LIFE
Devil Canyon Completed with $7.2 billion ($2.3 bn 1982)of
Revenue Bonds 1994 - 2002
STATE APPROPRIATION OF
$3.0 BILLION WITH 7%INFLATION AND 10%INTEREST
Watana Completed 1993 with $1.8 billion
($0.9 bn 1982)of Bonds 1991 - 93; Cover of
1.25 at 80 Mills/kWh in 1994
lrrrll
I Mill Rate Cost If
BestThermal Option ~If
If..-.~..
~#
~#
_----•••IIlI-~------1 I Susitna wholesale energyprice falls as~--energy increases to 2009 and rises~~.......slowly thereaftert··~!~!i~!i!!I!~iliJ::.···~.,~
II
I
J1----
Rev. 1
360
340
320
300
280
:c
~260.....:a
:E-;240
Q)
CJ.;:
CI.
"C 220c
l'lI
CI>...CI>8 200
>l:ll..
:g 180w
160
140
120
100
FIGURE 18.25 -ENERGY COSTCOMPARISON - STATE APPROPRIATION $3 BILLION (1982 $)
Years
94 5 6 7 8 9 2000 01
02 03 04 05 06 07 08 09 2010 11 12 13
l.__~~'--l.__L-.'---...
•131209 2010 11080706
Devil Canyon Completed with $6.8 billion ($2.1 bn 1982)of
Revenue Bonds 1994 - 2002
05040302
~~~#
IIII
I
Mill Rate Cost I It
BestThermal Option --I
l/Il'COST SAVINGS GROWING OVER
~.WHOLE OF SUSITNA LIFE~#,~
11#
11#
~
9 2000 018
Susitna Pricing Restricted to,
Maximum of Best Thermal Cost
7
Years
FIGURE 18.26 -ENERGY COST COMPARISON.$2.3 BILLION (1982 $) -MINIMUM STATE APPROPRIATION
6
WatanaCompleted 1993 with $3.3 billion
($1.7 bn 1982)of Bonds 1990 - 93; Cover of
1.25 at 137 Mills/kWh in 1994
MINIMUM STATE APPROPRIATION OF
$2.3 BILLION WITH 7%INFLATION AND 10%INTEREST
5
Susitna wholesaleenergyprice falls as...__-..I /1 energy increases to 2010 and rises
_----.....:-:-:.:::::::::::.:-:-:-:-...slowly thereafter
,*/***.......iill;;;;;lli;;;ill~'~~,,~II~:~~~~~~;;;'~8~if~~~:;1;lM~BN···.,,;
Ji Susitna Wholesale Energy Price,---
94
Rev. 1
380
360
340
320
300-.c
~280......
~
~
U>260
Qlu.;:
0..
"t:l 240c
ell
U>...U>
0 220(.)
>I:')..
Ql
C 200w
180
160
140
120
100
l;__i,__
Rev. 1
380
360
340
320
300
.c
~280--::£
~260
'"CD
U';:
Q.240
"Cc
<Il
'"~220o
>O'l
:v 200cw
180
STATE APPROPRIATION OF
$1.8 BILLION WITH 7%INFLATION AND 10%INTEREST
Mill Rate Cost
Best Thermal Option
III
IIIIICOST SAVINGS GROWING OVERIWHOLE OF SUSITNA LIFE
/t#
II
Susitna Price Tracks Cost of BestThermal Option
Until 1.25 Debt ServiceCover Established
140
FIGURE 18.27 -ENERGY COST COMPARISON-PRICING RESTl:tICTED 94/95 AND 03/04
WatanaCompleted with $4.4 billion ($2.4 bn 1982)of
Bonds 1989 - 93. Inadequate Cover Until 1996
[i]131209 2010 110807060504
Devil Canyon Completed with $6.9 billion ($2.1 bn in 1982)
Inadequate Cover Until 2004
03020120009876
Years
594
100
120
L,;L.---->
SENATE BILL 646 PROPOSAL - 100%STATE FINANCING
"...lIlIl1lllll•1II-
~....
".....
".~~
t"~
IIIIIII
.IIIJi
•
Susitna Wholesale
Energy Price
COST SAVINGS GROWING OVER
WHOLE OF SUSITNA LIFE
Devil Canyon Completed 2002
J~#.'lr~lllll~II
li
~#
!IlIIIl··__IIIlIIIIlIJ
~
99 2000 01 02 03 04 05 06 07 08 09 10 11 12 13
FIGURE 18.28 -ENERGY COST COMPARISON MEETING SB 646 REQUIREMENTS WITH 100%FINANCING
9897
MillRate Cost
Best Thermal Option Price
96
Years
9594
380
360
340
320
300
s:280~..:.:-.
~
:E 260
III
CII
U';:
240Q.
"tl
Cco
III...220III
0
(.)
>-Cll..200CIIew
180
160
140
120
100
l _L__
•.._.~-j
220
.....:-:.:.
'iIIIICOST SAVINGS GROWING OVER#,__JI W1HOLE OF SUSITNA LIFE
'A ~
i~~~~~~~iiiiii~~~~~i~~iiiii ~~~~~i~~}:~;;:::.;.:.......... . .
Operating Costs, Renewals and
Interest on Working Capital
Mill Rate Cost
Best Thermal Option
SENATE BILL 646 "MINIMUM"APP.ROPRIATION OF
$3.0 BILLION WITH 7%INFLATION AND 10%INTEREST
260
280
340
300
320
:c 240
~-~
~
200
1312111009080706
DEBT SERVICE
Devil Canyon Completed with $7.5 billion
($2.3 bn in 1982)of Revenue Bonds 1994 -2002
03 04 05
Years
029920000198
.Susitna Wholesale
Energy Price
97969594
180
FIGURE 18.29 -ENERGY COST COMPARISON MEETING SB 646 REQUIREMENTS WITH $3.0 BILLION APPROPRIATION
Operating Costs,Renewals and
Interest on Working Cap.i~~.I.:.;.:.
::::'!illt:it~~~i~f~~f~f~
801::;::::::::::::Watana Completed 1993 with $1.9 billion :}}}~
:;:;:;:;:::::;:($0.9 bn in 1982)of Bonds 1991 -1993 ;:::;:;:;:::;:
60 li~~~~~~~i~~~~~i~~~~~~~~3R~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ ~ ~ ~i~i~ ~ ~ ~ ~ ~ ~ ~ ~ ~
SPECIFIC RISK I: RISK OF BOND REQUIREMENT OVERRUN
[1
1.0
0.9
0.8
0.7
~IO.6
:g 0.5.coet 1 0.4
0.3
0.2
0.1
Forecast Watana Borrowing Requirement
in $2.3 bn Appropriation Case
/
1.0 1.7 2.0 3.0 4.0
)
J
Bond Requirements for Watana in $bn (1982)
FIGURE 18.30 - BOND FINANCING REQUIREMENTS
SPECIFIC RISK II:IMPAIRMENT OF STATE CREDIT
/Minimum Cover Requirement
u
[j
1.0
0.9
0.8
0.7
>-0.6.'!:
:c 0.51lI.ce 0.40-
0.3
0.2
0.1
0.0 1.0 1.25 2.0 3.0 4.0
Coverage on Bonds Issued for Watana
FIGURE 18.31 -DEBT SERVICE COVER
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II SPECIFIC FINANCING RISK III:EARLY YEAR NONVIABILll"Y I
ForecastWatanaCost
as %BestThermal
/
10 20 30 40 50 60 70 80 90 100 110 120 130
Watana Unit Cost as %of Best Thermal
0.3
0.2
0.1
0.0
-20 -10 0
1.0
0.9
0.8
0.7
.e-0.6
:g 0.5.cee,0.4
FIGURE 18.32 -WATANA UNIT COSTS AS PERCENT OF BEST THERMAL OPTION IN 1996
AGGREGATE RISK:POTENTIAL NET OPERATING EARNINGS
FIGURE 18.33 -CUMULATIVE NET OPERATING EARNINGS BY\2000
Forecast in $2.3 bn
State Approriation Case
/
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
Cumulative Net Operating Earnings in $ bn (1982)
1.0
0.9
0.8
0.7
>0.6.t::
:c 0.5IV.c
0...0.4c..
0.3
0.2
0.1
0.0
-0.6 -0.4 -0.2
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19 -CONCLUSIONS AND RECOMMENDATIONS
The proposed development of the hydroelectric potential of the Upper
Susitna River Basin is technically and economically feasible.Finan-
cing of this large undertaking is also feasible with appropriate state
funding assistance.Although the project will result in irreversible
environmental impacts,the consequences of these impacts are not severe
and adequate measures are economically available to mitigate against
them.It is therefore recommended that a FERC license application be
filed for construction of the project.
The findings set out in this Feasibility Report lead to the conclusions
and recommendations discussed in the following sections.
19.1 - Conclusions
It is concluded that:
-The projections of demand for electricity in the Railbelt by ISER and
Battelle'Pacific Northwest Laboratories,in December 1981, are rea-
sonably representative of possible load growth scenarios.Projected
energy demand in 2010 under a medi urn growth scenari 0 is 7,791 GWh,
requiring 1,537 MW of generating capacity;
-The proposed Susitna project of 1,020 MW in 1993/94 at Watana and 600
MWat Devil Canyon in 2002,represents the optimum basin development
plan from technical,economic,and environmental perspectives and use
of the available resource.This plan is also economically and en-
vironmentally superior to other thermal and hydroelectric alternative
generation plans;
-The proposed 1,020 MW Watana development will be capable of generat-
ing an average 3,450 GWh of electrical energy and the 600 MW Devil
Canyon project 3,340 GWh.Firm energy for each development is
estimated as 2,630 GWh and 2,770 GWh,respectively.Susitna will
represent more than two thirds of projected total Rai lbelt system
capacity in 2010;
-The only known seismically active faults in the region of the pro-
posed project sites are the Denali Fault 40 or more miles to the
north,the Castle Mountain Fault 65 miles or more to the south,and
the Benioff Zone 31 mi les or more beneath the sites.The proposed
project structures can be designed to safely withstand the maximum
earthquakes which can be predicted to occur on these faults,or as a
result of other possible seismic events,such as a Terrain earthquake
or reservoir induced seismicity;
-The construction of a 1,020 MW hydroelectric project at Watana in-
volving a 885-foot-high earthfill dam and appurtenant facilities,
19-1
can be accomplished within all applicable requirements of technical
feasibility,safety,and environmental impact in 1993/94;
-The construction of a 600 MW hydroelectric project at Devi 1 Canyon
involving a 645-foot-high concrete arch dam and appurtenant facili-
ties,can be accomplished within all applicable requirements of
technical feasibility,safety,and environmental impact by the year
2002 or ear l i er;
-An access road constructed from the Parks Highway south of Hurricane
to Gold Creek and thence south of the Susitna River to Devil Canyon
and north of the rlver to Watana,is the best compromi se of techni-
cal,economic,and environmental tradeoffs;
- A transmission line system consisting of up to five 345 kV lines
westward from the sites to Gold Creek, with 2 lines north to Falr-
banks,and 3 lines south to Anchorage via a cable crossing at Knik
Arm,is the best compromise of technical,economic,and environmental
tradeoffs;
-The environmental consequences of construction and operation of the
Susitna project are not unduly severe.The most important impacts
will occur on downstream fisheries;and adequate mitigation measures
to compensate for these and other impacts can be incorporated in the
project without adversely affecting the viability of the develop-
ment;and
-The Watana project,cost i ng $3647 ml 11 i on in 1982 doll ars and the
Devil Canyon project,costing $1480 million in 1982 dollars,repre-
s~nt an optimal plan for meeting projected Railbeltelectric energy
needs through 2010 and beyond.A minimum state appropriation of $2.3
billion in 1982 dollars,with residual financing from bonds,repre-
sents an appropriate mechanism for obtaining the necessary funds to
construct the project,which will realize an 11 percent return on the
state's investment.
19.2 -Recommendations
It---is recommended ttratr:
-The state authorize the filing of a FERC license application for
construction of the project by September 30,1982,with the objective
of receiving such license by December 31,1984.Environmental and
engineering studies necessary to provide additional information in
support of this application and development of mitigation plans,
should be continued as necessary;
-Planning,permitting,and related logistical support activities
should be initiated as soon as possible for construction of a pioneer
access road from Gold Creek to Watana to commence in mid-1983;
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-Planning,permitting,and related logistical support activities
should be initiated as soon as possible for geotechnical exploration
of the relict channel,riverbed,and construction material borrow
areas;
-Planning,permitting,and related logistical support activities
should be initiated in fiscal 1983 for geotechnical exploration and
engineering for the Watana project;
-Detailed design of the Watana Project and associated facilities
should commence in fiscal 1983;
- A decision to construct the Watana Project should be reviewed period-
ically in light of additional engineering,cost,environmental and
financial information generated during the design phase;and
-If a decision is taken to proceed with the project,discussions
should take place and agreement in principle be reached with Railbelt
utilities on the form of contractual relationships under which Susit-
na output should be committed for sale.
19-3
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SUSITNA HYDROELECTRIC PROJECT
ACCESS PLAN RECOMMENDATION REPORT
APPEND IX A-D
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1ST OF APPENDICES
A -IDENTIFICATION OF ACCESS ALTERNATIVES
B -ENVIRONMENTAL ISSUES
C -PREFERENCES OF NATIVE ORGANIZATIONS
D-RELATIONSHIP TO CURRENT LAND STEWARDSHIP,USES AND PLANS
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APPENDIX A
IDENTIFICATION OF ACCESS ALTERNATIVES
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Fig~re A.3 Route Plan:Access Plan 17 - Denali
A.2 Statement of the Susitna Hydroelectric Steering
Committee (dated November 5,1981)
Figure A.l Route Plan:Access Plan 13 - North
Figure A.2 Route Plan:Access Plan 16 - South
Table A.l
Access Plan Costs
Comments by Phase 2 Engineering BiddersA.ln
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APPENDIX A.I
July 29,1982
Gentlemen:
The Power Authority is currently engaged in final deliberations
leading to a selection of a preferred access route.This is the route
that will be reflected in the FERC license application.We have provid-
ed three (3) options to our Board of Directors,and some information
concerning those options.We will supplement that information in mid
August,and hopeful ly the Board will make a selection at their meeting
later that month.
Basically,the thre~'options presented involve access from the West
on the South side of the Susitna River;access from the West on the
North side of the Susitna River; and access'from the Denali Highway
directly to the Watana Dam site.
In recognition of the fact that the preferred access decision will
not be made until after the deadline for proposal submittals,do not try
to adjust your proposal to react to these three options.Instead.
continue to use the guidan,ce of our Rf?Amendment No ..3.
There are numerous issues associated with this decision.For the
most part~we feel we have adequate data in hand.However,we would
like to invite all proposers to comment on one particular aspect;the
question of limited versus open access to the construction sites.
A number of voices are concerned with maintaining to the maximum
degree possible the pristine wilderness character of the Susitna Basin.
They are apprehensive that free access to the project site will have
primary and secondary impacts that would be detrimental to a preserva-
tion objective.On the other side of the issue,there 1s a sentiment
that maximum transportation flexibility is necessary if the project is,
to successfully avoid undue logistics problems.As a result of pro-
longed evaluations and debate,the issue is now su~r1zed as a choice
between having project access from the existing road netwo~or only via
railroad.The limited access voices view access via ratlroad as facili-
tating access control,particularly if the objective is to have highly
restricted access.,Again, the opposing view is,the railroad is subject
to too many uncertainties to be a reliable supply gateway.
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We would welcome your comments on the issue of a railroad gateway
only versus a connection to the road network.If you choose to comment.
we would appreciate it if you would back up your position with examples
and other tangible information as might be suitable.We will provide .
your input to our Soard of Directors for their consideration.We weuld
like to include these inputs in the briefing package mentioned above;in
order to do that,we need to hear from you prior to August 9~1982.
. Let me emphasize that you are under no obligation to respond to
this invitation.Further~this invitation is a matter totally unrelated
to the Request for Proposals activities,and will not have any influence
an those proceedings.
Sincerely,
FOR THE EXECUTIVE DIRECTOR
David D.Wozniak
Project-Engineer
DDW:sf
Bechtel Civil &Minerals, Inc.
Engineers-Constructors
Fifty Beale Street
San Francisco.California
Mail Address:P.O.Box 3965, San Francisco.CA 94119
August 4,1982
Mr.David N.Wozniak
Project Engineer
Alaska Power Authority
334 West 5th Avenue
Anchorage,Alaska 99501
Dear Mr.Wozniak:
RECEIYEa....
AUG 51912
'AJ.}SKA POWER AUTHORI'IJ
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12110
With reference to your July 29,1982 letter regarding a "railroad gateway"to
the Susitna Project,we can offer the following comments:
o Construction of a railroad would probably cost in the order
of twice as much as a road ($120 million vs $60 million,
approximately).
a More significantly,a railroad would take at least one year
longer to build which would,of course,impact costs for all
of the rest of the project.
o Once the railroad is in place,we would not anticipate
significant negative impacts on project construction.The
Churchill Falls Project in Labrador was built essentially
"at the end of a railroad",although that railroad was in
place prior to project construction and all that was needed
was a relatively short connecting access road.
We can think of no reason why effective access limitations could not be
imposed during construction on a road built into Watana,restricting usage to
authorized personnel.Such limitations are in place on the James Bay Project
in Quebec,utilizing.gates,guard posts,etc.,and are working effectively.
This should minimize impacts on the wilderness character of the area during
the construction period.These limitations could,of course,be continued
during the period following construction completion.
For the period following construction,as a related matter,APA might wish to
consider the possibility of using single-status accommodations as an
alternative to the family village concept now planned for housing the permanent
operations staff..Under such an alternative,operators could be flown in and
out on a scheduled basis such as "10 days on,6 days off".This would place
their families in existing metropolitan areas,would eliminate the need for
a family-status operators'village with full support infrastructure,and
would therefore eliminate the need to maintain open on a full-time basis an
access road (or railroad)to the site from Gold Creek.
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Bechtel Civil &Minerals,Inc.
Mr.David N.Wozniak
August 4,1982
Page Two
There is a family-status operations village,which was originally used for
construction,in place on the Churchill Falls Project.At James Bay,the
original intent was also to use a family-status village for operations,and
some permanent village-type facilities were therefore constructed early so
that they could be used by contractors and the owner's supervisory staff.
Subsequently,after analysis,Hydro Quebec decided that it would be preferable
both from the cost and employee morale standpoints to operate this remote
project with single-status personnel only.It is now ant~cipated that
permanent apartment-type units will eventually be constructed.At present,
operators are flown.in and out,and are housed single-status in the family
village.This·experience emphasizes the importance of considering these
alternatives early in the final developmental phase of the Susitna Project.
I hope our comments are helpful to you.We look forward to submitting our
definitive proposal for the Susitna Project Phase II engineering services on
Monday,August 16th.
\
John A.Peterson
Business Development Manager
Hydro Projects
JAP:yt
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R.W BECK AND AsSOCIATES,INC
ENGINEERS ANDCONSULTANTS
P.O.BOX2400
SITKA.AlASKA
99B35
FILENO.HH-OOOO-BD-SW
A4-2
Mr.David D.Wozniak
Project Engineer
Alaska P.ower Authority
334 West 5th Avenue
Anchorage,Alaska 99501
Gentlemen:
TOWERBUILDING
7THAVENUEATOLl~~Y~E IV EO
SEATTLE,WASHINGTO~5fuf""
206·622·5000
AUG 91982
ALASKA POWER AUTHORITY
ao,BOX6B18
KETCHIKAN.AlASKA
99901
August 6,1982
Subject:Limited Versus Unlimited Access to
Susitna Project Site
We are pleased to comment on what we agree is a most'important
decision that needs to be made by the Power Authority.There is no question
that the SusitnaProject could be built with only the railroad'to handle all
materials,equipment and supplies but the logistics of using only the railroad
would add to scheduling problems,require load sLze limitations,do away with
competitive haul rates,and result in cost increases.,..
Several of our people have long experience records in the construc-
tion field especially in work outside the lower forty-eight states.None of
them can recall a project close to the size of Susitna that did'not utilize
every form of transportation available and in addition none recall a site that
did not have some available truck haul.If .the highway did not exist we doubt
that it would be built just for this project.With only the short 'access and
the fact that the highway leads to both Anchorage and Fairbanks,however,it
is logical and prudent to make the connection.While access from the Denali
Highway may be less expensive to construct,the all weather access from Parks
Highway is measurably shorter from the Anchorage supply base.
Limiting the access to the project would in fact be putting a
restraint on all operations of the prime contractors,supply contractors,
project managers,camp operations and especially on the local contractors who
are accustomed to using their own hauling equipment.This restraint would add
millions of dollars to the cost,and could possibly delay the·on-line dates of
the units.Recent construction and operation of the Trans-Alaska Pipeline
project demonstrates the desirability of road access for logistical and other
supplies.
With a population at the site between 2,000 and 4,500 workers for
several years the turnover coupled with the "R and R"traffic into the cities
of Anchorage and.Fai·rbanks will be enough to make a r oad'mandatory.Getting
people to work and live in the camp will be more difficult if they know their
only access to the outside is by rail.
Mr.David D.Wozniak - 2 -
August 6,1982
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While air service by fixed wing aircraft will be supplied,there
will be a continuous need for parts and supplies on a day by day basis that
can be handled most efficiently by truck.Also air service to the site would
be limited because of inclement weather.
Even though the area is closed off after completion of the project
there is no reason that access from the highway should not be available during
the construction period.Once the project is complete the.access could be
closed.
We believe that our wilderness should be preserved but we are also
of the opinion that a project such as Susitna should be made available for
every visitor and taxpayer to see.Projects such as these are monuments to
man's ingenuity and to hide them from all but a few doe~not seem to fit our
democratic system.
Very truly yours,
R.W.BECK AND ASSOCIATES,INC •
../James V.Williamson
\J Vice President
JVW/vla
Gibbs S Hill.Inc.
August 8,1982
Mr.iric Yould
Executive Director
Alaska 'ewer Authority
334 west 5th Ave.
Anctlorage,Alaska 99501
Dear Mr~YGuld:
Refel'9llce is made to your letter of July..2.9.1982."larding project..access
Hd more specifically·to the question of ·open'"versos ltlimtecfl access.
'".access it.,.the Dena 11 YighwaY ~1cn ..iscertiiily desirable frem a CQrae:t5'1"standpoint to have good
bigfrMly access fr'an tile cOBstruetion sites all ttle·way to tlIe"Parks
Kigllway ortne Denali Highway.several reaSORS may be sited:
a)Road access will anow the contractOf's and the oemer"
1:0 transport goOds independent of·the railroad.
The railroad has not _n particularly reliable in the
past..Road access.will allow the contractors and owner
.-ximmn f1eJ(ibni~to sdledule shipments"·aad as
1"equired,and not wRen 'tfley!!!1 be saipped.to fit the
rail road schedule-.Read,access w11 1 anow st.ipment.by
La (less tkan truckload)lots of day.to-da,y requ;f'ements'.
For example.a:to1m.truck or-trucks wauld daily shuttel
parts.-minor equipment.small tools and-exf:leRdables from
Andiorage to the-site.The peeatest need fo1"this service
_uld be urUe....in tile job before a good ivwentory is
warehoused.at the site..but normally such a senice continues
throughout the ·work...
b}·If Sllimitedaccess-wins out..APA sttould build a ran/true"
c:lfqIot a fillf m1'1es towards the site fY"OOl the mainline.
This ·!IIIill eAta'il clearing aRd grad1ag of a suntantia:l area
fw siding aRd waNttwses.tdtidl 'Will ave some effect..em·the-
-,"stiDe wil~.
e)Both 1..1.)and b)abeve'would M!SIIlt.inttigiHlr.costs if the
li.llritad access optien~dns aut.
el)Ia case of eeJ'1S~,deR.it..,be necessary to·evacuate
injured Of'-sick,persons from.the site and.weather-will Rot
pentit flyiag•.it..uld be".lldato".to beNt!:road access·by
ambu:tance to the _in .reads ..
.e)l'rauS,ortatioR in and out of families pet 'Single.mm·living
at.tbe sita 1IIOUld t:M!dicta facilitated ay connections to
roa4s..·do you.handle this otbenrise?Fly everyone in
od ouU Trat'8sport them by bus to the rail1iepot aAd then
by tl'".l'iR?This would be var:y awkward and not maG(e for a
hiI4JP.Y liYi.ng situation'for either families.or $11'91e persons.
..........'.'.:....
August a,1982
............:"..............-.....,,_..-.._"
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.'Com:]u.si~~..'............-,....."
';;;";;;O;...........ij3ilt[iDiol~il~.re Hsirale to have a conlM!C.tion to the road network fnm the
standpoints .of f1exibilit,y~ecoftl)i'(ly.,eme'gency and ease of,living..'It would
.,~ar ttat tile AM,could achieve:tliis i1ftd still limit access to tile site.
This·cOlItd easn...,be handled.~y QStablishing manned checkpoint just off'·the
ma:in highwi4J and allow only authOJ"ized vehicle accsss to the site..This was
done an the Alyeska Pr.ojet:t and an numerous other projects with gcod results...
Very truly yours,
....
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August 9$1982
Mt';.Eric,Yould-
Exeeut1ve:Dir«tor
Alaska Power Authority
334 west 5ttl ~enue,
Anchorage,Alaska:99501
Dear Nt'.Yould:
Reference is made ttl your-letter-Of July zgt-.19B!..and:oUf,':'reply,
of August 8,1982....Please'adcl the'followhag as a ret:oiIIIRmQ'tirm on
Pag&2 after-"Conc.lusioR~:
1.,Init.ia11y caRStr.uct at.te,Hatuta $i,w':6,,000-ft...&f road"
sur;n t.hat:this portion of,ti4e-road,will be lJSed..as it
landiDG strip f'w"DC;...31f)t'.-4 p:lane$.
t:...Equipment:to (onstFUct:the aforementioned l"OadlJ'UIIWaYi ca..,d:te",
mobilized during,tne',wiftw·manths.(eitbar'"overlami:Gl'"by,
helicopter)So.di·sass_l".tlieJt;reassembl......
3...Equipment.ami,ma:terial$~for'ttle rematlri11"rRd
,~tf'Uc:ti_should be .f!$t.atMisbed:.at strl'te!riC,prints.
..long the future road aligJliJent"likewise during the
wmter months..-
4.The M:IIRIining road itself Aft then:be reatlily con~
during the summer'mantks~
;;SIde
bee:S.Koretsky
S·.ShevekoV'
J.Silveira
P.Gafner
J.Johnston.
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Harza-Ebasco
400 -112th Avenue NE
Bellevue,WA 98004
(206/451-4500)
Alaska Power Authority
334 West Fifth Avenue
Anchorage,Alaska 99501
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Attention:
Subject:
Gentlemen:
August 6,1982 BeeE I VE Q
AUG·91982
ALAsKA POWER AUTHORITY,
Mr.David D.Wozniak,Executive Secretary
Selection Committee
Susitna Hydroelectric Project -Access Road
The Alaska Power Authority invited comments on the issue of a railroad
gateway only (limited access)versus an access'connection to a public
highway by letter dated July 29,1982.These comments are intended to
aid the Alaska Power Authority Board of Directors in their evaluation
of a preferred access route for construction and operation of the Watana
Project.
The key points which will be given consideration in selection of the
route include:
reliability --freedom from interruptions which may have
an impact on the construction schedule;
logistics --method and comparative cost of transport of
materials and personnel;and
multiple project savings --can a savings on the combined
projects,Watana and Devil Canyon,be realized?
Limited Access
Although the limited access approach,railhead.in the vicinity of Gold
creek with a restricted roadway·from the railhead to the site,with no
road construction to the Parks Highway maybe environmentally more
attractive,it is undersirable from a construction standpoint wherein
Page 2 Continued August 6,1982
Alaska Power Authority
Mr.David D.Wozniak,Executive Secretary
schedules and logistics are vulnerable to interrpution of traffic flow
on the railroad~
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Advantages
o Precludes public access.
o No major'bridge over Susitna
River 'at Gold Creek.
o Connects Watana and Devil
Canyon Project.
o Most economical construction
if both Watana and.Dev.il
Canyon are considered.
Disadvantages
o Dependency on a single mode of
transportation for mobilization
and support of'contracts can
seriously impact schedules,
which in the case of ri.ver diver-
sion or closure may result in the
loss of a full construction season.
o Lack of the flexibility of alter-
nate access roUtes will result in
higher bid prices for construction.
o The logistics 'of supply become
more complicated due to:
- LOnger lead time requirements.
Supply line availability is
beyond contractor's control and
dependent on the railroad ...
-Special railroad equipment is not
readily available at all times.
-Possibility of railroad worker's
strikes with resultant interrup-
tion of supply line for extended
periods.
-Dependency on train schedules.
o Emergency situations are more diffi-
cult to handle when direct access to
major highways is not possible.
Page 3 -Continued August 6,1982
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Alaska Power Authority
Mr.David D.Wozniak,Executiv.e Secretary
A recent example is provided of the effect of disruption of traffic on a
single access corridor,although not as serious in.nature:
Early ac~ess for delivery of.materials to the site of the
Satsop Nuclear Power Plant in'Washington was by way of a
single one-way road,wherein the breakdown of a truck
(there were as many as 40 in line)halted all travel until
it could be towed off the road.In the case of Watana,in.
addition to delay in delivery of materials,a camp full of
3,000 workers would depend upon an air shuttle for support.
The unsettled future ownership of the Alaska Railroad may'also affect
the reliability of this mode of transport.The railroad (limited access)
scheme is also subj ect to the same restraint that affects any access from
the west --possible schedule impact because of lack of a pioneer ~oad.
Access fXQIl\Parks Highway
Whether the route from Devil canyon to Watana is located on the north
side or the south side of'the Susitna River,the problems with this
access are.similar.The north side may be preferable environmentally,
but because of the high level bridge at Devil Canyon.required for that
route,the route em the south side of the river appears'less likely to
have schedule impact on Watana construction.Lacking a pioneer road,
the massive rock.excavation and high level bridge across Cheechako Creek
are the major deterrents to early access on this route.·
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Advantages
o Full access including rail-
head at Gold Creek for
construction supplies and
personnel.
o Connects Watana and Devil
Canyon Projects.
o Least restrictive -less
costly for logistics •.
o Greater flexibility and
reliability in case of
transportation interruption
with one mode of'transport.
o Lower construction and ser-
vice contract bids with
contractors'choice of
transportation.
o Transmission line location
can partially follow same
corridor.
Disadvantages
o Without early entry,project
schedule impacted by construc-
tion of major bridges.
o Potential detrimental effect to
preservation objective because
public access.
Page 4 -Continued August 6,1982
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Alaska Power Authority
Mr.David D.Wozniak,Executive Secretary
Access from Denali Highway'
Access road construction to serve the Watana site is simplified if'this
approach is adopted,since the length of new road construction is reduced,
the terrain is such that cost per mile will be less,and no major bridges
will be required.However,this route does not provide.access to the
Devil Canyon site.
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Advantages
o Can meet Project Schedule since
access construction c~~be com-
pleted in one construction
season.
o No major.~ridges.
o Full access for construction con-
tractors.
o Greater flexibility and relia-
bility in case of transportation
interrUption with one mode of trans-
port.
o Lower construction and service
contract bids with contractors'
choice of transportation.
o Access construction costs for
Watana is least expensive.How-·
ever if access to both projects
is provided,the total access
cost will be comparable to the
Parks Highway-Watana access.
Cost Impact~.
Disadvantages
o Estimated 50-mile longer road haul.
o No connection to Devil Canyon.
o Potential impact from public access~
o Impact on caribou calving area.and
summer range.
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The limited access logistics expense will not be materially different from
that which will be incUrred if access is provided from the Parks Highway,
since a combined through rate (lower'48 point of shipment to delivery at
site),inclUding rehandling costs at the railhead,can be negotiated.There
will be some added expense'of transporting more personnel by air.Large
pieces of equipment,which cannot pass through the 10'x 12'tunnel between
Whittier and Anchorage,will need to be rerouted through the port of Seward,
with a much longerra'il connection to Gold Creek~.
With the added 52 miles (approximate--depending on final.route selection
within the corridor)in road length from Anchorage to the Watana site,the
cost of road transport will increase.if the Denali Highway access is adopted.
Page 5 -Continued August 6,1982
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Alaska Power Authority
Mr.David D.Wozniak,Executive Secretary
However,this increa~e will not be proportional to length since less mile-
age will be at the off~highway rate.The added cost for all-truck trans-
port will have minimal effect on total logistics expense .for Watana since
the majority of material will move by rail to the railhead and be trans-
ferred to trucks at that point for the shorter road transport to the site.
We suggest that a marshalling yard be constructed at Broad Pass rather than
Cantwell,in the event that access from the north is adopted.Gravel is
readily available at Broad Pass,thereby minimizing the cost of construction.
Operation of the yard at this location should overcome any objections by the
residents to operation of a yard at Cantwell..
The added cost of rail transport to Broad Pass'rather than Gold Creek will
be a definite increase in the logistics expense;however,it will be
partially offset by the lesser distance from railhead to damsite.Using
quantities of materials previously estimated by the Power Authority,and
today's railroad tariffs,'we estimate that the added logistics expense for
Watana will be in the neighborhood of $8,000,000 in 1982 dollars.This
increase is far below the offsetting cost savings to be realized in access
road construction.
Potential.Schedule Impact
As can be seen from·the discussion above,the limited access approach has.
a potential for major schedule impacts.Because of the time span required
for construction of.an access road between Gold Creek-and Watana,the Parks
Highway access route has much greater potential,with upwards of one year
delay,for schedule impact than the'Denali Highway access route.
The Denali Highway access route has very little potential for schedule im-
pact.In addition,there is less roadway to be traversed beyond the limits
of state highway maintenance.
The Harza-Ebasco JeintVenture appreciates the opportunity to provide these
observations regarding.access to the Susitna Hydroelectric Project.Should
you have further questions or comments,please call.
Very truly yours
cc:Richard L.Meagher
II\,
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:.:.-o~_ .•--------
"
'_0.,',,;"',':'oi:._'":i\::~o;:j._!f toot :..,".!.••:'.l i _e
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THE
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STONE &WEBSTER •TAMS
ANCHORAGE,ALASKA
ADDRESS ALI.CORRESPONDENCE TO: SUITE l-BLDG.H
4791 BUSINESS PARK BLVD.ANCHORAGE,ALASKA 99603
August 6, 1982 AUG 91982
ALASKA POWER AUTHORITY
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Mr.David D.Wozniak
Project Engineer
Alaska Power Authori ty
334 West 5th Avenue
Anchorage,Alaska 99501
ACCESS ROUTES
SUSITNA HYDROELECTRIC PROJECT
Dear Mr.Wozniak:
We welcome the opportunity to reply to your July 29, 1982 letter in order to provide you
with our comments on the question of limited versus open access to the Susitna Project
construction sites.From our experiences on construction of major power projects,.we
believe that a total highway access route is the most reliable and least costly means of
access during construction of the Susitna Project.Also,the highway access can' be
provided with effective access control to include eliminating the access after
construction is complete.On the other hand,the limited access of a railroad gateway,as
shown in Amendment No.3,has a number of major disadvantages which will result in
severe additional construction-costs,possible schedule delays and possible adverse
environmental Impacts,Some of the most serious disadvantages of the railroad-highway
access,compared to the all-highway access,are as follows:
1.The majority of material shipped to the site would have to be handled at least one
additional time.Shipments of goods originating in Alaska would have to be handled
twice except for those generated at shipping points on the railroad.
2.Shipments would be "locked"into the·schedule established by the railroad.
Emergency and rush shipments would have to be made by air,if possible•.
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Mr.David Wozniak
Alaska Power Authority
August 6,1982
Page Two
3.Special handling equipment,le,carriers,trucks,tractors,and trailers,to be used
between the rail end and construction site would be captive to the'project and not
readily usable elsewhere.The materials and equipment.'entering the site will be
designated for-a number of different contractors,and it would be impractical and
excessively costly to have each do his own hauling..Therefore,APA would need to
award a contract that would have to provide and service this equipment.
Attachment No. 1 is our first cut estimate of the captive equipment needed for
hauling from the rail end to the site.
4..We estimate that total shipping time for materials leaving the Anchorage area to the
site will be 2 to 4 times longer over the railroad-highway access route.
5.Equipment for offloading rail cars and loading trucks,as shown on Attachment No. 1
would have to be permanently located at the rail end.Also,provisions for storage of
bulk materials,such as cement and fuel,would probably be required,and would
partially duplicate those required at the site.Facilities for maintaining this
equipment would be required at the rail terminals.
6. The activities and manpower required at the rail gateway will probably result in the
development of a small community or camp with all the facilities needed for human
habitation.This would be another center of human activity,with potential negative
impacts on the surrounding area.
7. Work stoppage or interruption of the railroad would curtail and possibly stop
construction activities.While this is also true for the all-highway access,our'
experience indicates such delays are of much greater duration with rail services..
Although it was not possible to quantify all of the above disadvantages,we did look at
shipment of two key construction materials,cement and structural steel,as a measure of
the impact of the railroad-highway access route..
Based on the present construction plans for'Watana,we estimate that it will require
200,000 tons of cement to be used in the four-year-period from 1989 through 1992.This'
will require receipt of about ten railroad cars of cement per week during the four years.
One could anticipate that during peak usage,cement deliveries could be two to three
times that average.We estimate that the additional costs associated with a
railroad-highway mode for transportation of cement only is in the'order of a million
dollars,not including the capital investment in trucks,storage and transfer facilities.For
the Devil's Canyon Project,which has the concrete arch dam,the cement tonnage may be
doubled,with another 2 million dollars impact.We estimate that extra handling of
structural steel,such as tunnel supports and reinforcing steel,will cost a half million
dollars for each of the two projects;or an added million dollars just for handling the steel
items.These are only two of the many materials that will need extra handling.If we
include the special handling and off-loading for major equipment l.e ..turbines,generators,
transformers,breakers,etc.,we are probably talking about a total added cost of 5 to 8
million dollars.
STONE Be WEBSTER-TAMS
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Mr.David Wozniak
Alaska Power Authority
August 6, 1982
Page Three
We understand that much of the opposition to overall highway access to the site is based
on the concern that the highway will provide ready access to the general public to a large
area which has not-been subjected to the pressures usually associated with heavy human
intrusion.We believe that during construction,use of the access road can be controlled
with only those with legitimate purposes at the site permitted on the road.The same
kinds of controls would be required on a railroad-highway access.
Upon completion of construction,there are several techniques available which can deny
use of the highway and severely limit the access of the motoring public to the area.
These are as follows:
1. Use of barriers and/or moveable spans on bridges across major river crosslnqs,Bridge
locations should be selected to ensure that motor vehicles cannot by-pass them.
2..Removal of the highway and return to natural contours and conditions of those
sections which can not readily be by-passed.
Given the limited time we have had to look at this matter,we hope this information is of
assistance in providinq input to your Board of Directors regarding the access issue.We
believe the project can be constructed using either access mode but that the all-highway
access is the less costly and offers many advantages during construction.. In our opinion,
the highway option can be constructed and operated during and after construction to limit
access of the general public to the area to the same degree as the railroad-highway access.
Very truly yours,
Bernard J.Roth
Project Manager
STONE &WEBSTER-TAMS
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AITACHMENT NO.1
ESTIMA TE OF MAJOR CAPTIVE EQUIPMENT FOR HAULING FROM TERMINUS
OF RAIL SPUR TO WATANA
8 Bulk cement trailers (25 ton capacity)with 8 tractors
6 25 ton capacity flatbed trailers with 3 tractors
2..Heavy duty Gooseneck trailers for hauling equipment
1 Tractor for'above
5 4 wheel drive snow plows
2.Rotary snow blowers
2 Road graders
2 Dozers
12 Enclosed trailers
2 Frozen food trailers
8 Gasoline tank trailers
8 Tractors for-above-
ESTIMA TE OF MAJOR CAPTIVE EQUIPMENT REQUIRED AT RAILHEAD FOR
OFFLOADING AND MAINTENANCE
1 Crane,approximately 90 ton
1 Large fork truck
1 Large cherry picker'30-40 ton
1 15 ton cherry picker
1 Road grader-
1 Dozer
Pumping facility for-transferring fuel
Facility for transferring cement'
Maintenance facility including electric power
STONE Be WEBSTER-TAMS.
APP'ENDl X A.2
The purpose of this letter is to transmit to the Alaska Power Authority
(APA)comments from the Susitna Hydroelectric Steering Committee (SHSC)con-
cerning APA's proposals for access to the proposed Susitna River dam sites.
These comments are in response to ,information provided the SHSC from two access
route meetings with APA and their contractors and the documents prepared by APA
contractors and distributed during these meetings. At the October 20,1981
meeting APA requested SHSC comments by November 6,19$1.The SHSC appreciates
the fact that APA continued detailed consideration and studies of several access
route options this year rather than focusing on a single route.
The SHSC review identified four areas of concern that merited comment.
Those four are:
JA Y S.HAMMOND,SOVfffNOR
323 E,4TH A VENUE
ANCHORAGE,ALASKA 99501276-2653
RECEIVED
/
:£JASKA.POVilER AUTHORiTY,
November 5,1981
DIVISIONOF RESEARCH &DEVELOPMENT
Mr.Eric Yould,Executive Director
Alaska Power Authqrity
333 West Fourth Avenue
Anchorage,Alaska 99501
Dear Mr.Yould:
iJlEPAIlTMENT 0 ..'NATURAl.H":SOURCES
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1. A critique of the studies of access routes which provide for construc-
tion of the dams.
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2.The relationship between timing of access route construction and
Federal Energy Regulatory Commission (FERC)approval for dams.
3.The relationship of access route decision and modes of access to
regional land use management policies.
4.The issues resultant from land status and land ownership affected by
the proposed project.
The assessment of corridor route alternatives should more adequately weigh
the potential impacts of borrow sites and access to these sites,and trans-
mission line(s)routing.Access corridors which serve a dual,or triple,purpose
in regard to these other project access needs would be highly desirable from all
decision-making criteria.'
The access preferences expressed below pertain to the general locations
cited for the corridors and are based upon the environmental data and conclu-
sions contained within the environmental documents prepared for Subtask 2.10.
Access Road Assessment.It does not represent our endorsement of a particular
1-mile-wide'corridor,as presented.
The SHSC agrees with the Terrestrial Environmental Specialists,Inc.posi-
tion that access via the Alaska Railroad to Gold Creek is environmentally pre-
ferable.Railroad access to at least Devil Canyon would alleviate the need for
a staging area at Gold Creek and the consequent human activity,land use, fuel
spills,and other impacts on the Gold Creek area.We recognized that a staging
area at Devil Canyon would be required in any case.The 'use of this area as the
terminus of a railroad appears to make a great deal of sense.Additionally,we
feel that the south side route from Gold Creek to Devil Canyon is preferable
since a trail already exists there.From Devil Canyon to Watana,we prefer a
route on the north side of the Susitna River. At the October 20,1981 meeting
the SHSC was informed by Mr.David Wozniak of APA that there were two (2)
additional railroad route/mode options (a total of 10).If feasible we gen-
erally prefer a rail mode of access to and within the project site.
The SHSC identified three (3)environmentally sensitive areas that should
be avoided.Those are:
November 5,1981Page-2-Mr.Eric Yould
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1.The routes from the Denali Highway.
2.The route crossing the Indian River and through wetlands to the Parks
Highway.
3.The route on the south side of the Susitna River from Devils Canyon to
the proposed Watana dam site.
In evaluating the access route selection process undertaken by the APA and
its contractors,the Steering Committee questions the validity of the power-on-
line in 1993 assumption/mandate.The "We1ve got to hurry up and put'in a'road
to meet the 1993 deadline"approach appears,from currently available reports
and the briefings received by the Susitna Hydroelectric Steering Committee on
October 20,1981,to point toward the n~cessity of a pioneer road constructed
before a FERC license is granted,or selection of an apparently environmentally
unacceptable Denali Highway access route.
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Local utilities are not approaching construction of a project the magnitude
of Susitna in 1993 as a foregone conclusion and are making contingency plans to
meet projected power needs.Gas and coal generated power option~are being
examined.In addition,feasibility studies are currently being undertaken by
the U.S.Army Corps of Engineers and the APA at numerous potential hydroelectric
generating sites.The Battelle Railbelt Electric Power Alternative Study should
provide insight into additional power generation options.As such,we believe
that the 1993 "deadline"for power-on-line from Susitnamay not be that firm and
imperative.Thus the SHSC does not believe the 1993 deadline should constrain
the overall decision-making process and the orderly progress of various studies
on project feasibility and environmental impacts.Permitting and resource
agencies,including FERC,should be expected to link a piorieer road to the
overall project.,
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Mr.Eric Yould Page -3-November 5,1981
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Public access to the dam sites and through the Upper Susitna Valley is
complex and a controversial subject and we believe this issue should be given
.thorough evaluation in the route selection process.How construction-related
access is obtained to a great extent determines the project~related wildlife and
socioeconomic impacts.The APA has been soliciting th~views of local residents
(Talkeetna,Trapper Creek,etc.)in regard to the access question.The majority
of residents want to minimize impacts to both their community and the Upper
Susitna Valley.The APA has solicited the views of the state and federal resource
agencies.It has been the predominant view of these agencies,which represent
public interests on a state or national level,that project-related wildlife
impacts should be limited to the maximum extent practicable.In addition,the
APA has expressed the desire to maximize the options for future public access.
We believe that these views mesh.Minimizing impacts and maximizing options for
future public access can be achieved by mimicking,to the extent possible,the
status quo. For example,to provide full pUbli~access through a road system,
forecloses the future option of maintaining the existing character of the Upper
Susitna Valley.
Use of rail as the access mode increases the potential for management and
control of socioeconomic and environmental impacts.Maximized rail use provides
for the following advantages over road access:
1. Maintains a maximum range of future decision options.
2. Provides for control of worker impacts on local communities and wild-
1ife.
3. Decreases the potential of hazardous material spills due to adverse
weather conditions and multiple handling.
4.Disturbance to wildlife adjacent to the route can be more easily
controlled.
5..Direct access right-of-way related habitat losses can be significantly
1imited.
Briefly the land status of the project area has not changed significantly
within the last year.There are several complex problems concerning land status
that have been brought to your attention by BLM.
Thank you for the opportunity to review and comment on the Access Road
Assessment documents.We look forward to receiving the final version of these
documents after November 15,1981,and anticipate providing additional recom-
mendations into this decision-making process.
Sincerely,
Al Carson,Chairman
Susitna Hydroelectric
Steering Committee
cc:D.Wozniak,APA
Steering Committee Members
R.Stoops
PLAN 1 2
Table:.'A·:.;l·Access Plan Costs
3 4 5 6
DESCRIPTION
ROADWAY:PARKS
HIGHWAY TO DEVIL
CANYON &WATANA
ON SOUTH SIDE OF
SUSITNA.
RAIL:GOLD CREEK
TO DEVIL CANYONc&
WATANAONSOUTH
SIDE OF SUSITNA.
ROADWAX:DENALI
HI GHWAY TO,WATANA.
.:PARKS.:HIGHWAVTO
DEVI lrCANYON··ON'~3~I~~Rt8~N~FCONN-
ECTING ROAD .:
ROADWAY:DENALI
HIGHWAY TO WATANA.
RAIL,GOLD CREEK TO
DEVIL CANYON ON
SOUTHSIDE OF SUS-
ITNA.NO CONNEC-
TING ROAD.
ROADWAY:PARKS
HIGHI4AY TO DEVIL
CANYON ON SOUTH
SIDE OF SUSITNA.
DEVIL CANYON.TO
WATANA ON NORTH
SIDE OF SUSITNA.
ROADWAY:DENALI
HIGHWAY TO WATANA.
RAIL:GOLD.CREEK
TO DEVIL CANYON
ON SOUTH SIDE OF
SUSITNA.CONNEC-
TING ROAD ON NORTH
SIDE OF SUSITNA.
..***Hileage Road 62 -91 65 81 107 .
Rail -58 -16 -16
Design and Construction Cost
(S x 1,000,000)170 149 157 123 160 180
Maintenance Cost
($x 1,000,000)9 5 7 5 8 12
Logistics Cost
(S x 1,000 ,000)214 214 228 228 216 228
Tota:Cost
(S ;<1,000,000)393 368 392 356 384 420
Construction Schedule
for Initial Access (Years) 1 3-4 1 1 2-3 r
Construction Schedule
for Full Access (Years)3-4 3-4 2-3 2-3 3-4 3
Bridges Major (>1000 ft)3 2 1 °2 0
nor «1000 ft)2 0 1 0 1 0
*Includes upgrading 21 miles of.tht;Oenali Highway Revision:0
Sheet 1 of 3
Table:A.l (cont'd)
PLAN
DESCRI PTION
7
ROADWAY:DENALI
HIGHWAY TO WATANA.
PARKS HIGHWAY TO
DEVIL CANYON ON
SOUTH SIDE OF
SUSITNA.CONN-senNG ROAD ON
NORTH SI DE OF
SUSITNA.
8
ROADWAY:GOLD
CREEK TO DEVIL
CANYON ON SOUTH
SIDE OF SUSITNA.
DEVIL CANYON TO
WATANA ON NORTH
SIDE OF SUSITNA.
9
RAIL:GOLD
CREEK TO DEVI.L
CANYON ON SOUTH
SIDE OF SUSITNA.
ROADWAY:DEVIL
CANYON TO WATANA
ON NORTH SIDE OF
SUSITNA..
10
RAIL:GOLD
CREEK TO DEVI L
CANYON ON SOUTH
SIDE OF SUSITNA.
ROADWAY:DEVIL
CANYON TO WATANA
ON SOUTH SIDE OF
SUSITNA.
11
ROADWAY:DENALI
HIGHWAY TO WATANA.
CONNECTING ROAD
BETWEEN WATANA
AND DEVIL CANYON
ON NORTH SIDE OF
SUSITNA.
1:2
ROADWAY:PARKS
HIGHWAY TO DEVIL
CANYON AND WATANA
ON NORTH SIDE OF
SUSITNA.
**Mileage Road 132 69 56 36 114 .61Rail--16 16
Design and Construction Cost
($x 1,000,000)215 117 126 136 172 127
Maintenance Cost
($x 1,000,000)9 7 6 6 11 7
Logistics Cost
(S x 1,000,000)228 216 216 214 258 225
Total Cost
($x L,000,000) .452 340 348 356 441 359
Construction Sthedule
for Initial Access (Years)1 2-3 3 2 1 2
Construction Schedule
for Full Access (Years)3 3 3 3 2-3 3-4
Sri dges ~laj or (>1000 ft)1 a 0 2 0 1Minor«1000 ft)1 1 1 1 1 2
*Includes upgrading 21 miles of the Denali Highwav Revi sian:D
Sheet 2 of 3
_.-
Table:A.l (cont'd)
PLAN 13 14 15 16 1'r
ROADWAY:PARKS RAIL/ROADWAY:GOLD RAIL/ROADWAY:GOLD ROADWAY:GOLD ROADWAY:DENALl
HIGHWAY TO WATANA CREEK RAI LROAD CREEK RAI LROAD CREEK TO WATANA HIGHWAY TO WATANA.
ON NORTH SIDE OF EXTENSION.ROADWAY:EXTENSION.ROADWAY:ON SOUTH SIDE OF CONNECTING ROAD TO
SUSITNA WITH BRANCH TO DEVIL CANYON AND TO DEVIL CANYON AND SUSITNA.CONN-DEVIL CANYON ON
DESCRIPTION ROAD TO SOUTH BANK WATANA ON SOUTH SIDE WATANA ON SOUTH sen NG ROAD TO SOUTH SIDE OF SUS-
AT DEVIL CANYON OF SUSITNA.CONNEC-SIDE OF SUSITNA.DEVIL CANYON AND lTNA.RAl L:GOLD
TING ROAD TO PARKS PARKS HIGHWAY.CREEK TO DEVIL
HIGHWAY.CANYON ON SOUTH
SJ DE OF SUS ITHA.
*~'1i 1eage Road 59 64 49 69 102
Rail -7 7 -14
Design and Construction Cost
($x 1,000,000)115 174 128 156 200
Maintenance Cost
(S x.1,000,000)7 9 6 10 12
Logistics Cost
($x 1,000,000)223 215 215 216 227
Total Cost
(S x 1,000,000)345 398 349 382 439
Construction Schedule
for Initial Access (Years)1 1 1 1 1
Construction Schedule
for Full Access (Years)3 3-4 3 3 3-4
Bridges Major (>1000 ft)1 2 1 2 1
Mi nor (1000 ft)2 2 1 2 1
*Includes upgradin9 21 miles of the Denali Highway Revision:0
Sheet 3 of 3