HomeMy WebLinkAboutAPA1793SUSITNA HYDROELECTRIC PROJECT
VOLUt~E 2
EXHIBIT B
STATEMENT OF PROJECT OPERATION
AND RESOURCE UTILIZATION
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SUSITNA HYDROELECTRIC PROJECT
VOLUME 2
EXHIBIT B
STATEMENT OF PROJECT OPERATION AND RESOURCE UTILIZATION
TABLE OF CONTENTS
1 -DAMSITE SELECTION ........................................... B-1-1
1.1-Previous Studies ...................•.................. B-1-1
(a) Early Studies of Hydroelectric Potential ......... B-1-1
(b) U.S. Bureau of Reel amation -1953 Study .......... B-1-2
(c) U.S. Bureau of Reclamation -1961 Study .......... B-1-2
(d) Alaska Po'fler Administration-1974 Study ......... B-1-3
(e) Kaiser Proposal for Development .................. B-1-3
(f) U.S. Army Corps Engineers ~ 1975 and 1979 Studies. B-1-3
1.2-Plan Formulation and Selection Methodology ............ B-1-4
1.3-Damsite Selection ....•...............•................ B-1-5
(a) Site Screening ................................... 8-1-6
(b) Engineering Layouts ....................•......... B-1-7
(c) Capital Costs .................................... B-1-11
1.4-Formulation of Susitna Basin Development Plans ........ B-1-11
(a) Tunnel Alternatives .............................. B-1-13
(b). Additional Basin Development Plan ................ B-1-14
(c) Selected Basin Development Plans .........•....... B-1-14
1.5-Evaluation of Basin Development Plans ................. B-1-16
(a) Evaluation Methodology ........................... B-1-16
(b) Evaluation Criteria .............................. B-1-21
(c) Results of Evaluation Process .................... B-1-22
1.6-Preferred Susitna Basin Development Plan .............. B-1-26
2-ALTERNATIVE FACILITY DESIGN, PROCESSES AND OPERATIONS ....... 8-2-1
2.1 -Susitna Hydroelectric Development ..................... B-2-1
2.2-Watana Project Formulation ............................ B-2-1
(a) Selection of Reservoir Level ..................... B-2-2
(b) Selection of Installed Capacity .......•.......•.. B-2-6
(c) Selection of Spillway Design Flood ............... B-2-8
(d) Main Dam Alternatives ............................ B-2-10
(e) Diversion Scheme Alternatives .................... B-2-14
(f) Spillway Facilities Alternatives ................. B-2-18
(g) Power Facilities Alternatives ....•............... B-2-19
2.3-Selection of Watana General Arrangement .............•. B-2-23
(a) Selection Methodology ••..........•..•.•.......... B-2-23
(b) Design Data and Criteria ..............••......... B-2-25
(c) Evaluation Criteria •...................•......... B-2-25
(d) Preliminary Review ...•........................... B-2-25
(e) Intermediate Review .............................. B-2-31
(f) Final Review ..................................... B-2-36
TABLE OF CONTENTS (Continued)
Page
2.4-Devil Canyon Project Formulation ...................... B-2-42
(a) Selection of Reservoir Level ..................... B-2-43
(b) Selection of Installed Capacity .................. B-2-43
(c) Selection of Spillway Capacity ................... B-2-44
(d) Main Dam Alternatives ............................ B-2-45
(e) Diversion Scheme Alternatives .•.................. B-2-49
(f) Spillway Alternatives ....................•....... B-2-51
(q) Power Facilities Alternatives .................... B-2-52
2.5-Selection of Devil Canyon General Arrangement ......... B-2-54
(a) Selection Methodology ............ ~ ............... B-2-54
(b) Design Data Criteria ............................. B-2-54
(c) Preliminary Review ............................... B-2-54
(d) Final Review .....•..•............................ B-2-59
2.6 -Se 1 ect ion of Access Road Corridor ..................... B-2-60
(a) Previous Studies ..............•.................. B-2-60
(b) Selection Process Constraints .................... B-2-61
(c) Corridor Identification and Selection ............ B-2-61
(d) Development of Plans ............................. B-2-62
(e) Eval.uation of Plans .............................. B-2-62
(f) Comparison of the Selected Alternative Plans ..... B-2-65
(g) Summary .......................................... B-2-73
(h) Final Selection of Plan ..... ; .................... B-2-73
2.7-Selection of 1ransmission Facilities .................. B-2-76
(a) Electric System Studies .......................... B-2-76
(b) Corridor Selection ............................... B-2-83
(c) Corridor Screening ............................... 8-2-94
(d) Selected Corridor ................................ B-2-103
(e) Route Selection .................................. B-2-110
(f) Towers, Foundations and Conductors ............... B-2-116
2.8-Selection of Project Operation ........................ B-2-121
(a) Pre-Project Flows ................................ B-2-12~
(b) Range of Post-Project Flows ...................... B-2-12S
(c) Timing of Flow Releases .......................... B-2-125
(d) Maximum Drawdown ................................. B-2-126
(e) Energy Production ................................ B-2-126
(f) Net Benefits ..................................... B-2-127
(g) Operational Flow Scenario Selection .............. B-2-127
(h) Instream Flow and Fishery Impact on
Flow Selection ................................... B-2-128
3-DESCRIPTION OF PROJECT OPERATION ........................... . B:..3-1
B-3-1
B-3-2
B-3-2
B-3-2
B-3-3
B-3-6
3.1 -
3.2
3.3 -
Operation within Railbelt Power System ............... .
Plant and System Operation Requirements .............. .
General Power Plant and System Railbelt Criteria ..... .
(a) Installed Generating Capacity ................... .
(b) Transmission System Capability .................. .
( c ) s umm ar y e I I I I I I co & oil 1!0 8 I I I e I I I n e I I I I I I I I I I .-I I I I I I I I I I
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TABLE OF CONTENTS (Continued)
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3.4 -Economic Dispatch of Units ....••............•......... B-3-6
(a) Merit-Order Schedule .....•.................•..... B-3-7
(b) Optimum Load Dispatching ...•.......•....•........ B-3-7
(c) Operating Limits of Units ..•...••..•..•••....•.•. B-3-8
(d) Optimum Maintenance Program ...................... B-3-8
3.5 -Unit Operation Reliability Criteria .................•. B-3-9
(a) Power System Analyses ............................ B-3-9
(b) System Response and Load-Frequency Control ....•.. B-3-9
(c) Protective Relaying System and Devices ........•.. B-3-9
3. 6 -Dispatch Contra 1 Centers •..................•.......... B-3-10
3. 7 -Sus itna Project Operation ....•....•..........•........ B-3-11
4-DEPENDABLE CAPACITY AND ENERGY PRODUCTION ....•.....•.•....•.. B-4-1
4.1 -Hydrology ...•.•.............•..•.•...............•.•.. B-4-1
(a) Historical Streamflow Records .....•....•..•.•.... B-4-1
(b) Water Resources .....•...............•....•....•.. B-4-1
(c) Streamflow Extension ........•.......•..•....•.... B-4-2
( d ) F 1 o ads .....•.....•....•.... ~ . . • . . . . . . . • . . . . • . . . . . B-4-2
(e) Flow Adjustments .....••.......•.......•....•..... B-4-3
4.2-Reservoir Data ..•..........•.•...............•....•..• B-4-4
(a) Reservoir Storage ..•..•.•..•....•.....•.•....•..• B-4-4
(b) Rule Curves ..•..•.......•.•..•................... B-4-4
Operating Capabilities of Susitna Units •.............. B-4-5
4.3 -(a) Watana ........................................... B-4-5
(b) Devil Canyon •..•..•..•••..........•.........•.... 8-4-6
(c) Dependable Capacity and Energy Production ..•...... B-4-7
4. 4 -Tai lwater Rating Curve •.....•...••............•....... B-4-8
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LIST OF TABLES
Number Tit 1 e
B.O Alaska Power Authority, Resource Aqency Consultation
Correspondence and Meeting Log Concerning Aquatic and
Fisheries Resources, 1980 Through 1983.
B.1 Potential Hydroelectric Development
B.2 Cost Comparisons
B.3 Dam Crest and Full Supply Levels
B.4 Capital Cost Estimate Summaries -Susitna Basin Dam
Schemes -Cost in $ Million 1980
B.5 Results of Screening Model
B.6 Information on the Devil Canyon Dam and Tunnel Schemes
B.? Devil Canyon Tunnel Schemes -Costs, Power Output and Average
Annual Energy
B.8 Capital Cost Estimate Summaries -Tunnel Schemes -Costs in $
Mill ion 1980
B.9 Susitna Development Plans
B.lO Susitna Environmental Development Plans
B.11 Results of Economic Analyses of Susitna Plans -
Medium Load Forecast
B.12 Results of Economic Analyses of Susitna Plans -
Low and High Load Forecast
B.13 Annual Fixed Carrying Charges
B.l4 Summary of Thermal Generating Resource Plant Parameters
B.l5 Economic Backup Data for Evaluation of Plans
B.16 Economic Evaluation of Devil Canyon Dam and
Tunnel Schemes and Watana/Devil Canyon and
High Devil Canyon/Vee Plans
B.l? Environmental Evaluation of Devil Canyon Dam and
Tunnel Schemes
B.18 Social Evaluation of Susitna Basin Development
Schemes/Plans
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LIST OF TABLES (Continued)
Number Tit 1 e
B.19 Energy Contribution Evaluation of the Devil Canyon
Dam and Tunnel Schemes ·
B. 20 Overall Evaluation of Tunnel Scheme and Devi 1 Canyon
Dam Scheme
B.21 Environmental Evaluation of Watana/Devil Canyon and
High Devil Canyon/Vee Development Plans
B.22 Energy Contribution Evaluation of the Watana/Devil
Canyon and High Devil Canyon/Vee Plans
B.23 Overall Evaluation of the High Devil Canyon/Vee and
Watana/Devil Canyon Dam Plans
B.24 Combined Watana and Devil Canyon Operation
B.25 Present Worth of Production Costs
B.26 Design Parameters for Dependable Capacity and Energy
Production
B.27 Watana -Maximum Capacity Required (MW) -Option 1 -Thermal
as Base
B.28 Watana -Maximum Capacity Required (MW) -Option 2 -Thermal
as Peak
B.29 Summary Comparison of Powerhouses at Watana
B.30
B.31
Design Data and Design Criteria for Final Review
of Layouts
Evaluation Criteria
B.32 Summary of Comparative Cost Estimates
8.33 Devil Canyon -Maximum Capacity Required (MW)
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LIST OF TABLES (Continued)
Number Title
B.34 Design Data and Design Criteria for Review of
Altenative Layouts
B.35 Summary of Comparative Cost Estimates
B.36 Power Transfer Requirements (MW)
B.37 Summary of Life Cycle Costs
B.38 Technical, Economic, and Environmental Criteria Used
in Corridor Selection
B.39 Environmental Inventory -Southern Study Area
B.40 Environmental Inventory -Central Study Area
B.41 Environmental Inventory -Northern Study Area
B.42 Soil Associations Within the Proposed Transmission
Corridors -General Description, Offroad Trafficability,
Limitations (ORTL), and Common Crop Suitability (CCS)
B.43 Definitions for Offroad Trafficability Limitations and
Common Crop Suitability of Soil Associations
B.44 Economical and Technical Screening -Southern Study Area
B.45 Economical and Technical Screening -Central Study Area
B.46 Economical and Technical Screening -Northern Study Area
8.47 Summary of Screening Results
B.48 Environmental Constraints -Southern Study Area
B.49 Environmental Constraints -Central Study Area
8.50 Environmental Constraints -Northern Study Area
B.51 Technical, Economic and Environmental Criteria Used
in Corridor Screening
B.52 Pre-project Flow at Watana
B.53 Pre-project Flow at Devil Canyon
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LIST OF TABLES (Continued)
Number Title
8.54 Monthly Flow Requirements at Gold Creek
B.55 Energy Potential of the Watana Development for Different
Downstream Flow Requirements
B.56 Energy Potential of Watana -Devil Canyon Developments
for Different Downstream Flow Requirements
8.57 Net Benefits for Susitna Hydroelectric Project
Operating Scenarios
B.58 System Generation Reserve
B.59 Transmission System Performance Under Double Contingency
B.60 Average Annual and Monthly Flow at Gage in the
Susitna Basin
8.61 Peak Flows of Record
B.62 Estimated Flood Peaks in Susitna River
B.63
B.64
Watana Flood Routing-Maximum Flows (cfs)
Estimated Evaporation Losses -Watana and Devil
Canyon Reservoirs
8.65 Flow Release at Watana for Watana Only
B.66 Flow Release at Devil Canyon for Watana/Devil Canyon
B.67 Water Appropriations Within One Mile of the
Susitna River
B.68 Turbine Operating Conditions
B.69 Total 1981 Alaska Energy Consumption
B.70 Railbelt 1981 Energy Consumption By Fuel Type For
8.71
Each Sector
Installed Capacity of the Anchorage-Cook Inlet
Area
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LIST OF TABLES (Continued)
Number Tit 1 e
B.72 Installed Capacity of the Fairbanks-Tanana Valley
Area
B.73 Generating Plants of the Railbelt Region
B.74 Monthly Distribution of Peak and Energy Demand
B.75 Projected Monthly Distribution of Peak and Energy Demand
8.76 Typical Daily Load Duration
B.77 Load Diversity in the Railbelt
B.78 Residential and Commercial Electric Rates -Anchorage-Cook
Inlet Area, March 1983
B.79 Residential and Commerical Electric Rates -Fairbanks-Tanana
Area, March 1983
B.80 Anchorage Municipal Light and Power, Cumulative Energy
Conservation Projections
B.81 Programmatic Versus Market Driven Enerqy Conservation
Projections in AMLP's Service Area
B.82 Average Annual Electricity Consumption Per Household
On the GVEA System 1972-1982
B.83 Historic Economic and Electric Power Data 1960-1982
B.84 Monthly Load Data from Electric Utilities of the
Anchorage-Cook Inlet Area 1976-1982
B.85 Monthly Load Data fromElectric Utilities of the
Fairbanks-Tanana Valley Area 1976-1982
B.86 Net Electric Power Generation By Electric Utilities
1976-1982
B.87 Simulation of Historical Economic Conditions
8.88 Comparison of Actual and Predicted Electricity
Consumption
B.89 Alternative Petroleum Price Projections 1983-2010
B.90 Level of Analysis Employed with World Oil Forecasts
8.91 Variables and Assumptions (PETREV Model)
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LIST OF TABLES (Continued)
Number Tit 1 e
B.92 Variabless and Assumptions -MAP Model
B.93 Summary of Exogenous Economic Assumptions
B.94 Variables and Assumptions -RED Model
B.95 Fuel Price Forecasts Used by RED
B.96 Housing Demand Coefficients
B.97 Example of Market Saturations of Appliances in Single
Family Homes for Anchorage-Cook Inlet Area
B.98 Parameter Values in RED Price Adjustment Mechanism
B.99 Percentage of Appliances Using Electricity and Averaqed
B.100
B.101
B.102
B.103
B.104
B.105
B.106
8.107
8.108
B.109
B .110
B.111
B .112
Annual Electricity Consumption~ Railbelt Load Centers
Growth Rates in Electric Appliance Capacity and Initial
Annual Average Consumption for New Appliances
Percent of Appliances Remaining in Service Years after
Purchase
Variables and Assumptions -OGP Model
Reference Case Forecast Summary of Input and Output Data
Reference Case Forecast -State Petroleum Revenues
Reference Case Forecast -State Government Fiscal
Conditions
Reference Case Forecast-Population
Reference Case Forecast -Employment
Reference Case Forecast -Households
Reference Case Forecast -Number of Households
Reference Case Forecast -Number of Vacant Households
Reference Case Forecast -Residential Use Per Household
Reference Case Forecast -Business Use Per Employee
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LIST OF TABLES (Continued )
Number Title
B.113 Reference Case Forecast -Summary of Price Effects and
Programmatic Conservation -Anchorage-Cook Inlet Area
8.114 Breakdown of Electricity Requirements -Anchoraqe-Cook
Inlet Area.
8.115 Reference Case Forecast -Summary of Price Effects and
Programmatic Conservation -Fairbanks-Tanana Valley Area
8.116 Reference Case Forecast -Breakdown of Electricity
Requirements -Fairbanks-Tanana Valley Area
B.117 Reference Case Forecast -Projected Peak and Ener~y Demand
8.118
B .119
8.120
8.121
B.122
B.123
B.124
B.125
Department of Revenue, Mean -Summary of Input and
Output Data
Department of Revenue, 50% -Summary of Input and
Output Data
Department of Revenue, 30% -SUmmary of Input and
Output Data
Data Resources Inc. -Summary of Input and
Output Data
FERC +2% -Summary of Input and
Output Data
FERC 0% -Summary of Input and
Output Data
FERC -1% -Summary of Input and
Output Data
FERC -2% -Summary of Input and
Output Data
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LIST OF TABLES (Continued )
Number Title r-
8.126 Results of MAP Model Sensitivity Tests
8.127 Results of RED Model Sensitivity Tests
8.128 Results of RED Model Sensitivity Tests
,-8.129 Results of RED Model Sensitivity Tests
8.130 Results of RED Model Sensitivity Tests
8.131 Results of RED Model Sensitivity Tests
I""" 8.132 List of Previous Forecasts
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LIST OF FIGURES
Number Title
8.1 Location Map
8.2 Damsites Proposed by Others
8.3 Susitna Basin Plan Formulation and Selection Process
B.4 Profile Through Alternative Sites
8.5 Mutually Exclusive Development Alternatives
8.6 Devil Canyon Hydro Development Fill Dam
8.7 Watana Hydro Development Fill Dam
B.8 Watana Staged Fill Dam
8.9 High Devil Canyon Hydro Development
8.10 Susitna III Hydro Development
8.11 Vee Hydro Development
8.12 Denali and Maclaren Hydro Developments
B.13 Schematic Representation of Conceptual Tunnel Schemes
B.14 Preferred Tunnel Scheme 3 Plan View
8.15 Preferred Tunnel Scheme 3 Sections
8.16 Generation Scenario with Susitna Plan E1.3
8.17 Generation Scenario with Susitna Plan E2.3
8.18 Generation Scenario with Susitna Plan E3.1
8.19 Watana Reservoir -Dam Crest Elevation/Present Worth
of Production Costs
B.20 Watana -Arch Dam Alternative
B.21 Watana -Alternative Dam Axes
8.22 Watana Diversion -Headwater Elevation/Tunnel Diameter
B.23 Watana Diversion -Upstream Cofferdam Costs
xii
LIST OF FIGURES (continued)
Number Title
8.24 Watana Diversion -Tunnel Cost/Tunnel Diameter
8.25 Watana Diversion -Total Cost/Tunnel Diameter
8.26 Watana-Preliminary Schemes
8.27 Watana-Scheme WP1 Plan
8.28 Watana -Scheme WP3 Sections
8.29 Watana -Scheme WP2 and WP 3
8.30 Watana -Scheme WP2 Sections
8.31 Watana-Scheme WP4 Plan
8.32 Watana -Scheme WP4 Sections
8.33 Watana -Scheme WP3A
8.34 Watana -Scheme WP4A
8.35 Devil Canyon Diversion -Headwater Elevation/Tunnel
Diameter
8.36 Devil Canyon Diversion -Total Cost/Tunnel Diameter
8.37 Devil Canyon -Scheme DC1
8.38 Devil Canyon -Scheme OC2
8.39 Devil Canyon -Scheme DC3
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8.40 Devil Canyon -Scheme DC4
8.41 Devil Canyon -Selected Scheme
8.42 Alternative Access Corridors
8.43 Access Plan 13 (North)
8.44 Access Plan 16 (South)
8.45 Access Plan 18 (Proposed)
8.46 Schedule for Access and Diversion
xiii
LIST OF FIGURES (Continued)
Number Title
8.47 Alternative Transmission Line Corridors -
Southern Study Area
8.48 Alternative Transmission Line Corridors -
Central Study Area
8.49 Alternative Transmission Line Corridors -
Northern Study Area
8.50 Recommended Transmission Line Corridor -
Southern Study Area
8.51 Recommended Transmission Line Corridor -
Southern Study Area
8.52 Recommended Transmission Line Corridor -
Central Study Area
8.53 Recommended Transmission Line Corridor -
Central Study Area
8.54 Recommended Transmission Line Corridor -
Northern Study Area
B.55 Recommended Transmission Line Corridor -
Northern Study Area
8.56 Recommended Transmission Line Corridor -
Northern Study Area
B.57 Recommended Transmission Line Corridor -
Northern Study Area
8.57A Transmission Reliability Studies
8.58 Typical Load Variation in Alaska Railbelt System
8.59 Data Collection Stations
8.60 Average Annual Flow Distribution Within the Susitna
River Basin
8.61 Monthly Average Flows in the Susitna River at Gold Gulch
8.62 Flow Duration Curve Mean Monthly Inflow at Watana
Pre-Project
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LIST OF FIGURES (continued)
Number Title
8.63
8.64
Flow Duration Curve IIJ!ean Monthly Inflow at Devil
Canyon Pre-Project
Frequency Analysis of Average Annual Energy for
Susitna Development
8.65 · Watana Hydrological Data -Sheet 1
B.66 Devil Canyon Hydrological Data -Sheet 1
B.67 Watana Hydrological Data -Sheet 2
B.68 Devil Canyon Hydrological Data -Sheet 2
8.69 Monthly Target Minimum Reservoir Levels
8.70 Watana-Unit Output
8.71 Watana-Turbine Performance (at Rated Head)
B. 72 Watana-Unit Efficiency (at Rated Head)
8.73 Devil Canyon-Unit Output
8.74 Devil Canyon -Turbine Performance (at Rated Head)
8.75 Devil Canyon-Unit Efficiency (at Rated Head)
B.76 Dependable Capacity
8.77 Railbelt Area of Alaska Showing Electrical Load Centers
8.78 Location Map Showing Transmission Systems
8.79 Monthly Load Variation for Rai"Jbelt Area
8.80 Daily Load Curves -1982
8.81 Historical Population Growth 1960-1980
8.82 Historical Growth in Net Generation 1960-1980
8.83 Relationship of Planning Models and Input Data
8.84 MAP Model System Flow Chart
XV
LIST OF FIGURES (Continued)
Number Title
B.85 MAP Economic Sub-Model Flow Chart
B.86 MAP Regionalization Sub-Model Flowchart
B.87 REO Information Flow
B.88 RED Uncertainty Module
B.89 RED Housing Module
B.90 RED Residential Consumption Module
B.91 RED Business Consumption Module
B.92 RED Program Induced Conservaton Module
B.93 RED Miscellaneous Consumption Module
B.94 RED Peak Demand Module
B.95 Optimization Generation Planninq (OGP) Model Information
Flows
B.96 OGP -Example of Conventional Hydro Operations
B.97 Data Resources Inc. -U.S. Oil Outlook, Crude Oil Prices
and Production
B.98 Free World Petroleum -and Broad Sources of Supply -SHCA
B.99 Alternative Oil Price Projections
B.lOO Alternative State General Fund Expenditure Forecasts
B.lOl Alternative Railbelt Population Forecasts
B.l02 Alternative Railbelt Households Forecasts
B.l03 Alternative Electric Energy Demand Forecasts
B.104 Alternative Electric Peak Demand Forecasts
Note; Figures B.76-B.80 in the February 1983 License Application are
replaced by new Figures B.77 throuqh B.l04 contained in Volume
2A.
xvi
1 -DAMSITE SELECTION
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EXHIBIT B -PROJECT OPERATION AND RESOURCE UTILIZATION
1 -DAMSITE SELECTION
This section summarizes the previous site selection studies and the
studies done during the Alaska Power Authority Susitna Hydroelectric
Project Feasibility Study (Acres 1982c, Vol. 1).
1.1 -Previous Studies
Prior to the undertaking of the Susitna Hydroelectric Project Feasi-
bility Study by the applicant, the hydroelectric development potential
of the Alaskan Railbelt had been studied by several entities.
(a} Early Studies of Hydroelectric Potential
Shortly after World War II ended, the United States Bureau of
Reclamation (USBR) conducted an initial investigation of hydro-
electrlc potential in Alaska and issued a report of the results in
1948. Responding to a recommendation made in 1949 by the nine-
teenth Alaska territorial legislature that Alaska be included in
the Bureau of Reclamation program, the Secretary of the Interior
provided funds to update the 1948 work. The resulting report,
issued in 1952, recognized the vast hydroelectric potential within
the territory and placed particular emphasis on the strategic
location of the Susitna River between Anchorage and Fairbanks as
well as its proximity to the connecting Railbelt (Figure B.1).
A series of studies was commissioned over the years to identify
damsites and conduct geotechnical investigations. By 1961, the
Department of the Interior proposed authorization of a two-dam
power system on the Susitna River involving the Devil Canyon and
the Denali sites (Figure B.2). The definitive 1961 report was
subsequently updated by the Alaska Power Administration (an agency
of the USBR) in 1974, at which time the desirability of proceeding
with hydroelectric development was reaffirmed.
The Corps of Engineers (COE) was also active in hydropower invest-
igations in Alaska during the 1950s and 1960s, but focused its
attention on a more ambitious development at Rampart on the Yukon
River. This project was capable of generating five times as much
annual electric energy as the prior Susitna proposal. The sheer
size and the technological challenges associated with Rampart cap-
tured the imagination of supporters and effectively diverted
attention from the Susitna basin for more than a decade. The
Rampart report was finally shelved in the early 1970s because of
strong environmental concerns and the uncertainty of marketing
prospects for so much energy, particularly in light of abundant
B-1-1
natural gas which had been discovered and developed in Cook
In 1 et.
The energy cns1s precipitated by the OPEC oil boycott in 1973
provided some further impetus for seeking development of renewable
resources. Federal funding was made available both to complete
the Alaska Power Admini5tration•s update report on Susitna in 1974
and to launch a prefeasibility investigation by the COE. The
State of Alaska itself commissioned a reassessment of the Susitna
project by the Henry J. Kaiser Company in 1974.
Salient features of the various reports to date are outlined in
the following sections.
(b) U.S. Bureau of Reclamation -1953 Study
The USBR 1952 report to the Congress on Al aska• s overall hydro-
electric potential was followed shortly by the first major study
of the Susitna basin in 1953. Ten damsites were identified above
the railroad crossing at Gold Creek. These sites are identified
on Figure B.2, and are listed below:
-Gold Creek
-Olson
-Dev i 1 Canyon
-Dev i 1 Creek
-Watana
-Vee
-\VIae 1 aren
-Denali
-Butte Creek
-Tyone (on the Tyone River).
Fifteen more sites were considered be 1 ow Go 1 d Creek. However,
more attention has been focused over the years on the upper Sus-
itna basin where the topography is better suited to dam construc-
tion and where less impact on anadromous fisheries is expected.
Field reconnaissance eliminated half the original upper basin
list, and further USBR consideration centered on Olson, Devil
Canyon, Watana, Vee, and Denali. All of the USBR studies since
1953 have regarded these sites as the most appropriate for further
investigation.
(c) U.S. Bureau of Reclamation -1961 Study
In 1961 a more detailed feasibility study resulted in a recom-
mended five-stage development plan to match the load growth curve
as it was then projected. Devil Canyon was to be the first devel-
opment--a 635-foot high arch dam with an installed capacity of
about 220 MW. The reservoir formed by the Devi 1 Canyon Dam
B-1-2
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alone would not store enough water to permit higher capacities to
be economically installed, since long periods of relatively low
flow occur in the winter months. The second stage would have
increased storage capacity by adding an earthfill dam at Denali in
the upper reaches of the basin. Subsequent stages involved adding
generating capacity to the Devil Canyon Dam. Geotechnical invest-
igations at Devil Canyon were more thorough than at Denali. At
Denali, test pits were dug, but no drilling occurred.
(d) Alaska Power Administration -1974 Study
(e)
Little change from the basic USBR 1961, five-stage concept ap-
peared in the 1974 report by the Alaska Power Administration.
This later effort offered a more sophisticated design, provided
new cost and schedule estimates, and addressed marketing, econ-
omics, and environmental considerations.
Kaiser Proposal for Development
The Kaiser study, commissioned by the Office of the Governor in
1974, proposed that the initial Susitna development consist of a
single dam known as High Devil Canyon located on Figure B.2. No
field investigations were made to confirm the technical feasibil-
ity of the High Devil Canyon location because the funding level
was insufficient for such efforts. Visual observations suggested
the site was probably favorable. The USBR had always been uneasy
about foundation conditions at Denali, but had to rely upon the
Denali reservoir to provide storage during long periods of low
flow. Kaiser chose to avoid the perceived uncertainty at Denali
by proposing to bu·ild a rockfill dam at High Devil Canyon which,
at a height of 810 feet, would creat.e a 1 arge enough reservoir to
overcome the storage prob 1 em. A 1 though the se 1 ected sites were
different, the COE reached a similar conclusion when it later
chose the high dam at Watana as the first to be constructed.
Subsequent developments suggest~~ by Kaiser included a downstream
dam at the 01 son site and an upstream dam at a site known as Sus-
itna III (Figure B.2). The information developed for these addi-
tional dams was confined to estimating energy potential. As in
the COE study, future development of Denali remained a possibility
if foundation conditions were found to be adequate and if the
value of additional firm energy provided economic justification at
some later date.
(f) U.S. Army Corps of Engineers -1975 and 1979 Studies
The most comprehensive study of the upper Susitna basin prior to
the current study was completed in 1975 by the COE. A total of 23
alternative developments were analyzed, including those proposed
by the USBR, as well as consideration of coal as the primary
B-1-3
energy source for Railbelt electrical needs. The COE agreed that
an arch dam at Devil Canyon was appropriate, but found that a high
dam at the Watana site would form a large enough reservoir for
seasonal storage and would permit continued generation during low
flow-periods.
The COE recorrmended an earthfi 11 dam at Watana with a height of
810 feet. In the longer term, development of the Denali site re-
mained a possibility which, if constructed, would increase the
amount of firm energy available in dry years.
An ad hoc task force was created by Governor Jay Hammond upon com-
pletion of the 1975 COE study. This task force recommended en-
dorsement of the COE request for Congressional authorization, but
pointed out that extensive further studies, particularly those
dealing with environmental and socioeconomic questions, were
necessary before any construction decision could be made.
At the federal level, concern was expressed at the Office of Man-
agement and Budget regarding the adequacy of geotechnical data at
the Watana site as well as the validity of the economics. The
apparent ambitiousness of the schedule and the feasibility of a
thin arch dam at Devil Canyon were also questioned. Further in-
vestigations were funded and the COE produced an updated report in
1979. Devil Canyon and Watana were reaffirmed as appropriate
sites, but alternative dam types were investigated. A concrete
gravity dam was analyzed as an alternative for the thin arch dam
at Devi 1 Canyon and the Watana Dam was changed from earthfi 11 to
rockfill. Subsequent cost and schedule estimates still indicated
economic justification for the project.
1.2 -Plan Formulation and Selection Methodology
The proposed plan which is the subject of this license application was
selected after a review and reassessment of all previously considered
sites (Acres 1982c, Vol. 1).
This section of the report outlines the engineering and planning stud-
ies carried out as a basis for formulation of Susitna basin development
plans and selection of the preferred plan.
In the description of the planning process, certain plan components and
processes are frequently discussed. It is appropriate that three par-
ticular terms be clearly defined:
Damsite -An individual potential damsite in the Susitna
basin, referred to in the generic process as .. can-
didate ...
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-
-
-
,-
-
-
-
-
·sasin Development
Plan
Generation
Scenario
-A plan for developing energy within the upper
Susitna basin involving one or more dams, each of
specified height, and corresponding power plants
of specified capacity. Each plan is identified by
a plan number and subnumber indicating the staging
sequence to be followed in developing the full
potential of the plan over a period of time.
- A specified sequence of implementation of power
generation sources capable of providing sufficient
power and energy to satisfy an electric load
growth forecast for the 1980-2010 period in the
Railbelt area. This sequence may include dif-
ferent types of generation sources such as hydro-
electric and coal-, gas-or oil-fired thermal.
These generation scenarios were developed for the
comparative evaluations of Susitna basin
generation versus alternative methods of
generation.
In applying the generic plan formulation and selection methodology,
five basic steps are required: defining the objectives, selecting can-
didates, screening, formulation of development plans, and, finally, a
detailed evaluation of the plans (Figure 8.3). The objective is to
determine the optimum Susitna basin development plan. The various
steps required are outlined in subsections of this section.
Throughout the planning process, engineering layout studies were made
to refine the cost estimates for power generation facilities or water
storage development at several damsites within the basin. These data
were fed into the screening and plan formulation and evaluation stud-
; es.
The second objective, the detailed evaluation of the various plans, is
satisfied by comparing generation scenarios that include the selected
Susitna basin development plan with alternative generation scenarios,
including all-thermal and a mix of thermal plus alternative hydropower
developments.
1.3 -Damsite Selection
In previous Susitna basin studies, twelve darnsites were identified in
the upper portion of the basin, i.e., upstream from Gold Creek. These
sites are listed in Table 8.1 with relevant data concerning facilities,
cost, capacity, and energy.
The longitudinal profile of the Susitna River and typical reservoir
levels associated with these sites are shown in Figure 8.4. Figure 8.5
illustrates which sites are mutually exclusive, i.e., those which can-
not be developed jointly, since the downstream site would inundate the
upstream site.
8-1-5
It can be readily seen that there are several mutually exclusive
schemes for power development of the basin. The development of the
Watana site precludes development of High Devil Canyon, Devils Creek,
Susitna III and Vee but fits well with Devil Canyon. Conversely, the
High Devil Canyon site would preclude Watana and Devil Canyon but fits
well with Olson and Vee or Susitna III. These downstream sites do not
preclude development of the upstream storage sites, Denali or Butler
Creek and Maclaren.
All relevant data concerning dam type, capital cost, power, and energy
output were assembled and are summarized in Table B.l. For the Devil
Canyon, High Devil Canyon, Watana, Susitna III, Vee, Maclaren, and
Denali sites, conceptual engineering layouts were produced and capital
costs were estimated based on calculated quantities and unit rates.
Detai 1 ed analyses were also undertaken to assess the power capabi 1 ity
and energy yields. At the Gold Creek, Devil Creek, Maclaren, Butte
Creek, and Tyone sites, no detailed engineering or energy studies were
undertaken; data from previous studies were used with capital cost
estimates updated in 1980 1 evel s. Approximate esti'mates of the poten-
tial average energy yield at the Butte Creek and Tyone sites were
undertaken to assess the relative importance of these sites as energy
producers.
The data presented in Table B.l show that Devil Canyon, High Devil Can-
yon, and Wat ana are the most economic 1 arge energy producers in the
basin. Sites such as Vee and Susitna III have only medium energy pro-
duction, and are slightly more costly that the previously mentioned
damsites. Other sites such as Olson and Gold Creek are competitive
provided they have additional upstream regulation. Sites such as
Denali and Maclaren produce substantially higher cost energy than the
other sites but can also be used to increase regulation of flow for
downstream use.
(a) Site Screening
The objective of this screening process was to eliminate sites
which would obviously not be included in the initial stages of the
Susitna basin development plan and which, therefore, did not
deserve further study at this stage. Three basic screening cri-
teria were used: environmental, alternative sites, and energy
contribution.
The screening process involved eliminating all sites falling in
the unacceptable environmental impact and alternative site cate-
gories. Those failing to meet the energy contribution criteria
were also eliminated unless they had some potential for upstream
regulation. The results of this process were as follows:
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-
-
-
-The 11 unacceptable site 11 environmental category eliminated the
Gold Creek, Olson, and Tyone sites.
-The alternative sites category eliminated the Devil Creek and
Butte Creek sites.
-No additional sites were eliminated for failing to meet the
energy contribution criteria. The remaining sites upstream from
Vee, i.e., Maclaren and Denali, were retained to insure that
further study be directed toward determining the need and via-
bility of providing flow regulation in the headwaters of the
Sus itna.
(b) Engineering Layouts
In order to obtain a uniform and reliable data base for studying
the seven sites remaining, it was necessary to develop engineering
layouts and reevaluate the costs. In addition, staged develop-
ments at several of the larger dams were studied.
The basic objective of these layout studies was to establish a
uniform and consistent development cost for each site. These lay-
outs are consequently conceptual in nature and do not necessarily
represent optimum project arrangements at the sites. Also, be-
cause of the lack of geotechnical information at several of the
sites, judgmental decisions had to be made on the appropriate
foundation and abutment treatment. The relati~e accuracy of cost
estimates made in these studies is on the order of plus or minus
30 percent.
( i ) Design Assumptions
In order to maximize standardization of the layouts, a set
of basic design assumptions was developed. These assump-
tions covered geotechnical, hydrologic, hydraulic, civil,
mechanical, and electrical considerations and were used as
guidelines to determine the type and size of the various
components within the overall project 1 ayouts. As stated
previously, other than at Watana, Devil Canyon, and Denali,
little information regarding site conditions was available.
Broad assumptions were made on the basis of the limited
data, and those assumptions and the interpretation of data
have been conservative.
It was assumed that the relative cost differences between
rockfi 11 and concrete dams at the site would either be
marginal or greatly in favor of the rockfill. The more
detailed studies carried out subsequently for the Watana and
Devil Canyon sites support this assumption. Therefore, a
rockfill dam has been assumed at all developments in order
to eliminate cost discrepancies that might result from a
consideration of dam-fi 11 unit costs compared to concrete
unit costs at alternative sites. '
B-1-7
(ii) General Arrangements
Brief descriptions of the general arrangements developed for
the various sites are given below. Descriptions of Watana
and Devil Canyon in this section are of the preliminary lay-
outs and should not be confused with the proposed layouts in
Exhibit A and Exhibit F. Figures 8.6 to 8.12 illustrate the
layout details. Table 8.3 summarizes the crest levels and
dam heights considered.
In laying out the developments, conservative arrangements
have been adopted, and whenever pass i b 1 e there has been a
general standardization of the component structures.
-Devil Canyon (Figure 8.6)
The development at Devil Canyon, located at the upper end
of the canyon at its narrowest point, consists of a rock-
fill dam, single spillway, power facilities incorporating
an underground powerhouse, and a tunnel diversion.
The rockfill dam would rise above the valley on the south
abutment and terminate in an adjoining saddle dam of simi-
1 ar construction. The dam waul d be 675 feet above the
lowest foundation level with a crest elevation of 1470 and
a volume of 20 million cubic yards.
The spillway would be located on the north bank and would
consist of a gated overflow structure and a concrete-lined
chute linking the overflow structure with intermediate and
terminal stilling basins. Sufficient spillway capacity
would be provided to pass the Probable Maximum Flood
safely.
The power facilities would be located on the north abut-
ment. The massive intake structure would be founded with-
in the rock at the end of a deep approach channel and
would consist of four integrated units, each serving indi-
vidual tunnel penstocks. The powerhouse would house four
150-MW vertically mounted Francis type turbines driving
overhead 165 MVA umbrella type generators.
As an alternative to the full power development in the
first phase of construction, a staged powerhouse alterna-
tive was also investigated. The dam would be completed to
its full height but with a initial plant installed capa-
city in the 300-MW range. The complete powerhouse would
be constructed together with penstocks and a tailrace
tunnel for the initial two 150-MW units, together with
concrete foundations for future units.
B-1-8
-
-Watana (Figure B.7 and B.S)
For initial comparative study purposes, the dam at Watana
is assumed to be a rockfill structure located on a similar
a 1 i gnment to that proposed in the previous COE studies.
It would be similar in construction to the dam at Devil
Canyon with an impervious core founded on sound bedrock
and an outer shell composed of blasted rock excavated from
a single quarry located on the south abutment. The dam
would rise 880 feet from the lowest point on the founda-
tion and have an overall volume of approximately 63 mil-
lion cubic yards for a crest elevation of 2225.
The spillway would be located on the north bank and would
be similar in concept to that at Devil Canyon with an
intermediate and terminal stilling basin.
The power facilities located within the south abutment
with simi 1 ar intake, underground powerhouse, and water
passage concepts to those at Devil Canyon would incorpor-
ate four 200-MW turbine/generator units giving a total
output of 800 MW.
As an alternative to the initial full development at
Watana, staging alternatives were investigated. These
included staging of both dam and powerhouse construction.
Staging of the powerhouse would be similar to that at
Devil Canyon, with a Stage I installation of 400 MW and a
further 400 MW in Stage II.
In order to study the alternative dam staging concept, it
was assumed that the dam would be constructed for a maxi-
mum operating water surface elevation some 200 feet lower
than that in the final stage (Figure B.8).
The powerhouse would be completely excavated to its final
size during the first stage. Three oversized 135-MW units
would be installed together with base concrete for an
additional unit. A low-level control structure and twin
concrete-lined tunnels leading into a downstream stilling
basin would form the first stage spillway.
For the second stage, the dam would be completed to its
full height, the impervious core would be appropriately
raised, and additional rockfill would be placed on the
downstream face. It was assumed that, before construction
commenced, the top 40 feet of the first stage dam would be
removed to ensure the complete integrity of the impervious
core for the raised dam. A second spillway control struc-
ture would be constructed at a higher level and would
B-1-9
incorporate a downstream chute leading to the Stage I
spillway structure. The original spillway tunnels would
be c 1 osed with concrete p 1 ugs. A new intake structure
would be constructed utilizing existing gates and hoists,
and new penstocks would be driven to connect with the
existing ones. The existing intake would be sealed off.
One additional 200-MW unit would be installed and the
required additional penstock and tailrace tunnel con-
structed. The existing 135-MW units would be upgraded to
200 MW.
-High Devil Canyon (Figure B.9)
The development would be located between Devil Canyon and
Watana. The 855-foot high rockfill dam would be simi 1 ar
in design to Devil Canyon, containtng an estimated 48 mil-
lion cubic yards of rockfill with a crest elevation of
1775. The south bank spillway and the north bank power-
house facilities would also be similar in concept to Devil
Canyon, with an installed capacity of 800 MW.
Two stages of 400 MW were envisaged in each which would be
undertaken in the same manner as at Devi 1 Canyon, with the
dam initially constructed to its full height.
-Susitna III (Figure 8.10)
The development would involve a rockfill dam with an
impervious core approximately 670 feet high, a crest ele-
vation of 2360, and a volume of approximately 55 million
cubic yards. A concrete-lined spillway chute and a single
stilling basin would be located underground, with the two
diversion tunnels on the south bank.
-Vee (Figure B.11)
A 610-foot high rock fill dam founded on bedrock with a
crest elevation of 2350 and total volume of 10 million
cubic yards was considered.
Since Vee is located farther upstream than the other major
sites, the flood flows are correspondingly lower, thus
allowing for a reduction in size of the spillway facili-
ties. A spillway utilizing a gated overflow structure,
chute, and flip bucket was adopted.
The power facilities would consist of a 400-MW underground
powerhouse located in the south bank with a tailrace out-
let well downstream of the main dam. A secondary rockfill
dam would also be required in this vicinity to seal off a
low point. Two diversion tunnels would be provided on the
north bank.
B-1-10
r
'
-Maclaren (Figure 8.12)
The development would consist of a 185-foot high earthfill
dam founded on pervious riverbed materials. The crest
elevation of the dam would be 2405. This reservoir would
essentially be used for regulating purposes. Diversion
waul d occur through three conduits 1 ocated in a open cut
on the south bank, and floods would be discharged vi a a
side chute spillway and stilling basin on the north bank.
-Denali (Figure 8.12)
Denali is similar in concept to Maclaren. The dam would
be 230 feet high, of earthfill construction, and would
have a crest elevation of 2555. As for Maclaren, no gen-
erating capacity would be included. A combined diversion
and spillway facility would be provided by twin concrete
conduits founded in open cut excavation in the north bank
and discharging into a common stilling basin.
(c) Capital Costs
For purposes of initial comparisons of alternatives, construction
quantities were determined for items comprising the major works
and structures at the site. Where detail or data were not suffi-
cient for certain work, quantity estimates were made on the basis
of previous development of similar sites and general knowledge of
site conditions reported in the literature. In order to determine
total capital costs for various structures, unit costs have been
developed for the items measured. These have been estimated on
the basis of review of rates used in previous studies, and of
rates used on similar works in Alaska and elsewhere. Where
applicable, adjustment factors based on geography, climate,
manpower and accessibility were used. Technical publications have
also been reviewed for basic rates and escalation factors.
The total capital costs developed are shown in Tables 8.1 and 8.2.
It should be noted that the capital costs for Maclaren and Denali
shown in Table 8.1 have been aqjusted to incorporate the costs of
generation plants with capacities of 55 MW and 60 MW, respec-
tively. Additional data on the projects are summarized in Table
8.3.
1.4 -Formulation of Susitna Basin Development Plans
The results of the site screening process described above indicate that
the Susitna basin development plan should incorporate a combination of
several major dams and powerhouses located at one or more of the fol-
lowing sites:
B-1-11
-Dev i 1 Canyon
-High Devil Canyon
-Wat ana
-Susitna III
-Vee.
Supplementary upstream flow regulation could be provided by structures
at Maclaren and Denali.
Cost estimates of these projects are itemized on Table B.4.
A computer-assisted screening process identified the plans of Devil
Canyon/Watana or High Devil Canyon/Vee as most economic. In addition
to these two basic development plans, a tunnel scheme which provides
potential environmental advantages by replacing the Devil Canyon Dam
with a long power tunnel and a development plan involving Watana Dam
was also introduced.
The criteria used at this stage of the process for selection of pre-
ferred Susitna basin development plans were mainly economic (Figure
B.3). Environmental considerations were incorporated into the further
assessment of the plans finally selected.
The results of the screening process are shown in Table B.5. Because
of the simplifying assumptions that were made in the screening model,
the three best solutions from an economic point of view are included in
the tab 1 e.
The most important conclusions that can be drawn are as follows:
-For energy requirements of up to 1750 GWh, the High Devil Canyon,
Devil Canyon or the Watana sites individually provided the most econ-
omic energy. The difference between the costs. shown on Table B.5 is
around 10 percent, which is similar to tile accuracy that can be
expected from the screening model.
-For energy requirements of between 1750 and 3500 GWh, the High Devil
Canyon site is the most economic.
-For energy requirements of between 3500 and 5250 GWh, the combina-
tions of either Watana and Devil Canyon or High Devil Canyon and Vee
are most economic.
-The total energy production capability of the Watana/Devil Canyon
development is considerably larger than that of the High Devil
Canyon/Vee alternative and is the only plan capable of meeting energy
demands in the 6000 GWh range.
8-1-12
(a)
r
-
.....
-
-
Tunnel Alternatives
A scheme involving a long power tunnel could conceivably be used
to replace the Devil Canyon Dam in the Watana/Devil Canyon devel-
opment plan. It could develop similar head for power generation
and may provide some environmental advantages by avoiding inunda-
tion of Devil Canyon. Obviously, because of the low winter flows
in the river, a tunnel alternative could be considered only as a
second stage to the Watana development.
Conceptually, the tunnel alternatives would comprise the following
major components in some combination, in addition to the Watana
Dam, reservoir and associated powerhouse:
-Power tunnel intake works;
One or two power tunnels up to 40 feet in diameter and up to 30
miles in length;
- A surface or underground powerhouse with a capacity of up to
1200 MW;
- A re-regulation dam if the intake works are located downstream
from Watana; and
Arrangements for compensation flow in the bypassed river reach.
Four basic alternative schemes were developed and studied. Figure
8.13 is a schematic illustration of these schemes. All schemes
assumed an initial Watana development with full reservoir supply
level at Elevation 2200 and the associated powerhouse with an
installed capacity of 800 MW. Table 8.6 1 ists all the pertinent
technical information. Table 8.7 lists the power and energy
yields for the four schemes. Table 8.8 itemizes the capital cost
estimate .
'Based on the foregoing economic information, Scheme 3 (Figures
B .14 and 8.15) produces the lowest cost energy by a factor of
nearly 2.
A, review of the environmental impacts associated with the four
tunnel schemes indicates that Scheme 3 would have the least im-
pact, primarily because it offers the best opportunities for regu-
1 at i ng daily. flows downstream from the project. Based on this
assessment and because of its almost 2 to 1 economic advantage,
Scheme 3 was selected as the only scheme worth further study. (See
Development Selection Report for detailed analysis.) The capital
cost estimate for Scheme 3 appears in Table B.a. The estimates
also incorporate single and double tunnel options. For purposes
of these studies, the double tunnel option has been selected
B-1-13
because of its superior reliability. It should also be recognized
that the cost estimates associated with the tunnels are probably
subject to more variation than those associated with the dam
schemes due to geotechnical uncertainties. In an attempt to com-
pensate for these uncertainties, economic sensitivity analyses
using both higher and lower tunnel costs have been conducted.
{b) Additional Basin Development Plan
As noted, the Watana and High Devil Canyon damsites appear to be
individually superior in economic terms to all others. An addi-
tional plan was therefore developed to assess the potential for
developing these two sites together. For this scheme, the Watana
Dam would be developed to its full potential. The High Devil Can-
yon Dam would be constructed to a crest elevation of 1470 to fully
utilize the head downstream from Watana.
(c) Selected Basin Development Plans
The essential objective of this step in the development selection
process was defined as the identification of those plans which
appear to warrant further, more detailed evaluation. The results
of the final screening process indicate that the Watana/Devil
Canyon and the High Devil Canyon/Vee plans are clearly superior to
all other dam combinations. In addition, it was decided to study
Tunnel Scheme 3 further as an alternative to the High Devil Canyon
Dam and a plan combining Watana and High Devil Canyon.
Associated with each of these plans are several options for staged
development. For this more detailed analysis of these basic
plans, a range of different approaches to staging the developments
was considered. In order to keep the total options to a reason-
able number and also to maintain reasonably large staging steps
consistent with the total development size, staging of only the
two larger developments (i.e., Watana and High Devil Canyon) was
considered. The basic staging concepts adopted for these develop-
ments involved staging both dam and powerhouse construction or,
alternatively, just staging powerhouse construction. Powerhouse
stages were considered in 400-MW increments ..
Four basic plans and associated subplans are briefly described
below. Plan 1 involves the Watana/Devil Canyon sites, Plan 2 the
High Devil Canyon/Vee sites, Plan 3 the Watana-tunnel concept, and
Plan 4 the Watana/High Devil Canyon sites. Under each plan sever-
al alternative subp1ans were identified, each involving a differ-
ent staging concept. Summaries of these plans are given in Table
B.9.
B-1-14
-
-
-
("i) P 1 an 1
-Subplan 1.1: The first stage involves constructing
Watana Dam to its full height and installing 800 MW.
Stage 2 involves constructing Devil Canyon Dam and
installing 600 MW.
-Subplan 1.2: For this subplan, construction of the
Watana Dam is staged from a crest elevation of 2060 to
2225. The powerhouse is also staged from 400 MW to 800
MW. As for Subplan 1.1, the final stage involves Devil
Canyon with an installed capacity of 600 MW.
-Subplan 1.3: This subplan is similar to subplan 1.2
except that only the powerhouse and not the dam at Watana
is staged.
(ii) Plan 2
-Subplan 2.1: This subplan involves constructing the High
Devil Canyon Dam first with an installed capacity of 800
MW. The second stage involves constructing the Vee Dam
with an installed capacity of 400 MW.
-Subplan 2.2: For this subplan, the construction of High
Devil Canyon is staged from a crest elevation of 1630 to
1775. The installed capacity is also staged from 400 to
800 MW. As for subplan 2.1, Vee follows with 400 MW of
installed capacity.
-Subplan 2.3: This subplan is similar to subplan 2.2
except that only the powerhouse and not the dam at High
Devil Canyon is staged.
{iii) Plan 3
-Subplan 3.1: This subplan involves initial construction
of Watana and installation of 800-MW capacity. The next
stage involves the construction of the downstream re-
regulation dam to a crest elevation of 1500 and a 15-mile
long tunnel. A total of 300 MW would be installed at the
end of the tunnel and a further 30 MW at the reregulation
dam. An additional 50 MW of capacity would be installed
at the Watana powerhouse to facilitate peaking opera-
tions.
-Subplan 3.2: This subplan is essentially the same as
subplan 3.1 except that construction of the initial 800-
MW powerhouse at Watana is staged.
B-1-15
( i v) Plan 4
This single plan was developed to jointly evaluate the
development of the two most economic damsites, Watana and
High Devil Canyon. Stage 1 involves constructing Watana to
its full height with an installed capacity of 400 MW. Stage
2 involves increasing the capacity at Watana to 800 MW.
Stage 3 i nvo 1 ves constructing High Devil Canyon to a crest
elevation of 1470 so that the reservoir extends to just
downstream of Watana. In order to develop the full head
between Watana and Portage Creek, an additional smaller dam
is added downstream of High Devil Canyon. This dam would
be located just upstream from Portage Creek so as not to
interfere with the anadromous fisheries, and would have a
crest elevation of 1030 and an installed capacity of 150
MW. For purposes of these studies, this site is referred
to as the Portage Creek site.
1.5 -Evaluation of Basin Development Plans
The overall objective of this step in the evaluation process was to
select the preferred basin development plan. A preliminary evaluation
of plans was initially undertaken to determine broad comparisons of the
available alternatives. This was followed by appropriate adjustments
to the plans and a more detailed evaluation and comparison.
In the process of initially evaluating the final four schemes, it
became apparent that there would be environmental problems associated
with allowing daily peaking operations from the most downstream reser-
voir in each of the plans described above. In order to avoid these
potential problems while still maintaining operational flexibility to
peak on a daily basis, re-regulation facilities were incorporated in
the four basic plans. These facilities incorporate both structural
measures such as re-regulation dams and modified operational pro-
cedures. Details of these modified plans, referred to as E1 to E4, are
listed in Table 8.10.
The plans listed in Table 8.10 were subjected to a more detailed analy-
sis as described in the following section.
(a) Evaluation Methodology
The approach to evaluating the various basin development plans
described above is twofold:
-For determining the optimum staging concept associated with each
basic plan (i.e., the optimum subplan), only economic criteria
are used and the least-cost staging concept is adopted.
B-1-16
-
-
-
-
-
-For assessing which plan is the most appropriate, a more de-
tailed evaluation process incorporating economic, environmental,
social and energy contribution aspects is taken into account.
Economic evaluation of any Susitna basin development plan requires
that the impact of the plan on the cost of energy to the Railbelt
area consumer be assessed on a systemwide basis. Si nee the con-
sumer is supplied by a large number of different generating sour-
ces, it is necessary to determine the total Railbelt system cost
in each case to compare the various Susitna basin development
options.
The primary tool used for system costs was the mathematical model
developed by the Electricity Utility Systems Engineering Depart-
ment of General Electric Company. The model is commonly known as
OGP5 or Optimized Generation Planning Model, Version 5. The fol-
lowing information is paraphrased from GE literature on the pro-
gram (General Electric 1979).
The OGP5 program was developed over ten years to combine the three
main elements of generation expansion plann·ing (system reliabil-
ity, operating and investment costs) and automate generation addi-
tion decision analysis. OGP5 will automatically develop optimum
generation expansion patterns in terms of economics, reliability
and operation. Many utilities use OGPS to study load management,
unit size, capital and fuel costs, energy storage, forced outage
rates, and forecast uncertainty.
The OGPS program requires an extensive system of specific data to
perform its planning function. In developing an optimal plan, the
program considers the existing and committed units (planned and
under construction) avail able to the system and the characteris-
tics of these units including age, heat rate, size and outage
rates as the base generation plan. The program then considers the
given load forecast and operation criteria to determine the need
for additional system capacity based on given reliability cri-
teria. This determines 11 how much 11 capacity to add and 11 When 11 it
should be installed. If a need exists during any monthly itera-
tion, the program will consider additions from a list of alterna-
tives and select the available unit best fitting the system needs.
Unit selection is made by computing production costs for the sys-
tem for each alternative included and comparing the results.
The unit resulting in the lowest system production cost is select-
ed and added to the system. Finally, an investment cost analysis
of the capital costs is completed to answer the question of 11 What
kind 11 of generation to add to the system.
The model is then further used to compare alternative plans for
meeting variable electrical demands, based on system reliability
and production costs for the study period.
B-1-17
A minor limitation inherent ·in the use of the OGP5 model is that
the number of years of simulation is limited to 20. To overcome
this, the study period of 1980 to 2040 has been broken into three
separate segments for study purposes. These segments are common
to all system generation plans.
The first segment has been assumed to be from 1980 to 1990. The
model of this time period included all committed generation units
and is assumed to be common to all generation scenarios.
The end point of this model becomes the beginning of each 1990-
2010 model.
The model of the first two time periods considered (1980 to 1990,
and 1990 to 2010) provides the total production costs on a year-
to-year basis. These total costs include, for the period of mod-
elin.g, all costs of fuel and operation and maintenance of all gen-
erating units included as part of the system. In addition, the
completed production costs include the annualized investment costs
of any production plans added during the period of study. A num-
ber of factors which contribute to the ultimate cost of power to
the consumer are not included in this model. These are common to
all scenarios and include:
All investment costs to plants in service prior to 1981;
-Costs of transmission systems in service both at the transmis-
sion and distribution level; and
-Administrative costs of utilities for providing electric service
to the public.
Thus, it should be recognized that the production costs modeled
represent only a portion of ultimate consumer costs and in effect
are only a portion, albeit major, of total costs.
The third period, 2010 to 2040, was modeled by assuming that pro-
duction costs of 2010 would recur for the additional 30 years to
2040. This assumption is believed to be reasonable given the lim-
itations on forecasting energy and load requirements for this per-
iod. The additional period to 2040 is required to at least take
into account the benefit derived or value of the addition of a
hydroelectric power plant which has a useful life of 50 years or
more.
The selection of the preferred generation plan is based on numer-
ous factors. One of these is the cost of the generation plan. To
provide a consistent means of assessing the production cost of a
given generation scenario, each production cost total has been
converted to a 1980 present worth basis. The present worth cost
B-1-18
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of any generation scenario is made up of three cost amounts. The
first is present worth cost (PWC) of the first ten years of study
(1981 to 1990), the second is the PWC of the scenario assumed dur-
ing 199Q to 2010, and the third is the PWC of the scenario in 2010
assumed to recur for the period 2010 to 2040. In this way the
long-term (60 years) PWC of each generation scenario in 1980
dollars can be compared.
A summary of the input data to the model and a discussion of the
results follow.
(i) Initial Economic Analyses
Table B.11 lists the results of the first series of economic
analyses undertaken for the basic Susitna~ basin development
plans listed in Table B.10. The information provided in-
cludes the specified on-line dates for the various stages of
the plans, the OGPS run index numb~r, the total installed
capacity at year 2010 by category,\ and the total system
present worth cost in 1980 for the period 1980 to 2040.
Matching of the Susitna development to the load growth for
Plans E1, E2, and E3 is shown in Figures 8.16, 8.17 and
B.18, respectively. After 2010, steady state conditions are
assumed and the then-existing generation mix and annual
costs for 2010 are applied to the years 2011 to 2040. This
extended period of time is necessary to ensure that the
hydroelectric options being studied, many of which only come
on line around 2000, are simulated as operating for periods
approaching their economic lives and that their full impact
on the cost of the generation·system is taken into account.
-Plan E1 -Watana/Devil Canyon
Staging the dam at Watana (Plan E1.2) is not as economic
as constructing it to its full height (Plan E1.1 and
E1.3). The present worth advantage of not staging the
dam amounts to $180 million in 1980 dollars.
The results indicate that, with the level of analysis
performed, there is no discernible benefit in staging
construction of the Watana powerhouse (Plan E1.1 and
E1.3). However, Plan E1.4 results indicate that, should
the powerhouse size at Watana be restricted to 400 MW,
the overall system present worth costs would increase.
Additional runs performed for variations of Plan E1.3
indicate that system present worth would increase by
$1,110 million if the Devil Canyon Dam were not con-
structed. A five-year delay in construction of the
Watana Dam would increase system present worth by $220
million.
B-1-19
-Plan E2 -High Devil Canyon/Vee
. The results for Plan E2.3 indicate that the system pres-
ent worth is $520 million more than Plan E1.3. Present
worth increases also occur if the Vee Dam stage is not
constructed. A reduction in present worth of approx i-
mately $160 million is possible if the Chakachamna
hydroelectric project is constructed instead of the Vee
Dam.
The results of Plan E2.1 indicate that total system
present worth waul d increase by $250 million if the
total capacity at High Devil Canyon were limited to 400
1'1W.
-Plan E3 -Watana-Tunnel
The results for Plan E3.1 illustrate that the tunnel
scheme versus the Devil Canyon Dam scheme ( El. 3) adds
approximately $680 million to the total system present
worth cost. The availability of reliable geotechnical
data would undoubtedly have improved the accuracy of the
cost estimates for the tunnel alternative. For this rea-
son, a sensitivity analysis ·was made as a check to deter-
mine the effect of halving the tunnel costs. This analy-
sis indicates that the tunnel scheme is still more costly
than constructing the Devil Canyon Dam.
-Plan E4 -Watana/High Devil Canyon/Portage Creek
The results indicate that system present worth associated
with Plan E4.1, excluding the Portage Creek site develop-
ment, is $200 million more than the equivalent E1.3 plan.
If the Portage Creek development is included, the present
worth difference would be even g~eater.
(ii) Load Forecast Sensitivity Analyses
The plans with the lowest present worth cost were subjected
to further sensitivity analysis. The objective of the anal-
ysis was to determine the impact on the development decision
of a variance in forecast. The load forecasts used for this
analysis were made by ISER and are presented in Section 5.1
of this Exhibit. These results are summarized in Table
8.12.
At the low load forecast, full capacity development of
Watana/Oevi 1 Canyon Scheme 1. 3 is not warranted. Under
Scheme 1.4, the most economic development includes a 400-MW
development at each site, as compared to Watana only.
B-1-20
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Similarly, it is more economic to develop High Devil Canyon
and Vee, as compared to High Devil Canyon only, but at a
total capacity of only 800 MW.
At this level of projected demand, the Watana/Devil Canyon
plan is more economic than the High Devil Canyon/Vee plan or
any singular development ($210 million, present worth ba-
sis). As individual developments, however, the High Devil
Canyon only plan is slightly superior economically to the
Watana project ($90 million, present worth basis).
At the high load forecast, the larger capacities are clearly
needed. In addition, both the High Devil Canyon/Vee and
Watana/Devil Canyon plans are improved economically by the
addition of the Chackacharnna project. This illustrates the
superiority of the Chackachamna project to the addition of
alternative coal and gas projects using the study price pro-
jections. Similar to the low load forecast, the Watana/
Devi 1 Canyon project is superior to the High Devi 1 Canyon/
Vee alternative but the margin of difference on a present
worth basis is much greater ($1.0 billion, present worth
basis).
(b) Evaluation Criteria
,..... The following criteria were used to evaluate the short-listed
basin development plans. These criteria generally contain the
requirements of the. generic process with the exception that an
additional criterion, energy contribution, is added in order to
ensure that full consideration is given to the total basin energy
potential developed by the various plans.
(i)
( i i ) -
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Economic
Plans were compared using 1 ong-term present worth costs,
calculated using the OGPS generation planning model. The
parameters used in calculating the total present worth cost
of the total Railbelt generating system for the period 1980
to 2040 are listed in Tables B.l3 and B.14. Load forecasts
used in the analysis are prese~ted in Section 5.1(b).
Environmental
A qualitative assessment of the environmental impact on the
ecological, cultural, and aesthetic resources is undertaken
for each plan. Emphasis is placed on identifying major
concerns so that these can be combined with the other eval-
uation attributes in an overall assessment of the plan.
B-1-21
I
( i i i ) Soc i a 1
This attribute includes determination of the potential non-
renewable resource displacement, the impact on the state
and local economy, and the risks and consequences of major
structural failures due to seismic events. Impacts on the
economy refer to the effects of an investment plan on econ-
omic variables.
(iv) Energy Contribution
The parameter used is the total amount of energy produced
from the specific development plan. An assessment of the
energy development foregone is also undertaken. The energy
loss that is inherent to the plan and cannot easily be re-
covered by subsequent staged deve 1 opments is of greatest
concern.
(c) Results of Evaluation Process
The various attributes outlined above have been determined for
each plan and are summarized in Tables B.l5 through B.23. Some of
the attributes are quantitative while others are qualitative.
Overall evaluation is based on a comparison of similar types of
attributes for each p 1 an. In cases where the attributes associ-
ated with one plan all indicate equality or superiority with res-
pect to another plan, the decision as to the best plan is clear
cut. In other cases where some attributes indicate superiority
and others inferiority, differences are highlighted and trade-off
decisions are made to determine the preferred development plan.
In cases where these trade-offs have had to be made, they were
relatively straightforward, and the decision-making process can
therefore be regarded as effective and consistent. In addition,
these trade-offs are clearly identified so that independent
assessment can be made.
The overall evaluation process is conducted in a series of steps.
At each step, only two plans are compared. The superior plan is
then taken to the next step for evaluation against a third plan.
(i) Devil Canyon Dam Versus Tunnel
The first step in the process involves the comparison of the
Watana/Devi 1 Canyon Dam p 1 an ( El. 3) and the Watana-tunne 1
plan (E3.1). Since Watana is common to both plans, the
evaluation is based on a comparison of the Devil Canyon Dam
and the Scheme 3 tunnel alternative.
B-1-22
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In order to assist in the evaluation in terms of economic
criteria, additional information obtained by analyzing the
results of the OGP5 computer runs is shown in Table B.l5.
This information illustrates the breakdown of the total sys-
tem present worth cost in terms of capital investment, fuel,
and operation and maintenance costs.
-Economic Comparison
From an economic point of view, the Watana/Devil Canyon
Dam scheme is superior. As summarized in Tables B.l5 and
B.l6, on a present worth basis the tunnel scheme is $680
million more expensive than the dam scheme. For a low
demand growth rate, this cost difference would be reduced
slightly to $650 million. Even if the tunnel scheme costs
are halved, the total cost difference would stil'l amount
to $380 million. As highlighted in Table B.l6, considera-
tion of the sensitivity of the basic economic evaluation
to potential changes in capital cost estimates, the period
of economic analysis, the discount rate, fuel costs, fuel
cost escalation, and economic plant life do not change the
basic economic superiority of the dam scheme over the tun-
nel scheme.
-Environmental Comparison
The environmental comparison of the two schemes is sum-
marized in Table B.17. Overall, the tunnel scheme is
judged to be superior because:
. It offers the potential for enhancing anadromous fish
populations downstream of the re-regulation dam due to
the more uniform flow distribution that will be achieved
in this reach;
It would inundate 13 miles less of resident fisheries
habitat in the river and major tributaries;
. It has a lower potential for inundating archaeological
sites due to the smaller reservoir involved; and
. It would preserve much of the characteristics of the
Devil Canyon gorge which is considered to be an aesthe-
tic and recreational resource.
-Social Comparison
Table B.l8 summarizes the evaluation of the two schemes in
terms of the social criteria. In terms of impact on state
and local economics and risks because of seismic exposure,
B-1-23
the two schemes are rated equal. However, due to its
higher energy yield, the dam scheme has more potential for
displacing nonrenewable energy resources and therefore has
a slight overall advantage in terms of the social evalua-
tlon criteria.
-Energy Comparison
Table 8.19 summarizes the evaluation in terms of the en-
ergy contribution criteria. The results show that the dam
scheme has a greater potential for energy production and
develops a larger portion of the basin•s potential. The
dam scheme is therefore judged to be superior from the en-
ergy contribution standpoint.
-Overall Comparison
The overall evaluation of the two schemes is summarized in
Table 8.20. The estimated cost saving of $680 million in
favor of the dam scheme plus the additional energy pro-
duced are considered to outweigh the reduction in the
overall environmental impact of the tunnel scheme. The
dam scheme is therefore judged to be superior overall.
(ii) Watana/Devil Canyon Versus High Devil Canyon/Vee
The second step in the development selection process in-
volves an evaluation of the Watana/Devil Canyon {E1.3) and
the High Devil Canyon/Vee {E2.3) development plans.
-Economic Comparison
In terms of the economic criteria (see Table 8.15 and
8.16) the Watana/Devil Canyon plan is less costly by $520
million. Consideration of the sensitivity of this deci-
sion to potential changes in the various parameters con-
sidered (i.e., load forecast, discounted rates, etc.) does
not change the basic superiority of the Watana/Devil
Canyon plan.
Under the low load-growth forecast, the Watana/Devil
Canyon plan is favored by only $210 million, while under
the high load-growth forecast the advantage is $1,040 mil-
lion.
-Environmental Comparison
The evaluation in terms of the environmental criteria is
summarized in Table 8.21. In assessing these plans, a
reach-by-reach comparison was made for the section of the
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Sus itna River between Portage Creek and the Tyone River.
The Watana/Devil Canyon scheme would create more potential
environmental impacts in the Watana ~creek area. However,
it is judged that the potential environmental impacts
which would occur above the Vee Canyon Dam with a High
Dev i 1 Canyon/Vee deve 1 opment are more severe in over a 11
comparison.
Of the seven environmental factors considered in Table
8.21, except for the increased loss of river valley, bird
and black bear habitat, the Watana/Devil Canyon develop-
ment plan is judged to be more environmentally acceptable
than the High Canyon/Vee plan.
The other six areas in which Wafana/Devil Canyon was
judged to be superior are fisheries, moose, caribou, fur-
bearers, cultural resources, aesthetics, and land use.
-Energy Comparison
The evaluation of the two plans in terms of energy contri-
bution criteria is summarized in Table 8.22. The Watana/
Devil Canyon scheme is assessed to be superior because of
its higher energy potential and the fact that it develops
a higher proportion of the basin 1 s energy potential.
The Watana/Devil Canyon plan annually develops 1160 GWh
and 1650 GWh more average and firm energy, respectively,
than the High Devil Canyon/Vee plans.
-Social Comparison
Table 8.18 summarizes the evaluation in terms of the so-
cial criteria. As in the case of the dam versus tunnel
comparison, the Watana/Devil Canyon plan is judged to have
a slight advantage over the High Devil Canyon/Vee plan.
This is because of its greater potential for displacing
nonrenewable resources. In other social impact areas
there are minimal differences between plans.
-Overall Comparison
The overall evaluation of the two schemes is summarized in
·Table 8.23. The $520 million estimated cost saving cou-
pled with the lower environmental impacts and a marginal
social advantage make the Watana/Devil Canyon plan super-
ior to High Devil Canyon/Vee.
B-1-25
1.6 -Preferred Susitna Basin Development Plan
One-on-one comparisons of the Watana/Devil Canyon plan with the Watana-
tunnel plan and the High Devil Canyon/Vee plan are judged to favor the
Watana/Oevil Canyon plan in each case.
The Watana/Oevil Canyon plan was therefore selected as the preferred
Susitna basin development plan, and the basis for continuation of more
detailed design optimization and environmental studies.
B-1-26
2 -ALTERNATIVE FACILITY DESIGN, PROCESSES
AND OPERATIONS
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2 -ALTERNATIVE FACILITY DESIGN, PROCESSES AND OPERATIONS
2.1 -Susitna Hydroelectric Development
As originally conceived, the Watana project initially comprised an
earthfill dam with a crest elevation of 2225 and 400 MW of generating
C'apacity scheduled to commence operation in 1993. An additional 400 MW
would be brought on line in 1996. At Devil Canyon, an additional 400
MW would be installed to commence operation in the year 2000. Detailed
studies of each project have led to refinement and optimization of
designs ·in terms of a number of key factors, including updated load
forecasts and economics. Geotechnical and environmental constraints
identified as a result of continuing field work have also greatly
influenced the currently recommended design concepts.
Plan formulation and alternative facility designs considered for the
Watana and Devil Canyon developments are discussed in this section.
Background information on the site characteristics as well as addition-
al detail on the plan formulation process are included in the Support-
ing Design Report of Exhibit F and the referenced reports.
2.2 -Watana Project Formulation
This section describes the evolution of the general arrangement of the
Watana project which, together with the Devil Canyon project, comprises
the development plan proposed. The process by which reservoir operat-
ing levels and the installed generating capacity of the power facil-
ities were established is presented, together with the means of hand-
ling floods expected during construction and subsequent project opera-
tion.
The main components of the Watana development are as follows:
-Main dam
-Diversion facilities
-Spillway facilities
Outlet facilities
-Emergency release facilities
-Power facilities.
A number of alternatives are available for each of these components and
they can be combined in a number of ways. The fo 11 owing paragraphs
describe the various components and methodology for the preliminary,
intermediate, and final screening and review of alternative general
arrangement of the components, together with a brief description of the
selected scheme. This section presents the alternative arrangements
studied for the Watana project.
B-2-1
(a) Selection of Reservoir Level
The selected elevation of the Watana Dam crest is based on consid-
erations of the value of the hydroelectric energy produced from
the associated reservoir, geotechnical constraints on reservoir
levels, and freeboard requirements. Firm energy, average annual
energy, construction costs, and operation and maintenance costs
were determined for the Watana development with dam crest eleva-
tions of 2240, 2190, and 2140. The relative value of energy pro-
duced in terms of the present worth of the long-term production
costs (L TPWC) for each of these three dam elevations was deter-
mined by means of the OGP5 generation planning model described in
Section 1 of this Exhibit. The physical constraints imposed on
dam height and reservoir elevation by geotechnical considerations
were reviewed and incorporated into the crest elevation selection
process. Finally, freeboard requirements for the Probable Maximum
Flood (PI~F) and settlement of the dam after construction or as a
result of seismic activity were taken into account.
(i) Methodology
Firm and average annual energy produced by the Susitna
development is based on 32 years of hydrological records.
The energy produced was determined by using a multi-reser-
voir simulation of the operation of the Watana and Devil
Canyon reservoirs. A variety of reservoir drawdowns was
examined, and drawdowns producing the maximum firm energy
consistent with engineering feasibility and cost of the
intake structure were selected. Minimum flow requirements
were established at both project sites based on downstream
fisheries considerations.
To meet system demand, the required maximum generating
capability at Watana in the period between 1994 and 2010
ranges from 665 MW to 908 MW. For the reservoir level
determinations, energy estimates were made on the basis of
assumed average annual capacity requirements of 680 MW at
Watana in 1994, increasing to 1020 MW at Watana in 2007,
with an additional 600 MW at Devil Canyon coming on line 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 sched-
ules. Further refinement of these layouts has taken place
during the optimization process. These refinements have no
significant impact on the reservoir level selection.
B-2-2
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(ii) Economic Optimization
( i i i)
Economic optimization of the Watana reservoir level was
bas.ed on an evaluation of three dam crest elevations of
2240, 2190, and 2140. These crest elevations applied to
the central portion of the embankment with appropriate
allowances for freeboard and seismic settlement, and cor-
respond 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 B.24, together with corres-
ponding project construction costs.
In the determination of LTPWC, the Susitna capital costs
were adjusted 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 month-
ly basis by the reservoir operation model to match as
closely as possible the projected monthly energy demand of
the Rail belt and then input to the OGP5 mode 1. The L TPWC
of meeting the Railbelt energy demand using the Susitna
development as the primary source of energy was then deter-
mined for each of the three reservoir levels.
The results of these evaluations are shown in Table B.25,
and a plot showing the variation of the LTPWC with dam
crest elevation is shown in Figure B.19. This figure indi-
cates that, on the basis of the assumptions used, the mini-
mum LTPWC occurs at a Watana crest elevation ranging from
approximately 2160 to 2200 (reservoir levels 2140 to 2180
feet). A higher dam crest will still result in a develop-
ment 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 cost of
additional energy produced at Watana is somewhat greater
than for the displaced thermal energy source. Hence, the
LTPWC of the overall system would increase. Conversely, as
the height of the dam is lowered, and thus Watana produces
1 ess energy, the unit cost of the energy produced by a
thermal generation source to replace the lost Susitna en-
ergy is more expensive than Susitna energy. In this case
also, the LTPWC increases.
Geotechnical Considerations
On the north side of the reservoir created by the Watana
Dam, a relict channel reaching 400 feet deep connects the
reservoir to Tsusena Creek. The potential problems caused
by the relict channel are:
B-2-3
breaching of the reservoir rim resulting in catastrophic
drawdown of the reservoir; and
-subsurface seepage resulting in potential downstream
piping and/or loss of energy.
Breaching of the reservoir rim could be caused by satura-
tion of the unconsolidated sediments within the channel
resulting in surface settlement or by liquefaction during
an earthquake.
Excessive subsurface seepage could be caused by a highly
permeable unit(s) within the channel that could provide a
continuous flow path between the reservoir and Tsusena
Creek.
Details of the geology and potential impacts of the relict
channel are addressed in Acres 1982a and l982e reports.
As a result of these potential problems, extensive con-
sideration was given to defining the reservoir level with
respect to the relict channel.
Raising the water surface up to and beyond Elevation 2200
would require the construction of a costly retaining dike
in a low area of the rel icit channel. Due to the uncer-
tainty of foundation conditions in this area (to include
material properties, groundwater, and permafrost) it was
determined that the normal reservoir level of 2185 would
provide the best energy development without incurring ex-
cessive costs in construction of additional water retaining
structures in the relict channel. This reservoir level
would require the construction of a small freeboard dike in
this area. The following conditions would exist for a
reservoir level of 2185:
-For flood magnitudes up to the 1:10,000-year event, there
would be no danger of overtopping the lowest point in the
relict channel.
-For the PMF, a 10-foot freeboard dike in the low area
would provide adequate protection. This dike would be
wetted only a few days during the PMF event.
If seismic settlement or settlement due to permafrost
melting did occur, the combination of the 10-foot free-
board dike constructed on a suitable foundation plus
normal reservoir level of 2185 feet would ensure that
breaching of the relict channel would not occur.
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(iv)
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Lowering the reservoir to Elevation 2185 does not, however,
lessen the possibility of subsurface seepage that could
result in loss of energy and/or downstream piping. Prelim-
inary analyses performed during the study (Acres 1982e)
showed that an average permeability of 10-2 em/sec
would be required in the relict channel to significantly
affect project power economics. No such continuous hori-
zons of low permeable materials have been found in the
relict channel to date. However, if future geotechnical
explorations find such a permeable unit(s), conventional
remedial work to include grouting and cutoffs can be imple-
mented to contain leakage. To facilitate the potential for
piping, a contingency of more than $100,000,000 has been
provided in the cost estimate for the construction of a
downstream filter blanket.
In summary, no further consideration was given to lowering
the reservoir below the inlet to the relict channel be-
cause:
This would require lowering the reservoir by more than
300 feet which would severely impact the energy provided
by the basin development plans.
-Costs for remedial work in the relict channel were con-
sidered small with respect to the economics of the proj-
ect.
Conclusions
It is important to establish clearly the overall objective
used as a basis for setting the Watana reservoir level. An
objective which would minimize the LTPW energy cost would
lead to selection of a slightly lower reservoir level than
an objective which waul d maximize the amount of energy
which could be obtained from the available resource, while
doing so with a technically sound project.
The three values of LTPWC developed by the OGP5 computer
runs defined a relationsh·ip between LTPWC and Watana Dam
height which is relatively insensitive to dam height. This
is highlighted by the curve of LTPWC versus dam height in
Figure 8.19. This figure shows that there is only a slight
variation in the LTPWC for the range of dam heights in-
cluded in the analysis. Thus, from an economic standpoint,
the opti-mum crest elevation could be considered as vary-
ing over a range of elevations from 2140 to 2220 with
little effect on project economics. The main factors in
B-2-5
establishing the upper limit of dam height were
consequently the geotechnical considerations discussed in
(iii) above.
The normal maximum operating level of the reservoir was
therefore set at Elevation 2185, allowing the objective of
maximizing the economic use of the Susitna resource still
to be satisfied.
(b) Selection of Installed Cap~city
The generating capacity to be installed at both Watana and Devil
Canyon was determined on the basis of generation planning studies
together with appropriate consideration of the following (Acres
1982c, Vol. 1):
-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 com-
mitted plant;
-Capital cost and annual operating costs for Watana and Devil
Can yon;
-Capital cost and annual operating costs for alternative sources
of energy and capacity;
-Environmental constraints on reservoir operation; and
-Turbine and generator operating characteristics.
Table B.26 lists the design parameters used in establishing the
dependable capacity at Watana.
( i ) Ins t a 11 ed Capacity
A computer simulation of reservoir operation over 32 years
of hydrological record was used to predict firm (depend-
able) and average energy available from Watana and Devil
Canyon reservoirs on a monthly basis. Seven alternative
reservoir operating rules were assumed, varying from a max-
imum power generation scenario which would result in signi-
ficant impact to downstream fisheries (Case A), through to
a scenario that provides guaranteed minimum summer releases
which minimize the impact on downstream fisheries (Case D).
For the preliminary design, Case C predicted energies have
been used to assess the required plant capacity.
The computer sirnul at ion gives an estimate of the monthly
energy available from each reservoir, but the sizing of the
plant capacity must take into account the variation of
demand load throughout each month on an hourly basis. Load
forecast studies have been undertaken to predict the hourly
variation of load through each month of the year and also
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( i i )
the growth in peak load (MW) and annual energy demand (GWh}
through the end of the planning horizon (2010).
The economic analysis for the proposed development assumes
that the average energy from each reservoir is available
every year. The hydrological record, however, is such that
this average energy is available only from a series of wet-
ter and drier years. In order to utilize the average ener-
gy, capacity must be available to generate the energy
available in the wet years up to the maximum requirement
dictated by the system energy demand, 1 ess any energy
available from other committed hydroplant.
Watana has been designed to operate as a peaking station,
if required. Tables B.27 and B.28 show the estimated maxi-
mum capacity required in the peak demand month (December)
at Watana to fully utilize the energy available from the
flows of record. If no thermal energy is needed (i.e., in
wetter years), the maximum requirement is controlled only
by the shape of the demand curve. If therma 1 energy is
required (in average to dry years), the maximum capacity
required at Watana will depend on whether the thermal ener-
gy is provided by high merit order plant at base load
(Option 1, Table 8.27), or by low merit order peaking plant
(Option 2, Table 8.28}.
On the basis of this evaluation, the ultimate power genera-
tion capability at Watana was selected as 1020 MW for de-
sign purposes to allow a margin for hydro spinning reserve
and standby for forced outage. This installation also pro-
vides a margin in the event that the load growth exceeds
the medium load forecast.
Unit Capacity
Selection of the unit size for a given total capacity is a
compromise between the initial least-cost solution, gener-
ally involving a scheme with a smaller number of large cap-
acity units, and the improved plant efficiency and security
of operation provided by a larger number of smaller capa-
city units. Other factors include the si'ze of each unit as
a proportion of the total system load and the minimum anti-
cipated load on the station. Any requirement for a minimum
downstream flow would also affect the selection. Growth of
the actual load demand is also a significant factor, since
the installation of units may be phased to match the actual
1 oad growth. The number of units and their individual
ratings were determined by the need to deliver the required
peak capacity in the peak demand month of December at the
8-2-7
Number
min irnum December reservoir 1 evel with the turbine wicket
gates fully open.
An examination was made of the economic impact on power
plant production costs of various combinations of a number
of units and rated capacity which would provide the sel-
ected total capacity of 1020 MW. For any given installed
capacity, plant efficiency increases as the number of units
increases. The assumed capitalized value used in this
evaluation was $1.00 per average annual kWh over project
life, based on the economic analysis completed for the
thermal generation system. Variations in the number of
units and capacity will affect the cost of the power in-
takes, penstocks, powerhouse, and tailrace. The differ-
ences in these capital costs were estimated and included in
the evaluation. The results of this analysis are presented
below.
Capitalized
Rated Value of
Capacity Additional Additional
of Unit Energy Capital Cost Net Benefit
of Units (MW) ($ Millions) ($Millions) ($Millions)
4
6
8
250
170 40 31 9
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 alternative. This scheme also offers a higher
degree of flexibility and security of operation compared to
the four-unit alternative, 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 advan-
tages 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 alternatives.
(c) Selection of the Spillway Design Flood
Normal design practice for projects of this magnitude, together
with applicable design regulations, require that the project be
capable of passing the PMF routed through the reservoir without
endange~ing the dam.
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In addition to this requirement, the project should have suffi-
cient spillway capacity to safely pass a major flood of lesser
magnitude than the PMF without damaging the main dam or ancillary
structures. The frequency of occurrence of this flood, known as
the spi·llway design flood or Standard Project Flood (SPF), is gen-
erally selected on the basis of an evaluation of the risks to the
project if the spillway design flood is exceeded, compared to the
costs of the structures required to safely discharge the flood.
For this study, a spillway design 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 Design Flood Basin Capacity
Peak PMF After Routing
Project Frequency Inflow (cfs) (cfs) (cfs)*
Mica, Canada PMF 250,000 250,000 150,000
Churchill Falls,
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,ooo,.ooo 1,000,000
Itaipu, Brazil 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.
The flood frequency analysis produced the following values:
Flood
Probable Maximum
Spi 11 way Design
Frequency
1:10,000 years
Inflow Peak
326,000 cfs
156,000 cfs
Additional capacity required to pass the PMF will be provided by
an emergency spillway consisting of a fuse plug and rock channel
on the right bank.
B-2-9
(d) Main Dam Alternatives
This section describes the alternative types of dams considered at
the Watana site and the basis for the selected alternative.
(i) 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 over-
burden, and the relative availability of construction
materials. Previous studies by the COE envisaged an
embankment dam at Watana. Initial studies completed as
part of this current evaluation included comparison of an
earthfill dam with a concrete arch dam at the Watana sit e.
An arrangement for a concrete arch dam alternative at
Watana is presented in Figure 8.20. The results of this
analysis indicated that the cost of the embankment dam was
somewhat lower than the arch dam, even though the concrete
cost rates used were significantly lower than those used
for the Devil Canyon Dam. This preliminary evaluation did
not indicate any overall cost savings in the project in
spite of some savings in the earthworks and concrete struc-
tures for the concrete dam layout. A review of the overall
construction schedule indicated a minimal savings in time
for the concrete dam project.
Based on the 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 eliminated from further
consideration.
(ii) Concrete Face Rockfill Type Dam
The selection of a concrete face rockfill dam at Watana
would appear to offer economic and schedule advantages when
compared to a conventional impervious-core rockfi 11 dam.
For example, one of the primary areas of concern with the
earth-core rockfill dam is the control of water content for
the core material and the available construction period
during each summer. The core material will have to be
protected against frost penetration at the end of each
season and the area c 1 eared and prepared to receive new
material after each winter. On the other hand, rockfill
materials can be worked almost year-round and the quarrying
and placing/compacting operations are not affected by rain
and only marginally by winter weather.
The concrete face rockfill dam would also require less
foundation preparation, since the critical foundation
contact area is much less than that for the impervious-
core/rock foundation contact. The side slopes for faced
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rockfill could probably be on the order of 1.5H:1V or
steeper as compared to the 2.5 and 2.0H:1V for the earth-
core rockfill. This would allow greater flexibility for
layout of the other facilities, in particular the upstream
and downstream portals of the diversion tunnels and the
tailrace tunnel portals. The diversion tunnels could be
shorter, givin~ further savings in cost and schedule.
However, the height of the Watana Dam as currently proposed
is 885 feet, some 70 percent higher than the highest con-
crete face rockfi 11 dam built to date (the 525-foot high
Areia Dam in Brazil completed in 1980). A review of con-
crete face rockfill dams indicates that increases in height
have been typically in the range of 20 percent; for exam-
ple, Paradela-370 feet completed in 1955; Alto Anchicaya
-460 feet completed in 1974; Areia-525 feet completed in
1980. A 1 though recent compacted . rockfill dams have gener-
ally performed well and a rockfill dam is inherently stable
even with severe leakage through the face, a one-step in-
crease in height of 70 percent over existing structures .is
well beyond precedent.
In addition to the height of the dam, other factors which
are beyond precedent include the seismic and climatic con-
ditions at Susitna. It has been stated that concrete face
rockfill dams are well able to resist earthquake forces and
it is admitted that they are very stable structures in
themselves. However, movement of rock leading to failure
of the face s 1 ab near the base of the dam caul d result in
excessive leakage through the dam. To correct such an·
occurrence would require lowering the water level in the
reservoir which would take many years and involve severe
economic penalties from loss of generating capacity.
No concrete face rockfill dam has yet been built in an
arctic environment. The drawdown at Watana is in excess of
100 feet and the upper section of the face s 1 ab will be
subjected to severe freeze/thaw cycles.
Although the faced rockfill dam appears to offer schedule
advantages, the overall gain in impoundment schedule would
not be so significant. With the earth-core rockfi 11 dam,
impoundment can be allowed as the dam is constructed. This
is not the case for a concrete face rockfi 11 s i nee the
concrete face slab is normally not constructed until all
rockfill has been placed and construction settlement taken
place. The slab is then poured in continuous strips from
the foundation to the crest. Most recent high faced rock-
fill dams also incorporate an impervious earth fill cover
B-2-11
over the lower section to m1n1m1Ze the risk of excessive
leakage through zones which, because of their depth below
normal water level, are difficult to repair. Such a zone
at Watana might cover the lower 200 to 300 feet of the slab
and require considerable volumes of impervious fill, none
of which could be placed until all other construction work
had been completed. This work would be on the critical
path with respect to impoundment and, at the same time, be
subject to interference by wet weather.
The two types of dam were not casted in detail because cost
was not considered to be a controlling factor. It is of
interest to note, however, that similar alternatives were
estimated for the LG 2 project in northern Quebec and the
concrete face alternative was estimated to be about 5 per-
cent cheaper. However, the managers, on the recommendation
of their consultants, decided against the use of a concrete
face rockfill dam for the required height of 500 feet in
that environment.
In summary, a concrete face rockfill dam at Watana is not
considered appropriate as a firm recommendation for the
feasibility stage of development of the Susitna project
because of:
the 70 percent increase in height over precedent; and
the possible impacts of high seismicity and climatic
conditions.
(iii) Selection of Dam Type
Selection of the configuration of the embankment dam cross
section was undertaken within the context of the· following
basic considerations:
-The availab·ility of suitable construction materials with-
in economic haul distance, particularly core material;
-The requirement that the dam be capable of withstanding
the effects of a significant earthquake shock as well as
the static loads imposed by the reservoir and its own
weight;
-The relatively limited construction season available for
placement of compacted fill materials.
The main dam would consist of a compacted core protected by
fine and coarse filter zones on both the upstream and down-
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stream slopes of the core. The upstream and downstream
outer supporting fill zones would 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 design of the
embankment. Two basic alternatives exist in this regard:
- A vertical core located centrally within the dam; and
-An inclined core with both faces sloping upstream.
A central vertical core was chosen for the embankment based
on a review of precedent design and the nature of the
available impervious material.
The exploration program undertaken during 1980-81 indicated
that adequate quantities of materials suitable for dam con-
struction were located within reasonable haul distance from
the site. The well-graded silty sand material is consid-
ered 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 content will be critical in achieving a dense
core with high shear strength.
Potential sources for the upstream and downstream shells
include either river gravel from borrow areas along the
Susitna River or compacted rockfill from quarries or exca-
vations for spillways.
During the intermediate review process, the upstream slope
of the dam was flattened from 2.5H:1V used during the ini-
tial review to 2.75H:1V. This slope was based on a con-
servative estimate of the effective shear strength para-
meters of the available construction materials, as well as
a conservative allowance in the design for the effects of
earthquake loadings on the dam.
During the final review stage, the exterior upstream slope
of the dam was steepened from 2.75H:1V to l.4H:1V, reflect-
ing the results of the preliminary static and dynamic
design analyses being undertaken at the same time as the
general arrangement studies. As part of the final review,
the volume of the dam with an upstream slope of 2.4H:lV was
computed for four alternative dam axes. The locations of
these alternative axes are shown on Figure B. 21. The dam
volume associated with each of the four alternative axes is
listed below:
B-2-13
Alternative
Axis Number
1
2
3
4
Tot a l V o l urn 3
(mill ion yd )
69.2
71.7
69.3
71.9
A section with a 2.4H:lV upstream slope and a 2H:1V down-
stream slope located on alternative axis number 3 was used
for the final review of alternative schemes.
(e) Diversion Scheme Alternatives
The topography of the site generally dicta\es that diversion of
the river during construction be accomplished using diversion tun-
nels with upstream and downstream cofferdams protecting the main
construction area.
The configuration of the river in the vicinity of the site favors
location of the diversion tunnels on the north bank, since the
tunnel length for a tunnel on the south bank would be approximate-
ly 2000 feet greater. In addition, rock conditions on the north
bank are more favorable for tunneling and excavation of intake and
outlet portals.
(i) Design Flood for Diversion
The recurrence interval of the design flood for diversion
is generally established based on the characteristics of
the flow regime of the river, the length of the construc-
tion period for which diversion is required and the prob-
able consequences of overtopping of the cofferdams. Design
criteria and experience from other projects similar in
scope and nature have been used in selecting the diversion
design flood.
At Watana, damage to the partially completed dam could be
significant or, more importantly, would probably result in
at least a one-year delay in the completion schedule. A
preliminary evaluation of the construction schedule indi-
cates that the diversion scheme would be required for four
or five years until the dam is of sufficient height to per-
mit initial filling of the reservoir. A design flood with
a return frequency of 1:50 years was selected based on
experience and practice with other major hydroelectric
projects. This approximates a 90 percent probability that
the cofferdam will not be overtopped during the five-year
construction period. The diversion design flood together
with average flow characteristics of the river significant
to diversion are presented below:
B-2-14
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Average annual flow
Maximum average monthly flow
Minimum average monthly flow
Design flood inflow (1:50 years)
(ii) Cofferdams
7,990 cfs
42,800 cfs (June)
570 cfs (March)
87,000 cfs
For the purposes of establishing the overall general
arrangement of the project and for subsequent diversion
opt imi zat ion studies, the upstream cofferdam section adop-
ted comprises an initial closure dam structure approxi-
mately 30 feet high placed in the wet.
(iii) Diversion Tunnels
Concrete-lined tunnels and unlined rock tunnels were com-
pared. Preliminary hydraulic studies indicated that the
design flood routed through the diversion scheme would re-
sult in a design discharge of approximately 80,500 cfs.
For concrete-lined tunnels, design velocities on the order
of 50 ft/sec have been used in several projects. For
unlined tunnels, maximum design velocities ranging from 10
ft/sec in good quality rock to 4 ft/sec in less competent
material are typical. Thus, the volume of material to be
excavated using an unlined tunnel would be at least 5 times
that for a lined tunnel. The reliability of an unlined
tunnel is more dependent on rock conditions than is a lined
tunnel, particularly given the extended period during which
the diversion scheme is required to operate. Based on
these considerations, given a considerably higher cost,
together with the somewhat questionable feasibility of four
unlined tunnels with diameters approaching 50 feet in this
type of rock, the unlined tunnels have been eliminated.
The following alternative lined tunnel schemes were exam-
ined as part of this analysis:
-Pressure tunnel with a free outlet
-Pressure tunnel with a submerged outlet
-Free flow tunnel.
(iv) Emergency Release Facilities
The emergency re 1 ease f aci 1 it i es influenced the number,
type, and arrangement of the diversion tunnels selected for
the final scheme.
At an early stage of the study, it was established that
some form of low-level release facility was required to
8-2-15
meet instream flow requirements during filling of the res-
ervoir, and to permit lowering of the reservoir in the
event of an extreme emergency. The most economical alter-
native available would involve converting one of the diver-
sion tunnels to permanent use as a low-level outlet facili-
ty. Since it would be necessary to maintain the diversion
scheme in service during construction of the emergency
facilities outlet works, two or more diversion tunnels
would be required. The use of two diversion tunnels also
provides an additional measure of ~ecurity to the diversion
scheme in case of the loss of service of one tunnel.
The low-level release facilities will be operated for
approximately three years during filling of the reservoir.
Discharge at high heads usually requires some form of
energy dissipation prior to returning the flow to the riv-
er. Given the space restrictions imposed by the size of
the diversion tunnel, it was decided to utilize a double
expansion system constructed within the upper tunnel.
(v) Optimization of Diversion Scheme
Given the considerations described above relative to design
flows, cofferdam configuration, and alternative types of
tunnels, an economic study was undertaken to determine the
optimum combination of upstream cofferdam height and tunnel
diameter.
Capital costs were developed for three heights of upstream
cofferdam embankment with a 30-foot wide crest and exterior
slopes of 2H:lV. A freeboard allowance of 5 feet for set-
tlement and wave runup and 10 feet for the effects of down-
stream ice jamming on tailwater elevations was adopted.
Capital costs for the 4700-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 asso-
ciated 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 various tunnel alternatives with submerged and free
outlets are presented in Figure 8.22. The relationship
between capital cost and crest elevation for the upstream
cofferdam is shown in Figure 8.23. The capital cost for
various tunnel diameters with free and submerged outlets is
given in Figure 8.24.
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The results of the opt imi zat ion study are presented in
Figure B.25 and indicate the following optimum solutions
for each alternative.
Type of Tunnel
Two pressure tunnels
Two free flow tunnels
Two free flow tunnels
Diameter
(feet)
30
32.5
35
Cofferdam Crest
Elevation (ft} Total Cost {$)
1595
1580
1555
66,000,000
68,000,000
69,000,000
The cost studies indicate that a relatively small cost dif-
ferential (4 to 5 percent) separates the various alterna-
tives for tunnel diameter from 30 to 35 feet.
(vi) Selected Diversion Scheme
An important consideration at this point is ease of coffer-
dam closure. For the pressure tunnel scheme, the invert of
the tunnel entrance is below riverbed elevation, and once
the tunnel is complete diversion can be accomplished with a
closure dam section approximately 10 feet high. The free
flow tunnel scheme, however, requires a tunnel invert
approximately 30 feet above the riverbed level, and diver-
sion would invoJve an end-dumped closure section 50 feet
high. The velocities of flows which would overtop the cof-
ferdam before the water 1 evel s were raised to reach the
tunnel invert level would be prohibitively higher, result-
ing in complete erosion of the cofferdam, and hence the
dual free flow tunnel scheme was dropped from considera-
tion.
Based on the preceding considerations, a combination of one
pressure tunnel and one free flow tunnel (or pressure tun-
nel with free outlet) was adopted. This will permit ini-
tial diversion to be made using the lower pressure tunnel,
thereby simplifying the critical closure operation and
avoiding potentially serious delays in the schedule. Two
alternatives were re-evaluated as follows:
Tunnel Diameter
(feet)
30
35
Upstream Cofferdam
Crest Elevation Approximate Height
(feet) {feet)
1595
1555
B-2-17
150
110
More detailed layout studies indicated that the higher cof-
ferdam associated with the 30-foot diameter tunnel alterna-
tive would require locating the inlet portal further
u-pstream into 11 The Fins 11 shear zone. Since good rock con-
ditions for portal construction are essential and the 35-
foot diameter tunnel alternative would permit a portal
location downstream of 11 The Fins 11
, this latter alternative
was adopted. As noted in (v). the overall cost difference
was not significant in the range of tunnel diameters con-
sidered, and the scheme incorporating two 35-foot diameter
tunnels with an upstream cofferdam crest elevation of 1555
was incorporated as part of the selected general arrange-
ment.
(f) Spillway Facilities Alternatives
As discussed in subsection (c) above, the project has been de-
signed to safely pass floods with the following return frequen-
cies:
Inflow
Flood Frequency Peak (cfs)
Total Spillway
Discharge ( cfs)
Spillway Design
Probable Maximum
1:10,000 years 156,000
326,000
120,000
150,000
Discharge of the spillway design flood will require a gated ser-
vice spillway on either the left or right bank. Three basic al-
ternative spillway types were examined:
-Chute spillway with flip bucket
-Chute spillway with stilling basin
-Cascade spillway.
Consideration was also given to combinations of these alternatives
with or without supplemental facilities such as valved tunnels and
an emergency spillway fuse plug for handling the PMF discharge.
Clearly, the selected spillway alternatives will greatly influence
and be influenced by the project general arrangement.
(i) Energy Dissipation
The two chute spillway alternatives considered achieve ef-
fective energy dissipation either by means of a flip bucket
which would direct 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 would
dissipate energy in a hydraulic jump. The cascade type
spillway would limit the free-fall height of the discharge
by utilizing a series of 20-to 50-foot steps down to river
level, with energy dissipation at each step.
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( i i )
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 erosion, and
with pressure relief drains and rock anchors in the founda-
tion.
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. Supersaturation occurs when aerated
flows are subjected to pressures greater than 30 to 40 feet
of head which forces excess nitrogen into solution. This
occurs when water is subjected to the high pressures that
occur in deep plunge pools or at large hydraulic jumps.
The excess nitrogen would not be dissipated within the
downstream Devil Canyon reservoir and a buildup of nitrogen
concentration could occur throughout the body of water. It
would 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 facil-
ities were designed to limit discharges of water from
either Watana or Devi 1 Canyon that may become supersat-
urated with nitrogen to a recurrence period of not 1 ess
than 1:50 years.
(g) Power Facilities Alternatives
Selection of the optimum power plant development involved consid-
eration 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
-Environmental constraints.
( i) Comparison of Surface and Underground Powerhouse
Studies were carried 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 pre-
liminary conceptual layouts assuming four or six units and
a total installed capacity of 840 MW. The comparative cost
estimates for powerhouse civil works and electrical and
mechanical equipment (excluding common items) indicated an
B-2-19
advantage in favor of the underground powerhouse of
$16,300,000. A summary comparison of the cost estimates
for the two types of powerhouses is in Table B.29. The
additional cost for the surface powerhouse arrangement is
primarily associated with the longer penstocks and the
steel linin.gs required.
The underground powerhouse arrangement is also better suit-
ed to the severe winter conditions in Alaska, is less
affected by river flood flows in summer. and is aesthetic-
ally less obtrusive. This arrangement has therefore been
adopted for further development.
(ii) Comparison of Alternative Locations
Preliminary studies were undertaken during the development
of conceptual project layouts at Watana to investigate both
right and left bank locations for power facilities. The
configuration of the site is such that south bank locations
required 1 anger penstock and/ or t a i 1 race t unne 1 s and were
therefore more expensive.
The location on the south bank was further rejected because
of indications that the underground facilities would be
located in relatively poor quality rock. The underground
powerhouse was therefore located on the north bank such
that the major openings 1 ay between the two major shear
features {"The Fins" and the "Fingerbuster~).
(iii) Underground Openings
Because no construction adits or extensive drilling in the
powerhouse and tunnel locations have been completed, it has
been assumed that full concrete-lining of the penstocks and
tailrace tunnels would be required. This assumption is
conservative and is for preliminary design only; in prac-
tice, a large proportion of the tailrace tunnels would
probably be unlined, depending on the actual rock quality
encountered.
The minimum center-to-center spacing of rock tunnels and
caverns has been assumed for layout studies to be 2.5 times
the width or diameter of the larger excavation.
{iv) Selection of Turbines
The selection of turbine type is governed by the available
head and flow. For the design head and specific speed,
Francis type turbines have been selected. Francis turbines
B-2-20
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have a reasonably flat load-efficiency curve over a range
from about 50 percent to 115 percent of rated output with
peak efficiency of about 92 percent.
The number and rating of individual units is discussed in
detail in subsection (b) above. The final selected
arrangement comprises 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.
(v) Transformers
(vi)
The selection of transformer type, size, location and step-
up rating is summarized below:
-Single-phase transformers are required because of trans-
port limitations on Alaskan roads and railways;
-Direct transformation from 15 kV to 345 kV is 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
- A grouped arrangement of three sets of three single-phase
transformers for each set of two units has been selected
(a total of nine transformers) to reduce the physical
size of the transformer gallery and to provide a trans-
former spacing comparable with the unit spacing.
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 min-
imum spacing between the penstocks, which in turn is dic-
tated by geotechnical considerations.
The preferred penstock arrangement comprises six individual
penstocks, one for each turbine. With this arrangement, no
inlet valve is required in the powerhouse since turbine
dewatering can be performed by c1osing the control gate at
the intake and draining the penstocks and sera 11 case
through a valved bypass to the tailrace. An alternative
arrangement with three penstocks was considered in detail
to assess any possible advantages. This scheme would
require a bifurcation and two inlet valves on each penstock
B-2-21
Item
Intake
and extra space in the powerhouse to accommodate the inlet
valves. Estimates of relative cost differences are sum-
marized below:
Cost Difference ($ x 106)
6 Penstocks 3 Penstocks
Base Case -20.0
Penstocks 0 -3.0
Bifurcations 0 + 3.0
Valves 0 + 4.0
Powerhouse 0 + 8.0
Capitalized Value of Extra Head Loss 0 + 6.0
Total 0 -2.0
Despite a marginal saving of $2 million (or less than 2
percent in a total estimated cost of $120 million) in favor
of three penstocks, the arrangement of six individual pen-
stocks has been retained. This arrangement provides im-
proved flexibility and security of operation.
The preliminary design of the power facilities involves two
tailrace tunnels leading from a common surge chamber. An
alternative arrangement with a single tailrace tunnel was
also considered, but no significant cost saving was appar-
ent.
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 opt imi zat ion, the construct ion 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.
(vii) Environmental Constraints
Apart from the potential nitrogen supersaturation problem
discussed, the major environmental constraints on the de-
sign of the power facilities are:
-Control of downstream river temperatures
-Control of downstream flows.
The intake design has been modified to enable power plant
flows to be drawn from the reservoir at four different lev-
els throughout the anticipated range of reservoir
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drawdown for energy production in order to control the
downstream river temperatures within acceptable 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 constraint on the reservoir operation and
influence the computation of average and firm energy pro-
duced by the Susitna development.
The Watana development will be operated as a daily peaking
plant for load following. The actual extent of daily peak-
ing will be dictated by unit availability, unit size, sys-
tem demand, system stability, generating costs, etc.
2.3 -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.
(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 cri-
teria, and establish evaluation criteria.
-Step 2: Develop preliminary layouts and design criteria
based on the above data including ~11 plausible
alternatives for the constituent facilities and
structures.
-Step 3: Review all layouts on the basis of technical
feasibility, readily apparent cost differences,
safety, and environmental impact.
B-2-23
-Step 4: Select those layouts that can be identified as
most favorable, based on the evaluation criteria
established in Step 1, and 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
1 eve 1 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.
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.
B-2-24
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(b)
(c)
(d)
-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 a 11 major struc-
tures.
Review cost components within a preliminary con-
tractor•s type estimate using the most recent
data and criteria, and develop a construction
schedule.
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.
Design Data and Criteria
As discussed above, the review process included assembling rele-
vant design data, establishing preliminary design criteria, and
expanding and refining these data during the intermediate and
final reviews of the project arrangement. The design data and
design criteria which evolved through the final review are pre-
sented in Table B.30.
Evaluation Criteria
The various layouts were evaluated at each stage of the review
process on the basis of the criteria summarized in Table 8.31.
These criteria illustrate the progressively more detailed evalua-
tion process leading to the final selected arrangement.
Preliminary Review
The development selection studies (Acres 1982c, Vol. 1; Acres
1981) involved comparisons of hydroelectric schemes at a number of
sites on the Susitna River. As part of these comparisons a pre-
liminary conceptual design was developed for Watana incorporating
a double stilling basin type spillway.
Eight further layouts were subsequently prepared and examined for
the Watana project during this preliminary review process in
B-2-25
addition to the scheme shown on Figure B.7. These eight 1 ayouts
are shown in schematic form on Figure 8.26. Alternative 1 of
these layouts was the scheme recommended for further study.
This section describes the preliminary review undertaken of al-
ternative Watana layouts.
(i) Basis of Comparison of Alternatives
Although it was recognized that provision would have to be
made for downstream releases of water during filling of the
reservoir and for emergency reservoir drawdown, these fea-
tures were not incorporated in these preliminary layouts.
These facilities would either be interconnected with the
diversion tunnels or be provided for separately. Since the
system selected would be similar for all layouts with mini-
mal cost differences and little impact on other structures,
it was decided to exclude these facilities from overall
assessment at this early stage.
Ongoing geotechnical explorations had identified the two
major shear zones crossing the Susitna River and running
roughly parallel in the northwest direction. These zones
enclose a stretch of watercourse approximately 4500 feet in
length. Preliminary evaluation of the existing geological
data indicated highly fractured and altered materials with-
in the actual shear zones which would pose serious problems
for conventional tunneling methods and would be unsuitable
for founding of massive concrete structures. The original-
ly proposed dam axis was located between these shear zones;
since no apparent major advantage appeared to be gained
from large changes in the dam location, layouts generally
were kept within the confines of these bounding zones.
An earth and rockfi 11 dam was used as the basis for all
layouts. The downstream slope of the dam was assumed as
2H:1V in all alternatives, and 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 preliminary arrangements
except the one shown on Figure B.7, cofferdams were incor-
porated 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 facility. In such
B-2-26
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( i i )
instances, under large surcharges, these spillways would
not act as efficient energy dissipaters but would be
drowned out, acting as steep open channels with the possi-
bility 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
preliminary review, it appeared that an underground power-
house could be located on either side of the river. A sur-
face powerhouse on the north bank appeared feasible but was
precluded from the south bank by the close proximity of the
downstream toe of the dam and the adjacent broad shear
zone. Locating the powerhouse further downstream waul d
require tunneling across the shear zone, which would be
expensive and would require excavating a talus slope. Fur-
thermore, it was found that a south bank surface powerhouse
would either interfere with a south bank spillway or would
be directly impacted by discharges from a north bank spill-
way.
Description of Alternatives
-Double Stilling Basin Scheme
The scheme as shown on Figure B.? has a dam axis loca-
tion similar to that originally proposed by the COE, and
a north bank double stilling basin spillway. The spill-
way 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 dissipated within each
stilling basin is approximately 450 feet. Within world
experience, cavitation and erosion of the chute and
basins should not be a prob 1 em. if the structures are
properly designed. Extensive erosion downstream would
not be expected.
The diversion follows the shortest route, cutting the
bend of the river on the north bank, and has inlet port-
als as far upstream as possible without having to tunnel
through "The Fins." It is possible that the underground
powerhouse is in the area of "The Fingerbuster," but the
powerhouse could be located upstream almost as far as
B-2-27
the system of drain holes and galleries just downstream
of the main dam grout curtain.
-Alternative 1
This alternative {Figure B.26) is recommended for fur-
ther study and is similar to the layout described above
except that the north side of the dam has been rotated
clockwise, the axis relocated upstream, and the spillway
changed to a chute and flip bucket. The revised dam
alignment resulted in a slight reduction in total dam
volume compared to the above alternative. A localized
downstream curve was introduced in the dam close to the
north abutment in order to reduce the length of the
spillway. The alignment of the spillway is almost par-
allel to the downstream section of the river and it dis-
charges into a pre-excavated plunge pool in the river
approximately 800 feet downstream from the flip bucket.
This type of spillway should be considerably less costly
than one incorporating a stilling basin, provided that
excessive 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 buildup of material downstream which could cause
elevation of the tailwater levels.
-Alternatives 2 through 20
Alternative 2 consists of a south bank cascade spillway
with the main dam axis curving downstream at the abut-
ments. The cascade spillway would require an extremely
large volume of rock excavation, but it is probable that
most of this material, with careful scheduling, could be
used in the dam. The excavation would cross 11 The Fing-
erbuster11 and extensive dental concrete would be re-
quired in that area. In the upstream portion of the
spillway, velocities would be relatively high because of
the narrow configuration of the channel, and erosion
could take place in this area in proximity to the dam.
The discharge from the spillway enters the river perpen-
dicular to the general flow, but velocities would be
relatively low and should not cause substantial erosion
problems. The powerhouse is in the most suitable loca-
tion for a surface alternative where the bedrock is
close to the surface and the overall rock slope is
approximately 2H:lV.
B-2-28
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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 o~ upstream channel while
maintenance 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 north bank in
the alternative described above. However, the slope of
the ground is less than the rather steep north bank and
may be easier to construct, a (actor which may part 1 y
mitigate the cost of the longer structure. The dis-
charge is at a sharp angle to the river and more concen-
trated than the cascade, which could cause erosion of
the opposite bank.
Alternative 2C is a derivative of 2B with a similar
arrangement, except that the double stilling basin
spillway is reduced in size and augmented by an addi-
tional emergency spillway in the form of an inclined,
unlined rock channel. Under this arrangement the con-
crete spillway 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 erodible fuse plug. The problems of erosion
of the opposite bank still remain, although these could
be overcome by excavation and/or slope protection. Ero-
sion of the chute would be extreme for significant
flows, although it is highly unlikely that this emer-
gency spillway would ever be used.
Alternative 2D replaces the cascade of Alternative 2
with a lined chute and flip bucket. The comments rela-
tive to the flip bucket are the same as for Alternative
1 except that the south bank location in this instance
requires a longer chute, partly offset by 1ower con-
struction costs because of the flatter slope. The flip
bucket discharges into the river at an angle which may
cause erosion of the opposite bank. The underground
powerhouse is located on the north bank, an arrangement
which provides an overall reduction of the length of the
water passages.
-Alternative 3
This arrangement has a dam axis location slightly up-
stream from Alternative 2, but retains the downstream
B-2-29
curve at the abutments. The main spillway is an unlined
rock cascade on the south 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 north bank. A gated
control structure is provided for this auxiliary spill-
way which gives it the flexibility to be used as a back-
up if maintenance should be required on the main spill-
way. Erosion of the cascade may be a problem, as men-
tioned previously, but erosion downstream should be a
less important consideration because of the low unit
discharge and the infrequent operation of the spillway.
The diversion tunnels are situated in the north
abutment, as with previous arrangements, and are of
similar cost for all these alternatives.
-Alternative 4
This alternative involves rotating the axis of the main
dam so that the south abutment is relocated approxi-
mately 1000 feet downstream from its Alternative 2 loca-
tion. The relocation results in a reduction in the
overall dam quantities but would require siting the
impervious core of the dam directly over 11 The Finger-
buster11 shear zone at maximum dam height. The south
bank spillway, consisting of chute and flip bucket, is
reduced in length compared to other south bank l oca-
tions, as are the power facility water passages. The
diversion tunnels are situated on the south bank; there
is no advantage to a north bank location, since the tun-
nels are of similar length owing to the overall down-
stream relocation of the dam. Spillways and power
facilities would also be lengthened by a north bank
location with this dam configuration.
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 obvious 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.
Location of the spillway on the north bank results in a
shorter distance to the river and allows discharges
almost parallel to the general direction of river flow.
The double stilling basin arrangement would be extremely
expensive, particularly if it must be designed to pass
the probable maximum flood. An alternative such as 2C
B-2-30
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(e)
would reduce the magnitude of design flood to be passed
by the spillway but would only be acceptable if an emer-
gency spillway with a high degree of operational pre-
dictability could be constructed. A flip bucket spill-
way on the north bank,· discharging directly down the
river, would appear to be an economic arrangement, al-
though some scour might occur in the plunge pool area.
A cascade spillway on the south bank could be an accept-
able solution provided that most of the excavated mater-
; al caul d be used in the dam, and adequate rock condi-
t ions exist.
The length of diversion tunnels can be decreased if they
are located on the north bank. In addition, the tunnels
would be accessible by a preliminary access road from
the north, which is the most likely route. This loca-
tion would also avoid the area of 11 The Fingerbuster 11 and
the steep cliffs which would be encountered on the south
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 preceding layouts, or variations of them,
were selected for further study:
A variation of the double stilling basin scheme, but
with a single stilling basin main spillway on the
north bank, a rock channel and fuse plug emergency
spillway, a south bank underground powerhouse and a
north bank diversion scheme;
Alternative 1 with a north bank flip bucket spillway,
an underground powerhouse on the south bank, and north
bank diversion;
A variation of Alternative 2 with a reduced capacity
main spillway and a north bank rock channel with a
fuse plug serving as an emergency spillway; and
Alternative 4 with a south bank rock cascade spillway,
a north bank underground powerhouse, and a north bank
diversion.
Intermediate Review
For the intermediate review process, the four schemes selected as
a result of the preliminary review were examined in more detail
B-2-31
and modified. A description of each of the schemes is given below
and shown on Figures B.27 through B.32. 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 proposed project.
(i) Description of Alternative Schemes
The four schemes are shown on Figures B.27 through B.32.
Scheme WP1 (Figure B.27)
This scheme is a refinement of Alternative 1. The up-
stream slope of the dam is flattened from 2.5:1 to
2.75:1. This conservative approach was adopted to pro-
vide an assessment of the possible impacts on project
layout of conceivable measures which may prove necessary
in dealing with severe earthquake design conditions.
Uncertainty with regard to the nature of river alluvium
also led to the location of the cofferdams outside the
limits of the main dam embankment. As a result of these
conditions, the intake portals of the diversion tunnels
on the north bank are also moved upstream from 11 The
Fins 11 • A chute spillway with a flip bucket is located
on the north bank. The underground powerhouse is lo-
cated on the south bank.
Scheme WP2 (Figures B.29 and B.30)
This scheme is derived from the double stilling basin
layout. The main dam and diversion facilities are sim-
ilar to Scheme WP1 except that the downstream cofferdam
is relocated further downstream from the spillway outlet
and the diversion tunnels are correspondingly extended.
The main spillway is located on the north bank, but the
two st i 11 i ng basins of the pre 1 imi nary scheme (Acres
19Bl) are combined into a single stilling basin at the
river level. An emergency spillway is also located on
the north 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 dis-
charging the flow differential between the probable max-
imum flood and the surcharged capacity of the main
spillway. The underground powerhouse is located on the
south bank.
B-2-32
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Scheme WP3 (Figures B.28 and B.29)
This scheme is similar to Scheme WPl in all respects
except that an emergency spillway is added consisting of
north bank rock channel and fuse plug.
Scheme WP4 (Figures B.31 and B.32)
The dam location and geometry for Scheme WP4 are similar
to that for the other schemes. The diversion is on the
north bank and discharges downstream from the powerhouse
tailrace outlet. A rock cascade spillway is located on
the south bank and is served by two separate control
structures with downstream st i 11 i ng basins. The under-
ground powerhouse is located on the north bank.
(ii) Comparison of Schemes
The main dam is in the same location and has the same con-
figuration for each of the four layouts considered. The
cofferdams have been 1 ocated outside the 1 imits 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 probabJy be made after more detailed study.
The diversion tunnels are located on the north bank. The
upstream flattening of the dam slope necessitates the loca-
tion of the diversion inlets upstream from 11 The Fins .. shear
zone which would 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 north bank in the area of
the relict channel and requires approximately a 50-foot
high saddle dam for closure, given the reservoir operating
level assumed for the comparison study. However, the fi-
nally selected reservoir operating level will require only
a nominal freeboard structure at this location.
A summary of capital cost estimates for the four alterna-
tive schemes is given in Table B.32.
The results of this intermediate analysis indicate that the
chute spillway with flip bucket (Scheme WPl) is the least
costly spillway alternative.
The scheme has the additional advantage of relatively sim-
ple operating characteristics. The control structure
B-2-33
has prov1s1on for surcharging to pass the design flood.
The probable maximum flood can be passed by additional sur-
charging up to the crest level of the dam. In Scheme WP3 a
similar spillway is provided, except that the control
structure is reduced in size and discharges above the rout-
ed design flood are passed through the rock channel emer-
gency spill way. The arrangement in Scheme WPl does not
provide a backup facility to the main spillway, so that if
repairs caused by excessive plunge pool erosion or damage
to the structure itself require removal of the spillway
from service for any length of time, no alternative dis-
charge facility would be available. The additional spill-
way of Scheme WP3 would permit emergency discharge if it
were required under extreme circumstances.
The stilling basin spillway (Scheme WP2) would reduce the
potential for extensive erosion downstream, but high veloc-
ities in the lower part of the chute could cause cavitation
even with the provision for aeration of the discharge.
This type of spillway would be very costly, as can be seen
from Table B.32.
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 excavated material which can be used
in the dam. For determining the capital cost of Scheme
WP4, conservative assumptions were made regarding surface
treatment and the portion of material that would have to be
wasted.
The diversion tunnels are located on the north bank for all
alternatives examined in the intermediate review. For
Scheme WP2, the downstream portals must be located down-
stream from the stilling basin, resulting in an increase of
approximately 800 feet in the length of the tunnels. The
south bank location of the powerhouse requires its place-
ment 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 1000 feet in the length of the tailrace. The
south-side location is remote from the main access road,
which will probably be on the north side of the river, as
will the transmission corridor.
(iii) Selection of Schemes for Further Study
Examination of the technical and economic aspects of
Schemes WPl through WP4 indicates there is little scope for
adjustment of the dam axis owing to the confinement imposed
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by the upstream and downstream shear zones. In addition,
passage of the diversion tunnels through the upstream shear
zone could result in significant delays in construction and
additional cost.
From a comparison of costs in Tab 1 e B .32, 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 undesirable to use it as the only discharge
facility. A mid-level release will be required for emer-
gency drawdown of the reservoir, and use of this release as
the first-stage service spillway with the flip bucket as a
backup facility would combine flexibility and safety of
operaticm with reasonable cost. The emergency rock channel
spillway would be retained for discharge of PMF flows.
The stilling basin spillway is very costly and the operat-
ing head of 800 feet is beyond precedent experience. Ero-
sion downstream should not be a problem but cavitation on
the chute could occur. Scheme WP2 was therefore eliminated
from further consideration.
The cascade spillway was also not favored for technical and
economic reasons. However, this arrangement does have an
advantage in that it provides a means of preventing nitro-
gen supersaturation in the downstream discharges from the
project which could be harmful to the fish population. A
cascade configuration would reduce the. dissolved nitrogen
content; hence, this alternative was retained for further
evaluation. The capacity of the cascade was reduced and
the emergency rock channel spillway was included to pass
the extreme floods.
The results of the intermediate review indicated that the
following components should be incorporated into any scheme
carried forward for final review:
Two diversion tunnels located on the north bank of the
river;
-An underground powerhouse also located on the north
bank;
-An emergency spillway, compr1s1ng a rock channel exca-
vated on the north bank and discharging well downstream
from the north abutment. The. ch anne 1 is sea 1 ed by an
erodible fuse plug of impervious material designed to
fail if overtopped by the reservoir; and
B-2-35
- A compacted earthfi 11 and rockfi 11 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 north bank to
pass the spillway design flood, with a mid-level release
system designed to operate for floods with a frequency of
up to about 1:50 years; or
-A cascade spillway on the south bank.
Accordingly, two schemes were developed for further evalua-
tion as part of the final review process. These schemes
are described separately in the paragraphs below.
(f) Final Review
The two schemes considered in the final review process were essen-
tially derivations of Schemes WP3 and WP4.
(i) Scheme WP3A (Figure 8.33)
This scheme is a modified version of Scheme WP3 described
above. Because of scheduling and cost considerations, it
is extremely important to maintain the diversion tunnels
downstream from "The Fins.11 It is also important to keep
the dam axis as far upstream as possible to avoid conges-
tion 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 11 The
Fins. n The upstream cofferdam and main dam are maintained
in the upstream locations as shown on Figure 8.33. As men-
tioned previously, additional criteria have necessitated
modifications in the spillway configuration, and low-level
and emergency drawdown outlets have been introduced.
The main modifications to the scheme are as follows:
-Main Dam
Continuing preliminary design studies and review of world
practice suggest that an upstream slope of 2.4H:lV would
be acceptable for the rock shell. Adoption of this slope
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results not only in a reduction in dam fill volume but
also a reduction in the base width of the dam which per-
mits the main project components to be located between
the major shear zones.
The downstream slope of the dam is retained as 2H:1V.
The cofferdams remain outside the 1 imits of the dam in
order to allow complete excavation of the riverbed allu-
vium.
-Diversion
In the intermediate review arrangements, diversion tun-
nels passed through the broad structure of 11 The Fins, 11 an
intensely sheared area of breccia, gouge, and infi 11 s.
Tunneling of this material would be difficult, and might
even require excavation in open cut from the surface.
High cost would be involved, but more important would be
the time taken for construction in this area and the pos-
sibility 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 port-
als with respect to the river flow directions.
A separate low-level inlet and concrete-lined tunnel is
provided, leading from the reservoir at approximate Ele-
vation 1550 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
12,000 cfs during reservoir filling. It would also pass
up to 30,000 cfs under 500-foot head to allow emergency
draining of the reservoir.
Initial closure is made by lowering the gates to the tun-
nel located closest to the river and constructing a con-
crete 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 contra ll ed discharges are passed downstream. The
closure gates within the second diversion tunnel portal
are then closed and a concrete closure plug constructed
in line with the grout curtain. After closure of the
gates, filling of the reservoir would commence.
-Outlet Facilities
As a provision for drawing down the reservoir in case of
emergency, a mid-1 eve 1 re 1 ease is provided. The intake
B-2-37
to these facilities is located at depth adjacent to the
power facilities intake structures. Flows would then be
passed downstream through a concrete-1 ined tunnel, dis-
charging beneath 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 equivalent routed 50-year
flood). Eight feet of reservoir storage is utilized to
reduce valve capacity. Six cone valves are required,
located on branches from a steel manifold and protected
by individual upstream closure gates. The valves are
partly incorporated into the mass concrete block forming
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.
-Spillways
As discussed above, the designed operation of the main
spillway facilities was arranged to limit discharges of
potentially nitrogen-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 p 1 unge poo 1 in the downstream river bed. Re-
1 eases are contro 11 ed by a three-gated ogee structure
located adjacent to the out let faci 1 it i es and power in-
take structure just upstream from the dam centerline.
The design discharge is approximately 120,000 cfs, cor-
responding to the routed 1: 10,000-year flood (150 ,000
cfs) reduced by the 31,000 cfs flows attributable to out-
let and power facilities discharges. Maximum reservoir
level is 2194 feet. The plunge pool is formed by exca-
vating the alluvial river deposits to bedrock. Since the
excavated plunge pool approaches the limits of the calcu-
lated maximum scour hole, it is not anticipated that,
given the infrequent discharges, significant downstream
erosion will occur.
An emergency spillway is provided by means of a channe 1
excavated in rock on the north bank, discharging well
downstream from the north abutment in the direction of
Tsusena Creek. The channel is sealed by an erodible fuse
plug of impervious material designed to fail if over-
topped by the reservoir, although some preliminary exca-
vation may be necessary. The crest level of the plug
will be set at Elevation 2230, well below that of the
main dam. The channel will be capable of passing, in
conjunction with the main spillway and outlet facilities,
the probably maximum flood of 326,000 cfs.
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Power F ac i 1 it i es
The power intake is set slightly upstream from the dam
axis deep within sound bedrock 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 reservoir. This facility also provides for draw-
ing water from the different temperature strata within
the upper part of the reservoir and thus regulating the
temperature of the downstream discharges close to the
natural temperatures of the river or temperatures advan-
tageous to fishery enhancement. 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 openings at the required level. Downstream from
these shutters each unit has a pair of wheel-mounted
closure gates which will isolate the individual pen-
stocks.
The six penstocks are 18-foot diameter, concrete-lined
tunnels inclined at 55° immediately downstream from the
intake to a nearly horizontal portion leading to the
powerhouse. 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 with-
in 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 over-
head crane which runs the length of the powerhouse and
into the service area adjacent to the units. Switch-
gear, maintenance room and offices are located within
the main cavern, with the transformers situated down-
stream in a separate gallery excavated above the tail-
race tunnels. Six inclined tunnels carry the connecting
bus ducts from the main power 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 directly overhead. Downstream
from the transformer gallery the underlying draft tube
tunnels merge into two surge chambers (one chamber for
B-2-39
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-lined, low-
pressure tailrace tunnels carry the discharges to the
river. Because of space restrictions at the river, one
of these tunnels has been merged with the downstream end
of the diversion tunnel. The other tunnel emerges in a
separate portal with provision for the installation of
bulkhead gates.
The orientation of water passages and underground cav-
erns is such as to avoid, as far as possible, alignment
of the main excavations with the major joint sets.
Access
Access is assumed to be from the north side of the
river. Permanent access to structures close to the
river is by a road along the north downstream river bank
and then via a tunnel passing through the concrete form-
ing the flip bucket. A tunnel from this point to the
power cavern provides for vehicular access. A secondary
access road across the crest of the dam passes down the
south bank of the va 11 ey and across the 1 ower part of
the dam.
(ii) Scheme WP4A (Figure 8.34)
This scheme is similar in most respects to Scheme WP3A pre-
viously discussed, except for the spillway arrangements.
Main Dam
The main dam axis is similar to that of Scheme WP3A,
except for a slight downstream rotation at the south
abutment at the spillway control structures.
Diversion
The diversion and low-level releases are the same for
the two schemes.
Outlet Facilities
The outlet facilities used for emergency drawdown are
separate from the main spi 11 way for this scheme. The
B-2-40
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"Utlet facilities consist of a low-level gated inlet
structure discharging up to 30,000 cfs into the river
through a concrete-lined, free-flow tunnel with a ski
jump flip bucket. This facility may also be operated as
an auxiliary outlet to augment the main south bank
spi 11 way.
Spillways
The main south bank spillway is capable of passing a
design flow equivalent to the 1:10,000-year flood
through a series of 50-foot drops into shall ow pre-
excavated plunge pools. The emergency spillway is
designed to operate during floods of greater magnitude
up to and including the PMF.
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 quality of the rock in the area, requir-
ing both durability to withstand erosion caused by
sp·i llway flows and a high percentage of sound rockfi 11
material that can be used from the excavation directly
in the main dam.
On the basis of the site information developed concur-
rently with the general arrangement studies, it became
apparent that the major shear zone known to exist in the
·south bank area extended further downstream than initial
studies had indicated. The cascade spillway channel was
therefore lengthened to avoid the shear area at the low-
er end of the cascade. The arrangement shown on Figure
8.34 for Scheme WP4A does not reflect this relocation,
which waul d ·increase the over a 11 cost of the scheme.
The emergency spillway consisting of rock channel and
fuse plug is similar to that of the north bank spillway
scheme.
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 arrange-
ment (the main spillways and the discharge arrangements at
B-2-41
the downstream end of the outlets) indicates a saving 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 appro-
priate proportion of excavated materia 1 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 administration
costs.
As discussed above, although limited information exists
regarding the quality of the rock in the downstream area on
the south bank, it is known that a major shear zone runs
thro~gh and is adjacent to the area presently allocated to
the spillway in Scheme WP4. This would require relocating
the south bank cascade spillway several hundred feet far-
ther downstream into an area where the rock quality is
unknown and the topography less suited to the gentle over-
all slope of the cascade. The cost of the excavation would
substantially increase compared to previous assumptions,
irrespective of the rock quality. In addition, the resist-
ance of the rock to erosion and the suitability for use as
excavated material in the main dam would become less cer-
tain. The economic feasibility of this scheme is largely
predicated on this last factor, since the ability to use
the material as a source of rockfi 11 for the main dam
represents a major cost saving.
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 spill-
way. Since this scheme presents a more economic solution
with fewer potential problems concerning the geotechnical
aspects of its design, the north bank chute arrangement
(Scheme WP3A) has been adopted as the final selected
scheme.
Subsequent to adoption of this final scheme, minor changes
to the design criteria have been made and are presented in
Exhibit F.
2.4 -Devil Canyon Project Formulation
This section describes the development of the general arrangement of
the Devil Canyon projt7ct. The method of handling floods during con-
struction and subsequent project operation is also outlined in this
section.
The reservoir level fluctuations and inflow for Devil Canyon will es-
sentially be controlled by operation of the upstream Watana project.
This aspect is also briefly discussed in this section.
B-2-42
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(a) Selection of Reservoir Level
(b)
The selected normal maximum operating level at Devil Canyon Dam is
Elevation 1455. Studies by the USBR and COE on the Devil Canyon
project were essentially based on a similar reservoir level which
corresponds to the average tailwater level at the Watana site.
Although the narrow 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 1 evel.
Although significantly lower reservoir levels at Devil Canyon
would lead to lower dam costs, 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 regarding
safety from scouring at the toe of the dam which have already led
to rejection of such schemes.
Selection of Installed Capacity
The methodology used for the preliminary selection of installed
capacity at Devil Canyon is similar to the Watana methodology des-
cribed in Section 2.2(b).
The decision to operate Devil Canyon primarily as a base-loaded
plant was governed by the following main considerations:
Daily peaking is more effectively performed at Watana than at
Devil Canyon; and
-Excessive fluctuations in discharge from the Devil Canyon Dam
may have an undesirable impact on mitigation measures incorpor-
ated in the final design to protect 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 rec-
ord, as modified by the reservoir operation rule curves. In years
where the energy from Watana and Devil 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.
Table B.33 shows an assessment of maximum plant capacity required
at Devil Canyon in the peak demand month (December). The Devil
Canyon capacity is the same whether thermal energy is used for
B-2-43
base load or for peaking since Devil Canyon is designed for peak-
ing only.
The selected total installed capacity at Devil Canyon has been
established as 600 MW for design purposes. This will provide some
margin for stand by during forced outage and poss i b 1 e acce 1 erated
growth in demand.
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 power facilities at Devil Canyon have been developed using
four 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
des i rab 1 e. However, the uncertainty of 1 oad forecasts and the
additional contractual costs of mobilization for equipment instal-
lation 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 drawdown occurring during an extremely dry year;
this means that, in an average year, with higher reservoir levels
the full station output can be maintained even with one unit on
forced outage.
(c) Selection of Spillway Capacity
A flood frequency of 1:10,000 years was selected for the spillway
design on the same basis as described for Watana. An emergency
spillway with an erodible fuse plug will also be provided to safe-
ly discharge the probable maximum flood. The development plan
envisages completion of the Watana project prior to construction
at Devil Canyon. Accordingly, the inflow flood peaks at Devil
Canyon will 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
B-2-44
Inflow Peak (cfs)
165,000
345,000
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(d)
The avoidance of nitrogen supersaturation in the downstream flow
for Watana also will apply to Devil Canyon. Thus, the discharge
of water possibly supersaturated with nitrogen from Devil Canyon
will be limited to a recurrence period of not less than 1:50 years
by the use of fixed-cone valves similar to Watana.
Main Dam Alternatives
The location of the Devil Canyon damsite was examined during pre-
vious studies by the USBR and COE. These studies focused on the
narrow entrance to the canyon and led to the recommend at ion of a
concrete arch dam. Notwithstanding this initial appraisal, a com-
parative analysis was undertaken as part of this feasibility study
to evaluate the relative merits of the following types of struc-
tures at the same location:
-Thick concrete arch
-Thin concrete arch
-Fill embankment.
(i) Comparison of Embankment and Concrete Type Dams
The geometry was developed for both the thin concrete arch
and the thick concrete arch dams, and the dams were anal-
yzed and their behavior compared under static, hydrostatic,
and seismic loading conditions. The project layouts for
these arch dams were compared to a layout for a rockfi 11
dam with its associated structures.
Consideration of the central core rockfill dam layout indi-
cated relatively small cost differences from an arch dam
cost estimate, based on a cross section significantly
thicker than the finally selected design. Furthermore, no
information was avai 1 able to indicate that impervious core
material in the necessary quantities could be found within
a reasonable distance of the damsite. The rockfill dam was
accordingly dropped from further consideration. It is fur-
ther noted that, since this alternative dam study, seismic
analysis of the rockfill dam at Watana has resulted in an
upstream slope of 1:2.4, thus indicating the requirement to
flatten the 1:2.5 slope adopted for the rockfill dam
alternative at Devil Canyon.
Neither of the concrete arch dam 1 ayouts was intended as
the final site arrangement, but were sufficiently represen-
tative of the most suitable arrangement associated with
each dam type to pro vi de an adequate bas is for comparison.
Each type of dam was located just downstream from where the
river enters Devil Canyon and close to the canyon's
B-2-45
narrowest point, which is the optimum location for all
types of dams. A brief description of each dam type and
configuration is given below.
Rockfi 11 Dam
For this arrangement the dam axis would be some 625 feet
downstream of the crown section of the concrete dams.
The assumed embankment slopes would be 2. 25H: 1 V on the
upstream face and 2H:1V on the downstream face. The
main dam would be continuous with the south bank saddle
dam, and therefore no thrust blocks would be required.
The crest length would be 2200 feet at Elevation 1470;
the crest width would be 50 feet.
The dam would be constructed with a central impervious
core, inclined upstream, supported on the downstream
side by a semi-pervious zone. These two zones would be
protected upstream and downstream by filter and
transition materials. The shell sections would be
canst ructed of rockfi ll obtai ned from blasted bedrock.
For preliminary design all dam sections would be assumed
to be founded on rock; external cofferdams would be
founded on the river alluvium, and would not be
incorporated into the main dam. The approximate volume
of material in the main dam would be 20 million cubic
yards.
A single spillway would be provided on the north
abutment to control all flood flows. It would consist
of a gate control structure and a double stilling basin
excavated into rock; the chute sections and stilling
basins would be concrete-lined, with mass concrete
gravity retaining walls. The design capacity would be
sufficient to pass the 1:10,000-year flood without
damage; excess capacity would be provided to pass the
PMF without damage to the main dam by surcharging the
reservoir and spillway.
The powerhouse would be located underground in the north
abutment. The multi-level power intake would be
constructed in a rock cut in the north abutment on the
dam centerline, with four independent penstocks to the
150-MW Francis turbines. Twin concrete-lined tailrace
tunnels would connect the powerhouse to the river via an
intermediate draft tube manifold.
Thick Arch Oam
The main concrete dam would be a single-center arch
structure, acting partly as a gravity dam, with a verti-
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cal cylindrical upstream face and a sloping downstream
face inclined at 1V:0.4H. The maximum height of the dam
would be 635 feet with a uniform crest width of 30 feet,
a crest length of approximately 1400 feet, and a maximum
foundation 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 exca-
vated riverbed. This central section would incorporate
the main spillway with sidewalls anchored into solid
bedrock and gated orifice sp"lllways discharging down the
steeply inclined downstream 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 south abutment thrust block would
incorporate an emergency gated control spillway struc-
ture 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 south abutment would be closed by
means of a rockfill dike founded on bedrock. The power-
house would house four 150-MW units and would be located
underground within the north 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. The probable maximum flood
is passed by combined discharges through the main
spillway, outlet facility, and emergency spillway.
Thin Arch Dam
The main dam would be a two-center, doub 1 e-curved arch
structure of similar height 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
section would be founded on a concrete pad, and the
extreme upper portion of the dam would terminate in con-
crete thrust blocks located on the abutments.
The main spillway would be located on the north abutment
and would consist of a conventional gated control struc-
ture discharging down a concrete-lined chute terminating
in a flip bucket. The bucket would discharge into an
unlined plunge pool excavated in the riverbed alluvium
and located sufficiently downstream to prevent under-
mining of the dam and associated structures.
B-2-47
The main spillway would be supplemented by orifice type
spillways located in the center portion of the dam which
would discharge into a concrete-lined plunge pool imme-
diately downstream from the dam. An emergency spillway
consisting of a fuse plug discharging into an unlined
rock channel terminating well downstream would be loca-
ted beyond the saddle dam on the south abutment.
The concrete dam would terminate in a massive thrust
block on each abutment which, on the south abutment,
would adjoin a rockfill saddle dam.
The main and auxiliary spillways would be designed to
discharge the 1:10,000-year flood. The probable maximum
flood would be discharged through the emergency south
abutment spillway, main spillway and auxiliary spill-
way.
Comparison of Arch Dam Types
Sand and gravel for concrete aggregates are believed 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 production of aggregates after screen-
ing and washing.
The bedrock geology of the site is discussed in the
1980-81 Geotechnical Report (Acres 1982a). 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 would 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 would produce stresses of a great-
er magnitude 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 under-
stressed area of concrete will be greater for the thick
arch, and the factor of safety for the dam would be cor-
respondingly higher. The thin arch is, however, a more
efficient design and better utilizes the inherent prop-
erties of the concrete. It is designed around accept-
able 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
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(e)
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and would be more expensive because of the larger volume
of concrete needed. Studies therefore continued on
refin·ing the feasibility of the thin arch alternative.
Diversion Scheme Alternatives
In this section the selection of general arrangement and the basis
for sizing of the diversion scheme are presented.
(i) General Arrangements
The steep-walled valley at the site essentially dictated
that diversion of the river during construction be accom-
plished using one or two diversion tunnels, with upstream
and downstream cofferdams protecting the main construction
area.
The selection process for establishing the final general
arrangement 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 con-
struction strongly favored the south bank or abutment, the
obvious approach being via the alluvial fan. The total
length of tunnel required for the south bank is approxi-
mately 300 feet greater; however, access to the north bank
could not be achieved without great difficulty.
(ii) Design Flood for Diversion
The recurrence interval of the design flood for diversion
was estab 1 i shed 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 period for each year of crit-
ical construction exposure. The critical construction
time is estimated at 2.5 years. The main dam could be sub-
jected to overtopping during construction without causing
serious damage, and the existence of the Watana facility
upstream would offer considerable assistance in flow regu-
lation in case of an emergency. These considerations led
to the selection of the design flood with a return frequen-
cy of 1:25 years.
The equivalent inflow, together with average flow charac-
teristics of the river significant to diversion, are pre-
sented below:
-Average annual flow: 9,080 cfs
-Design flood inflow (1:25 years routed
through Watana reservoir): 37,800 cfs
B-2-49
(iii) Cofferdams
As at Watana, the ·considerable depth of riverbed alluvium
at both cofferdam sites indicates that embankment-type cof-
ferdam structures would be the only technically and econom-
ically feasible alternative at Devil Canyon. For the pur-
poses of establishing the overall general arrangement of
the project and for subsequent diversion optimization stud-
; es, the up-stream cofferdam section adopted will comprise
an initial closure section approximately 20 feet high con-
structed in the wet, with a zoned embankment constructed in
the dry. The downstream cofferdam wi11 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 achieved by means of a grouted
zone. The coarse nature of the a1luvium at Devil Canyon
led to the selection of a grouted zone rather than a slurry
wa 11.
(iv) Diversion Tunnels
Although studies for the Watana project indicated that
concrete-lined tunnels are the most economically and tech-
nically feasible solution, this aspect was reexamined at
Devil Canyon. Preliminary hydraulic studies indicated that
the design flood routed through the diversion scheme wou1d
result in a design discharge of approximately 37,800 cfs.
For concrete-lined tunnels, design velocities of approxi-
mately 50ft/sec wou1d permit the use of one concrete-lined
tunnel with an equivalent diameter of 30 feet.
Alternatively, for un1ined tunnels a maximum design
velocity of 10 ft/sec in good quality rock would require
four unlined tunnels, each with an equivalent 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 sufficient to eliminate consideration
of unlined tunnels for the diversion scheme.
For the purposes of optimization studies, only a pressure
tunnel was considered, since previous studies indicated
that cofferdam closure problems associated with free flow
tunnels would more than offset their other advantages.
(v) Optimization of Diversion Scheme
Given the considerations described above relative to design
flows, cofferdam configuration, and alternative types of
tunnels, an economic study was undertaken to determine the
optimum combination of upstream cofferdam elevation
(height) and tunnel diameter.
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(f)
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Capital costs were developed for a range of pressure tunnel
diameters and corresponding upstream cofferdam embankment
crest elevations with a 30-foot wide crest and exterior
slopes of 2H:1V. A freeboard a.llowance of 5 feet was
included for settlement and wave runup.
Capital costs for the tunnel alternatives included allow-
ances for excavation, concrete liner, rock bolts, and steel
supports. Costs were a 1 so deve 1 oped for the upstream and
downstream portals, including excavation and support. The
cost of an intake gate structure 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 2000 feet.
Rating curves for the single-pressure tunnel alternatives
are presented in Figure B.35. The relationship between
capital costs for the upstream cofferdam and various tunnel
diameters is given in Figure B.36.
The results of the optimization study indicated that a
single 30-foot diameter pressure tunnel results in the
overall least cost (Figure B.36). An upstream cofferdam 60
feet high, with a crest elevation of 945, was carried for-
ward as part of the selected general arrangement.
Spillway Alternatives
The project spillways have been designed to safely pass floods
with the following return frequencies:
Inflow Peak
Flood
Spillway Design
Probable Maximum
Discharge
Frequency
1:10,000 years
Inflow
(cfs)
165,000
345,000
A number of alternatives were considered singly and in combination
for Devil Canyon sp·illway facilities. These included gated ori-
fices 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 spillway was influenced by
the general arrangement of the major structures. The main spill-
way facilities would discharge the spillway design flood through a
gated spillway control structure with 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 above, restrictions
with respect to limiting nitrogen supersaturation in selecting
B-2-51
acceptable spillway discharge structures have been applied. The
various spillway arrangements developed in accordance with these
considerations are discussed in Section 2.5.
(g) Power Facilities Alternatives
The selection of the optimum arrangements for the power facilities
involved consideration of the same factors as described for
Watana.
(i) 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 fa-
vored an underground arrangement. In addition to cost, the
underground powerhouse 1 ayout has been se 1 ected 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, particularly under earthquake loading, and
would require significant changes in the arch dam geo-
metry; and
-The outlet facilities located in the arch dam are de-
signed to discharge directly into the river valley; these
would cause significant winter icing and spray problems
to any surface structure below the dam.
(ii) Comparison of Alternative Locations
The underground powerhouse and related facilities have been
located on the north bank for the following reasons:
-Generally superior rock quality at depth;
-The south bank area behind the main dam thrust block is
unsuitable for the construction of the power intake; and
-The river turns north downstream from the dam, and hence
the north bank power development is more suitable for
extending the tailrace tunnel to develop extra head.
(iii) Selection of Units
The turbine type selected for the Devil Canyon development
is governed by the design head and specific speed and by
B-2-52
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-(iv)
(v) -
(vi)
-'
-
economic considerations. Francis turbines have been adop-
ted for reasons similar to those discussed for Watana in
Section 2.2(g).
The selection of the number and rating of individual units
is discussed in detail in Section 2.4(b). The four units
will be rated to deliver 150 MW each at full gate opening
and minimum reservoir level in December (the peak demand
month).
Transformers
Transformer selection is similar to Watana (Section
2.2(g)(v)).
Power Intake and Water Passages
For flexibility of operation, individual penstocks are pro-
vided to each of the four units. Detailed cost studies
showed that there is no significant cost advantage in using
two larger diameter penstocks with bifurcation at the pow-
erhouse compared to four separate penstocks.
A single tailrace tunnel with a length of 6800 feet to
develop 30 feet of additional head downstream from the dam
has been incorporated in the design. Detailed design may
indicate that two smaller tailrace tunnels for improved
reliability may be superior to one 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 se 1 ected diameter and number of the penstocks and
the minimum penstock 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.
Environmental Constraints
In addition to potential nitrogen-supersaturation 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
intake design at Devil Canyon would aid in controlling
downstream water temperatures.
B-2-53
Consequently, the intake design at Devil Canyon incorpor-
ates two levels of draw-off.
The Devil Canyon station will normally be operated as a
base-loaded plant throughout the year to satisfy the re-
quirement of no significant daily variation in power flow.
2.5 Selection of Devil Canyon General Arrangement
The approach to selection of a general arrangement for Devil Canyon was
a similar but simplified version of that used for Watana.
(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 four schemes were ini-
tially developed and evaluated. During the final review, the sel-
ected layout was refined based on technical, operational and envi-
ronmental 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 are presented in Table B.34. Subsequent to selec-
tion of the preferred Dev i1 Canyon scheme, the information was
refined and updated as part of the ongoing study program.
{c) Preliminary Review
Consideration of the options available for types and locations of
various structures led to the development of four primary layouts
for examination at Devil Canyon in the preliminary 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 economic location was at the upstream entrance to
the canyon. The dam axis has been fixed in this location for all
a 1tern at i ves.
{i) 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 abut-
ments, the south block extending approximately 100 feet
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-
-
above the existirig bedrock surface and supporting the upper
arches of the dam. The thrust block on the north abutment
makes the cross-river profile' of the dam more symmetrical
and contributes to a more uniform stress distribution.
Scheme DC1 (Figure 8.37)
In this scheme, diversion facilities comprise upstream
and downstream earthfill and rockfill cofferdams and two
24-foot diameter tunnels beneath the south abutment.
A rockfi 11 saddle dam occupies the lower-lying area
beyond the south abutment running from the thrust block
to the higher ground beyond. The impervious fill cut-
off for the saddle dam is founded on bedrock appro xi-
mately 80 feet beneath the existing ground surface. The
maximum height of this dam above the foundation is
approximately 200 feet.
The routed 1:10,000-year design flood of 165,000 cfs is
passed by two spillways. The main spillway is located
on the north abutment. It has a design discharge of
120,000 cfs, and flows are controlled by a three-gated
agee contra 1 structure. This discharges down a con-
crete-1 ined chute and over a 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 Eleva-
tion 925, approximately 35 feet above the river level.
An auxiliary spillway discharging a total of 35,000 cfs
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 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, in con-
junction with the main spillway and auxiliary spillway,
a probable maximum flood of 345,000 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 Susitna River.
The upstream end of the channel is closed by an earth-
fill fuse plug. The plug is designed to be eroded if
overtopped by the reservoir. Since 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 f aci 1 it i es are located on the
north bank of the river, within the bedrock forming the
B-2-55
dam abutment. The rock within this abutment is of bet-
ter quality with fewer shear zones and a lesser degree
of jointing than the rock on the south side of the can-
yon, 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 penstocks for each unit lead to the power-
house.
The powerhouse contains four 150-MW turbine/generator
units. The turbines are Francis type units coupled to
overhead umbrella type generators. The units are ser-
viced by an overhead crane running the length of the
powerhouse and into the end service bay. Offices·, the
control room, switchgear room, ma·intenance room, etc.,
are located beyond the service bay. The transformers
are housed in a separate upstream gallery located above
the lower horizontal section of the penstocks. Two ver-
tical cable shafts connect 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 bifurcations at the tailrace tun-
nels 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
north side of the canyon.
The switchyard is located on the south 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.
Scheme DC2 (Figure B.38)
The layout is genera 11 y simi 1 ar to Scheme DCl except
that the chute spillway is located on the south side of
the canyon. The concrete-1 i ned chute terminates in a
flip bucket high on the south side of the canyon which
drops the discharges into the river below. The design
flow is 120,000 cfs, and discharges are controlled by a
three-gated agee-crested control structure simi 1 ar to
that for Scheme DCl which abuts the south 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.
B-2-56
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'
-i
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( i i)
Scheme DC3 (See Figure B.39)
The 1 ayout is similar to Scheme DC1 except that the
north-side main spillway takes the form of a single
tunnel rather than an open chute. A two-gated ogee-
control structure is located at the head of the tunnel
and discharges into an inclined shaft 45 feet in
diameter at its upper end. The structure will discharge
up to a maximum of 120,000 cfs.
The concrete-lined tunnel narrows to 35 feet in 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 spillway is excavated on the south
abutment.
The layout of dams and power facilities are the same as
for Scheme DC1.
-Scheme DC4 (See Figure B.40)
The dam, power facilities, and saddle dam for this
scheme are the same as those for Scheme DC1. The major
difference is the substitution of a stilling basin type
spillway on the north bank for the chute and flip buck-
et. A 3-gated ogee control structure is located at the
end of the d~n thrust block and controls the discharges
up to a maximum of 120,000 cfs.
The concrete-lined chute is built into the face of the
canyon and discharges into a 500-foot 1 ong by 115-foot
wide by 100-foot high concrete stilling basin formed
below river level and deep within the north side of the
canyon. Central orifices in the dam and the south bank
rock channel and fuse plug form the auxiliary and emer-
gency spillways, respectively, as in the other alterna-
tive schemes.
The downstream cofferdam is 1 ocated beyond the stilling
basin and the diversion tunnel outlets are located far-
ther downstream to enable construction of the stilling
basin.
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 com-
parison of the spillway facilities.
B-2-57
As can be seen from a comparison of the costs in Tab 1 e
B.35, the flip bucket spillways are substantially less
costly to construct than the stilling basin type of Scheme
OC4. The south-side spillway of Scheme DC2 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 l anger period of operation, scour of the heavily
jointed rock could cause undermining of the canyon sides
and their subsequent instability. The possibility also
exists of deposition of material in the downstream riverbed
with a corresponding elevation of the tailrace. Construc-
tion of a spillway on the steep south side of the river
could be more difficult than on the north side because of
the presence of deep fissures and large unstable blocks of
rock which are present on the south side close to the top
of the canyon.
The two north-side flip bucket spill way schemes, based on
either an open chute or a tunnel, take advantage of a down-
stream bend in the river to discharge parallel to the
course of the river. This will reduce the effects of ero-
sion but could still present a problem if the estimated
maximum possible scour hole would occur.
The tunnel type spillway could prove difficult to construct
because of the large diameter inclined shaft and tunnel
paralleling the bedding planes. The high velocities en-
countered in the tunnel spillway could cause problems with
the possibility of spiraling flows and severe cavitation
both occurring.
The stilling basin type spillway of Scheme DC4 reduces
downstream erosion problems within the canyon. However,
cavitation could be a problem under the high flow veloci-
ties experienced at the base of the chute. This would be
somewhat alleviated by aeration of the flows. There is,
however, l itt 1 e precedent for stilling basin operation at
heads of over 500 feet; even where floods of much less than
the design capacity have been discharged, severe damage has
occurred.
(iii} Selection of Final Scheme
The chute and flip bucket spillway of Scheme DC2 could gen-
erate downstream erosion problems which could require con-
siderable maintenance costs and cause reduced efficiency in
operation of the. project at a future date. Hydraulic de-
sign problems exist with Scheme DC3 which may also have
B-2-58
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,r-:-
,....
l
r
-I
severe cavitation problems. Also, there is no cost advan-
tage in Scheme DC3 over the open chute Scheme DC1. In
Scheme DC4, the operating characteristics of a high head
stilling basin are little known, and there are few examples
of successful operation. Scheme DC4 also costs consider-
ably more than any other scheme (Table B.35).
All spillways operating at the required heads and dis-
charges 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 reasonable approach to
reduce erosion and eliminate nitrogen supersaturation prob-
lems 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 S-cheme DC4, and since the 1 atter offers no relative
operational advantage, Scheme DC1 has been selected for
further study as the selected scheme.
Subsequent to the adoption of this scheme, minor modifica-
tions to the design criteria were made as presented in
Exhibit F.
(d) Final Review
The layout selected in the previous section was further developed
in accordance with updated engineering studies and criteria. The
major change compared to Scheme DC1 is the elimination of the high-
level gated orifices and introduction of low-level fixed-cone
valves, but other modifications that were introduced are described
below.
The revised layout is shown on Figure B.41. A description of the
structures is as.follows.
( i) Main Dam
( i i )
The maximum operating level of the reservoir was raised to
Elevation 1455 in accordance with updated information rela-
tive to the Watana tailwater level. This requires raising
the dam crest to Elevation 1463 with the concrete parapet
wall crest at Elevation 1466. The saddle dam was raised to
Elevation 1472.
Spillways and Outlet Facilities
To eliminate the potential for nitrogen supersaturation
problems, the outlet facilities were designed to restrict
supersaturated flow to an average recurrence interval of
greater than 50 years. This led to the replacement of the
high-level gated orifice spillway by outlet facilities in-
corporating seven fixed-cone valves, three with a diameter
B-2-59
of 90 inches and four with a diameter of 102 inches,
capable of passing a design flow of 38,500 cfs.
The chute spillway and flip bucket are located on the north
bank, as in Scheme DC1; however, the chute 1 ength was de-
creased and the elevation of the flip bucket raised com-
pared to Scheme DC1.
More recent site surveys indicated that the ground 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.
(iii) Diversion
The previous twin diversion tunnels were replaced by a
single tunnel scheme. This was determined to provide all
necessary security and wi 11 cost approximately one-half as
much as the two tunnel alternative.
(iv) Power Facilities
The drawdown range of the reservoir was reduced, allowing a
reduction in height of the power intake. In order to lo-
cate 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 pow-
er f ac i1 it i es. -
2.6 -Selection of Access Road Corridor
(a) Previous Studies
The potential for hydroelectric power generation within the Sus-
itna basin has been the subject of considerable investigation over
the years as described in Section 1.1 of this exhibit. These
studies produced much information on alternative development plans
but little on the question of access.
The first report to incorporate an access plan was that of the
Corps of Engineers in 1975. The proposed plan consisted of a 24-
foot wide road with a design speed of 30 miles per hour that con-
nected with the Parks Highway near Chulitna Station, paralleled
the Alaska Railroad south and east to a crossing of the Susitna
River, then proceeded up the south side of the river to Devil Can-
yon. The road continued on the south side of the Susitna River to
Watana, passing by the north end of Stephan Lake and the west end
of the Fog Lakes. In addition, a railhead facility was to be con-
structed at Gold Creek. This plan is similar to one of the selec-
ted alternative plans, Plan 16 {South), discussed later in this
section.
B-2-60
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(b)
-
(c)
-
F
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-
Other studies concerning the Susitna Hydroelectric Project men-
tioned access only in passing and did not involve the development
of an access plan.
Selection Process Constraints
Throughout the development, evaluation and selection of the access
plans, the foremost objective has been to provide a transportation
system that would support construction activities and allow for
the orderly development and maintenance of site facilities.
Meeting this fundamental objective involved the consideration not
only of economics and technical ease of development, but also many
other diverse factors. Of prime importance was the potential for
impacts to the environment, namely impacts to the local fish and
game populations. In addition, since the Native villages and the
Cook Inlet Region will eventually acquire surface and subsurface
rights, their interests were recognized and taken into account as
were those of the local communities and general public.
With so many different factors influencing the choice of an access
plan, it is evident that no one plan will satisfy all interests.
The aim during the selection process has been to consider all fac-
tors in their proper perspective and produce a plan that repre-
sents the most favorable solution to meeting both project-related
goals and minimizing impacts to the environment and surrounding
communities.
Corridor Identification and Selection
Three general corridors were identified leading from the existing
transportation network to the damsites. This network consists of
the Parks Highway and the Alaska Railroad to the west of the dam-
sites and the Denali Highway to the north. The three general cor-
ridors are identified in Figure B.42.
Corridor 1 From the Parks Highway to the Watana dams ite via the
north side of the Susitna River.
Corri dar 2 -From the Parks Highway to the Watana dams i te via the
south side of the Susitna River.
Corridor 3 -From the Denali Highway to the Watana dams it e.
The access road studies identified a total of eighteen alternative
plans within the three corridors. The alternatives were developed
by laying out routes on topographical maps in accordance with
accepted road and rail design criteria. Subsequent field investi-
gations resulted in minor modifications to reduce environmental
impacts and improve alignment.
B-2-61
(d) Development of Plans
At the beginning of the study a plan formulation and initial sel-
ection process was developed. The criteria that most significant-
ly affected the selection process were identified as:
1\lli nimi zing impacts to the environment;
Minimizing total project costs;
Providing transportation flexibility to minimize
construction risks;
Providing ease of operation and maintenance; and
Pre-construction of a pioneer road.
During evaluation of the access plans, input from the public agen-
cies and Native organizations was sought and their response resul-
ted in an expansion of the original list of eight alternative
plans to eleven. These studies culminated in the production of
the Access Route Selection Report (Acres l982b) which recommended
Plan 5 as the route which most closely satisfied the selection
criteria. Plan 5 starts from the Parks Highway near Hurricane and
traverses southeast along the Indian River to Gold Creek. From
Gold Creek the road continues east on the south side of the Susit-
na River to the Devil Canyon damsite, crosses a low-level bridge
and continues east on the north side of the Susitna River to the
Watana damsite. For the project to remain on schedule it would
have been necessary to construct a pioneer road along this route
prior to the FERC license being issued.
In March of 1982 the Alaska Power Authorfty (APA) presented the
results of the Susitna Hydroelectric Feasibi 1 ity Report (Acres
1982c), of which access Plan 5 was a part, to the public, agencies
and organizations. During April, comment was obtained from these
groups relative to the feasibility study. As a result of these
comments, the pioneer road concept was eliminated, the evaluation
criteria were refined, and six additional access alternatives were
developed.
During the evaluation process the APA formulated an additional
plan, thus increasing the total number of plans under evaluation
to eighteen. This subsequently became the plan recommended by APA
staff to the APA Board of Directors, and was formally adopted as
the Proposed Access Plan in September 1982.
(e) Evaluation of Plans
The refined criteria used to evaluate the eighteen alternative
access plans were:
No pre-license construction
Minimize environmental impacts
Minimize construction duration
Provide access between sites during project operation phase
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Provide access flexibility to ensure project is brought on
line within budget and schedule
Minimize total cost of access
l"'inimize initial investment required to provide access to
the Watana damsite
Minimize risks to project schedule
Accommodate current land uses and plans
-Accommodate agency preferences
Accommodate preferences of Native organizations
Accommodate preferences of local communities
Accommodate public concerns
All eighteen plans were evaluated using these refined criteria to
determine the most responsive access p 1 an in each of the three
basic corridors.
To meet the overall project schedule requirements for the Watana
development, it is necessary to secure initial access to the
Watana damsite within one year of the FERC license being issued.
The constraint of no pre-license construction resulted in the
elimination of any plan in which initial access could not be
completed within one year. This constraint eliminated six plans
(plans 2, 5, 8, 9, 10, 12) from further consideration.
On completion of both the Watana and Devil Canyon Dams it· is
planned to operate and maintain both sites from one central loca-
tion, Watana. To facilitate these operation and maintenance ac-
tivites, access plans with a road connection between the sites
were considered superior to those plans without a road connection.
Plans 3 and 4 do not have access between the sites and were
discarded.
The abi 1 ity to make full use of both rai 1 and road systems from
southcentral ports of entry to the railhead facility provides the
project management with far greater flexibility to meet contingen-
cies, and control costs and schedule. Limited access plans utili-
zing an all-rail or rail-link system with no road connection to an
existing highway have less flexibility and would impose a re-
straint on project operation that could result in delays and sig-
nificant increases in cost. Four plans with limited access (plans
8, 9, 10 and 15) were eliminated because of this constraint.
Residents of the Indian River and Gold Creek communities are gen-
erally not in favor of a road access near their communities. Plan
1 was discarded because plans 13 and 14 achieve the same objec-
tives without impacting the Indian River and Gold Creek areas.
B-2-63
Plan 7 was eliminated because it includes a circuit route connec-
ting to both the George Parks and Denali Highways. This circuit
route was considered unacceptable by the resource agencies since
it aggravated the control of public access.
The seven remaining plans found to meet the selection criteria
were plans 6, 11, 13, 14, 16, 17 and 18. Of these plans, plans
13, 16 and 18 in the North, South, and Denali corridors, respec-
tively, were selected as being the most responsive plan in each
corridor. The three plans are described below and the route loca-
tions shown in Figures B.43 through B.45.
(i) Plan 13 'North' (see Figure B.43)
This plan utilizes a roadway from a railhead facility adja-
cent to the George Parks Highway at Hurricane to the Watana
damsite following the north side of the Susitna River. A
spur road, seven miles in length, would be constructed at a
later date to service the Devil Canyon development. This
route is mountainous and includes terrain at high eleva-
tions. In addition, extensive sidehill cutting in the
region of Portage Creek wi 11 be necessary; however, con-
struction of the road would not be as difficult as plan
16.
(ii) Plan 16 'South' (see Figure B.44)
This route generally parallels the Susitna River, travel-
ing west to east from a railhead at Gold Creek to the Devil
Canyon damsite, and continues following a southerly loop to
the Watana damsite. Twelve miles downstream of the Watana
damsite a temporary low-level crossing across the Susitna
River wil be used until completion of a permanent bridge.
A connecting road from the George Parks Highway to Devi 1
Canyon with a major high-level bridge across the Susitna
River is necessary to provide full road access to either
site. The topography from Devil Canyon to Watana is moun-
tainous and the route involves the most difficult construc-
tion of the three plans, requiring a number of sidehill
cuts and the construction of two major bridges. To provide
initial access to the Watana damsite this route presents
the most difficult construction problems of the three
routes and has the highest potential for schedule delays
and related cost increases.
(iii) Plan 18 'Denali-North' (see Figure B.45)
This route originates at a railhead in Cantwell, utilizing
the existing Denali Highway to a point 21 miles east of the
junction of the George Parks and Denali Highways. A new
road will be constructed from this point due south to the
Watana damsite. The majority of the new road will traverse
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(f)
relatively flat terrain which will allow construction using
side borrow techniques, resulting in a minimum of distur-
bance to areas away from the alignment. This is the most
easily constructed route for initial access to the Watana
site. Access to the Devil Canyon development will consist
primarily of a railroad extension from the existing Alaska
Railroad at Gold Creek to a railhead facility adjacent to
the De vi 1 Canyon camp area. To provide access to the
Watana damsite and the existing highway system, a connec-
ting road will be constructed from the Devil Canyon rail-
head following a northerly loop to the Watana damsite.
Access to the north side of the Sus itna River wi 11 be
attained via a high-level suspension bridge constructed
approximately one mile downstream of the Devil Canyon Dam.
In general the alignment crosses terrain with gentle to
moderate slopes which will allow roadbed construction with-
out deep cuts.
Comparison of the Selected Alternative Plans
To determine which access plan best accommodates both project-
related goals and the concerns of the resource agencies, Native
organizations and affected communitites, the three selected alter-
native plans were subjected to a multi-disciplinary evaluation and
comparison. The key issues addressed in this evaluation and com-
parison were:
( i ) Costs
For the deve 1 opment of access to the Watana site, the
Denali-North Plan has the least cost and the lowest
probabi 1 ity of increased costs resulting from unforeseen
conditions. The North Plan is ranked second. The North
Plan has the lowest overall cost while the Denali-North has
the highest. However, a large portion of the cost of the
Denali-North Plan would be incurred more than a decade in
the future. When converting costs to equivalent present
value, the overall costs of the Denali-North and the South
Plans are approximately equal. The costs of the three
alternative plans can be summarized as follows:
Estimated Total Cost ($ x 106)
Plan Watana Devil Canyon Total Discounted Total
North ( 13) 241
South (16) 312
Denali-North (18) 224
127
104
213
368
416
437
287
335
326
The costs are in terms of 1982 dollars and include all
costs associated with design, construction, maintenance and
logistics.
8-2-65
(ii) Schedule
The schedule for providing initial access to the Watana
site was given prime consideration since the cost ramifica-
tions of a schedule delay are highly significant. The eli-
mination of pre-license construction of a pioneer access
road has resulted in the compression of on-site construc-
tion activities in the 1985-86 period. With the present
overall project scheduling, should diversion not be comple-
ted prior to spring runoff in 1987, dam foundation prepara-
tion work will be delayed one year, and hence cause a delay
to the overall project of one year. It has been estimated
that the resultant increase in cost would likely be in the
range of 100-200 million dollars. The access route that
assures the quickest completion and hence the earliest
delivery of equipment and material to the site has a dis-
tinct advantage. The forecasted construction period, in-
cluding mobilization, for the three plans is:
Dena 1 i -North
North
South
6 months
9 months
12 months
It is evident that, with the Denali-North Plan, site activ-
ities can be supported at an earlier date than by either of
the other routes. Consequently the Denali-North Plan
offers the highest probab·ility of meeting schedule and
hence the least risk of project delay and increase in cost.
The schedule for access in relation to diversion is shown
for the three plans in Figure 8.46.
(iii) Environmental Issues
Outlined below are the key environmental impacts which have
been identified for the three routes. The specific mitiga-
tion measures necessary to avoid, minimize or compensate
for these impacts are discussed in Exhibit E.
Wildlife and Habitat
The three selected alternative access routes are made up
of five distinct wildlife and habitat segments:
1. Hurricane to Devil Canyon: This segment is composed
almost entirely of productive mixed forest, ripar-
ian, and wetlands habitats important to moose, fur-
bearers, and birds. It includes three areas where
slopes of over 30 percent will require side hill
cuts, all above wetland zones vulnerable to erosion-
related impacts.
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2. Go 1 d Creek to Devil Canyon: This segment is com-
posed of mixed forest and wetland habitats, but
includes less wetland habitat and fewer wetland hab-
itat types than the Hurricane to Devil Canyon seg-
ment. Although this segment contains habit at suit-
able for moose, black bears, furbearers and birds,
it has the least potential for adverse impacts to
wildlife of the five segments considered.
3. Devil Canyon to Watana (North Side): The following
comments apply to both the Denali -North and North
routes. This segment traverses a varied mixture of
forest, shrub, and tundra habitat types, generally
of medi um-to-1 ow productivity as wildlife habitat.
It crosses the De vi 1 s and Tsusena Creek drainages
and passes by Swimming Bear Lake which contains hab-
itat suitable for furbearers.
4. Devil Canyon to Watana (South Side): This segment
is highly varied with respect to habitat types, con-
taining complex mixtures of forest, shrub, tundra,
wetlands, and riparian vegetation. The western por-
tion is mostly tundra and shrub, with forest and
wetlands occurring along the eastern portion in the
vicinity of Prairie Creek, Stephan Lake, and Tsusena
and Deadman Creeks. Prairie Creek supports a high
concentration of brown bears and the lower Tsusena
and Deadman Creek areas support 1 i ght 1 y hunted con-
centrations of moose and black bears. The Stephan
Lake area supports high densities of moose a~d
bears. Access development in this segment waul d
probably result in habitat loss' or alteration,
increased hunting and human-bear conflicts.
5. Denali Highway to Watana: This segment is primarily
composed of shrub and tundra vegetation types, with
1 itt 1 e productive forest habitat present. Although
habitat diversity is relatively low along this seg-
ment, the southern portion along Deadman Creek con-
tains an important brown bear concentration and
browse for moose. This segment crosses a peripheral
portion of the range of the Nel china caribou herd
and there is evidence that, as herd size increases,
caribou are likely to migrate across the route and
calve in the vicinity. Although it is not possible
to predict with any certainty how the physical pres-
ence of the road itself or traffic will affect cari-
bou movements, population size or productivity, it
is likely that a variety of site-specific mitigation
measures will be necessary to protect the herd.
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The three access plans are made up of the following com-
binations of route segments:
North
South
Denali-North
Segments 1 and 3
Segments 1, 2, and 4
Segments 2, 3, and 5
The North route has the least potential for creating
adverse impacts to wildlife and habitat, for it travers-
es or approaches the fewest areas of productive habitat
and zones of species concentration or movement. The
wildlife impacts of the South Plan can be expected to be
greater than those of the North Plan due to the proxim-
ity of the route to Prairie Creek, Stephan Lake and the
Fog Lakes, which currently support high densities of
moose and black and brown bears. In particular, Prairie
Creek supports what may be the highest concentration of
brown bears in the Susitna basin. Although the Denali-
North Plan has the potential for disturbances of
caribou, brown bear and black bear concentrations and
movement zones, it is considered that the potential for
adverse impacts with the South Plan is greater.
Fisheries
All three alternative routes would have direct and indi-
rect impacts on the fisheries. Direct impacts include
the effects on water quality and aquatic habitat whereas
increased angling pressure is an indirect impact. A
qualitative comparison of the fishery impacts related to
the alternative plans was undertaken. The parameters
used to assess impacts along each route included: the
number of streams crossed, the number and length of lat-
eral transits (i.e., where the roadway parallels the
streams and runoff from the roadway can run directly
into the stream), the number of watersheds affected, and
the presence of resident and anadromous fish.
The three access plan alternatives incorporate combina-
tions of seven distinct fishery segments~
1. Hurricane to Dev i1 Canyon: Seven stream crossings
will b~ required along this route, including Indian
River which is an important salmon spawning river.
Both the Chulitna River watershed and the Sus itna
River watershed are affected by this route. The
increased access to Indian River will be an impor-
tant indirect impact to the segment. Approximately
1.8 miles of cuts into banks greater than 30 degrees
occur along this route requiring erosion control
measures to preserve the water quality and aquatic
habitat.
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2. Gold Creek to Devil Canyon: This segment crosses
six streams and is expected to have minimal direct
and indirect impacts. Anadromous fish spawning is
1 ikely in some streams but impacts are expected to
be minimal. Approximately 2.5 miles of cuts into
banks greater than 30 degrees occur in this section.
In the Denali-North Plan, this segment would be
railroad whereas in the South Plan it would be
road.
3. Devil Canyon to Watana (North Side, North Plan):
This segment crosses twenty streams and 1 aterally
transits four rivers for a total distance of approx-
imately 12 miles. Seven miles of this lateral
transit parallels Portage Creek which is an impor-
tant salmon spawning area.
4. Devil Canyon to Watana (North Side, Denali-North
Plan): The difference between this segment and seg-
ment 3 described above is that it avoids Portage
Creek by traversing through a pass 4 mi 1 es to the
east. The number of streams crossed is consequently
reduced to twelve, and the number of lateral trans-
its is reduced to two with a total distance of 4
miles.
5. Devil Canyon to Watana {South Side): The portion
between the Susitna River crossing and Devil Canyon
requires nine steam crossings, but it is unlikely
that these contain significant fish populations.
The portion of this segment from Watana to the
Susitna River is not expected to have any major
direct impacts; however, increased angling pressure
in the vicinity of Stephan Lake may result due to
the proximity of the access road. The segment
crosses both the Sus itna and the Ta 1 keetna water-
shed. Seven miles of cuts into banks of greater
than 30 degrees occur in this segment.
6. Denali Highway to Watana: The segment from the
Denali Highway to the Watana damsite has· twenty-two
stream crossings and passes from the Nenana into the
Susitna watershed. Much of the route crosses or is
in proximity to seasonal grayling habitat and runs
parallel to Deadman Creek for nearly 10 miles. If
recruitment and growth rates are low along this seg-
ment, it is unlikely that resident populations could
sustain heavy fishing pressure. Hence, this segment
has a high potential for impacting the local gray-
ling population.
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7. Denali Highway: The Denali Highway from Cantwell to
the Watana access turnoff will require upgrading.
The upgrading will involve only minor realignment
and negligible alteration to present stream cross-
ings. The segment crosses eleven streams and later-
ally transits two rivers for a total distance of 5
miles. There is no anadromous fish spawning in this
segment and little direct or indirect impact is ex-
pected.
The three alternative access routes are comprised of the
following segments:
North
South
Denali-North
Segments 1 and 3
Segments 1, 2, and 5
Segments 2, 4, 6 and 7
The Denali-North Plan is likely to have a significant
direct and indirect impact on grayling fisheries given the
number of stream crossings, lateral transits, and watershed
affected. Anadromous fisheries impact will be minimal and
will only be significant along the railroad spur between
Gold Creek and Devil Canyon.
The South Plan is likely to create significant direct and
indirect impacts at Indian River, which is an important
salmon spawning river. Anadromous fisheries impacts will
also occur in the Gold Creek to Devil Canyon segment as for
the Denali-North Plan. In addition, indirect impacts may
occur in the Stephan Lake area.
The North Plan, like the South Plan, may impact salmon
spawning activity in Indian River. Significant impacts are
1 i kely along Portage Creek due to water quality impacts
through increased erosion and due to indirect impacts such
as increased angling pressure.
With any of the selected plans, direct and indirect effects
can be minimized through proper engineering design and
prudent management. Criteria for the development of borrow
areas and the design of bridges and culverts for the pro-
posed access plan together with mitigation recommendations
are discussed in Exhibit E.
(iv) Cultural Resources
A level-one cultural resources survey was conducted over a
large portion of the three access plans. The segment of
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(v)
the Denali-North Plan between the Watana damsite and the
Denali Highway traverses an area of high potential for cul-
tural resource sites. Treeless areas along this segment
lack appreciable soil deposition, making cultural resources
visible and more vulnerable to secondary impacts. Common
to both the Denali-North and the North Plans is the segment
on the north side of the Susitna River from the Watana dam-
site to where the road parallels Devils Creek. This seg-
ment is also largely treeless making it highly vulnerable
to secondary impacts. The South Plan traverses 1 ess ter-
rain of archaeological importance than either of the other
two routes. Several sites exist along the southerly Devil
Canyon to Watana segment; however, since much of the route
is forested, these sites are less vulnerable to secondary
impacts.
The ranking from the least to the highest with regard to
cultural resources impacts is South, North, Denali-North.
However, impacts to cultural resources can be fully mitiga-
ted by avoidance, protection or salvage; consequently, this
issue was not critical to the selection process.
,,
Socioeconomics
Socioeconomic impacts on the Mat-Su Borough as a who 1 e
would be similar in magnitude for all three plans. How-
ever, each of the three plans affects future socioeconomic
conditions in differing degrees in certain areas and commu-
nities. The important differences affecting specific com-
munities are outlined below.
Cantwell: The Denali-North Plan would create signifi-
cant increases in population, local employment, business
activity, housing and traffic. These impacts result
because a railhead facility would be located at Cantwell
and because Cantwell would be the nearest community to
the Watana damsite. Both the North and South Plans
would impact Cantwell to a far lesser extent.
Hurricane: The North Plan would significantly impact
the Hurricane area since currently there is little popu-
lation, employment, business activity or housing. Chan-
ges in socioeconomic indicators for Hurricane would be
less under the South Plan and considerably less under
the Denali-North Plan.
B-2-71
Trapper Creek and Talkeetna: Trapper Creek would exper-
ience slightly larger changes in economic indicators
with the North Plan than under the South or Denali-North
Plans. The South Plan would impact the Talkeetna area
slightly more than the other two plans.
Gold Creek: With the South Plan, a railhead facility
would be developed at Gold Creek creating a significant
increase in socioeconomic indicators in this area. The
Denali-North Plan includes construction of a railhead
facility at the Devil Canyon site, which would create
impacts at Gold Creek, but not to the same extent as the
South Plan. Minimal impacts would result in Gold Creek
under the North Plan.
The affected public•s responses to these potential changes
are mixed. The people of Cantwell are generally in favor
of some economic stimulus and development in their commu-
nity. Residents of Trapper Creek and Talkeetna have indi-
cated that rapid, uncontrolled change is not desired. This
and other feedback to date indicates that the Denali-North
Plan will come closest to creating socioeconomic changes
that are acceptable to or desired by landholders and resi-
dents in the potentially impacted areas and communities.
(vi) Preferences of Native Organizations
The Tyonek Native Corporation, Cook Inlet Region Inc.
(CIRI) and the CIRI Village residents all prefer the South
Plan since it provides full road access to their lands
south of the Susitna River. The Ahtna Native Region Cor-
poration and the Cantwell Village Corporation support the
Denali-North Plan. None of the Native organizations sup-
ports the North Plan.
(vii) Relationship to Current Land Stewardships, Uses and Plans
Much of the land required for project development has been
or may be conveyed to Native organizations. The remaining
1 ands are generally under state and federal control. The
South Plan traverses more Native-selected lands than either
of the other two routes; and, although present land use is
low, the Native organizations have expressed an interest in
potentially developing their lands for mining, recreation,
forestry or residential use.
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The other land management plans that have a large bearing
on access deve 1 opment are the Bureau of Land Management • s
(BLM) recent decision to open the Denali Planning Block to
mjneral exploration, and the Denali Scenic Highway Study
being initiated by the Alaska Land Use Council. The Denali
Highway to Deadman Mountain segment of the Denali-North
Plan would be compatible with BLM's plans. During the con-
struction phase of the project the Denali-North Plan could
create conflicts with the development of a Denali Scenic
Highway; however, after construction, the access road and
project facilities could be incorporated into the overall
Scenic Highway planning.
By providing public access to a now relatively inaccess-
ible, semi-wilderness area, conflict may be imposed with
wildlife habitats necessitating an increased level of wild-
1 ife and people management by the various resource agen-
cies.
In general, however, none of the plans will be in major
conflict with any present federal, borough or Native man-
agement plans.
(g) Summary
In reaching the decision as to which of the three alternative
access plans would be recommended, it was necessary to evaluate
the highly complex interplay that exists between the many issues
involved. Analysis of the key issues indicates that no one plan
satisfied all the selection criteria nor accommodated all the con-
cerns of the resource agencies, Native organizations and the pub-
lic. Therefore, it was necessary to make a rational assessment of
trade-offs between the sometimes conflicting environmental
concerns of. impacts on fisheries, wildlife, socioeconomics, land
use and recreational opportunities on the one hand, with project
cost, schedule, construction risk and management needs on the
other. With all these factors in mind, it should be emphasized
that the primary purpose of access is to provide and maintain an
uninterrupted flow of materials and personnel to the damsite
throughout the 1 ife of the project. Should this fundamental
objective not be achieved, significant schedule and budget
overruns will occur.
(h) Final Selection of Plan
(i) Elimination of •south Plan•
The South route, Plan 16, was eliminated primarily because
of the construction difficulties associated with building a
major low-level crossing 12 miles downstream of the Watana
damsite. This crossing would consist of a floating or
B-2-73
fixed temporary bridge which would need to be removed prior
to spring breakup during the first three years of the proj-
ect (the time estimated for completion of the permanent
bridge). This would result in a serious interruption in
the flow of materials to the site. Another drawback is
that floating bridges require continual maintenance and are
generally subject to more weight and dimensional limita-
tions than permanent structures.
A further limitation of this route is that for tne first
three years of the project all construction work must be
supported solely from the railhead faGility at Gold Creek.
This problem arises because it will take an estimated three
years to complete construction of the connecting road
across the Susitna River at Devil Canyon to Hurricane on
the George Parks Highway. Limited access such as this does
not provide the flexibility needed by the project manage-
ment to meet contingencies and control costs and schedule.
Delays in the supply of materials to the damsite, caused by
either an interruption of service of the railway system or
the Susitna River not being passable during spring breakup,
could result in significant cost impacts. These factors,
together with the realization that the South Plan offers no
specific advantages over the other two plans in any of the
areas of environmental or social concern, led to the South
Plan being eliminated from further consideration.
(ii) Schedule Constraints
The choice of an access plan thus narrowed down to the
North and Denali-North plans. Of the many issues addressed
during the evaluation process, the issue of 11 SChedule" and
11 Schedule risk" was determined to be the most important in
the final selection of the recommended plan.
Schedule plays an extremely important role in the evalua-
tion process because of the special set of conditions that
exist in a sub-arctic environment. Building roads in these
regions involves the consideration of many factors not
found in other environments . Specifically, the chief con-
cern is one of weather, and the consequent short duration
of the construction season. The roads for both the North
and Denali -North Plans wi 11, for the most part, be con-
structed at elevations in excess of 3000 feet. At these
elevations the likely time available for uninterrupted con-
struction in a typical year is 5 months, and at most 6
months.
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The forecasted construction period including mobilization
is 6 months for the Denali-North Plan and 9 months for the
North. At first glance a difference in schedule of 3
months does not seem great; however, when considering that
only 6 months of the year are available for construction,
the additional 3 months become highly significant.
If diversion is not achieved prior to spring runoff in
1987, dam foundation preparation work will be delayed one
year, and hence cause a delay to the overall project of one
year.
Cost Impacts
The increase in costs resulting from a one-year delay have
been estimated to be in the range of 100-200 million dol-
lars. This increase includes the financial cost of invest-
ment by spring of 1987, the financial costs of rescheduling
work for a one-year delay, and replacement power costs.
( i v ) Summary
(v)
(vi)
The Denali-North Plan has the highest probability of meet-
ing schedule and least risk of increase in project cost for
two reasons. First it has the shortest construction sched-
ule (six months). Second, a passable route could be con-
structed even under winter conditions due to the relatively
flat terrain along its length. In contrast the North route
is mountainous and involves extensive sidehill cutting,
especially in the Portage Creek area. Winter construction
along sections such as this would present major problems
and increase the probability of schedule delay.
Plan Recommendation
It is recommended that the Denali -North route be selected
so as to ensure completion of initial access to the Watana
damsite by the end of the first quarter of 1986, for it is
considered that the risk of significant cost overruns is
too high with any other route.
Environmental Concerns -Recommended Plan
The main disadvantage of the Denali-North route is that it
has a higher potential for adverse environmental impacts
than the North route alternative. These impacts have been
identified and, following close consultation with environ-
mental subconsultants, many of the impacted areas have been
avoided both by careful alignment of the road and the
B-2-75
development of design criteria which do not detract from
the semi-wilderness character of the area. Some
environmental impacts and conflicts are unavoidable,
however, and where these impacts occur, specific mitigation
measures have been developed to reduce them to a minimum.
These measures are outlined in detail within the relevant
sections of Exhibit E.
2.7 -Selection of 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
-Dispatch center and communications.
(a) Electric System Studies
Transmission planning criteria were developed to ensure the design
of a reliable and economic electrical power system, with compon-
ents 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 excessive cost. In the interest of economy and long-term sys-
tem performance, these criteria were temporarily relaxed during
the early development stages of the project. Although allowing
for satisfactory operation during early system development, final
system parameters must be based on the ultimate Sus itna poten-
tial .
The criteria are intended to ensure maintenance of rated power
flow to Anchorage and Fairbanks during the outage of any single
line or transformer element. The essential features of the cri-
teria are:
-Total power output of Susitna to be delivered to one or two sta-
tions at Anchorage and one at Fairbanks;
-
11 Breaker-and-a-half 11 switching station arrangements;
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-Overvoltages during line energizing not to exceed specified lim-
its;
-System voltages to be within established 1 imits during normal
operation;
-Power delivered to the loads to be maintained and system volt-
ages to be kept within established limits for system operation
under emergency conditions;
-Transient stability during a 3-phase line fault cleared by
breaker action with no reclosing; and
-Where performance 1 imits are exceeded, the most cost-effective
corrective measures are to be taken.
( i )
( i i )
Existing System Data
Data compiled in a report by Commonwealth Associates Inc.
( 1980) have been used for preliminary transmission system
analysis. Other system data were obtained in the form of
single line diagrams from the various utilities.
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 requirements of this
transmission system are determined by the following fac-
tors:
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 concentrated in the Anchorage urban area. The
second largest load center is Fairbanks. Two small load
centers (Willow and Healy) are located along the Susitna
transmission route. The only other significant load cen-
ters in the Railbelt region are Glennallen and Valdez; how-
ever, 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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Load Area
Anchorage -Cook Inlet
Fairbanks-Tanana Valley
Glennallen -Valdez
Percent of
Total
Railbelt Load
78
20
2
Considering the geographic location and the currently pro-
jected magnitude of the total load in the area, transmis-
sion to Glennallen-Valdez is not likely to be economical in
the foreseeable future. If it is ever to be economical, it
would likely be a direct radial extension, either from Sus-
itna or from Anchorage. In either case, its relative mag-
nitude is too small to have significant influence on either
the viability or development characteristics of the Susitna
project or the transmission from Susitna to the Anchorage
and Fairbanks areas.
Accordingly, it has been assumed for study purposes that
approximately 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
Sus itna 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.
The potential of the Susitna Hydroelectric Project is ex-
pected to be developed in three or four stages as the sys-
tem load grows over the next two decades. The transmission
system must be designed to serve the ultimate Susitna de-
velopment, but staged to provide reliable transmission at
every intermediate stage. Present plans call for three
stages of Susitna development: 680 MW at Watana in January
1994, followed by an additional 340 MW in July 1994 and 600
MW at Devil Canyon in 2002.
Development of other generation resources could alter the
geographic load and generation sharing in the Railbelt,
depending on the location of this development. However,
current studies indicate that no other very large projects
are likely to be develo~ed until the full potential of the
Susitna project is utilized. The proposed transmission
configuration and design should, therefore, be able to sat-
isfy 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 resulting power transfer requirements for the Susitna
transmission system are indicated in Table 8.36.
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Transmission Alternatives
Because of the geographic location of the various centers,
transmission from Sus itna to Anchorage and Fairbanks wi 11
result in a radial system configuration. This allows sig-
nificant freedom in the choice of transmission voltages,
conductors, and other parameters for the two line sections,
with only 1 imited dependence between them. Transmission
alternatives were developed for each of the two system
areas, including voltage levels, number of circuits re-
quired, and other parameters, to satisfy the necessary
transmission requirements of each area.
To maintain a consistency with standard ANSI voltages used
in other parts of the United States, t~e following voltages
were considered for Susitna transmission:
o Watana to Devil Canyon and
on to Anchorage:
o Devil Canyon to Fairbanks:
Susitna to Anchorage
500 kV or 345 kV
345 kV or 230 kV
Transmission at either of two different voltage levels
(345 kV or 500 kV) could reasonably provide the necess-
ary power transfer capabi 1 ity over the distance of ap-
proximately 140 mi 1 es between Devil Canyon and Anchor-
age. The required transfer capability of 1377 MW is 85
percent of the ultimate generating capacity of 1620 MW.
At 500 kV, two circuits would provide more than adequate
capacity. At 345 kV, either three circuits uncompensa-
ted or two circuits with series compensation are re-
quired to provide the necessary reliability for the
single contingency outage criterion. At lower voltages,
an excessive number of parallel circuits are required,
while above 500 kV, two circuits are still needed to
provide service in the event of a line outage.
Susitna to Fairbanks
Applying the same reasoning used in choosing the trans-
mission alternatives to Anchorage, two circuits of eith-
er 230 kV or 345 kV were chosen for the section from
Devil Canyon to Fairbanks. The 230 kV alternative re-
quires series compensation to satisfy the planning cri-
teria in case of a line outage.
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-Total System Alternatives
The transmission section alternatives mentioned above
were combined into five realistic total system alterna-
tives. Three of the five alternatives have different
voltages for the two sections. The principal parameters
of the five transmission system alternatives analyzed in
detail are as follows:
Sus itna to Anchorage Susitna to Fairbanks
Number of Number of
Alternative Circuits Voltage Circuits voltar (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
energizing, 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 alterna-
tive. All five transmission alternatives were found to
have acceptable performance characteristics. The most
significant difference was that single-voltage systems
(345 kV, Alternatives 1 and 2) and systems without ser-
ies compensation (Alternative 2) offered reduced com-
plexity of design and operation and therefore were like-
1 y to be marg ina 11 y more re 1 i ab 1 e. The present worth
life cycle costs of Alternatives 1 through 4 were all
within 1 percent of each other. Only the cost of the
500/230 kV scheme (Alternative 5) was 14 percent above
the others. A summary of the life cycle cost analyses
for the various alternatives is shown in Table B.37.
A technical and economic comparison was also carried out
to determine possible advantages and disadvantages of
HVDC transmission, as compared to an ac system, for
transmitting Sus itna power to Anchorage and Fairbanks.
HVDC transmission was found to be technically and
operationally more complex as well as having higher life
c yc 1 e cost s .
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{iv} Configuration at Generation and Load Centers
Interconnect ions between generation and load centers and
the transmission system were developed after reviewing the
existing system configurations at both Anchorage and Fair-
banks as well as the possibilities and current development
plans in the Susitna, Anchorage, Fairbanks, Willow, and
He a 1 y areas.
-Susitna Configuration
Preliminary development plans indicated that the first
project to be constructed would be Watana with an ini-
tial installed capacity of 680 MW, to be increased to
1020 MW in the second development stage. The next proj-
ect, and the last to be considered in this study, would
be Devil Canyon, with an installed capacity of 600 MW.
-Switching at Willow
Transmission from Susitna to Anchorage is facilitated by
the introduction of an intermediate switching station.
This has the effect of reducing line energizing over-
voltages and reducing the impact of line outages on sys-
tem stability. Willow is a suitable location for this
intermediate switching station; in addition, it would
make it possible to supply local load when this is jus-
tified by development in the area. This local load is
expected to be less than 10 percent of the total Rai 1-
belt area system load, but the availability of an EHV
line tap would definitely facilitate future power sup-
ply.
-Switching at Healy
A switching station at Healy was considered early in the
analysis but was found to be unnecessary to satisfy the
planning criteria. The predicted load at Healy is small
enough to be supplied by local generation and the exist-
ing 138 kV transmission from Fairbanks.
-Anchorage Configuration
Analysis of system configuration, distribution of loads,
and development in the Anchorage area led to the conclu-
sion that a transformer station near Palmer would be of
1 ittle benefit. Most of the major loads are concen-
trated in and around the urban Anchorage area at
B-2-81
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 was chosen
from the following three possible alternatives:
o 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 ships' anchors. which has been the experi-
ence with existing cables. resulting in questionable
transmission reliability.
o 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, ap-
proval for this route is unlikely since overhead
transmission through this developed area is considered
environmentally unacceptable. A longer overland route
around the developed area is considered unacceptable
because of the mountainous terrain.
o Submarine Cable Crossin1~ of Knik Arm. In the Area of
Lake Lorraine and Six Mi e Creek
This option. approximately parallel to the new 230 kV
cable under construction for Chugach Electric Associa-
tion (CEA), includes some 3 to 4 miles of submarine
caDTe 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 transmis-
sion link. and one that does not have to cross envi-
ronmentally sensitive conservation areas.
The third alternative is clearly the best of the three
options.
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 cir-
cuits 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 construc-
tion and operation as a result of poor access.
8-2-82
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Fairbanks Configuration
Susitna power for
be delivered to a
located at Ester.
consideration.
the Fairbanks area is recommended to
single EHV/138 kV transformer station
No alternatives were given detailed
(b) Corridor Selection
( i)
( i i)
Methodology
Development of the proposed Susitna project will require a
transmission system to deliver electric power to the Rail-
belt area. The building of the Anchorage to Fairbanks
Intertie system will result in a defined corridor and route
for the Susitna transmission lines between Willow and
Healy. Therefore, three areas require study for corridor
selection: the northern area to connect Healy with Fair-
banks, the central .area to connect the Watana and Devil
Canyon damsites with the Intertie, and the southern area to
connect Willow with Anchorage.
Using the selection criteria discussed below, corridors
three to five miles wide were selected in each of the three
study areas. These corridors were then evaluated to
determine which ones meet the more specific screening
criteria. This screening process resulted in one corridor
in each area being designated as the recommended corridor
for the transmission line.
Selection Criteria
Since the corridors studied range in width from three to
five miles, the base criteria had to be applied in broad
terms. The study also indicated that the criteria listed
for techni ca 1 purposes could reappear in the economic or
environmental classification. The technical criteria were
defined as requirements for the normal and safe performance
of the transmission system and its reliability.
The selection criteria were in three categories: technical,
economic and environmental. The criteria are listed in
Tab 1 e B .38.
(iii) Identification of Corridors
As discussed previously, the Susitna transmission line cor-
ridors studied are located in three geographical areas,
namely:
8-2-83
-The southern study area between Willow and Anchorage
-The central study area between Watana, Devil Canyon, and
the Intertie
-The northern study area between Healy and Fairbanks.
(iv) Description of Corridors
Figures 8.47 through 8.49 portray the corridors evaluated
in the southern, central, and northern study areas, respec-
tively. For purposes of simplification, only the center-
line of the three-to-five-mile wide corridors are shown in
the figures.
In each of the three figures, each corridor under consider-
ation has been identified by the use. of letter symbols.
The various segment intersections and the various segments,
where appropriate, have been designated. Thus, segments in
each of the three study areas can be separately referenced.
Furthermore, the segments are joined together to form cor-
ridors. For example, in the northern study area Corridor
ABC is composed of Segments AB and BC.
The alternative corridors selected for each study area are
described in detai 1 in the following paragraphs. In addi-
tion, Tables 8.39, 8.40 and 8.41 contain detailed environ-
mental data for each corridor segment.
South~rn Study Area
o Corridor One-Willow to Anchorage via Palmer
Corridor ABC•, consisting of Segments AB and sc•, be-
gins at the it~tersection with the Intertie in the
vicinity of Willow. From here, the corridor travels
in a southeasterly direction, crossing wetlands, Wil-
low Creek, and Willow Creek Road before turning
slightly to the southeast following the drainage of
Deception Creek. The topography in the vicinity of
this segment of the corridor is relatively flat to
gently rolling with standing water and tall-growing
vegetation in the vicinity of the creek drainages.
At a point northwest of Bench Lake, the corridor turns
in an easterly direction crossing the southern foot-
hills of the Talkeetna f'lountains. The topography here
is gently to moderately rolling with shrub-to tree-
sized vegetation occurring throughout. As the cor-
ridor approaches the crossing of the Little Susitna
River, it turns and heads southeast again, crossing
the Little Susitna River and Wasilla Fishhook Road.
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Passing near Wolf Lake and Gooding Lake, the corridor
then crosses a secondary road, some agricultural
1 ands, State Route 3, and the Glenn Highway, before
intersecting existing transmission lines south of
Palmer. In the vicinity of the Little Susitna River,
the topography is gently rolling. As the corridor
travels toward Palmer, the land flattens, more lakes
are present, and some agricultural development is oc-
curring. After crossing the Glenn Highway, the corri-
dor passes through a residential area before crossing
the broad floodplain of the Matanuska River.
Just west of Boden burg Butte, the corridor turns due
south through more agricultural land before crossing
the Knik River and eventually connecting with the
Eklutna Power Station. All of the land south of
Palmer is very flat with some agricultural develop-
ment. Just south of Palmer, the propo$ed carr i dor
intersects existing transmissi~n facilities and paral-
lels or replaces them from a point just south of
Palmer, across the river and into the vicinity of the
Eklutna Power House. From here into Anchorage, the
corridor as proposed would parallel existing facili-
ties, crossing near or through the communities of
Eklutna, Peters Creek, Birchwood, and Eagle River by
using one of the two existing transmission line
rights -of -way in this area. The 1 and here is flat to
gently rolling with a great deal ~f residential devel-
opment. This corridor segment is the most easterly of
the three considered in the southern study area and
avoids an underwater crossing of Knik Arm.
o Corridor Two-Willow to Point MacKe.nzie via Red Shirt
La e
Corridor ADFC, consisting of Segments ADF and FC, com-
mences again at the point of intersection with the In-
tertie in the vicinity of Willow but immediately turns
to the southwest, first cross i n·g the rail road, then
the Parks Highway, then Willow Creek just west of Wil-
low. The land in the vicinity of this part of the
segment is very flat, with wetlands dominating the
terrain.
Southwest of Florence Lake, the proposed corridor
turns, crosses Rolly Creek, and heads nearly due
south, passing through extensive wetlands west and
south of Red Shirt Lake. The corridor in this area
parallels existing tractor trails crossing very flat
lands with significant amounts of tall-growing vegeta-
tion in the better drained locations.
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Northwest of Yohn Lake, the corridor segment turns to
the southeast, passing Yohn Lake and My Lake before
crossing the Little Susitna River. Just south of My
Lake, the corridor turns in a generally southerly
direction, passing Middle Lake, and east of Horseshoe
Lake before finally intersecting the existing Beluga
230 kV transmission line at a spot just north of
MacKenzie Point. From here, the corridor parallels
MacKenzie Point's existing transmission facilities
before crossing under Knik Arm to emerge on the east-
erly shore of Knik Arm in the vicinity of Anchorage.
The land in the vicinity of this segment is extremely
flat and very wet, supporting dense stands of tall-
growing vegetation on any of the higher or better
drained areas.
o Corridor Three -Will ow to Point 1'-lacKenzi e vi a Lynx
La e
Corridor AEFC is very similar to and is a derivation
of Corridor ADFC; it consists of Segments AEF and FC.
This corridor also extends to the southwest of Willow.
West of the Parks Highway, however, just north of Wil-
low Lake, this corridor turns and travels southwest of
Willow and east of Long Lake, passing between Honeybee
Lake and Crystal Lake. The corridor then turns south-
eastward to pass through wetlands east of Lynx Lake
and Butterfly Lake before crossing the Little Susitna
River. The land is well developed in this area. It
is very flat and, while it is wet, also supports dense
stands of tall-growing vegetation on the better
drained sites. Corridor Three rejoins Corridor Two at
a point south of My Lake.
Central Study Area
The central study area encompasses a broad area in the
vicinity of the damsites. From Watana, the study area
extends to the north as far as the Denali Highway and to
the south as far as Stephan Lake. From this point west-
ward, the study area encompasses the foothills of the
Alaska Range and, to the south, the footh i 11 s of the
Talkeetna Mountains. Included in this study area are
lands under consideration by the Intertie Project in-
vestigators. The alternative corridors would connect
both Devil Canyon and Watana Dams with the Intertie at
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one of four locations, which are identified in Figure
8.48.
As for the southern study area, individual corridor seg-
ments are listed in the text. This is to aid the reader
both in determining corridor locations in the figures
and in examining the environmental inventory data listed
for each segment in Tables 8.39, 8.40, and 8.41.
o Corri dar One -Watana to Intert i e vi a South Shore,
Susitna River
Corridor ABCD consists of three segments: AB, BC, and
CD. This corridor originates at the Watana damsite
and follows the southern boundary of the river at an
elevation of approximately 2000 feet from Watana to
Devil Canyon. From Devil Canyon, the corridor contin-
ues along the southern shore of the Susitna River at
an elevation of about 1400 feet to the point at which
it connects with the Intertie, assuming the Intertie
follows the railroad corridor. The land surface in
this area is relatively flat, though incised at anum-
ber of locations by tributaries to the Susitna River.
The relatively flat hills are covered by discontinuous
stands of dense, tall-growing vegetation.
o Corridor Two -Watana to Intertie via Stephan Lake
ABECD, the second potential corridor, is essentially a
derivation of Corridor One and is formed by replacing
Segments BC with BEG. Originating at Point B, Corri-
dor Segment BEG leaves the river and generally paral-
lels one of the proposed Watana Dam access road corri-
dors. This corridor extends southwest from the river,
passing near Stephan Lake to a point northwest of Dan-
eka Lake. Here the route turns back to the northwest
and intersects Corridor One at the Devil Canyon dam-
site. The terrain in this area, again, is gently
rolling hills with relatively flat benches. Vegeta-
tion cover ranges from sparse at the higher elevations
to dense a 1 ong the river bottom and a 1 011g gent 1 er
slopes of the Susitna River and its tributaries.
o Corridor Three -Watana to Intert i e vi a North Shore,
Susitna River
Corridor Three (AJCF), located on the north side of
the river, consists of Segments AJ and CF. Starting
at the Watana dams ite, the corridor crosses Tsusena
Creek and heads westerly, following a small drainage
B-2-87
tributary to the Susitna River. Once crossing Devi 1
Creek, the corridor passes north and west of High
Lake.
The corridor stays below an elevation of 3700 feet as
it crosses north of the High Lake area, east of Devil
Creek, on its approach to Devil Canyon. From Devi 1
Canyon, the corridor again extends to the west, cross-
ing Portage Creek and intersecting the Intertie in the
vicinity of Indian River. In the drainages, to eleva-
tions of about 2000 feet, tree heights r.ange to 60
feet. Between Devil Creek and Tsusena Creek, however,
at the higher elevations, very little vegetation grows
taller than 3 feet. Once west of Devil Creek, discon-
tinuous areas of tall-growing vegetation exist.
o Corridor Four -Watana to Intertie via Devil Creek
Pass/East Fork Chulitna River
Another means of connecting the two dam schemes with
the Intertie is to follow Corridor One from Watana to
Devil Canyon and then exit the Devil Canyon project to
the north (ABCJHI). This involves connecting Corridor
Segments AB, BC, CJ, HJ, and HI. With this alterna-
tive, the corridor extends northeast at Devil Canyon
past High Lake to Devil Creek drainage. From there,
it moves northward to a point north of the south boun-
dary of the Fairbanks Meridian. The corridor then
follows the Portage Creek drainage beyond its point of
origin to a site within the Tsusena Creek drainage.
Likewise, it follows the Tsusena Creek drainage to a
point near Jack River, at which point it parallels
this drainage into Caribou Pass. From Car·ibou Pass,
the corridor turns to the west, following the Middle
Fork Chulitna River until meeting the Intertie in the
vicinity of Summit Lake.
While along much of this corridor the route follows
river valleys, the plan also requires crossing high
mountain passes in rugged terrain. This is especially
true in the crossing between Portage Creek and Tsusena
Creek drainages, where elevations of over 4600 feet
are involved. Tall-growing vegetation is restricted
to the lower elevations along the river drainages with
little other than low-growing forbs and shrubs present
at higher elevations.
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o Corridor Five -Watana to Intert i e vi a Stephan Lake
and the East Fork Chulitna River
A variation of Corridor Four, Corridor Five (ABECJHI)
replaces Segment BC with Corridor Segment BEC (of Cor-
ridor Two). This results in a corridor that extends
from the Watana damsite southwesterly to the vicinity ·
of Stephan Lake, and from Stephan Lake into the Devil
Canyon damsite. From De vi 1 Canyon to the Intert i e,
the corridor follows the Devil Creek, Portage Creek,
and Middle Fork Chulitna drainages previously
mentioned. As before, the corridor crosses rolling
terrain throughout the length of the paralleled
drainages, with some confined, higher elevation passes
encountered between Portage Creek and Tsusena Creek.
o Corridor Six -Devil Canyon to the Intertie via
Tsusena Creek/Chulitna River
Another option (CBAHI) for connecting the dam projects
to the Intertie involves connecting Devi 1 Canyon and
Watana along the south shore of the Susitna River via
Corridor Segment CBA, then exiting Watana to the north
on Segments AH and HI along Tsusena 'Creek to follow
this drainage to Caribou Pass. The corridor then con-
tains the previously-described route along the Jack
River and Middle Fork Chulitna until connecting with
the Intertie near Summit Lake. The terrain in this
corridor proposal would be of moderate elevation with
some confined, higher elevation passes between the
drainages of Tsusena Creek and the Jack River.
o Corridor Seven -Devil Canyon to Intertie via Stephan
Lake and Chulitna River
This alternative uses Corridor Six but replaces
ment BC with Segment BEC from Corridor Two.
route would thus be designated CEBAHI. Terrain
tures are as described in Corridors Two and Six.
Seg-
This
fea-
o Corridor Eight Devil Canyon to Intert i e vi a
Deadman/Brushkana Creeks and Denali Hlghway
Yet another option to the previously-described corri-
dors is the interconnection of Devil Canyon with
Watana via Corridor One (Segment CBA), with a segment
then extending from Watana northeasterly along the
Deadman Creek drainage (Segment AG). The segment pro-
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ceeds north of Deadman Lake and Deadman Mountain, then
turns to the west and intersects the Brushkana Creek
drainage. It then fo 11 ows Brushkana Creek north to a
point east of the Kana Bench Mark. This segment of
the corridor would parallel one of the proposed access
roads. From there, the corridor turns west, generally
parallel to the Denali Highway, to the point of inter-
connection with the Intertie in the vicinity of Cant-
well. The area encompasses rolling hills with modest
elevation changes and some forest cover, especially at
the lower elevations.
o Corridor Nine -Devil Canyon to Intertie via Stephan
Lake and Denali Highway
Corridor Nine (CEBAG) is exactly the same as Corridor
Eight with the exception of Corridor Segment BEC, uti-
lized to replace Segment BC. Each combination of seg-
ments has been previously described.
o Corridor Ten -Devil Canyon to Intert i e vi a North
Shore, Susitna River, and Denali Highway
Corridor Ten connects Devil Canyon-Watana with the
Intertie in the vicinity of Cantwell by means of Cor-
ridor Segments CJAG. Segment CJA is part of Corridor
Three and, as such, has been previously described.
Segment AG has a 1 so been described above as part of
Corridor Eight. As noted earlier, the Corridor Ten
terrain consists of mountainous stretches with accom-
panying gently-rolli~g to moderately-rolling hills and
flat plains covered in places with tall-growing vege-
tation.
o Corridor Eleven -Devil Canyon to the Intertie via
Tsusena Creek/Chulitna River
Another northern route connecting De vi 1 Canyon with
Watana is that created by connecting Corridor Segment
CJA (part of Corridor Three) with Segment AHI of Cor-
ridor Six.
o Corridor Twelve -Devil Canyon-Watana to the Intertie
via Devil Creek/Chulitna River
Another route under consideration is Corridor JA-CJHI.
From north to south, this involves a corridor extend-
ing from the Intertie near Summit Lake, heading
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easterly along the Middle Fork Chulitna drainage into
Caribou Pass. From here, it parallels the Jack River
and connects with the Portage Creek-Devil Creek route,
Segment HJ. At point J, 1 ocated in the Devi 1 Creek
drainage east of High Lake, the corridor splits, with
one segment extending westerly to Devil Canyon and the
other extending east to the Watana damsite along pre-
viously-described Corridor Segments JC and JA, respec-
tively. Terrain features of this route have been pre-
viously described.
o Corridor Thirteen -Watana to Devi 1 Canyon vi a South
Shore, Devil Canyon to Intertie via North Shore,
Susitna River
Corridor Segments AB, BC, and CF are combined to form
this corridor. Descriptions of the terrain crossed by
these segments appear in discussions of Corridor One
(ABCD) and Corridor Three (AJCF).
o Corridor Fourteen -Watana to Devil Canyon via North
Shore, Dev1 1 Canyon to Intert1e via South Shore,
Susitna River
This corridor would connect the damsites in the direc-
tionally opposite order of the previous corridor, and
include Corridor Segment AJCD. Again, as parts of
Corridors One and Three, the terrain features of this
corridor have been previously described.
o Corridor Fifteen -Watana to Devil Canyon via Stephan
Lake, Devil Canyon to Intertie via North Shore,
Susitna R1ver -
Corridor Two (ABEC) and Corridor Three (CF) form to
create this study-area corridor. Terrain features
have been presented under the discussions of each of
these two corridors.
Northern Study Area
In the northern study area, four transmission line cor-
ridor options exist for connecting Healy and Fairbanks
(Figure B .49).
o Corridor One -Healy to Fairbanks via Parks Highway
Corridor One (ABC), consisting of Segments AB and BC,
starts in the vicinity of the Healy Power Plant. From
here, the corridor heads northwest, crossing the
B-2-91
existing Golden Valley Electric Association Trans-
mission Lin.e, the railroad, and the Parks Highway
before turn1ng to the north and paralleling this road
to a point due west of Browne. Here, as a result of
terrain features, the corridor turns northeast, cross-
ing the Parks Highway once again as well as the exist-
ing transmission line, the Nenana River, and the rail-
road, and continues northeasterly 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,
first crossing Little Goldstream Creek, then the Parks
Highway just north of the Bonanza Creek Experimental
Forest. Before reaching the drainage of Ohio Creek,
this corridor turns back to the northeast, crossing
the old Parks Highway and heading info the Ester sub-
station west of Fairbanks.
Terrain along this entire corridor segment is r-ela-
tively flat, with the exception of the foothills north
of the Tanana River. Much of the route, especially
that portion between the Nenana and the Tanana River
crossings, is very broad and flat, has standing water
during the summer months and, in some places, is over-
grown by dense stands of tall-growing vegetation.
This corridor segment crosses the foothills northeast
of Nenana, also a heavily-wooded area.
An option to the above (and not shown in the figures),
that of closely paralleling and sharing rights-of-way
with the existing Healy-Fairbanks transmission line,
has been considered. While it is usually attractive
to parallel existing corridors wherever possible, this
option necessitates a great number of road crossings
and 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. These features, in combination,
eliminated this corridor from further evaluation.
o Corridor Two -Healy to Fairbanks via Crossing Wood
1Ver
The second corridor (ABDC) is a variation of Corridor
One and consists of Segments AB and BDC. At point B,
east of the Clear MEWS, instead of turning north, the
corridor continues to the northeast, crossing Fish
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i
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Creek, the Totatlanika River, Tatlanika Creek, the
Wood River, and Crooked Creek before turning to the
north. At a point equidistant from Crooked and Willow
Creeks, the corridor turns north, crosses the Tanana
River east of Hadley Slough, and extends to the Ester
substation. North of the Tanana River, this corridor
segment a 1 so crosses Rose Creek and the Parks High-
way.
Where it diverges from the original corridor, this
corridor traverses extensive areas of flat ground,
with standing water very prevalent throughout the sum-
mer months. Heavily-wooded areas occur in the broad
floodplain of the Tanana River, in the vicinity of the
river crossing, and in the foothills around Rose
Creek.
o Corridor Three -Healy to Fairbanks via Healy Creek
and Japan H1 11 s
Corridor Three (AEDC), consisting of Segments AE and
EDC, exits the Healy Power Plant in an easterly direc-
tion. Instead of proceeding northwest, this corridor,
following its interconnection with the Intertie Proj-
ect, heads east up Healy Creek, passing the Usibelli
Coal Mine. Near the headwaters of Healy Creek, the
corridor cuts to the east, crossing a high pass of ap-
proximately 4700 feet elevation and descending into
the Cody Creek drainage. From Healy to the Cody Creek
drainage, the terrain is relatively gentle but bounded
by very rugged mountain peaks. The elevation gain
from the Healy Power Plant to the pass between the
Healy Creek-Cody Creek drainages is approximately 3300
feet. From here, the segment turns to the northeast,
following the lowlands accompanying the Wood River.
The corridor next parallels the Wood River from the
Anderson Mountain area, past Mystic Mountain, and out
into the broad floodplain of the Tanana River east of
Japan Hills. Near the confluence of Fish Creek and
the Wood River, the corri dar turns north and inter-
sects the north-south portion of Corridor Two (Segment
DC), after first passing through Wood River Buttes.
Much of the area north of Japan Hills is flat and very
wet with stands of dense, tall-growing vegetation.
B-2-93
o Corridor Four -Healy to Fairbanks via Wood River and
Fort Wainwright
Corridor Four (AEF) is a derivation of Corridor Three
and is composed of Segments AE and EF. Point E is lo-
cated just north of Japan Hills along the Wood River.
From here, the corridor deviates from Corridor Three
by running north across the Blair Lake Air Force
Range, Fort Wainwright, and several tributaries of the
Tanana River, before reaching the crossing of Sal-
chaket Slough. Corridor Four passes Clear Creek Butte
on the east. A new substation would be located on the
Fairbanks side of the Tanana River just north of Goose
Island. From Point E to Point F, the terrain of the
corridor is flat and very wet, and again, dense stands
of tall-growing vegetation exist both in the better
drained portions of the flat land~ and in the vicinity
of the river crossing.
(c) Corridor Screening
The objectives of the screening process were to focus on the pre-
viously-selected corridors and select those best meeting techni-
cal, economic, and environmental criteria.
(i) Reliability
Reliability is an uncomprom1s1ng factor in screening alter-
native transmission line corridors. Many of the criteria
utilized for economic, environmental, and technical reasons
also relate to the selection of a corridor within which a
line can be operated with minimum power interruption. Six
basic factors were considered in relation to reliability:
-Elevation:
-Aircraft:
-Stability:
-Existing
Power
Lines:
Lines located at elevations below 4000 feet
will be less exposed to severe wind and ice
conditions, which can interrupt service.
Avoidance of areas near aircraft landing and
takeoff operations will minimize risks from
collisions.
Avoidance of areas susceptible to land, ice,
and snow slides wi 11 reduce chance of power
failures.
Avoidance of crossing existing transmission
lines will reduce the possibility of lines
touching during failures and will facilitate
repairs.
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-Topography: Lines located in areas with gentle relief
will be easier to construct and repair.
-Access: Lines located in reasonable proximity to
transportation corridors will be more quick-
ly accessible and therefore more quickly
repaired if any failures occur.
Technical Screening Criteria
Four primary and two secondary technical factors were con-
sidered in the screening of alternative corridors.
Primary Aspects:
o Topography
o Climate and Elevation
Low temperatures, snow depth, 1c1ng, and severe winds
are very importa~t parameters in transmission design,
operation, and reliability.
Climatic factors become more severe in the mountains,
where extreme winds are expected for exposed areas and
passes. The Alaska Power Administration believes that
elevations above 4000 feet in ,the Alaska Range and
Talkeetna Mountains are completely unsuitable for
locating major. transmission facilities. Significant
advantages of reliability and cost are expected if the
lines are routed below 3000 feet in elevation. This
elevation figure was used in the screening process.
o Soils
Although transmission lines are less affected by soils
and foundation limitations than railroads and pipe-
lines, it is more reliable to build a transmission
1 i ne on soil that does not appear to be under 1 a in by
seismically-induced ground failures or on a swampy
area where maintenance and inspection may create prob-
lems. These factors were utilized in the screening
process. Because of the vast areas of wetlands in the
study area, particularly in the southern portion,· it
was not possible to locate a corridor that would avoid
all wet 1 and areas.
B-2-95
o Length of Corridors
Secondary Aspects:
o Vegetation and Clearing
Heavily-forested areas must be cleared prior to con-
struction of the transmission line. Clearing the veg-
etation will cause some disruption of the soil. If
not properly stabilized through restor at ion and vege-
tation, increased erosion will result. If the vegeta-
tion is cleared up to river banks on stream crossings,
additional sedimentation may result. During the cor-
ridor screening, those corridors crossing through
large expanses of heavily-timbered areas were elimina-
ted.
o Other
Highway and river crossings were avoided where possi-
ble.
(iii) Economic Screening Criteria
Three primary and one secondary aspect of the economic cri-
teria were considered.
Primary Aspects:
o Length
o Right-of-Way
Whenever possible~ existing rights-of-ways were shared
or paralleled to avoid problems associated with pion-
eering a corridor in previously inaccessible areas.
o Access Roads
Secondary Aspects:
In addition to the major considerations concerning econ-
omic screening of corridors, some other aspects were al-
so considered. These include topography (since it is
more economical to build a line on a flat corridor than
on a rugged or a mountainous one) and 1 imit ing the num-
ber of stream, river, highway, road, and railroad cross-
ings in order to minimize costs.
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Environmental Screening Criteria
Because of the potential adverse environmental impacts from
transmission line construction and operation, environmental
criteria were carefully scrutinized in the screening pro-
cess. Past experience has shown the primary environmental
considerations to be:
-Aesthetic and Visual (including impacts to recreation)
-Land Use (including ownership and presence of existing
rights-of-way)
Also of significance in the evaluation process are:
-Length
-Topography
-Soils
-Cultural Resources
-Vegetation
-Fishery Resources
-Wildlife Resources
A description and rationale for use of these criteria are
presented below:
-Primary Aspects:
o Aesthetic and Visual
The presence of large transmission line structures in
undeveloped areas has the potential for adverse aes-
thetic impacts. Furthermore, the presence of these
lines can conflict with recreational use, particularly
those nonconsumptive recreational activities such as
hiking and bird watching where great emphasis is
placed on scenic values. The number of road crossings
encountered by transmission line corridors is also a
factor that needs to be inventoried because of the
potential for visual impacts. The number of roads
crossed, the manner in which they are crossed, the
nature of existing vegetation at the crossing site
(i.e., potential visual screening), and the number and
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type of motorists using the highway all influence the
desirability of one corridor versus another.
Therefore, when screening the previously-selected
corridors, consideration was focused on the presence
of recreational areas, hiking trails, heavily utilized
lakes, vistas, and highways where views of
transmission line facilities would be undesirable.
o Land Use
The three primary components of 1 and use considera-
tions are: 1) land status/ownership, 2) existing
rights-of-way, and 3) existing and proposed develop-
ment .
. Land Status/Ownership
The ownership of land to be crossed by a transmis-
sion line is important because certain types of own-
ership present more restrict ions than others. For
ex amp 1 e, some recreation areas such as state and
federal parks and areas such as game refuges and
military lands, among others, present possible con-
straints to corr i dar routing. Private 1 andowners
generally do not want transmission lines on their
lands. This information, when known in advance,
permits corridor routing to avoid such restrictive
areas and to occur in areas where 1 and use conflicts
can be minimized .
. Existing Rights-of-Way
Paralleling existing rights-of-way tends to result
in less environmental impact than that which is
associated with a new right-of-way because the crea-
tion of a new right-of-way may pro vi de a means of
access to areas normally accessible only on foot.
This can be a critical factor if it opens sensitive,
ecological areas to all-terrain vehicles.
Impact on soils, vegetation, stream crossings, and
other inventory categories can also be lessened
through the paralleling of existing access roads and
cleared rights-of-way. Some impact is still felt,
however, even though a right-of-way may exist in the
area. For example, cultural resources may not have
been identified in the original routing effort.
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Wetlands present under existing transmission lines
may likewise be negatively influenced if ground
access to the vicinity of the tower locations is
required.
There are common occasions where paralleling an
existing facility is not desirable. This is partic-
ularly true in the case of highways that offer the
potential for visual impacts and in situations where
paralleling a poorly sited transmission facility
would only compound an existing problem.
Existing and Proposed Developments
This inventory identifies such items as agricultural
use, planned urban developments (such as the pro-
posed capital site), existing residential and cabin
developments, the location of airports and lakes
used for float planes, and similar types of informa-
tion. Such information is essential for locating
transmission line corridors appropriately, as it
presents conflicts with these land use activities.
Secondary Aspects:
o Length
The length of a transmission line is an environmental
factor and, as such, was considered in the screening
process. A longer line will require more construction
activity than a shorter 1 i ne, will disturb more 1 and
area, and wi 11 have a greater inherent probabi 1 ity of
encountering environmental constraints.
o Topography
The natural features of the terrain are significant
from the standpoint that they offer both positive and
negative aspects to transmission line routing. Steep
slopes, for example, present both difficult construc-
tion and soil stabilization problems with potentially
long-term, negative environmental consequences. Also,
ridge crossings have the potential for visual impacts.
At the same time, slopes and elevation changes present
opportunities for routing transmission lines so as to
screen them from both travel routes and existing com-
munities. Hence, when planning cor:ridors the identi-
fication of changes in relief is an important factor.
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o Soils
Soils are important from several standpoints. First
of all, scarification of the land often occurs during
the construction of transmission lines. As a result,
vegetation regeneration is affected, as are the rela-
ted features of soil stability and erosion potential.
In addition, the development and installation of ac-
cess roads, where necessary, are very dependent upon
soil types. Tower designs and locations are dictated
by the types of soi 1 s encountered in any particular
corridor segment. Consequently, the review of exist-
ing soils information is very significant. This in-
ventory was conducted by means of a Soil Associations
Table, Table B.42. Table B.43 presents the related
definitions as they apply to the terms used in Table
B .42.
o Cultural Resources
The avoidance of known or potential sites of cultural
resources is an important component in the routing of
transmission lines. A level-one cultural resources
survey has been conducted along a large portion of the
transmission corridors. In those areas where no in-
formation has been collected to date an appropriate
program for i dent ifyi ng and mitigating impacts will be
undertaken. This program is discussed in more detail
in Section 4 of Exhibit E.
o Vegetation
The consideration of the presence and location of var-
ious plant communities is essential in transmission
line siting. The inventory of plant communities, such
as those of a tall-growing nature or wetlands, is sig-
nificant from the standpoint of construction, clear-
ing, and access road development requirements. In
addition, identification of locations of _endangered
and threatened plant species is also critical. While
several Alaskan plant species are currently under re-
view by the U.S. Fish and Wildlife Service, no plant
species are presently listed under the Endangered
Species Act of 1973 as occurring in Alaska. No corri-
dor currently under consideration has been identified
as traversing any 1 ocat ion known to support these
identified plant species.
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o Fishery Resources
The presence or absence of resident or anadromous fish
in a stream is a significant factor in evaluating
suitable transmission line corridors. The corridor's
effects on a stream's resources must be viewed from
the standpoint of possible disturbance to fish spe-
cies, potential loss of habitat, and possible destruc-
tion of spawning beds. In addition, certain species
of fish are more sensitive than others to di stur-
bance.
Closely related to this consideration is the number of
stream crossings. The nature of the soils and vegeta-
tion in the vicinity of the streams and the manner in
which the streams are to be crossed are also important
environmental considerations when routing transmission
lines. Potential stream degradation, impact on fish
habitat through disturbance, and long-term negative
consequences resulting from siltation of spawning beds
are all concerns that need evaluation in corridor
routing. Therefore, the number of stream crossings
and the presence of fish species and habitat value
were considered when data were available.
o Wildlife Resources
The three major groups of wildlife which must be con-
sidered in transmission corridor screening are big
game, birds, and furbearers. Of all the wildlife
species to be considered in the COIJrse of routing
studies for transmission lines, big game species (to-
gether with endangered species) are most significant.
Many of the big game species, including grizzly bear,
caribou, and sheep, are particularly sensitive to
human intrusion into relatively undisturbed areas.
Calving grounds, denning areas, and other important or
unique habitat areas as identified by the Alaska
Department of Fish and Game were identified and
incorporated into the screening process.
Many species of birds such as raptors and swans are
sensitive to human disturbance. Identifying the pres-
ence and location of nesting raptors and swans permits
avoidance of traditional nesting areas. Moreover, if
this category is investigated, the presence of endan-
gered species (viz, peregrine falcons) can be deter-
mined.
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Important habitat for furbearers exists along many
potential transmission line corridors in the Railbelt
area, and its loss or disruption would have a direct
effect on these animal populations. Investigating
habitat preferences, noting existing habitat, and
identifying populations through available information
are important steps in addressing the selection of
environmentally acceptable alternatives.
(v) Screening Methodology
-Technical and Economic Screening Methodology
The parameters required for the technical and economic
analyses were extracted from the environmental inventory
tables (Tables 8.39 through 8.41). These tables, and
Tables 8.44 through 8.50 are derived from studies
carried out prior to the issuance of the Feasibility
Report in March 1982; at that time the routing of the
proposed access route was undecided. Subsequent to the
publication of the Feasibilty Report the decision was
made to select the Denali-North Plan as the proposed
access route. Since the location of the access route is
of major importance in relation to the transmission line
within the central study area, the tables have been
modified to reflect this decision and the ratings
assigned to each corridor adjusted accordingly. The
reasons for changing these ratings are discussed in more
detail in subsection 2.7(d).
The tables, together with the topographic maps, aerial
photos, and existing published materials, were used to
compare the alternative corridors from a technical and
economic point of view. The parameters used in the an-
alysis were: length of corridors, approximate number of
highway/road crossings, approximate number of river/
creek crossings, land ownership, topography, soils, and
existing rights-of-way. The main factors contributing
to the economic and technical analyses are combined and
listed in Tables 8.44, 8.45, and 8.46. It should be
noted that most of the parameters are in miles of line
length, except the tower construction. In this
analysis, it was decided to assign 4.5 towers for each
mile of 345 kV line.
In order to screen the most qualified corridor, it was
decided to rate the corridors as follows:
Corridor rated A -recommended
Corridor rated C -acceptable but not preferred
Corridor rated F -unacceptable
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From a technical point of view, reliability is the main
objective. An environmentally and economically sound
transmission line was rejected if the line was not reli-
able. Thus, any line which received an F technical rat-
ing, was assigned an overall rating of F and eliminated
from further consideration.
The ratings appear in each of the economic and technical
screening tables (Tables 8.44, 8.45, and 8.46) and are
summarized in Table 8.47. ·
Environmental Screening Methodology
In order to compare the alternative corridors (Figures
8.47, 8.48, and 8.49) from an environmental standpoint,
the environmental criteria discussed above wete combined
into environmental constraint tables (Tables 8.48, 8.49,
and 8.50). These tables combine information for each
corridor segment into the proper corridors under study.
This permits the assignment of an environmental rating,
which identifies the relative rating of each corridor
within each of the three study areas. The assignment of
environmental ratings is a subjective, qualitative tech-
nique intended as an aid to corridor screening. Those
corridors that are recommended are identified with an
11 A,11 while those corridors that are acceptable but not
preferred are identified with a 11 C.11 Finally, those
corridors that are considered unacceptable are identi-
fied with an 11 F.11
(d) Selected Corridor
,-·The selected corridor consists of the following segments:
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-Southern Study Area:
-Central Study Area:
-Northern Study Area:
Corridor ADFC (Figures 8.50 and 8.51)
Corridor AJCD (Figures 8.52 and 8.53)
Corridor ABC (Figures 8.54 through 8.57)
Specifics of these corridors and reasons for rejection of others
are discussed below. More detail on the screening process and the
specific technical ratings of each alternative are in Chapter 10
of Ex hi bit E.
(i) Southern Study Area
In the southern study area, Corridor Segment AEF and,
hence, Corridor Three (AEFC) were determined unacceptable.
This results primarily from the routing of the segment
through the relatively well-developed and heavily-utilized
Nancy Lake state recreation area. Adjustments to this
route to make it more acceptable were attempted but no
alterations proved successful. Consequently, it was recom-
8-2-103
mended that this corridor be dropped from further consider-
ation.
Corridor One (ABC •), i dent ifi ed as accept ab 1 e but not pre-
ferred, was thus given the Crating. Its great length, its
traversing of residential and other developed lands, and
the numerous creek crossings and extensive forest clearing
involved relegate this corridor to this environmental rat-
ing. Economically and technically, this corridor has more
difficulties than the other two considered. This is a
longer 1 ine and crosses areas which may require easements
in the area north of Anchorage.
Corridor Two (ADFC) was identified ·as the candidate which
would satisfy most of the screening criteria. This corri-
dor is shown in Figures 8.50 and B.51 and stretches from an
area north of Willow Creek to Point MacKenzie in the south.
The corridor is located east of the lower Susitna River and
crosses the Little Susitna River. The corridor also cross-
es an existing 138 kV line owned and operated by Chugach
Electric Association (CEA), which starts at Point MacKenzie
and extends to Teeland Substation.
Up to this point in the corridor selection study, Point
MacKenzie has been considered a terminal point for Susitna
power. It was assumed that an underwater cab 1 e crossing
would be provided at this location. Upon further study and
data gathering it has become known that the existing cross-
ing at Point MacKenzie has experienced power interruptions
caused by ship's anchors snagging the submarine cables.
CEA, which owns the submarine cables, required additional
transmission capacity to Anchorage. After thoroughly
studying the matter, it has opted for a combined submarine/
overhead cable transmission across Knik Arm and on to Anch-
orage. This was the most desirable option to CEA from both
the environmental and technical point of view.
The CEA crossing will be located approximately 8 miles
northeast of Point MacKenzie on the west shore of the Knik
Arm and across from Elmendorf Air Force Base in the vicin-
ity of Six Mile Creek. This crossing is located northeast
of Anchorage Harbor, away from heavy ship traffic, thereby
reducing the risk of anchor damage to the cable.
It is intended to terminate Corridor ADFC at this new
crossing point and extend the transmission corridor to
Elmendorf Air Force Base and beyond to Anchorage.
Although the crossing is approximately 8 miles northeast of
Point MacKenzie, it does not influence the results of this
corridor selection and screening process. The best corri-
dor has been selected and screened. During routing studies
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minor deviations outside the corridor will have to occur in
order to terminate at the revised crossing point. However,
preliminary investigations indicate it will be possible to
select a technically, economically, and environmentally
acceptable route, particularly since an existing transmis-
sion line can likely be paralleled from the selected
corridor to the revised crossing point. Furthermore, CEA
has received the necessary permits and is constructing an
underwater crossing at Knik Arm, indicating acceptable
levels of environmental impact.
Central Study Area
In the central study area, several corridor segments and
their associated corridors were determined to be unaccep-
table. The first of these, Corridor Segment BEC, appears
as part of Corridors Two (ABE CD), Five (ABECJHI), Seven
(CEJAHI), Nine (CEBAG), and Fifteen {ABECF). The primary
reason for rejecting this segment is that the developed
recreation area around Stephan Lake would be needlessly
harmed because viable options exist to avoid intruding into
this area. An acceptable modification could not be found
and, consequently, it is recommended that these five corri-
dors be dropped from further consideration.
Corridor Segment AG was also determined not to warrant fur-
ther consideration because of its approximate 65-mile
length, two-thirds of which would possibly require a pion-
eer access road. Also, extensive areas of clearing would
be required, opening the corridor to view in some scenic
locations. Finally, the impacts on fish and wildlife habi-
tats are potentially severe. These preliminary findings,
coupled with the fact that more viable options to Segment
AG exist, suggest that cons-ideration of this corridor seg-
ment and therefore Corridors Eight ( CBAG) and Ten ( CJAG)
should be terminated.
Corridors Eleven (CJAHI) and Twelve (JA-CJHI) were identi-
fied as not acceptable. This rating arose from the fact
that, as shown in Environmental Constraint Table B.49,
numerous constraints affect this routing. Information from
recently completed field investigations suggest that these
constraints cannot be overcome and the routes should be re-
jected. Furthermore, the technical and economical ratings
preclude these corridors from further consideration.
Corridor Segment HJ has been moved so that it no longer
parallels the Devil Creek drainage; the new location HC is
selected to avoid both High Lake and the Devil Creek drain-
age. It then follows the Portage Creek drainage to the
point of intersection with Corri dar Segment JH, near the
creek • s headwaters. Subsequent investigations have con-
B-2-105
firmed that this corridor segment is not viable and, conse-
quently, Corridors Four and Five are eliminated from fur-
ther consideration.
Corridor Six (CBAHI) intrudes on valuable wildlife habitat
and would cross numerous creeks, none of which are
currently crossed by existing access roads. In addition, a
high mountain pass and its associated shallow soils, steep
slopes, and surficial bedrock constrain this routing.
Finally, its crossing of areas over 4000 feet in elevation
makes it technically unacceptable, so this corridor is
dropped from further consideration.
The four remaining corridors (Corridors One, Three,
Thirteen and Fourteen) were each identified as being
acceptable in terms of the technical, economic and
environmental criteria described in subsection 2.7(c).
The Dena 1 i -North P 1 an was selected as the proposed access
route for the Susitna development (subsection 2.6(h)). The
location of existing and proposed access is of prime
importance both from an economic and environmental
standpoint. Therefore, subsequent to the access decision,
each of the four corridors was subjected to a more detailed
evaluation and comparison. In order to more directly
compare the four corridors a preliminary route was selected
in each of the segments. The final route selection process
leading to the perferred route in the corridor, which was
subsequently recommended, is discussed in more detail in
subsection 2.7(e). The four corridors are comprised of the
following segments:
-Corridor One ABCD
-Corridor Three AJCF
-Corridor Thirteen ABCF
-Corridor Fourteen AJCD
Segments ABC and AJC link Watana with Devil Canyon and,
similarly, segments CD and CF link Devil Canyon with the
Intertie. On closer examination of the possible routes
between Devil Canyon and the Intertie, segment CD was found
to be superior to segment CF for the following reasons.
-Economic
A four-wheel drive trail is already in existence on the
south side of the Susitna River between Gold Creek and
the proposed location of the railhead facility at Devil
Canyon. Therefore, the need for new roads along segment
CD, both for construction and operation and maintenance,
is significantly less than for segment CF, which requires
the construction of a pioneer road. In addition, the
proposed Gold Creek to Devil Canyon railroad extension
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will also run parallel to segment CD. The lengths of
Segments CD and CF are 8.8 miles and 8.7 miles, respec-
tively--not a significant factor. Among the secondary
economic considerations is that of topography. Segment
CF crosses more rugged terrain at a higher elevation than
segment CD and would therefore prove more difficult and
costly to construct and maintain. Hence, segment CD was
considered to have a higher overall economic rating.
-Technical
Although both segments are routed below 3000 feet eleva-
tion, segment CF crosses more rugged, exposed terrain
with a maximum elevation of 2600 feet. Segment CD, on
the other hand, traverses generally flatter terrain and
has a maximum elevation of 1800 feet. The disadvantages
of segment CF are somewhat offset, however, by the Susit-
na River crossing that will be needed at river mile 150
for segment CD. Overall, the technical difficulties
associated with the two segments may be regarded as being
simi 1 ar.
-Environmental
One of the main concerns of the various environmental
groups and agencies is to keep any form of access away
from sensitive ecological areas previously inaccessible
other than by foot. Creating a pioneer road to construct
and maintain a transmission line along segment CF would
open that area to all-terrain vehicles and public use,
and thereby increase the potential for adverse impacts to
the environment. The potential for environmental impacts
along segment CD would be present regardless of where the
transmission line was built since there is an existing
four-wheel drive trail together with the proposed rail-
road extension in that area. It is clearly desirable to
restrict environmental impacts to a single common corri-
dor; for that reason, segment CD is preferable to segment
CF.
Because of potential environmental impacts and economic
ratings, segment CF was dropped in favor of segment CD.
Consequently, corridors Three (AJCF) and Thirteen (ABCF)
were eliminated from further consideration.
The two corridors remaining are therefore corridors One
(ABCD) and Fourteen (AJCD). This reduces to a comparison
of segment ABC on the south side of the Susitna River and
. segment AJC on the north side. The two segments were
then screened in accordance with the criteria set out in
subsection 2.7(c). The key points of this evaluation are
outlined below:
B-2-107
-Economic
For the Watana development, two 345 kV transmission lines
will be constructed from Watana through to the Intertie.
When comparing the relative lengths of transmission line,
it was found that segment ABC was 33.6 miles in total
length compared to 36.4 miles for the northern route
using segment AJC. Although at first glance a difference
in length of 2.8 miles (equivalent to 12 towers at a
spacing of 1200 feet) seems significant, other factors
were taken into account. Segment ABC contains mostly
woodland, black spruce in segment AB. Segment BC
contains open and woodland spruce forests, low shrub, and
open and closed mixed forest in about equal amounts.
segment AJC, on the other hand, contains significantly
less vegetation and is composed predominantly of low
shrub and tundra in segment AJ and tall shrub, low shrub
and open mixed forest in segment JC. Consequently, the
amount of clearing associated with segment AJC is
considerably less than with segment ABC, resulting in
savings not only during construction but also during
periodic recutting. Additional costs would also be
incurred with segment ABC due to the increased spans
needed to cross the Susitna River (at river mile 165.3)
and two other major creek crossings. In summary, the
cost differential between the two segments would probably
be marginal.
-Technical
Segment AJC traverses generally moderately-sloping
terrain ranging in height from 2000 feet to 3500 feet
with 9 miles of the segment being at an elevation in
excess of 3000 feet. Segment ABC traverses more rugged
terrain, crossing several deep ravines and ranges in
elevation from 1800 feet to 2800 feet. In general there
are advantages of reliability and cost associated with
transmission lines routed under 3000 feet. The 9 miles
of segment AJC at elevations in excess of 3000 feet will
be subject to more severe wind and ice loadings than
segment ABC, and the towers will have to be designed
accordingly. However, these additional costs will be
offset by the construction and maintenance problems with
the more rugged topography and major river and creek
crossings of segment ABC. The technical difficulties
associated with the two segments are therefore considered
similar.
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-Environment a 1
From the previous analysis, it is evident that there are
no significant differences between the two segments in
terms of technical difficulty and economics. The
deciding factor therefore reduces to the environmental
impacts. The access road routing between Watana and
Devil Canyon was selected because it has the least
potenti~l for creating adverse impacts to wildlife,
wildlife habitat and fisheries. Similarly, Segment AJC,
within which the access road is located, is
environmentally less sensitive than Segment ABC, for it
traverses or approaches fewer areas of productive habitat
and zones of species concentration or movement. The most
important consideration, however, ·is that for ground
access d~ring operation and maintenance, it will be
necessary to have some form of trail along the
transmission line route. This trail would permit human
entry into an area which is relatively inaccessible at
present, causing both direct and indirect impacts. By
placing the transmission line and access road within the
same general corridor as in Segment AJC, impacts will be
confined to that one corridor. If access and
transmission are placed in separate corridors, as in
Segment ABC, environmental impacts would be far greater.
Segment AJC is thus considered superior to Segment ABC.
Consequently, Corridor One (ABCD) was eliminated and
Corridor Fourteen (AJCD) selected as the proposed route.
Northern Study Area'
Corridors Three (AEDC) and Four (AEF) were determined unac-
ceptable because of many constraints, and thus rated F.
They include: the lack of an existing access road; prob-
lems in dealing with tower erection in shallow bedrock
zones; the need for extensive wetland crossings and forest
clearing; the 75 river or creek crossings involved; and the
fact that prime habitat for waterfowl, peregrine falcons,
caribou, bighorn sheep, golden eagle, and brown bear would
be crossed. In addition, Corridor Four crosses areas of
significant land use constraints and elevations of over
4000 feet.
Corridor Two (ABDC) was identified as acceptable but not
preferred, and thus rated C. Certain constraints identi-
fied for this corridor suggest that an alternative is pref-
erab 1 e. Compared with Corridor One, Corridor Two crosses
addition a 1 wet 1 ands and requires the deve 1 opment of more
access roads and the clearing of additional forest lands.
B-2-109
Corridor One (ABC), shown in Figures B.54 to B.57, was the
only recommended corridor in the northern study area.
While many constraints were identified under the various
categories, it appears possible to select a route within
this corridor to minimize constraint influences. This cor-
ridor is attractive economically, because it is close to
access roads and the Parks Highway. The visual impact can
be lessened by strategic placement of the line. This line
also best meets technical and economical requirements.
(e) Route Selection
(i) Methodology
After identification of the preferred transmission line
corridors, the next step in the route selection process in-
volved the analysis of the data as gathered and presented
on the base map. Overlays were compiled so that various
constraints affecting construction or maintenance of a
transmission facility could be viewed on a single map. The
map was used to select possible routes within each of the
three selected corridors. By placing all major constraints
(e.g., areas of high visual exposure, private lands, endan-
gered species, etc.) on one map, a route of least impact
was selected. Existing facilities, such as transmission
lines and tractor trails within the study area, were also
considered during the selection of a minimum impact route.
Whenever possible, the routes were selected near existing
or proposed access roads, sharing wherever possible exist-
ing rights-of-way.
The data base used in this analysis was obtained from the
following sources:
-An up-to-date land status study
-Existing aerial photos
-New aerial photos conducted for selected sections of the
previously-recommended transmission line corridors
-Environmental studies including aesthetic considerations
-Climatological studies
-Geotechnical exploration
-Additional field studies
-Public opinions.
(ii) Selection Criteria
The purpose of this section is to identify three selected
routes: one from Healy to Fairbanks, the second from the
B-2-110
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Watana and Devil Canyon damsites to the intertie, and the
third from Willow to Anchorage.
The previously-chosen corridors were subject to a process
of refinement and evaluation based on the same technical,
economic, and environmental criteria used in corridor sel-
ection. In addition, special emphasis was placed on the
following points:
-Satisfying the regulatory and permit requirements
-Selection of routing that provides for minimum visibility
from highways and homes
-Avoidance of developed agricultural lands and dwellings.
(iii) Environmental Analysis
The corridors selected were analyzed to arrive at the route
which is most compatible with the environment and also
meets engineering and economic objectives. The en vi ron-
mental analysis was conducted by the process described
bel ow:
Literature Review
Data from various literature sources, agency communica-
tions, and site visits were reviewed to inventory exist-
ing environmental variables. From such an inventory, it
was possible to identify environmental constraints in
the recommended corridor locations. Data sources were
cataloged and filed for later retrieval.
-Avoidance Routing by Constraint Analysis
To establish the most appropriate location for a trans-
mission line route, it was necessary to identify those
environmental constraints that could be impediments to
the development of such a route. Many specific con-
straints were identified during the preliminary screen-
ing; others were determined during the 1981 field inves-
tigations.
By utilizing information on topography, existing and
proposed land use, aesthetics, ecological features, and
cultural resources as they exist within the corridors,
and by careful placement of the route with these consid-
erations in mind, impact on these various constraints
was minimized.
B-2-111
Base Maps and Overlays
Constraint analysis information was placed on base maps.
Constraints were identified and presented on overlays 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 transmission line route within the preferred corridor
and then placed on maps of the corridors. Environmental
constraints were identified and recorded directly onto
the base maps. Overlays to the base maps were prepared
i nd i cat i ng the type and extent of the encountered con-
straints.
Three overlays were prepared for each map: one for vis-
ual constraints, one for man-made, and one for biolog-
ical constraints. These maps are presented as a separ-
ate document (Acres, TES 1982).
(iv) Technical and Economic Analysis
Route location objectives are to obtain an optimum combina-
tion of reliability and cost with the fewest environmental
problems. In many cases, these objectives are mutually
compatible.
Throughout the evaluation, much emphasis was placed on
locating the route relatively close to existing surface
transportation facilities 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 vegetation and river and highway crossings.
These factors are detailed in Tables B.38 and B.51.
Selection of Alternative Routes
The next step in the route selection process involved
analysis of the data 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 also taken into con-
sideration during the selection of a least impact
route.
B-2-112
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(v)
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-Evaluation of a Primary 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 processes
and data previously described. Preliminary routes were
compared to determine the route of least impact within
the primary corridors of each study area. For example,
such variables as number of stream and road crossings
required were noted. Then, following the field studies
and through a comparison of routing data, including the
route's total length and its use of existing facilities,
one route was designated the primary route. Land use,
1 and ownership, and visual impacts were key factors in
the selection process.
Route Soil Conditions
Description
Baseline geological and geotechnical information was
compiled through photo interpretation and terrain unit
mapping. The general objective was to document the con-
ditions that would significantly affect the design and
construction of the transmission line towers. More spe-
cifically, these conditions included the origins of var-
ious land forms, noting the occurrence and distribution
of significant geologic features such as permafrost,
potentially unstable slopes, potentially erodible soils,
possible active fault traces, potential construction
materials, active floodplains, organic materials, etc.
Work on the air photo interpretation consisted of sever-
al activities culminating in a set of terrain unit maps
showing surface materials, geologic features and condi-
tions in the project area.
The first activity consisted of a review of the litera-
ture concerning the geology of the intertie corridors
and transfer 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 frame-
work which assisted in interpretation of the low-level
1:30,000 project photos. Major terrain divisions iden-
tified 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 cov-
ering about 300 square miles of varied terrain. The
1 and area covered in the mapping exercise is shown on
map she.ets and displayed in detail on photo mosaics (R&M
Consultants 1981a).
B-2-113
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 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 proper-
ties of each terrain unit were considered and a chart
for each corridor was developed. These charts identify
the terrain units as they have been mapped and charac-
terize their properties in numerous categories. This
allows an assessment of each unit 1 s influence on various
project features.
Terrain Unit Analysis
The terrain unit is a special purpose term compns1ng
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-
Fairbanks transmission line show the aerial extent of
the specific terrain units which were identifed during
the air photo investigation and were corroborated in
part by a limited on-site surface investigation. The
units document the general geology and geotechnical
characteristics of the area.
The north and south corridors 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 corri dar. The land-
forms or individual terrain units mapped in both corri-
dors were briefly described.
Several of the landforms have not been mapped i nde-
pendently 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 sedi-
ments overlying till. Complex terrain units have been
mapped where the surficial exposure pattern of two land-
forms are so intricately related that they must be
mapped as a terrain unit complex, such as some areas of
B-2-114
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(vi) -
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bedrock and colluvium. The compound and complex terrain
units were described as a composite of individual land-
forms comprising them. The stratigraphy, topographic
position, and aerial extent of all units, as they appear
in each corridor, were summarized on the terrain unit
properties and engineering interpretations chart (R&M
Consultants 198la).
Results and Conclusions
A study of existing information and aerial overflights, to-
gether with additional aerial coverage, was used to locate
the recommended route in each of the southern, central, and
northern study areas.
Terrain unit maps describing the general material expected
in the area were prepared specifically for transmission
1 i ne studies and were used to locate the routes away from
unfavorable soil conditions wherever possible. Similarly,
environmental constraint analysis information was placed on
base maps and overlays (Acres, TES 1982) and the route mod-
ified accordingly.
Subsequent to the submission of the Feasibility Study
(Acres 1982c), additional environmental and land status
studies made it possible to further refine the alignments
to the extent that most environmentally sensitive areas and
areas where land acquisition may present a problem have
been avoided. In the Fairbanks-to-Healy and the Willow-to-
Anchorage line sections, these refinements have resulted in
an improved alignment which is generally in close proximity
to the earlier proposal.
Also subsequent to the Feasibility Study, the proposals for
access to the power development were reassessed. As
mentioned earlier, this resulted in a decision to provide
access to Watana from-the Denali Highway and bui 1 d a
connecting road. between the dams on the north side of the
Susitna River. The earlier line routing proposals were
accordingly reviewed to establish the optimum alignment.
The desire to limit environmental impacts to a single
corridor led to the routing of the transmission line more
or less parallel to the access road. Hence, between the
dams, the line shares the same general corridor as the
access road to the north of the Susitna River. From Devil
Canyon to the intersection with the Intertie (at a
switching station approximately four mi 1 es northeast of
Gold Creek), the line is located south of the Susitna River
paralleling the proposed railroad extension, and an
existing four-wheel drive trail.
B-2-115
The original corridors which were three to five miles in
width were narrowed to a half mile and, after final adjust-
ment, to a finalized route with a defined right-of-way.
The selected transmission 1 ine route for the three study
areas is presented in Exhibit G. Preliminary studies have
indicated that, for a hinged-guyed X-configuration tower
having horizontal phase spacing of 33 feet, the following
right-of-way widths should be sufficient:
- 1 tower
- 2 towers
- 3 towers
- 4 towers
190 feet
300 feet
400 feet
510 feet
These right-of-way widths will be subject to minor local
variation where the need for special tower structures dic-
tates or where difficult terrain is encountered and will be
addressed fully in the final design phase of the project.
(f) Towers, Foundations and Conductors
The Anchorage and Fairbanks Intertie will consist of existing
lines and a new section between Willow and Healy. The new section
will be built to 345 kV standards but will be temporarily operated
at 138 kV and will be fully compatible with Susitna requirements.
(i) Transmission Line Towers
Selection of Tower Type
Because of the unique soil conditions in Alaska which
are characterized by extensive regions of muskeg and
permafrost, conventional self-supporting or rigid towers
will not provide a satisfactory solution for the pro-
posed transmission line.
Permafrost and seasonal changes in the soil are known to
cause large earth movements at some locations, requiring
towers with a high degree of flexibility and capability
to sustain appreciable loss of structural integrity.
A guyed tower is well suited to these conditions; these
include the guyed-V, guyed-Y, guyed delta, and guyed
portal type structures. The type of structure selected
for the construction of the Intertie is the hinged-guyed
steel X-tower, a refinement of the guyed structure con-
cept. This type of tower is therefore a prime candidate
B-2-116
for use on the Watana transmission system. Guyed pole-
type structures wi 11 be used on 1 arger angle and dead
end structures; a similar arrangement will be used in
especially heavy loading zones.
The design features of the X-tower include hinged con-
nections between the legs and the found at ion and four
longitudinal guys attached in pairs to two guy anchors,
providing a high degree of flexibility with excellent
structural strength. The wide leg spacing results in
relatively low foundation forces which are carried on
pile type footings in soil and steel grillage or rock
anchor footings where rock is close to the surface.
In narrow right-of-way situations, cantilever steel pole
structures are anticipated with foundations consisting
of cast-in-place concrete augered piles.
In the final design process, experience gained in the
construction and operation of the Intertie will be used
in the final selection of the structure type to be used
for the Watana transmission.
All tower structures will be of "weathering" type steel
which matures to a dark brown color over a period of a
few years and is considered to have a more aesthetically
pleasing appearance than either galvanized steel or alu-
minum.
-Climatic Studies and Loadings
Climatic studies for transmission lines were performed
to determine probable maximum wind and ice loads based
on historical data. A more detailed study incdrporating
additional climatic data was carried out for the Inter-
tie final design. These studies have resulted in the
selection of preliminary loading for the l·ine design
(Acres 1982c, Vol. 4).
Preliminary loadings selected for line design should be
confirmed by a detailed study, similar to that performed
for the Intertie, that will examine conditions for the
Healy-to-Fairbanks, Wi 11 ow-to-Anchorage and Gold Creek-
to-Watana sections of the route together with an update
of the Healy-to-Willow study incorporating any data from
field measurement stations collected in the interim pe-
riod.
B-2-117
Based on data currently available, it appears that the
line can be divided up into zones as far as climatic
loading is concerned as follows:
-Normal Loading Zone
-Heavy Ice Loading Zone
-Heavy Wind Loading Zone
The heavy ice and heavy wind zones will have an addi-
tional critical loading case included to reflect the
special nature of the zone.
-Tower Family
A family of tower designs will be developed as follows:
Suspension towers will be provided for both standard
span plus angle (up to 3°) application and for long
span or light angle (Oo to 8°) application.
Tension towers will be provided for light angle and
dead end (0° to 8°), for large angle and dead end (8°
to 50°), and for minimum angle and dead end (50° to
90°).
The maximum wind span and weight span ratios to be util-
ized will be set in final design to reflect the rugged
nature of the terrain along the line route. Some trial
spotting of towers in representative terrains will be
used to guide this selection. Minimum weight span to
wind span ratio limits will be set during tower spotting
and a 11 low temperature template used to check that un-
expected uplift will not develop at low weight span tow-
ers for very low temperatures.
The span to be used in design will be the subject of an
economic optimization study. A span of not less than
1200 feet is expected with spans in the field varying to
greater and lesser values in specific cases depending
upon span ratio and loading zone.
(ii) Tower Foundations
-Geotechnical Conditions
The generalized terrain analysis (R&M Consultants 198la)
was conducted to collect 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.
B-2-118
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When evaluating the suitabi1 ity of a terrain unit for a
specific use, the actual properties of that unit must be
verified by on-site 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 material which requires special
design details; and
• Rock material defined as material in which drilled-in
anchors and concrete footings can be used.
Based on aerial, topographic, and terrain unit maps, the
following was noted:
For the southern study area: Wet 1 and 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
materia 1 s 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.
Types of Foundation
The types of tangent tower envisaged for these 1 i nes
wi 11 require foundations to support the 1 eg or mast
capable of carrying ·a predominantly vertical load with
some lateral shear, and a guy anchor foundation.
The cantilever pole structure foundation is required to
resist the high overturning moment inherent in the can-
tilever arrangement.
The greater part of the combined maximum reactions on a
transmission tower footing is usually from short dura-
tion loads such as broken wire, wind, and ice. With the
exception of heavy-angle, dead end or terminal struc-
tures, only a part of the total reaction is of a perman-
ent nature. As a consequence, the permissible soil
B-2-119
pressure, as used in the design of building foundations,
may be considerably increased for footings for
transmission structures.
The permissible values of soil pressure used in the
footing design will depend on the structure and the sup-
porting soil. The basic criterion is that displacement
of the footing not be restricted because of the flexi-
bility of the selected X-frame tower and its hinged con-
nection to the footing. The shape and configuration of
the selected tower are important factors i'n foundation
considerations.
Loads on the tower consist of vertical and horizontal
loads and are transmitted down to the foundation and
then distributed to the soi 1. In a tower placed at an
angle or used as dead end in the line, the horizontal
loads are responsible 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 forces on the
footing.
To enable the selection of a safe and economical tower
foundation design for each tower site, it is necessary
to select a footing which takes account of the actual
soil conditions at the site. This is done by matching
the soil conditions to a series of ranges in soil types
and groundwater conditions which have been predetermined
during the design phase to cover the full range of soils
expected to be encountered along the line length.
Preconstruction drilling, soil sampling, and laboratory
testing at representative locations along the line
enable the design of a family of footings to be prepared
for each tower type from which a selection of the
appropriate footing for the specific site can be made
during construction.
The foundation types for structure 1 egs and masts wi 11
be grouted anchor wher~ rock is very shallow or at sur-
face and steel grillage with granular backfill where
soil is competent and not unduly frost-sensitive. In
areas where soi 1 s are weak and where permafrost or par-
ticularly forest-heave prone material is encountered,
driven steel piles will be used.
Guy anchors wi 11 use grouted anchors in rock. Grouted
earth or helical plate screw-in anchors with driven
piles will be used in permafrost or very weak soils.
B-2-120
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(iii)
Proof load testing of piles and drilled-in anchors will
be required both for design and to check on the as-built
capacity of these foundation elements during constru-
ti on.
Voltage Level and Conductor Size
Economic studies were carried out of transmission utilizing
500 kV, 345 kV, and 230 kV ac. At each voltage level an
optimum conductor capacity was developed. Schemes
involving use of 500 kV or 345 kV on the route to Anchorage
and 345 kV or 230 kV to Fairbanks were investigated. The
study recommeded the adoption of two 345 kV units to
Fairbanks and three 345 kV units to Anchorage. Comparative
studies were carried out on the possible use of HVDC.
However, these studies indicated no economic advantage of
such a scheme.
The 345 kV system studies indicated that a conductor
capacity of 1950 MCM per phase was economical with due
account for the value of losses. A phase bundle consisting
of twin 754 MCM Rail (45/7) ACSR was proposed as meeting
the required capacity and also having acceptable corona and
radio interference performance. Detailed design studies as
part of the final design will compare the econbmics of this
conductor configuration with the use of alternatives such
as twin 954 MCM Cardinal (54/7) ACSR and single 215.6 r"ICfvi
Bluebird (84/19) ACSR which could give comparable electri-
cal performance with better structural performance.
Cardinal, because of a 15 percent superior strength-to-
weight ratio, can be sagged tighter than Rail, thereby
resulting in savings in tower height and/or increased
spans. Bluebird, because of a smaller circumference and
projected area compared with a twin conductor bundle,
attracts some 15 percent less load from ice or wind.
Together with its greater strength, this leads to less sag
under heavy loadings and lighter loads for the structures
to carry. Conductor swing angles will also be reduced,
thus reducing tower head size requirements and edge of
right-of-way clearing.
2.8 -Selection of Project Operation
A reservoir simulation model was used to evaluate the optimum method of
operati~g the Susitna Hydroelectric Project for a range of post-project
flows at the Gold Creek gaging station 15 miles downstream of the Devil
Canyon damsite. The model is essentially a monthly simulation of
reservoir operation under historical streamflow conditions given the
phys i ca 1 parameters associ a ted with the dams, powerhouses, and reser..;.
voirs. The model is driven by four criteria which are listed below in
the order of their application:
8;...2-121
1"1inimum Downstream Flow Requirements
The simulation model checks downstream flow requirements against the
sum of the total powerhouse flow and spi 11 age from the most
downstream damsi te. For the operations considered, generally the
outflow exceeds the downstream flow requirement in the winter months
of October through April. In the summer months, the energy
generation outflow is at the lowest level because of low energy
demand and the retention of river runoff in storage for release
during the following winter. The exception to this is in late
summer, usually September, when reservoirs can be full and spills
could occur. When the required do·wnstream flow is greater than the
power. flow simulated, additional discharge is made through the
powerhouse to meet the downstream requirement. Consideration is
made of the contribution flow between the damsite and Gold Creek.
Environmental considerations require the release of suitable flows
during critical fish spawning, incubation, and rearing periods.
Consultations through numerous meetings, correspondence, and
workshops have been conducted with state and federal resource agency
personnel to discuss recommended release schedu~es as part of the
mitigation options for the Susitna Project. Table B.O presents a
summary of the correspondence with resource agencies which are
appended to Exhibit E, Chapter 11.
In 1980 and 1981, prior to publication of the Feasibility Report,
these meetings consisted of discussions to establish acceptable
release schedules as part of project mitigation. On three
occasions, specific recommendations and comments on the
environmental sections of the proposed Susitna Project have been
requested from state and federal resource agencies prior to formal
submittal of the license Application. These included a request for
comment on the Feasibility Report (September 2, 1982) and a request
for comment on the draft Exh1bit E of the license Application
(November 15, 1982). In addition, agency representatives attended a
workshop on the Draft Exhibit E held November 29 to December 3,
1982. The Feasibility Report, the workshop and Exhibits Band E of
the Draft License Application included discussion of pre-and
B-2-122
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,,.,..
post-project flows. Agency comments resulting from review of these
reports and a synopsis of the workshop are also contained in Exhibit
E, Chapter 11.
Another specific request for recommendations of suitable flow
regimes was made to the key federal and state resource agencies in
May of 1983. This request was sent to the National Marine Fisheries
Service, U.S. Fish and Wildlife Service, and the Alaska Departments
of Fish and Game, Natural Resources, and Environmental Conservation.
In response to this request, as in previous discuss ions of flow
regimes, the resource agencies which responded, dec 1 i ned to
recommend specific flow regimes until additional information is
available. Data concerning incremental flows will be available in
the fall of 1983 to provide additional information for the
consultation process. Additional detailed information for all
riverine habitats and all seasons will be available by the summer of
1984. Agencies will continue to be asked for recommendations on
flow preferences and consultation will continue until appropriate
flow releases, considering agency requests and power generation
requirements, are finalized.
Since specific agency recommendations on flow are lacking, several
alternative flow regimes have been considered in order to provide a
complete analyses of the range of potential flow regimes for both
power generation and protection of downstream fisheries
resources. The seven flow regimes set forth in the license
application filed February 28, 1983 have been supplemented by three
additional flow regimes (E,F, & G). These flow regimes (see Table
8.54) range from those which optimized project economics (Case A) to
those which approximate pre-project flows (Case G). These regimes
are believed to encompass all possible flow regimes which could be
proposed by resource agencies, especially since the regimes
presented include one which reflects average pre-project or
run-of-river conditions (Case G).
Minimum Energy Demand
The energy patent used in the model is based on monthly load
forecasts discussed in Section 5 of this Exhibit. This pattern is
imposed as demand on the Susitna hydroelectric system and reservoir
operaton is simulated to yield this energy at all times. Downstream
flow requirements may cause exceedence of this minimum energy
requirement. Likewise, this minimum energy requirement may cause
exceedence of minimum downstream flow needs.
Reservoir Operating Rule Curve
The minimum energy demand controls the reservoir operation and
energy production during critical low inflow periods. During other
periods, it is apparent that additional energy could be produced
B-2-123
because of larger runoff volumes and consequent higher reservoir
l eve l s.
Essentially, with a reservoir rule curve which establishes minimum
reservoir levels at different times during the years, particularly
in winter, than by following a set energy patent. At the same time,
the rule curve ensures that low flow sequences do not materially
reduce the energy potential below a set minimum or firm annual
energy. The rule curve also reduces the occurrence of spi 11 age
during summer months by creating additional flood storage
potentia 1 .
Maximum Usable Energy Level
Maximum energy is established by the load growth for the Railbelt
system for a given year in the planning horizon, for example, year
2010. If maximum usable energy is exceeded due to high downstream
flow requirements, flow is shifted from the powerhouse to the outlet
facilities in sufficient quantities to reduce energy production
while maintaining downstream flows.
The physical characteristics of the two reservoirs, the operational
characteristics of the powerhouses, and either the monthly or weekly
average flow at each dams ite and Gold Creek for the number of years
to be simulated are input to the simulation program. The program
then uses the hierachy listed above to satisfy the minimum flow
requirement at Gold Creek and the minlmum energy requirement. The
reservoir operating rule curve is checked and if "extra water" is in
storage, the "extra water" is used to produce additional energy up
to the maximum usable energy level. A further consideration is that
the reservoir cannot be drawn below the maximum allowable drawdown
limit. The energy produced, the flow at the damsites and at Gold
Creek, and the reservoir levels are determined for the period of
record input to the model.
B-2-124
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,_
....
The model algorithm which relates energy produced to powerhouse
flows and reservoir heads is:
where: TP -Total power output (kW)
= Average monthly head in upper and
lower reservoir, respectively
=Mean monthly powerhouse flow (cfs);
upper reservoir
= Mean monthly powerhouse
(cfs); lower reservoir
K1 = Unit Conversion Constant = 0.084773
E = Efficiency = 0.85
flow
For power computations using the above equations, monthly head is
used and is determined from the average water surface elevation at
the beginning and end of each month less tailwater elevation. A
constant tailwater elevation of 1455 and 850 has been assumed for
Watana and Devil Canyon, respectively. This is considered
acceptable since the variation in tailwater elevation for the range
of flows expected is +5 feet from the assumed values and is within
the reasonable limit of accuracy of the tailwater elevation
discharge curves.
Storage is depleted or replenished depending upon the magnitude of
monthly inflow and outflow. Generally, storage is depleted during
the months of October through May and replenished from June to
September. The conversion from storage to flow is:
Q = SDm/K 2
Where: Q = Discharge (cfs)
s = Change in storage (acre-feet)
K2 = Constant (cfs days to acre-feet) = 1.984
OM = Number of days in month M.
The water surface elevation is determined by linear interpolation of
the storage-elevation curves input to the model. The power potential
determined is effectively the average power during the month.
Multiplying this power by the number of hours in each month results
in monthly energy in kilowatt-hours.
When outflow is be 1 ow downstream flow requirements, either further
powerhouse flows are released or spillage occurs depending on demand
B-2-125
for additional energy or powerhouse capacity. This will deplete
storage or replenish it more slowly depending upon inflow.
The rule curve followed has been derived from several iterations of
the reservoir operation and is believed to be close to the best fit
for the energy produced up to the year 2010 and with the forecast
developed by Battelle. In practice, with increase in system demand,
the rule curve could be modified to yield energy that would fit into
the system demand in a more economical manner.
The model procedure allows the reservoir to be drawn down each month
to the rule curve levels when the water surface elevation at the
start of the month is above these levels. Starting elevations below
the target suggests that a dry sequence is experienced.
When the reservoir is being refilled during high streamflows, a
further condition specifies the amount of surplus water that should
be placed into storage. This is to ensure that during the early
months of the filling sequence {May and June) the reservoir does not
end up full too early in the summer. If filling occurred quickly,
it is possible that spillage would be high in August and September.
Preventing such spillage results in the production of more energy in
May, June and July and a reduction in spillage amounts later on.
The process that led to the selection of the flow sc.enario used in
this license application includes the following steps:
Determination of pre-project flows at Gold Creek, Watana ana
Devil Canyon for 32 years of record
Selection of range of flows to be included in the analysis
Selection of timing of flow releases to match fishery
requirements
Selection of maximum drawdown at Watana
Determination of energy produced for the ten flow release
scenarios being studied
Determination of net benefits for each flow scenario
Selection of range of flows acceptable based on economic factors
Influence of instream flow and fishery considerations on
selection of project operational flows.
A summary discussion of the detailed analysis is presented in the
following paragraphs.
B-2-126
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(a) Pre-Project Flows
(b)
(c)
The USGS has operated a gaging station (Station 15292000) at Gold
Creek on the Susitna River continuously since 1950. They have
also operated the Cantwell gage near Vee Canyon on the upper end
of the proposed Watana reservoir since 1961. These two gaging
stations combined with a regional analysis were used to develop a
32-year record for the Cantwell gage. The flow at Watana and
Devil Canyon was then calculated using the Cantwell flow as the
base and adding an incremental flow proportional to the additional
drainage area between the Cant we 11 gage and the dams i tes. The
resulting flows at Watana and Devil Canyon are presented in Tables
B.52 and B.53.
Range of Post-Project Flows
During investigation of the full range of flows appropriate for
use as operation a 1 target flows at Gold Creek, two factors were
considered: that operational flow which would produce the maximum
amount of winter energy from the project, neglecting all other
considerations (Case A), and that operation a 1 summer flow thought
to have minimum impact on downstream fishery and instream flow
uses (Case G). Between these two end points, eight additional
flow scenarios were established. The minimum target flows for all
ten flow scenarios are presented in Table B.54.
Timing of Flow Releases
In the reach of the river between Talkeetna and Devil Canyon, it
is presently perceived that an important aspect of successful
salmon spawning is providing access to the side channel and slough
areas connected to the ma i nstem of the river. Access to these
areas is primarily a function of water level (flow) in the main
channel of the river during the period when the salmon mu~t gain
access to the spawning areas. Field studies during 1981 and 1982
have indicated that access should be provided in late July,
August, and early September. Thus, tile project operational flow
has been scheduled to satisfy this requirement; i.e., the flow
will be increased the last week of July, held constant during
August and the first two weeks of September, and then decreased to
a level specified by energy demands in mid-to late September.
This release of water for access to spawning areas is in
competition with the timing of releases for optimal energy
generation. For energy generation, releases would be less in the
summer when demand for energy is less. Flows \vould be stored in
the reservoir for use during other seasons when energy demand is
higher and inflow to the reservoir is less. Case A (Table B.54)
distributes the release of flows in the optimal fashion throughout
the year for winter energy generation, given reservoir storage
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constraints. Case 0 on the other hand, sets flow releases in the
summer at those which have minimal impact on the access to spawn-
ing areas (19,000 cfs, Trihey 1982), and distributes the flows
throughout the rest of the year in a pattern consistent with best
energy production given the extent of summer releases.
Cases E and F provide not only for immigration of adults in
August, but also provide a greater margin of safety for outmigra-
tion of juveniles during early summer. For example, flows of
10,290 and 16,000cfs for May and June, respectively, for Case E,
are provided to facilitate outmigration. For Case F, flows of
10,480 and 18,000 cfs for May and June, respectively, are provided
(See Table 8.54 for specifics on these proposed release schedules)
to ensure that adequate flows are available for outmigration of
juvenile salmonids. Case G consists of essentially run-of-river
conditions based on average flows for the previous 32 years. Case
G flows should avoid all impacts to the fisheries other than those
encountered naturally under pre-project conditions.
Results of ongoing instream flow and fisheries habitat investiga-
tions may a 11 ow the Power Authority and the resource agencies to
agree upon flow regimes which could enhance fisheries over
pre-project levels and provide suitable power for the Ranbelt
area. Results of the economic analysis of these cases in terms of
annu a 1 average energy and average firm energy are presented in
Table 8.55 and 8.56 for the Watana only and the Watana/Devil
Canyon stages of the project, respectively. Dependable capacity
for both project stages is presented in Figure 8.76. Net benefits
to the project of all flow regimes considered are presented in
Table 8.57.
(d) Maximum Drawdown
The maximum drawdown was selected as 140 feet for Watana and 50
feet for Devil Canyon (Acres 1982c, Vol. 1). Because the Devil
Canyon maximum drawdown would be controlled by technical consider-
atons, the 50-foot drawdown was not reconsidered and has been
retained as the upper limit for Devil Canyon. On the other hand,
the Watana maximum drawdown is governed by intake structure cost,
energy production, and downstream flow considerations; thus, it
was refined during the 1982 studies. This refinement process
resulted in the selection of 1120 feet as the maximum drawdown for
the Watana development.
(e) Energy Production
Using the pre-project flows, the ten flow release scenarios and
the maximum drawdowns established in subsection (a)-(d) above
B-2-128
(f)
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were input to the reservoir simulation model. The amount of
energy produced, the flow at Gold Creek and the reservoir levels
were determined for the 32 years of record. A summary of the
energy produced usitlg the ten flow scenarios is presented in Table
8.56, and B.57 respectively for Watana operating alone and for
Watana and Devil Canyon operating together.
It can be seen in Tables 8.56 and 8.57 that there are significant
differences in total potential energy produced. Case G produces
about 29 percent less energy than Case A for Watana and Devil
Canyon operating together. However, these potentials must be
analyzed in light of the energy usable by the system. Under Case
G, a great deal of energy is produced in June through September,
corresponding to a time when demand is also lowest. Additionally,
the Case G firm energy, which reflects the dependable capacity of
the project (See Section 4.3), is much less ·in December in
comparison to Case A. This_ discounts the value of the project
capacity and requires the system to need other power generation
projects to meet reliability criteria. --
Net Benefits
To measure the economic impacts of the decreased and rescheduled
energy from Case A to Case G, the ten flow cases were tested in
the reservoir operation model using a regression equation based on
the results of previous OGP analysis for the load forecast
presented in the February 1983 license application. The long-
term present worth of net benefits for each of the ten operational
flow cases were calculated and tabulated in Table B. 57. The
regression equation was used to determine the present worth value
(1982 dollars) of the long-term production costs (LTPWC) of
supplying the Railbelt energy needs with each of the ten Susitna
cases plus other needed generation. The LTPWC of each of the flow
cases was then compared to the best non-Sus i tna seen ari o
(developed in Exhibit D). Table 8.57 presents the LPTWC of each
of the ten cases. The February 1983 1 icense application load
forecast used to develop Tab 1 e B. 57 corresponds to the Reference
Case forecast in approximately year 2018.
The net benefit presented in Table 8.57 is the difference between
the LTPWC for the "best thermal option" and the LTPWC for the
various Susitna options. In Table B.57, Case A represents the
maximum usable energy option and results in a benefit of $1,359
million. As flow is transferred from the net winter to the
August-September time period the usable energy decreases. This
decrease is not significant until the flow provided at Gold Creek
during August reaches the 12,000 to 14,000 cfs range. For a
summer flow of 20,000 cfs at Gold Creek, the Susitna project
becomes less attractive than the thermal alternative. A summer
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flow of 20,000 cfs corresponds to the Case G flow scenario wnich
represents minimum downstream fishery impact.
(g) Operational Flow Scenario Selectio8
Based on the economic analysis discussed above, it was judged
that, while Case A flows produced the maximum net benefit, the
loss in net benefits (compared to Case A) for Cases A1, A2
and C were of an acceptable magnitude. The loss associated with
Case C1 is on the borderline between acceptable and
unacceptable.
As fishery and instream flow impact (and hence mitigation costs
associated with the various flow scenarios) are further
quantified, the decrease in mitigation costs associated with high
flows may warrant selecting a higher flow case such as C1.
However, the loss in net benefits associated with Case C2
through G was not considered acceptable and it is doubtful that
the mitigation cost -reduction associated with these higher flows
will bring them into the acceptable range.
(h) Instream Flow and Fishery Impact on Flow Selection
As noted earlier, the primary function controlled by the late
summer flow is the ability of the salmon to gain access to their
traditional spawning grounds. In stream flow assessment conducted
during 1981 (the wettest July-August on record) and 1982 (one of
the driest July-August on record) has indicated that, for flows of
the Case A magnitude, severe impacts would occur wnich cannot be
mitigated except by compensating through hatchery construction.
For flows in the 12,000 cfs range (flows similar to those that
occurred in August 1982) the salmon can, with difficulty, obtain
access to their spawning grounds. To help salmon obtain access to
spawning areas during flows of 12,000 cfs, physical mitigation
measures were incorporated into the mitigation plan presented in
Chapter 3 of Exhibit E.
Based on this assessment, the Case Al and A2 flow seen ari os
are considered unacceptable, thus establishing a lower limit for
the acceptable flow range as approximately 12,000 cfs (Case C) at
Gold Creek during August.
As a result, by combining the economic analysis and the instream
flow considerations, the Case C scenario, providing a flow of
12,000 cfs at Gold Creek during August (see Table 8.54), has been
selected as the project operational flow. As a more refined
assessment of fishery impact, mitigation costs and projected
project net benefits becomes available, the project operational
flow will be adjusted.
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3 -DESCRIPTION OF PRO,JECT OPERATION
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3 -DESCRIPTION OF PROJECT OPERATION
3.1 -Operation Within Railbelt Power System
A staged development is planned for implementation of Susitna power
generation. The following schedule for unit start-up is proposed:
No. and Size of Total Susitna
Start-up Units (MW) On-line Capacity*
Date Dams i te Brought on Line (MW)
1994 (Jan.) Watana 4 X 170 680
1994 (July) Watana 2 X 170 1020
2002 Devi 1 Canyon 4 X 150 1620
As shown above, the first four units are scheduled to be on line at
Watana in early 1994, followed by the remaining two Watana units in mid
1994. Start-up of all four units at Devil Canyon is planned for 2002.
This section describes the operation of the Watana and Devil Canyon
power plants in the Railbelt electrical system. Under current
conditions in the Railbelt, a total of nine utilities share
responsibility for generation and distribution of electric power, with
1 imited interconnections. The proposed arrangement for opt imi zat ion
and control of the dispatch of Susitna power to Railbelt load centers
is based on the expectation that single entity will eventually be set
up for this purpose.
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 pro-
duction 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.
*Installed generating capacity.
B-3-1
3.2 -Plant and System Operation Requirements
The main function of system p1anning and operation contro1 is the
allocation of generating plant on a short-term operational basis so
that the total system demand is met by the avail able generation at
minimum cost consistent with the security of supply. The objectives
are generally the same for long-term planning or short-term operation
load dispatching, but with important differences in the latter case.
In the short-term case, the actual state of the system dictates system
reliability requirements, overriding economic considerations in load
dispatching. An important factor arising from economic and reliability
considerations in the system planning and operation is the provision of
stationary reserve and spinning reserve capacity. Figure B.58 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).
3.3 -General Power Plant and System Reliability Criteria.
Reliability criteria for electric power system operation
divided into those criteria which apply to generation
requirements and those which apply to transmission
assessment.
can be
capacity
adequacy
The following basic reliability standards and criteria have been
adopted for planning the Susitna project.
(a) Installed Generating Capacity
Sufficient generating capacity is installed in the system to
insure that the probability of occurrence of load exceeding the
available generating capacity shall not be greater than one day in
ten years (Loss-of-load probability (LOLP) of 0.1). The
evaluation of generation reserve by probability techniques has
been used for many years by utilities and the traditionally
adopted value of LOLP has been about one day in ten years ,1 Z
Many utilities and reliability councils in the lower-48 states
continue to employ such a criterial.3 Although there has been
lulowering Reliability Offers Little Benefit, .. Sebesta, D,
Electrical World July 1, 1978 pp. 70-1,
z.,Power System Reliability Evaluation, .. IEEE Tutorial Course, 1982
p. 54' 56.
3usymposium on Reliability Criteria for System Dynamic Performance"
IEEE Power Engineering Society 1977 Winter Meeting pp. 15, 34,36.
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no economic evaluation of reliability criteria in the Railbelt, at
least one major utility has expressed the aim of achieving a LOLP
of one day in ten years. 4 Therefore for the present level of
study a LOLP of one day in ten years has been adopted.
The above generation reliability criteria was used as an input to
the generation planning model described in Section 1.5 of this
Exhibit. This generation planning model was used to evaluate the
generation expansion with the Susitna project and an all thermal
expansion program as presented in Exhibit D.
The system generation reserve under each expansion program for
each year from 1993 to 2010 is shown on Table 8.58. As can be
seen from Table 8.58 the average percent reserve for the Susitna
program is about 12 percentage points higher than the thermal
program. However, this difference is due to the entrance of large
blocks of hydro units in 1993 and 2002 rather than the reliability
criteria. The average percent reserve for both programs are about
equal if the years of large block hydro influence are excluded
from the Susitna program average. Thus, from a generation
standpoint the Sus i tna project pro vi des the same level of
reliability as a thermal alternative with about the same average
reserve margin.
(b) Transmission System Capability
1he high-voltage transmission system should be operable at all
load levels to meet the following unscheduled single or double
contingencies without instability, cascading or interruption of
load.
The single contingency situation is the loss of any single
generating unit, transmission line, transformer, or bus (in
addition to normal scheduled or maintenance outages) without
exceeding the applicable emergency rating of any facility; and
The double contingency situation is the subsequent outage of
any remaining equipment, except for line, without exceeding the
short time emergency rating of any facility.
In the single contingency situation, the power system must be
capable of readjustment so that all equipment would be loaded
4Letter of June 22, 1983 from Thomas R. Stahr, General Manager,
Anchorage Municipal Light and Power.
B-3-3
within normal ratings and, in the double contingency situation,
within emergency ratings for the probable duration of the outage.
During any contingency:
Sufficient reactive power
controls is installed to
voltage profiles.
(MVAR)
maintain
capacity with adequate
acceptable transmission
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 location.
Having the transmission lines in parallel, instead of one line
only, improves greatly the reliability of the transmission system.
Besides removing the necessity of hot lines maintenance, the
frequency of failure of the transmission system will be lowered by
a factor of about 15.
The transmission system performance was examined by performing
load flow and transient stability studies. Load flow studies
examined the system under normal operating conditions with all
elements in service, then by removal of first one line segment
critical circuit breaker verified adequate system performance
under single contingency. Double contingency operating was
verified by further removal of a second element (not including a
second line).5
The following criteria were used for the load flow studies:
1. Energization while system in normal status:
a. Voltage at the sending end should not be reduced below 0.90
per unit.
b. Initial voltage at the receiving end should not exceed 1.10
per unit.
c. Following the switching of transformers and VAR control
devices onto the system, the voltage at the receiving end
should not exceed 1.05 per unit.
2. In case of normal status or single contingency and peak load:
a. The voltages at all buses tapped for loading shall stay
between 0.95 and 1.05 per unit.
5The loss of two parallel line circuits would result in loss of
the load center served and was not considered in double con-
tingency studies.
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b. The voltage/load angle between the Susitna generators and
any point of the system should not exceed 45°.
3. In case of double contingency and peak load:
a. The voltages at all buses tapped for loading shall stay
between 0.90 and 1.10.
b. The voltage/load angle between the Susitna generators and
any point of the system should not exceed 55°.
Both the 1993 and 2002 system configurations were tested for
energization (no load), and for peak load flows (1020 and 1971 MW,
respectively) under normal conditions and under selected
contingency conditions.
Figure 8.57A is a one-line diagram showing 1993 system performance
under a critical double contingency condition, in this case with
one of the Devil Canyon-Willow lines out of service and with the
additional loss of one of the Willow-Knik Arm lines.
The critical parameters of the above case are shown in Table 8.59.
As can be seen from Tab 1 e B. 59, the system performs within the
criteria established above.
Figure B. 57 A shows the 2002 system configuration and the double
contingency case which is the same 1993 double contingency case.
Table 8.59 shows the critical parameters for the 2002 case. From
Table 8.59, it can be seen that the transmission system is capable
of satisfactory operation under the double contingency conditions
shown.
In addition to the load flow studies, the dynamic stability
studies also indicated that the system remains stable following
the clearing of the severest disturbance that could occur, namely
a three phase fault at Devil Canyon.
The loss of two circuits on the same right-of-way has a low level
of probability if the spacing between the two circuits are set far
apart to minimize this potential problem. Part of the reserve
capacity shown on Table B.58 will be in the form of spinning
reserve. As determined in the generation planning studies this
spinning reserve will be from the next most economical increment
of capacity over those units required to meet load considering the
system as a whole. In addition to spinning reserve, standby
reserve can be maintained by the utilities in individual load
centers using less economical units. The cost of this spinning
and standby reserve have been included in the economic analyses
presented in Exhibit D.
8-3-5
(d) Summary
Operational reliability criteria thus fall into four main
categories:
LOLP of 0.1, or one day in ten years, is maintained for the
recommended plan of operation;
The single and double contingency requirements are maintained
for any of the more probable outages in the plant or
transmission system;
System stability and voltage regulation are assured from the
electrical system studies. Detailed 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; and
The loss of all Susitna transmissions lines on a single
right-of-way has a low level of probability. In the event of
the loss of all lines serving a load center, standby reserve in
the affected load center can be brought on line to meet
critical loads.
The Railbelt utilities have no specific reliability criteria at
the present time. Statistical data are not readily available.
However, the foregoing criteria would represent significant
i~provements over the present system reliability and bring the
quality of service closer in line 1-Jith other major utility
systems in the country.
3.4 -Economical Dispatch of Units
A Susitna Area Control Center wi 11 be located at Watana to control
both the Watana and the Devil Canyon power plants. The control center
wi 11 be 1 inked through the supervisory system to the Central Dispatch
Control Center at Willow.
Operation will be semi-automatic with generation instructions input
from the Central Dispatch Center at Willow, but with direct control of
the Susitna system at the control center 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
-Man-machine communication through visual display units (VDU) and
console.
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In addition, the computer system will be capable of retrieval of
technical data, design criteria, equipment characteristics and operat-
ing limitations, schematic diagrams, and operating/maintenance records
of the units.
The Susitna Area Control Center will be capable of completely
independent control of the Central Dispatch Center in case of system
emergencies. Similarly, it will be possible to operate the Susitna
units in an emergency situation from the Central Dispatch Center,
although this chould be an unlikely operation considering the size,
complexity, and impact of the Susitna generating plants on the system.
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 11 0rder-of-merit 11 schedule, short-
term demand forecasts, limits of operation of units, and unit main-
tenance 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 11 0rder-of-merit 11 schedule. The schedule gives the
capacity 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 Contra l 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
capacity to be used is determined by 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-dominated power system (such as the Railbelt 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-
dominated power system. The planned hydro units at Watana
typically are well suited to load following and frequency
regulation of the system and providing spinntng reserve. Greater
flexibility of operation was a significant factor in the selection
of six units of 170 MW capacity at Watana, rather than fewer
larger-size units.
B-3-7
(c) Operating Limits of Units
There are strict constraints on the minimum load and the loading
rates of machines; to dispatch load to these machines requires a
systemwide dispatch program taking these constraints into
consideration. In general, hydro units have excellent start-up
and load following characteristics; thermal units have good
part-loading characteristics .
. Typical plant loading limitations are given below:
(i) Hydro Units
Reservoir regulation
not-to-exceed maximum
daily or seasonally.
constraints
and minimum
res u 1t i ng in
reservoir levels,
Part loading of units is impossible in the zone of rough
turbine operation (typically from above no-load-speed to
50 percent load) due to vibrations 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.
-The units have a minimum economic shutdown period (about
three hours).
The total cost of using conventional units includes
banking, raising pressure and part-load operations prior
to maximum economic operation.
(iii) Gas Turbines
' Cannot be used a spinning reserve because of very poor
efficiency and reduced service life.
-Require eight to ten minutes for normal start up from
cold. Emergency start-up times are of the order of five
to seven minutes.
(d) Optimum Maintenance Program
An important part of operational planning which can have a
significant effect on operating costs is maintenance programming.
The program specifies the times in the year and the sequence in
which plant is released for maintenance.
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3.5 -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
considering operational reliability are system response, load-frequency
control, and spinning reserve capabilities.
(a)
(b)
(c)
Power System Analyses
Load-frequency response studies determine the dynamic stability
of the system due to the sudden forced outage of the largest unit
(or generation block) in the system. The generation and load are
not balanced, and, if the pick-up rate of new generation is not
adequate, loss of load will eventually result from under-voltage
and under frequency re]__p.y 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 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 1.67 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 recommeded that a factor of 1.5 times the largest unit size
be considered as a mimimum for the Alaska Railbelt system, with 2
times the largest unit size as a fairly conservative value (i.e.,
300 to 340 MW).
The quickest response in system generation will 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
seconds. This is one of the particularly important advantages of
the Susitna hydro units. Gas turbines can only respond in a
second-stage operation within five to ten minutes and would not
strictly qualify as spinning reserve. If thermal units are run
part-loaded (e.g., 75 percent), this 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 economic loading resulting from such an operation.
Protective Relaying System and Devices
The primary protective relaying systems provided for the
generators and transmission system of the Susitna project are
designed to disconnect the faulty equipment from the system in the
8-3-9.
fastest possible time. Independent
installed to the extent necessary to
backup for the primary protective system
damage, to limit the shock to the system
of service. The relaying systems are
restrict the normal or necessary network
the power system.
3.6 -Dispatch Control Centers
protective systems are
provide a fast-clearing
so as to limit equipment
and to speed restoration
designed so as not to
transfer capabilities of
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:
manag~ the main system energy transfers, advises system configura-
tion and checks overall security.
-Area Control Center (Generation connected to 345 kV system; for
example, Watana and Devil Canyon): deals with the loading of
generators connected directly to the 345 kV network, switching and
safety precautions of local systems, checks security of intercon-
nections to main system.
-District or Load Centers (138 kV and lower voltage networks):
generation and distribution at lower voltage levels.
For the Anchorage and Fairbanks areas, the district center functions
are incorporated in the respective area control centers.
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
-Devil Canyon reservoir regulation criteria
-Turbine loading and de-loading rates
-Part-loading and maximum loading characteristics of turbines and
generators
-Hydraulic transient characteristics of waterways and turbines
-Load-frequency control of demands of the system
-Voltage regulation requirements of the system
The Watana Area Contra l Center
control system to efficiently
is equipped with
carry out these
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a computer-aided
functions. The
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computer-aided control system allows a m1n1mum of highly trained and
skilled operators to perform the control and supervision 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 each unit individually as well as the plant/reservoir and project
operation as a whole.
3. 7 -Susitna Project Operation
The Watana development will operate as a base load project until the
Devil Canyon development enters operation at which time the Devil
Canyon development will operate on base and the Watana development will
operate on peak and reserve. The operation simulation of the
reservoirs 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. An optimum reservoir operation pattern was estab 1 i shed by
an iterative process to minimize net system operating costs while
maximizing firm and average annual energy production. This process is
discussed in Section 2 and resulted in the selection of flow regime C
as that selected for operation of the two developments. Referring to
flow regime C and the energy production given in Tables B.55 and B.56,
the annual plant factors for the developments, based on installed
capacity, are as fa 11 ows:
Watana Plus Devil Canyon
Development Watana Only6 Dev i1 Canyon Increment
Installed Capacity, MW 1020 1620 600
Annual Energy GWh/yr
Average 3499 6934 3435
Firm 2618 5451 2833
Ann ua 1 Plant Factor, %
Average 39 49 65
Firm 29 38 54
The energy generated by the project under flow regime C during dry and
mean water years-is shown on Tables B.55 and B.56. The year of lowest
energy generations after reservoir regulation during the 32 years of
record is 1971. For the combined Watana plus Devil Canyon development
the lowest energy generation, which is defined as firm energy
6Although Watana has an installed capacity on 1020 MW, its base load
dependable capacity in the month of December is 520 MW as discussed
in-Section 4.3 of this Exhibit. When related to the dependable
capacity, Watana operating alone would have average and firm annual
plant factors of 77 and 57 percent, respectively.
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generation, has a recurrence frequency approximately equal to 1 in 32
years as shown on Figure B. 64. Under a high flow year, say the wettest
year of the 32 years of record, energy generation for Watana only will
reach 3837 GWh per year and for Watana plus Devil Canyon, 8036 GWh per
year.
The determination of the dependable capacity and sensitivity to various
flow regimes is discussed in Section 4.
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4 -DEPENDABLE CAPACITY AND ENERGY PRODUCTION
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4 -DEPENDABLE CAPACITY AND ENERGY PRODUCTION
Table 8.26 summarizes design parameters for dependable capacity and
energy production levels .
4.1 -Hydrology
(a)
(b)
Historical Streamflow Records
Historical streamflow data are available for several gaging
stations on the Susitna River and its main tributaries.
Continuous gaging records were avail able for the following eight
stations on the river and its tributaries: Maclaren River near
Paxson, Denali, Cantwell, Gold Creek and Susitna Stations on the
Susitna River, Chulitna Station on the Chulitna River, Talkeetna
on the Talkeetna River, and Skwentna on the Skwentna River. The
longest period of record available is for the station at Gold
Creek (32 years from 1949 to 1981). At other stations, record
1 ength varies from 6 to 23 years. Gaging was continued at all
these stations as part of the project study program. A gaging
station was established at the Watana damsite in 1980, and
streamflow records are available for the study period. Partial
streamflow records are avail able at several other stations on the
river for varying periods; the station locations are sho1-1n in
Figure B.59. It should be noted that gaging will continue as the
project progresses in order to improve the streamflow record, as
well as after project completion at selected sites required for
project operation.
Water Resources
-Above its confluence with the Chulitna River, the Susitna
contributes approximately 20 percent of the mean annual flow
measured at Susitna Station near Cook Inlet. Figure B.60 sho1-1S
how the mean annual flow of the Susitna increases towards the
mouth of the river at Cook Inlet.
Seasonal variation of flow in the river is extreme and ranges from
very low values in winter (October to April) to high summer values
(May to September). For the Susitna River at Gold Creek, the
average winter and summer flows are 2210 and 20,200 cfs,
respectivley; i.e., a one to ten ratio. This large seasonal
difference is mainly due to effects of glacial and snow melt in
the summer.
The monthly average flows in the Susitna River at Gold Creek are
given in Figure B.61. Some 40 percent of the streamflow at Gold
Creek originates above the Denali and Maclaren gages. This
catchment generally comprises the glaciers and associated high
mountains. On the average, approximately 87 percent of the
streamflow recorded at Gold Crek Station occurs during the summer
months.
B-4-1
At higher elevations in the basin the distribution of flows is
concentrated even more in the summer months. For the Maclaren
River near Paxson (Elevation 4520), the average winter and summer
flows are 144 and 2100 cfs, respectivley; i.e., a 1 to 15 ratio.
The monthly percent of annual discharge and mean monthly
discharges for the Susitna river and tributaries at the gaging
stations above the Chulitna confluence are given in Table B.60.
(c) Streamflow Extension
Synthesized flows at the Watana and Devil Canyon damsites are
presented in Tables B.52 and B.53. Flow duration curves based on
these monthly estimates are presented for the Watana and Devil
Canyon damsites in Figures B.62 and B.63.
The FILLIN computer program developed by the Texas Water
Development Board was used to fill in gaps in historical
streamflow records at the eight continuous gaging stations. The
32-year record (up to 1981) at Gold Creek was used as the base
record. The procedure adopted for filling in the data gaps uses a
multisite regression technique which analyzes monthly time-series
data. Flow sequences for the 32-year period were generated at the
remaining seven stations. Using these flows at Cantwell Station
and observed Gold Creek flows, 32-year monthly flow sequences at
the Watana and Devil Canyon damsites were generated on the basis
of prorated drainage areas. Recorded streamfl ows at Watana and
Devil Canyon were included in the historical record where
avail able.
(d) Floods
The most common causes of flood peaks in the Sus itn a River basin
are snowmelt or a combination of snowmelt and rainfall over a
large area. Annual maximum peak discharges generally occur
between May and October with the majority (approximately 60
percent) occurring in June. Some of the annual maximum flood
peaks have also occurred in August or later and are the result of
heavy rains over large areas augmented by significant snowmelt
from higher elevations and glacial runoff. Table B.61 presents
selected flood peaks recorded at different gaging stations.
A regional flood peak and volume frequency analysis was carried
out using the recorded floods in the Susitna River and its
principal tributaries. These analyses were conducted for two
different time periods. The first period, after the ice breakup
and before freezup (May through October), contains the largest
floods which must be accommodated by the project. The second
period represents that portion of time during which ice conditions
occur in the river (October through May). These floods, although
smaller, can be accompanied by ice jamming and must be considered
during the construction phase of the project in planning the
design of cofferdams for river diversion.
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(e)
A set of multiple linear regression equations was developed using
physiographic basin parameters such as catchment area, stream
length, precipitation, snowfall amounts, etc., to estimate flood
peaks at ungaged sites in the basin. In conjunction with the
analysis of shapes and volumes of recorded large floods at Gold
Creek, a set of project design flood hydrographs of different
recurrence intervals was developed (see Figures B.65 and 8.66).
The results of the above analysis were used for estimating flood
hydrographs at the damsites and ungaged streams and rivers along
the access road alignments for design of spillways, culverts, etc.
Table 8.62 lists mean annual, 50-, 100-, and 10,000-year floods at
the Watana and Devil Canyon damsites and at the Gold Creek gage.
The proposed reservoirs at Watana and Devil Canyon would be
classified as 11 large 11 and with 11 high hazard potential" according
to the guidelines for safety inspection of dams laid out by the
Corps of Engineers. This would indicate the need for the probable
maximum flood (PMF) to be considered in the evaluation of the
proposed projects. Estimated peak discharges during the PMF at
selected locations are included in Table B.62, and the PMF hydro-
graph is presented in Figure B.66.
Table 8.63 lists the maximum flows through the various dam
facilities for the 50, 10,000 and PMF events.
Flow Adjustments
Evaporation from the proposed Watana and Devil Canyon reservoirs
has been evaluated to determine its significance. Evaporation is
influenced by air and water temperatures, wind, atmospheric pres-
sure, and dissolved solids within the water. However, the
evaluation of these factors 1 effects on evaporation is difficult
bee a use of their interdependence on each other. Consequently,
more simplified methods were preferred and have been utili zed to
estimate evaporation losses from the two reservoirs.
The monthly evaporation estimates for the reservoirs are presented
in Table 8.64. The estimates indicate that evaporation losses
will be less than or equal to additions due to precipitation on
the reservoir surface. Therefore, a conservative approach was
taken, with evaporation losses and precipitation gains neglected
in the energy calculations.
Leakage is not expected to result in significant flow losses.
Seepage through the relict channel is estimated as less than
one-half of one percent of the average flow and therefore has been
neglected in the energy calculations to date. This approach will
be reviewed when further investigations of the re 1 i ct channe 1 are
completed.
Minimum flow releases are required throughout the year to maintain
downstream river stages. The most significant factor in determin-
ing the minimum flow value is the maintenance of downstream
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fisheries. The monthly flow requirements that were used in deter-
mination of project energy potential are given in Table 8.54.
The numbers shown in Table 8.54 represent the minimum streamflow
required at Gold Creek. These requirements would remain constant
for all phases of project development. The actual flows released
from the project at Watana (when Watana is operating alone) and at
Devil Canyon (for combined operation of both dams) will be less
than the required Gold Creek flows prorated on the basis of
streamflow contributions from the intervening basin area. Table
8.65 and B.66 give the typical minimum required flow releases at
Watana and Devil Canyon for a 32-year period of record.
After completion of Devil Canyon, flow releases from Watana will
be regulated by system operation requirements. Because th~ tail-
water of the Devil Canyon reservoir will extend upstream to the
Watana tailrace, there will be no release requirements for
streamflow maintenance of Watana for the Watana/Devil Canyon
combined operating configuration.
Existing water rights in the Susitna basin were investigated to
determine impacts on downstream flow requirements. Based on
inventory information provided by the Alaska Department of Natural
Resources, it was determined that existing water-users will not be
affected by the project. A listing of all water appropriations
located within 1 mile of the Susitna River is provided in Table
8.67.
4.2 -Reservoir Data
(a) Reservoir Storage
Gross storage volume of the Watana reservoir at its normal maximum
operating level of 2185 feet is 9.5 million acre-feet, which is
about 1.6 times the mean annual flow {MAF) at the damsite. Live
storage in the reservoir is 3.7 million acre-feet. Devil Canyon
reservoir has a gross storage of 1.1 million acre-feet and 1 i ve
storage of 0.35 million acre-feet.
The area-capacity curves for the Watana and Devi 1 Canyon reser-
voirs are provided in Figures 8.67 and Figure 8.68, respectively.
(b) Rule Curves
Operation of the reservoirs for energy production is based on
target water surface levels set for the end of each month. The
target level represents that level below which no energy beyond
firm energy can be produced. In other words, if the reservoir
level drops below the target, only firm energy will be produced.
In wetter years when the reservoir leve 1 surpasses the target
level, energies greater than firm energy can be produced, but only
as great as the system energy demand allows.
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With a reservoir rule curve which establishes m1n1mum reservoir
levels at different times during the year, it will be possible to
produce more energy in wetter years during winter than by
fo ll owing a set energy pattern. At the same time, the ru 1 e curve
ensures that low flow sequences do not materially reduce the
energy potential below a set minimum or firm annual energy.
The rule curves for Watana and Devil Canyon under combined
operation are shown in Figure B.68.
4.3 -Operating Capabilities of Susitna Units
The operating conditions of both the Watana and Devil Canyon turbines
are summarized in Table B.65.
(a) Watana
The Watana powerhouse will have six generating units with a
nominal capacity of 170 MW corresponding to the minimum December
reservoir level (Elevation 2114).
The gross head on the plant will vary from 610 feet to approx i-
mate l y 735 feet. The maximum unit output will change with head,
as shown on Figure B.70.
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, and at 680 feet rated net head.
Maximum and minimum heads on the units will be 725 feet and 600
feet, respectively. The full-gate output of the turbines will be
about 275,000 hp at 725 feet net head and 209,000 hp at 600 feet
net head. Overgating of the turbines may be possible, providing
approximately five percent additional power; however, at high
heads the turbine output will be restricted to avoid overloading
the generators. The best-efficiency point of the turbines will be
established at the time of preparation of bid documents for the
generating euqipment 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 turbine 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 one
percent lower at minimum head. The preliminary performance curve
for the turbine is shown on Figure B.71.
The Watana plant output may vary from zero, with the units at
standstill or at spinning reserve, to approximately 1200 when all
six units are operating under maximum output at maximum head. A
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graph of plant efficiency versus output and the number of on-1 ine
units is shown in Figure 8.72. The load following requirements of
the plant result in widely varying loading, but because of the
multiple unit installation the total plant efficiency varies only
s 1 i ght 1 y 0
(b) Devil Canyon
The Devil Canyon powerhouse will have four generating units with a
nominal capacity of 150 MW based on the minimum reservoir level
(Elevation 1405) and as corresponding gross head of 555 feet in
the station.
The gross head on the plant will vary from 555 feet to 605 feet.
The maximum unit output will change with head as shown in Figure
8.73.
The rated average operating net head for the turbine has been
est ab 1 i shed at 590 feet. A 11 owing for generator 1 osses, this
results in a rated turbine output of 225,000 hp (168 MW) at full
gate.
The generator rating has been selected as 167 MVA with a 90
percent power factor. The generators will be capable of contin-
uous operation at 115 percent rated power. Because of the high
capacity factor for the Devil Canyon station, the generators will
be sized on the basis of maximum turbine output at maximum head,
allowing for a possible 5 percent addition in power from the
turbine. This maximum turbiune output (250,000 hp) is within the
continuous overload rating of the generator.
Maximum and minimum net heads on the units will be 596 feet and
547 feet, respectively. The full-gate output of the turbines will
be about 235,000 hp at maximum net head and 201,000 hp at minimum
net head. Overgating of the turbines may be possible, providing
approximately five 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 efficiency of the turbines wi 11 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 8.74.
The Devil Canyon plant output may vary from zero to 700 MW with
all four units operating at maximum output. The combined plant
efficiency varies with output and number of units operating, as
shown in Figure 8.75. As with Watana, the plant efficiency varies
only slightly with loading due to the load following capabilities
of multiple units.
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Dependable Capacity and Energy Production
I
The dependable capacity of a hydroelectric project is defined as
the capacity, which for specified time interval and period, can be
relied upon to carry system load, provide assured reserve and meet
firm power obligations, taking into account unit operating varia-
bles, hydrologic conditions, and seasonal or other characteristics
of the load to be supplied.
Sections (a) and (b) above describe the operating variables of the
units to be installed at Watana and Devil Canyon based on the
hydrologic conditions discussed in Section 4.1 and the. reservoir
operation studies presented in Section 2.8. Based on those
operation studies, the average and firm annual energy production
from Watana operating alone and 1rJatana and Devil Canyon operating
together were determined for 10 flow regime cases shown on Tab 1 e
8.54. Average annual energy and firm energy production using the
10 flow-eases are presented on Tables B. 56 and B. 57 for Watan a
alone, and for Watana and Devil Canyon together, respectively. As
discussed in Section 2.8, Case C was selected for Project
operation. Case A was evaluated to maximize energy production.
The other cases which were evaluated were derived to encompass
possible Agency recommendations for avoiding impacts to the
fisheries resources (as discussed in Section 2.8). The firm and
average annual energy production for some of these cases are as
fa 11 ows:
Firm Annual1 Average Annual
Flow Regime Energy Production GWh Energy Generating GWh
Watana Watana Plus Watana Watana Plus
Only Devil Canyon Only Devil Canyon
A 2665 5509 3495 6962
c 2618 5451 3499 6934
D 2553 4765 3303 6355
G 2282 4064 2911 4927
A comparison of the monthly peak loads as shown on Figure B.58 to
the capacity available from Watana alone and Watana and Devil
Canyon operating together shows that the maximum exceedance of
plant capability by peak load in both cases occurs in the month of
December. The Susitna units were dispatched under the typical
winter weekday load curve shown on Figure 8.58 to determine the
dependable capacity of Watana alone and Watana and Devil Canyon
operating together.
As stated in Section 3.7, the Watana development will operate as a
base load project until the Devil Canyon development begins opera-
1 Minimum annual energy ba~ed on 32 years of streamflow.
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tion at which time the Devil Canyon development will operate on
base and the Watana development will operate on peak and reserve.
Figure 8. 76 shows the dependab 1 e capacity of Watana and
Devil Canyon in relation to the peak load forecast for each of the
four flow regimes mentioned above. As can be seen from Figure
8.76, the dependable capacity of the developments increases as the
peak load increases unti 1 such time as the capacity 1 imit of the
units, based in opeating variables and hydrologic conditons, is
reached. That dependable capacity in 2020 achieved under each
flow regime is as follows:
Flow Regime
Dependab 1 e
Capacity in 2020~ MW
Dev1l
Watana Canyon Total
A
c
0
G
947
893
850
697
4.4 -Tailwater Rating Curve
425
379
347
225
1372
1272
1197
922
The tailwater rating curve for the Watana development is shown on
Figure 8.67 and for the Devil Canyon development on Figure 8.68.
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TABLES
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TABLE B.O
ALASKA POWER AUTHORITY, RESOURCE AGENCY CONSULTATION CORRESPONDENCE AND
MEETING LOG CONCERNING AQUATIC AND FISHERIES RESOURCES, 1980 THROUGH 1983
DATE TOPIC
July 1980 Establishment of Susitna Hydro
Steering Committee
Aug. 21, 1981 ADF&G letter relative to the impact of
the Transmission Route on fisheries
Dec. 31, 1981 NMFS review of the 1980 Fish Ecology
Annual Report
April 1981 Fishery reports (1980) provided to DNR,
ADF&G, NMFS, USFWS, EPA, BLM to keep
those agencies up to date on the
progress of the fishery program
Fall 1981 Establishment of the Susitna Fisheries
mitigation Review Committee -letter
from NMFS, COE, EPA, ADF&G, DNR
Dec. 30, 1981 Letter to Acres from ADF&G regarding
the development of the Fish and
Wildlife Mitigation Policy
Feb. 23, 1982 Acres response to ADF&G letter
Dec. 30, 1982 Letter to APA from USFWS regarding the
development of the Fish and Wildlife
IV!itigaton Pol icy
Feb. 24, 1982 Acres response to USFWS letter
Dec. 31, 1981 Letter to APA from NMFS regarding the
development of the Fish and Wildlife
Mitigation Policy
Feb. 23, 1982 Acres response to NMFS letter
REFERENCE
Exhibit E
Pg. E-11-3 &
Tab 1 e E . 11. 8
Exhibit E
Chapter 11
Appendix E11C
Exhibit E
Chapter 11
Appendix E11C
Exhibit E
Chapter 11
Appendix E11c
Ex hi bit E
Chapter 11
Appendix E11E
Exhibit E
Chapter 11
Appendix E11E
Exhibit E
Chapter 11
Appendix E11E
Exhibit E
Chapter 11
Apendi x E11E
Exhibit E
Chapter 11
Appendix EllE
Exhibit E
Chapter 11
Apendix EllE
Exhibit E
Chapter 11
Appendix EllE
B.O (continued)
FISHERY COORDINATION CORRESPONDENCE
DATE TOPIC
Jan.20, 1982 Meetings of Fisheries Mitigation
Review Group to discuss Fish and
Wildlife Mitigation Policy and
fisheries mitigation options (ADF&G,
EPA, NMFS, DNR, BLM, USFWS)
April 1, 1982 Fish and Wildlife Mitigation Policy
distributed for final review (EPA
DEC, DNR, NMFS, USFWS, ADF&G, BLM)
May 13, 1982 Minutes meeting of Fisheries Mitigation
Review Group
July 27, 1982 Letter from AOF&G to APA regarding
Fisheries Impact Assessment
Sept. 1982 APA Response to ADF&G letters
Sept. 1982 Letter from APA requesting review of
the Feasibility Report and Agency
responses
Oct. 1982
Oct. 1982
Letter from NMFS regarding fisheries
flow release, with APA response
Letter from USFWS regarding aquatic
studies, with APA response
REFERENCE
Exhibit E
Chapter 11
Appendix EllE
Exhibit E
Chapter 11
Appendix EllE
Exhibit E
Chapter 11
Appendix E11E
Exhibit E
Chapter 11
Appendix EllE
Ex hi bit E
Chapter 11
Appendix E11E
Ex hi bit E
Chapter 11
Appendix E11E
Exhibit E
Chapter 11
Appendix El1E
Exhibit B
Chapter 11
Appendix E11E
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B.O (continued)
FISHERY COORDINATION CORRESPONDENCE
DATE TOPIC
Nov. 29-Dec. 3, Workshop with APA, all environmental
1982 subcontractors, Acres, and EPA, ADF&G
NMFS, DNR, DEC, BLM, and USFWS
Jan. 1983
Jan. 1983
Letter from USFWS setting forth
USFWS Resource Categories, with
APA response
Agency comments on Draft License
Application
REFERENCE
Ex hi bit E
Chapter 11
Appendix EllE
Exhibit E
Chapter 11
Appendix EllE
Exhibit E
Chapter 11
Appendix El1J
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TABLE B.l: POTENTIAL HYDROElECTRIC DEVELOPMENT
Capi-tal Average Economlc 1
Dam Cost Instal led Annual Cost of Source
Proposed Height Upstream $million Capacity Energy Ener-8y of
Site Type Ft. Regulation ( 1980) (MW) GWh $/10 0 kWh Da-ta
Gold. Creek2 Fill 190 Yes 900 260 1,140 31 USBR 1953
Olson
(Susltna I I) Concrete 160 Yes 600 200 915 31 USBR 1953
KAISER 1974
COE 1975
Dev i I Canyon Concrete 675 No 830 250 1,420 27 This Study
Yes 1,000 600 2,980 17 "
High Devi I Canyon " (Susltna I) FIll 855 No 1,500 800 3,540 21 II
Dev I I Creek 2 Fill Approx No
850
Watana Fill 880 No 1,860 800 3,250 28 If
Susitna Ill Fill 670 No 1,390 350 1,580 41 II
Vee F iII 610 No 1,060 400 1, 370 37 II
Maclaren 2 F iII 185 No 530 4 55 180 124 II
Denali Fill 230 No 480 4 60 245 81 "
Butte Creek2 Fi II Approx No 40 130 3 USBR 1953
150
Tyone 2 Fi II Approx No 6 22 3 -USBR 1953
60
Notes:
(1) Includes AFOC, Insurance, Amor-tization, and Operation and Maintenance Costs.
(2) No detailed engineering or energy studies undertaken as par-t·of this study.
(3) These are approximate estimates and serve only to represent the potential of these two damsites In perspective.
(4) Include estimated costs of power generation facility.
. J
DAM
Site Type
Gold Creek Fill
Olson
(Sus ltna II) Concrete
Dev i I Canyon Fill
Concrete
Arch
Concrete
Gravity
High Devil Canyon
(Susltna I)
Fi II
Devil Creek Fll r
Watana Fill
Susltna Ill Fill
Vee Fi II
Maclaren FJ I I
DenalI Fi II
Notes:
(1) DependabJe.Capaclty
TABLE B.2 -COST COMPARISONS
Capital Cost Estimate2
A c R E s 1980
Instal led Capital Cost
Capacity-MW S million
600
800
800
350
400
55
60
1,000
1, 500
1,860
1,390
1,060
530
480
Installed
Capac Jty -MW
776
776
700
792
445
l'bne
(1980 $)
oTRERS
Capital Cost
$ ml Ilion
890
550
6:30
910
1,480
1,630
770
500
(2> Excluding Anchorage/Fairbanks transmission lntertle, but Including local access and transmission •
J _j -J J
SOurce and
Date of Data
USRB 1968
COE 1975
COE 1975
COE 1978
COE 1975
COE 1978
KAISER 1974
COE 1975
COE 1975
.)
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TABLE B.3: DAM CREST AND FULL SUPPLY LEVELS
Average Staged Full Dam bitm
Dam Supply Crest Tail water Helght 1
Site Construction Level -Ft. Level -Ft. Level -ft. ft.
Gold Creek tb 870 880 680 290
Olson No '~~20 l,OlO 810 310
Portage Creek No 1,02~ 1,.030 870 250
Oev II Canyon -
Intermediate
!"""' height tb 1,250 1,270 890 465
Devil Canyon -
full height tb 1,450 1,470 890 675 -High Devll Canyon No 1, 610 1,630 1,030 710
No 1, 750 1, 775 1,030 855
Watana Yes 2,000 2,060 1,465 . 680
Stage 2 2_,200 2,225 1,465 880
Susitna Ill No 2,340 2~360 1, 810 670 ,-Vee tb 2.,330 2,350 1, 925 610
Maclaren No 2,395 2,405 2,300 185
!""" Denali tb 2, 540 2, 555 2,405 230
~=
( 1) To fo.undation l-evel.
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TABLE B.4 ·-CAPITAL COST ESTIMATE SUt+tARIES
SUSITN\ BASIN DAM SQ-IEMES
COST IN $MILLION 1980
Dev II Canyon HIgh Dev II Canyon Watana Susltna II I Vee Maclaren Denali
1470 tt Crest 1775 tt Crest 2225 ft Crest 2360 +t Crest 2350 ft Crest 2405 ft Crest 2250 ft Crest
Item 600 MW 800 MW 800 MW 330 MW 400 MW No eower No eower
1 ) Lands, Damages & Reservoirs 26 11 46 13 22 25 38
2) Diversion Works 50 48 71 88 37 118 112
3) Main Dam 166 432 536 398 183 106 100
4) Auxiliary Dam 0 0 0 0 40 0 0
5) Power System 195 232 244 140 175 0 0
6) Sp II I way System 130 141 165 121 74 0 0
7) Roads and Bridges 45 68 96 70 80 57 14
8) Transmission Line 10 10 26 40 49 0 0
9) Camp Fac I titles and Support 97 140 160 130 100 53 50
1 0) Miscellaneous 1 8 8 8 8 8 5 5
11) Mobilization and Preearatlon 30 47 57 45 35 15 14
Subtotal 757 1137 1409 1053 803 379 .. 333
Contingency (20%> 152 227 282 211 161' 76 67
Engineering and Owner's
Administration (12%> 91 136 169 126 96 45 40
TOTAL 1000 1500 1860 1390 1060 500 440
Notes:
(I) Includes recreational tacit ltles, buildings and grounds and permanent operating equipment.
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TABLE B.5-RESULTS OF SCREENING MODEL
Total Demand Optimal Solution First Suboptimal Solution Second Suboptimal Soultion
Max. lnst. Total Max. I nsf. Tota I Max. lnst. Total
Cap. Energy Site Water Cap. Cost Site Water Cap. Cost Site Water Cap. Cost
Run MW GWh Names Level MW $ mi II ion Names Level MW $ million Names Level MW $ mi II ion
400 1750 High 1580 400 885 Devi I 1450 400 970 Watana 1950 400 980
Devi I Canyon
Canyon
2 800 3500 High 1750 800 1500 Watana 1900 450 1130 Watana 2200 800 1860
Devil
Canyon
Devi I
Canyon 1250 350 710
TOTAL 800 1840
3 1200 5250 Watana 2110 700 1690 High 1750 800 1500 High 1750 820 1500
Devi I Devil
Canyon Canyon
Devi I 1350 500 800 Vee 2350 400 1060 Susitna 2300 380 1260
Canyon Ill
TOTAL 1200 2490 TOTAL 1200 2560 TOTAL 1200 2760
4 1400 6150 Watana 2150 740 -1770
N 0 S 0 L U T I 0 N N 0 S 0 L U T I 0 N
Devi I 1450 660 1000
Canyon
TOTAL 1400 2770
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TABLE 8.6: INFORMATION ON THE DEVIL CANYON DAM AND TUNNEL SCHEMES
Dev II Canyon Tunnel Scheme
Item Dam 1 2 3 4
Reservoir Area
(Acres) 7,500 320 0 3,900 0
River Miles
Flooded 31.6 2.0 0 15.8 0
Tunnel Length
(Mi I es) 0 27 29 13.5 29 -Tunnel V~l ume
( 1000 Yd ) 0 JJ 1976 12,863 3,732 5, 131
Compensating Flow
Release (cts) 0 1,000 1,000 1,000 1,000
Reservoir Volume
( 1000 Acre-teet) 1,100 9.5 --350 --
Dam Hei9ht
(feet) 625 75 --245 --
Typical Dally
Range of Discharge
From Oev II Canyon 6,000 4,000 4,000 8,300 3,900
Powerhouse to to to to to
(cfs) 13,000 14,000 14,000 8,900 4,2oq
Appr-ax I mate
Maximum Dally j -Fluctuations In
Reservoir (feet) 2 15 --4 --
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TABLE B.7 -DEVIL CANYON TUNNEL SCHEMES
COSTS, POWER OUTPUT AND AVERAGE ANNUAL. ENERGY
Stage
STAGE 1:
lnsta II ed
Capacity <MW)
Watana Dev i I Canyon
Tunnel
Watana Dam BOO
STAGE 2:
Tunnel:
-Scheme
-Scheme 22 Scheme 3
-Scheme 4
Notes:
BOO
70
B50
BOO
550
1, 150
330
365
Increase 1 In
Installed Capacity
(MW)
550
420
3BO
365
(1) Increase over single Watana, 800 MW development 3250 GWh/yr
(2) Includes power and energy produced at re-regulatlon dam
Dev I I Canyon
Average Annual
Energy
CGWh)
2,050
4,750
2,240
2,490
(3) Energy cost is based on an economic analysis (i.e. using 3 percent Interest rate)
1 Increase In
Average
Annua I Energy
CGWh)
2,050
1,900
2,1BO
B90
Tunne I , Scheme
Tota I Project
Costs
$Million
1980
2320
1220
1490
3 Cost of
Addition' I
Energy
· Cml lis/kWh)
42.6
52.9
24.9
73.6
- l
TABLE 6.8 -CAPITAL COST ESTIMATE Sut41ARIES
TUNNEL SCHEMES
COSTS IN $MILLION 1980
Item
Land and damages, reservoir clearing
Diversion works
Re-regulatlon dam
Power system
(a) Main tunnels
(b) Intake, powerhouse, tailrace
and sw I tchyard
Secondary power station
Spl I lway system
Roads and bridges
Transml ss Jon I I nes
Camp facl 1 Jtles and support
M I see I le1neous
Mobl I izatlon and preparation
TOTAL CONSTRUCTION COST
Contingencies (20%>
Engineering, and Owner's Administration
TOTAL PROJECT COST
557
123
Two 36 ft
dla tunneis
14
35
102
680
21
42
42
15
131
8
47
1,137
227
136
1,500
453
123
One 40 ft
dla tunnel
14
35
102
576
21
42
42
15
117
8
47
1,015
203
. 122
1,340
, ...•
-
-
-
-
-I
-
-
~·
l 1 ) l ) -~ l 1
TABLE B.9. SUSITNA DEVELOPMENT PLANS
Cumulative
Stage/Incremental Data System Data
Annual
Maximum Energy
Capital Cost Earliest Reservoir Seasonal Production Plant
$ Millions On-line Ful I Supply Draw-Firm Avg. Factor
Plan Stage Construction ( 1980 va I ues) Date 1 Level -ft. down-ft GWh GWh $
1. 1 1 Watana 2225 ft 800MW 1860 1993 2200 150 2670 3250 46
2 Dev I I Canyon 1470 ft
600 MW 1000 1996 1450 100 5500 6230 51
TOTAL SYSTEM 1400 MW 2860
1. 2 1 Watana 2060 ft 400 MW 1570 1992 2000 100 1710 2110 60
2 Watana raIse to
2225 ft 360 1995 2200 150 2670 2990 85
3 Watana add 400 MW
capacity 130 2 1995 2200 150 2670 3250 46
4 Dev I I Canyon 1470 ft
600 MW 1000 1996 1450 100 5500 6230 51
TOTAL SYSTEM 1400 MW 3060
1.3 Watana 2225 ft 400 MW 1740 1993 2200 150 2670 2990 85
2 Watana add 400 MW
capacity 150 1993 2200 150 2670 3250 46
3 Dev I I Canyon 1470 ft
600 MW 1000 1996 1450 100 5500 6230 51
TOTAL SYSTEM 1400 MW 2890
TABLE B.9 (Continued)
Cumulative
Stage/Incremental Data System Data
Annual
Maximum Energy
Capital Cost Earliest Reservoir Seasonal Production Plant
$ Mi II ions On-I ine Full Supply Draw-Firm Avg. Factor
Plan Stage Construction ( 1980 va I ues) Datal Level -ft. down-ft. GWh GWh %
2. 1 High Devil Canyon
1775 ft 800 MW 1500 1994 3 1750 150 2460 3400 49
2 Vee 2350 ft 400 MW 1060 1997 2330 150 3870 4910 47
TOTAL SYSTEM 1200 MW 2560
2.2 High Devl I Canyon
1630 ft 400 MW 1140 1993 3 1610 100 1770 2020 . 58
2 High Devil Canyon
add 400 MW capacity
raise dam to 1775 tt 500 1996 1750 150 2460 3400 49
3 Vee 2350 ft 400 MW 1060 1997 2330 150 3870 4910 47
TOTAL SYSTEM 1200 MW 2700
2.3 HIgh Dev I .1 Canyon
1775 ft 400 MW 1390 1994 3 1750 150 2400 2760 79
2 High Devl I Canyon
add 400 MW capacity 140 1994 1750 150 2460 3400 49
3 Vee 2350 ft 400 MW 1060 1997 2330 150 3870 4910 47
TOTAL SYSTEM 1200 MW 2590
3. 1 1 Watana 2225 ft 800 MW 1860 1993 2200 150 2670 3250 46
2 Watana add 50 MW
tunnel 330 MW 1500 1995 1475 4 4890 5430 53
TOTAL SYSTEM 1180 MW 3360
J ] J j J J
l 1
TABLE 6.9 (Continued)
Cumulative
Stage/Incremental Data System Data
Annual
Maximum Energy
Capital Cost Earliest Reservoir Seasonal Production Plant
$ Ml I lions On-I ine Ful I Supply Draw-Firm Avg. Factor
Plan Stage Construction ( 1960 va l~o~es) Date 1 Leve I -ft. down-ft. GWh GWh %
3.2 1 Watana 2225 ft 400 MW 1740 1993 2200 150 2670 2990 65
2 Watana add 400 MW
capacity 150 1994 2200 150 2670 3250 46
3 Tunnel 330 MW add
50 MW to Watana 1500 1995 1475 4 4690 5430 53
3390
4.1 Watana
2225 ft 400 MW 1740 19953 2200 150 2670 2990 65
2 Watana add 400 MW
capacity 150 1996 2200 150 2670 3250 46
3 High Devl I Canyon
1470 ft 400 MW 660 1996 1450 100 4520 5260 50
4 Portage Creek
1030 ft 150 MW 650 2000 1020 50 5110 6000 51
TOTAL SYSTEM 1350 MW 3400
NOTES: --.-
(I) AI lowing for a 3 year overlap construction period between major dams.
(2) Plan 1.2 Stage 3 Is less expensive than Plan 1.3 Stage 2 due to lower mobl llzatlon costs.
(3) Assumes FERC I I cense can be f II ed by June 1964, I e. 2 years later than for the Watana/Dev I I Canyon PI an 1.
TABLE B.10. SUSITNA ENVIRONMENTAL DEVELOPMENT PLANS
Cumulative
Stage/Incremental Data System Data
Annual
Maximum Energy
Capital Cost Earliest Reservoir Seasonal Production Plant
$ Millions On-I jne Full Supply Draw-Firm Avg. Factor
Plan Stage Construction (1980 values) Date Level -ft. down-ft GWh GWh %
E 1. 1 Watana 2225 ft 800MW
and Re-Regulatlon
Dam 1960 1993 2200 150 2670 3250 46
2 Dev i I Canyon 1470 ft
40Qt.1W 900 1996 1450 100 5520 6070 58
TOTAL SYSTEM 1200MW 2860
El.2 I Watana 2060 ft 400MW 1570 1992 2000 roo 1710 2110 60
2 Watana raise to
2225 ft 360 1995 2200 150 2670 2990 85
3 Watana add 400MW
capacity and
Re-Regulation Dam 230 2 1995 2200 150 2670 3250 46
4 Devil Canyon 1470 ft
400MW 900 1996 1450 100 5520 6070 58
TOTAL SYSTEM 1200MW 3060
E1.3 1 Watana 2225 ft 400MW 1740 1993 2200 150 2670 2990 85
2 Watana add 400MW
capacity and
Re-Regulation Dam 250 1993 2200 150 2670 3250 46
3 Devi I Canyon 1470 ft
400 MW 900 1996 1450 100 5520 6070 58
TOTAL SYsTEM 1200MW 2690
_J -) J
... 1
TABLE B.lO (Continued)
Cumulative
Stage/Incremental Data System Data
Annual
Maximum Energy
Capital Cost Earliest Reservoir Seasonal Production Plant
$ Mi II ions On-line Full Supply Draw-Firm Avg. Factor
Plan Stage Construction ( 1980 va I ues) Date 1 Level -ft. down-ft. GWh GWh %
E 1.4 1 Watana 2225 ft 400MW 1740 1993 2200 150 2670 2990 85
2 Devil Canyon 1470 ft
400MW 900 1996 1450 100 5190 5670 81
TOTAL SYSTEM 800MW 2640
E2. 1 High Devil Canyon
1775 ft 80oMW and
Re-Regulatlon Dam 1600 1994 3 1750 150 2460 3400 49
2 Vee 2350ft 400MW 1060 1997 2330 150 3870 4910 47
TOTAL SYSTEM 1200MW 2660
E2.2 High Devil Canyon
1630 f t 400MW 1140 1993 3 1610 100 1770 2020 58
2 HIgh Dev I I Canyon
raise dam to 1775 ft
add 400MW and
Re-Regu I at I on Dam 600 1996 1750 150 2460 3400 49
3 Vee 2350 ft 400 MW 1060 1997 2330 150 3870 4910 47
TOTAL SYSTEM 1200MW 2800
E2.3 High Devil Canyon
1775 f t 400MW 1390 1994 3 1750 150 2400 2760 79
2 High Devil Canyon
add (OOMW capacity
and Re-Regulatlon
Dam 240 1995 1750 150 2460 3400 49
3 Vee 2350 ft 400MW 1060 1997 2330 150 3870 4910 47
TOTAL SYSTEM 1200 2690
,
TABLE B. 10 (Continued)
Cumulative
Stage/Incremental Data Slstem Data
Annual
Maximum Energy
Capital Cost Earliest Reservoir Seasonal Production Plant
$ Millions On-ljne Full Supply Draw-Firm Avg. Factor
Plan Stage Construction ( 1980 va I ues) Date Level -ft. down-ft. GWh GWh %
E2.4 High Devil Canyon
1755 ft 400MW 1390 1994 3 1750 !50 2400 2760 79
2 High Devil Canyon
add 400MW capacity
and Portage Creek
Dam 150 ft 790 1995 1750 !50 3170 4080 49
3 Vee 2350 ft
400MW 1060 1997 2330 150 4430. 5540 47
TOTAL SYSTEM )2<fO
E3.2 Watana
2225 ft 400MW 1740 1993 2200 !50 2670 2990 85
2 Watana add
400 MW capac I ty
and Re-Regulatlon
Dam 250 1994 2200 150 2670 3250 46
3 Watana add SOMW
Tunnel Scheme 330MW 1500 1995 1475 4 4890 5430 53
TOTAL SYSTEM 1180MW "3490"
E4.1 Watana
2225 ft 400MW 1740 19953 2200 150 2670 2990 85
2 Watana
add 400MW capacity
and Re-Regulatlon
Dam 250 1996 2200 150 2670 3250 46
3 High Devil Canyon
1470 ft 400MW 860 1998 1450 100 4520 5280 50
4 Portage Creek
1030 ft 150MW 650 2000 1020 50 5110 6000 51
TOTAL SYSTEM 1350 MW 3500"
NOTES:
~Allowing for a 3 year overlap construction period between major dams.
(2) Plan 1.2 Stage 3 Is less expensive than Plan 1.3 Stage 2 due to lower mobilization costs.
(3) Assumes FERC license can be filed by June 1984, le. 2 years later than for the Watana/Devll Canyon Plan 1.
_j J J J
) l } l
TABLE 8.11 -RESULTS OF ECONOMIC ANALYSES OF SUSITNA PLANS -MEDIUM LOAD FORECAST
Susltna Develoement Plan Inc. Installed Capacity (MW) by Total System Total System
On-11 ne Dafes Categor~ In 2010 Installed Present Remarks Pertaining to
Plan Stages OGP5 Run Thermal H~dro Capacity In Worth Cost the Susitna Basin
No. 2 3 4 I d. No. Coal Gas Oi I Other Susltna 2010-MW $ Million Development Plan
E 1. 1 1993 2000 LXE7 300 426 0 144 1200 2070 5850
E1.2 1992 1995 1997 2002 L5Y9 200 501 0 144 1200 2045 6030
E 1.3 1993 1996 2000 L8J9 300 426 0 144 1200 2070 5850
1993 19-96 L7W7 500 651 0 144 800 2095 6960 Stage 3, Devil Canyon Dam
not constructed
1998 2001 2005 LAD7 400 276 30 144 1200-2050 6070 Delayed implementation
schedule
El.4 1993 2000 LCK5 200 726 50 144 800 1920 5890 Total development limited
to 800 MW
Modified
E2.1 1994 2000 LB25 400 651 60 144 800 2055 6620 High Devil Canyon lim !ted
to 400 MW
E2.3 1 1993 1996 2000 L601 300 651 20 144 1200 2315 6370
1993 1996 LE07 500 651 30 144 800 2125 6720 Stage 3, Vee Dam, not
constructed
Modified
E2.3 1993 1996 2000 LEB3 300 726 220 144 1300 2690 6210 Vee Dam rep I aced by
Chakachamna Dam
3.1 1993 1996 2000 L607 200 651 30 144 1180 2205 6530
Special
3. 1 1993 1996 2000 L615 200 651 30 144 1180 2205 6230 Capital cost of tunnel
reduced by 50 percent
E4.1 1995 1996 1998 LTZ5 200 576 30 144 1200 2150 6050 Stage 4 not constructed
NOTES:
(I) Adjusted to Incorporate cost of re-regulation dam
TABLE 6.12-RESULTS OF ECONOMIC ANALYSES OF SUSJTNA PLANS-LOW AND HIGH LOAD FORECAST
Susltna Develoement Plan Inc. Installed Capacity (MW) bt Total SysTem Total System
On'-II ne Dates Categor~ In 2010 Installed Present Remarks PertaInIng to
Plan Stages OGP5 Run Thermal H~dro Capacity In Worth Cost the Susltna Basin
No. 2 3 4 ld. No. Coal ~as Oil OTher Susifna 2010-MW $ Mill ion DeveJoemenT Plan
VERY LOW FORECAST 1
Et.4 1997 2005 L767 0 651 50 144 800 1645 3650
LOW LOAD FORECAST
E1.3 1993 1996 2000 Low energy demand does not
warrant plan capaciTies
E1.4 1993 2002 LC07 0 351 40 144 800 1335 4350
1993 LBK7 200 501 80 144 400 1325 4940 Stage 2, Dev II Canyon Dam,
not constructed
E2. 1 1993 2002 LG09 100 426 30 144 800 1500 4560 HIgh Dev I I Canyon limited
to 400 MW
1993 LBUt 400 501 0 144 400 1445 4850 Stage 2, Vee Dam, not
constructed
E2.3 1993 1996 2000 --Low energy demand does not
warrant plan capacities
Special
3. 1 1993 1996 2000 L613 0 576 20 144 780 1520 4730 Capital cost of tunnel
reduced by 50 percent
3.2 1993 2002 L609 0 576 20 144 780 1520 5000 Stage 2, 400 MW addition
to Watana, not constructed
HIGH LOAD FORECAST
E1.3 1993 1996 2000 LA73 1000 951 0 144 1200 32~5 10680
Modified
E1.3 1993 1996 2000 2005 LBV7 800 651 60 144 1700 3355 10050 Chakachamna hydroelectric
generating station (480 MW>
brought on line as a fourth
stage
E2.3 1993 1996 2000 LBV3 1300 951 90 144 1200 3685 11720
Modified
E2.3 1993 1996 2000 2003 LBYt 1000 876 10 144 1700 3730 11040 Chakachamna hydroelectric
generating station (480 MW)
brought on line as a fourth
stage
NOTE:
(1) Incorporating load management and conservation
I J j J -~) ] ~l __ ___) J ·~ ~ ) J J J
I"""'
TABLE B.13-ANNUAL FIXED CARRYING CHARGES
Economic Parameters
Economic Cost of
Ll fe Money Amortization Insurance
Project T::r:J:!e -Years %
Thermal -Gas TurbIne
(0 It FIred) 20 3. 00
-Diesel, Gas Turbine
(Gas Fired} and
Large Steam
Turbine 30 3. 00
-Small Steam Turbine 35 3. 00
Hydropower 50 3. 00
FUEL COSTS AND ESCALATION RATES
Market PrIces
Natural Gas
Base Period (January 1980)
-Prices ($/million Btu>
Shadow (Opportunity} Values
$1. 05
2. 00
Coal
$1. 15
.1. 15
Rea I Esca I at I on Rates <Percentage>
-Change Compounded (Annually)
1980 -1985
1986 -1990
1991 -1995
Composite (average} 1980-1995
1996 -2005
2006 -2010
1. 79%
6. 20
3. 99
3. 98
3. 98
0
9. 56%
2. 39
-2.87
2. 93
2. 93
0
%
3.72
2. 10
1. 65
0. 89
%
o.· 25
a. 25
0. 25
a. 10
Distillate
$4.00
4. 00
3. 38%
3. 09
4. 27
3. 58
3. 58
0
TABLE 8.14-SUMMARY OF THERMAL GENERATING RESOURCE PLANT PARAMETERS
P L A N T T Y P E
~~A[-FIRED STEAM C~BINED GAS
Parameter CYCLE TURBINE DIESEL
500 MW 250 MW 100 MW 250 MW 75 MW 10 MW
Heat Rate (Btu/kWh) 10,500 10,500 10,500 8,500 12,000 11,500
O&M Costs
Fixed O&M ($/yr/kW) 0.50 1.05 1. 30 2.75 2.75 0.50
Variable O&M ($/MWh) 1.40 1.80 2.20 0.30 0.30 5.00
Outages
Planned Outages <%> 11 11 11 14 11 1
Forced Outages <%> 5 5 5 6 3.8 5
Construction Period (yrs) 6 6 5 3 2
Start-up Time (yrs) 6 6 6 4 4
Total Ca~ltal Cost
($ mill ion)
Rail belt: 175 26 7.7
Beluga: 1,130 630 290
Unit Ca~ltal Cost ($/kW) 1
Rail belt: 728 250 718
Beluga: 2473 2744 3102
Notes:
(1) Including AFDC at 0 percent escalation and 3 percent Interest.
) . . __ j J
"""' I
TABLE B.15-ECONOMIC BACKUP CATA FOR EVALUATION OF PLANS
Parameter
Capital Investment
Fuel
Operation and Maintenance
TOTAL:
To"tal Present Worth COst for 1981 -2040
Period S Mllllon (~ Total)
Generation PI an
With High Devil
Canyon -Vee
2800 (44)
3220 (50)
350 (6)
6370 (I 00)
Generation Plan Generation PI an
WIth Watana -WIth Watana -
Dev I I Canyon Dam T unne I
2740 (47) 3170 (49)
2780 (47) 3020 (46)
330 (6) 340 (5)
5850 ( 100) 6530 (100)
AI I Thermal
Generat,lon Plans
2520 (31)
5240 (64)
370 (5)
8130 ( 100)
TABLE B.16-ECONOMIC EVALUATION OF DEVIL CANYON DAM AND TUNNEL SCHEMES AND WATANA/DEVIL CANYON AND HIGH DEVIL CANYON/VEE PLANS
ECONOMIC EVALUATION:
-Base Case
SENSITIVITY ANALYSES:
-Load Growth
-Capital Cost Estimate
-Period of Economic
Analysis
-Discount Rate
-Fuel Cost
-Fuel Cost Escalation
-Economic Thermal Plant
Life
J J
Low
High
Period shortened to
(1980 -2010)
5,%
8% (Interpolated)
9,%
80,% baste fuel cost
O% fuel escalation
O% coal escalation
50% extension
O% extension
)
Present Worth of Net Benefit($ mil lion) of Total Generation
System Costs for the:
Devil Canyon Dam over Watana/Devll Canyon Dams over
the Tunnel Scheme the High Devil Canyon/Vee Dams
680
650
N.A.
520
210
1040
Higher uncertainty assoc-Higher uncertainty associated with
lated with tunnel scheme. H.D.C./Vee plan.
230 160
As both the capital and fuel costs associated with the tunnel
scheme and H.D.C./Vee Plan are higher than for Watana/Devll
Canyon plan any changes to these parameters cannot reduce the
Devl I Canyon or Watana/Devl I Canyon net benefit to below zero.
Remarks
Economic ranking: Devil Canyon
Dam scheme Is super .1 or .. to tunne I
scheme. Watana/Dev.ll Canyon Dam
plan Is superior to the. High
Devil Canyon Dam/Vee Dam plan.
The net benefit of the
Watana/Devll Canyon plan remains
pos It I ve tor the range of load
forecasts considered. No change
in ranking.
Higher cost.uncertalntles associ-
ated with higher cost
schemes/plans. Cost uncertainty
therefore does not affect
economic ranking.
Shorter period of evaluation
decreases economic differences.
Ranking remains unchanged.
RankIng remains unchanged.
Environmental
Attribute
Ecological:
-Downstream Fisheries
and Wildlife
Resident Fisheries:
WI ldllfe:
Concerns
Effects resulting
from changes In
water quantity and
qua llty.
Loss of res I dent
fisheries habitat.
Loss of wi I dl ife
habitat,
TABLE 8.17-ENVIRONMENTAL EVALUATION OF DEVIL CANYON DAM AND TUNNEL SCHEME
Appraisal
(Differences in impact
of two schemes)
No significant differ-
ence between schemes
regarding effects down-
stream of Devil Canyon.
Difference In reach
between Dev I I Canyon
dam and tunnel re-
regu I at I on dam.
Minimal differences
between schemes.
Minimal differences
between schemes.
Identification
of difference
With the tunnel scheme con-
trolled flows between regula-
tion dam and downstream power-
house offers potential for
anadromous fisheries enhance-
ment In this 11 mile reach of
the river.
Devil Canyon Dam would Inundate
27 miles of the Susltna River
and approximately 2 miles of
Devi I Creek. The tunnel scheme
would Inundate 16 miles of the
Susltna River.
The most sensitive wildlife ha-
bitat in this reach is upstream
of the tunnel re-regulation dam
where there is no significant
difference between the schemes.
The Devl I Canyon Dam scheme in
addition Inundates the river
va I I ey between the two dam-
sites resulting In a moderate
increase in impacts to wildlife.
Appraisal Judgment
Not a factor In evaluation of
scheme.
If fisheries enhancement oppor-
tunity can be realized the tun-
nel scheme offers a positive
mitigation measure not available
with the Devil Canyon Dam
scheme. This opportunity Is
considered moderate and favors
the tunnel scheme. However,
there are no current plans for
such enhancement and feasibil-
Ity Is uncertain. Potential
value Is therefore not signi-
ficant relative to additional
cost of tunnel.
Loss of habitat with dam scheme is
less than 5% of total for Susitna
main stem. This reach of river Is
therefore not considered to be
highly significant for resident
fisheries and thus the difference
between the schemes is minor and
favors the tunnel scheme.
Moderate wildlife populations of
moose, black bear, weasel, fox,
wolverine, other smal I mammals
and songbirds and some riparian
cliff habitat for ravens and
raptors, in 11 miles of river,
would be lost with the dam scheme.
Thus, the difference in loss of
wildlife habitat Is considered
moderate and favors the tunnel
scheme.
Scheme judged to have
the least potential Impact
Tunnel i DC
X
X
X
TABLE B.17 (Continued)
Environmental
Attribute
Cu ltura I:
Land Use:
Appraisal
(Differences In Impact
Concerns of two schemes)
Inundation of Potential differences
archeological sites. between schemes.
Inundation of Devil
Canyon.
Significant differen~e
between sche~e-s.
Identification
of difference
Due to the larger area inun-
dated the probability of inun-
dating archeological sites is
increased.
The Devl I Canyon Is considered
a unique resource, 80 percent
of which would be inundated by
the Devi I Canyon Dam scheme.
This would result In a loss of
both an aesthetic value plus
the potential for white water
recreation.
OVERALL EVALUATION: The tunnel scheme has overal I a lower impact on the environment.
Scheme judged to have
the least potential impact
Appraisal Judgment
Significant archeological
sites, if identified, can proba-
bly be excavated. Additional
costs could range from several
hundreds to hundreds of thousands
of dollars, but are stilI consider-
ably less than the additional cost
of the tunnel scheme. This concern
is not considered a factor In scheme
evaluation.
The aesthetIc. and to some extent
the recreational losses associ-
ated with the development of the
Devl I Canyon Dam Is the main
aspect favoring the tunnel scheme.
However, current recreational uses
of Devil Canyon are low due to
I lmited access. Future posslbl lites
include major recreational develop-
ment with construction of restau-
rants, marinas, etc. Under such
conditions, neither scheme would be
more favorable.
Tunnel DC
X
l l
Social
Aspect
Potential
non-renewable
resource
displacement
Impact on
state economy
Impact on
local economy
Seismic
exposure
Overall
Evaluation
--1 1 l .... J
TABLE B.IB-SOCIAL EVALUATION OF SUSITNA BASIN DEVELOPMENT SCHEMES/PLANS
Parameter
Million tons
Beluga coal
over 50 years
J
Risk of major
structural
failure
Potential
Impact of
fall ure on
hJman II fe.
Tunnel
Scheme
Dev II Canyon
Dam Scheme
High Devil Canyon/
Vee Plan .·
· Watana/Dev II
Canyon Plan
80 110 170 210
All projects would have similar Impacts on the state and
local economy.
AI I projects designed to similar levels of safety.
Any dam failures would effect the same downstream
population.
1. Devil Canyon Dam superior to tunnel.
2. Watana/Devll Canyon superior to High Devil Canyon/Vee plan.
Remarks
Devil Canyon Dam scheme
potential higher than
tunnel scheme. Watana/
Devl I Canyon plan nigher
than High Devil Canyon/
Vee plan.
Essent I a I I y no difference
between plans/schemes.
TABLE B.19 -ENERGY CONTRIBUTION EVALUATION OF THE DEVIL
CANYON DAM AND TUNNEL SCHEMES
Parameter Dam Tunnel Remarks,
Total Energ~ Production
Ca~ab I II t:t
Annual Average Energy GWh 2850 2240 Dev II Canyon dam annua I I y
develops 610 GWh and 540
Firm Annual Energy GWh 2590 2050 GWh more average and firm
energy respectively than
the tunnel scheme.
%Basin P~tentlal
Developed 43 32 Dev I I Canyon scheme
develops more of the
basin potential.
Energ~ Potential Not
Developed GWh 60 380 As currently envisaged,
the Devil Canyon Dam does
not develop 15 ft gross
head between the Watana
site and the Devil Canyon
reservol r. The tunnel
scheme Incorporates addl-
tiona! friction losses In
tunnels. Also the compen-
satlon flow released from
re-regulatlon dam Is not
used In conjunction with
head between re-regulatlon
dam and Devil Canyon.
Notes:
(1) Based on annua I average energy. Fu II potential based on USBR tour
dam scheme.
....
-
-
-
-
-
-
-
-
-
-
-
-
-
TABLE B.20 -OVERALL EVALUATION OF TUNNEL SCHEME AND DEVIL CANYON DAM SCHEME
ATTRIBUTE
Economic
Energy
Contribution
Environmental
Social
Overall
Evaluation
SUPERIOR PLAN
Dev I I Canyon Dam
Devil Canyon Dam
Tunnel
Devil Canyon Dam (Marginal)
Devil Canyon Dam scheme Is superior
Tradeoffs made:
Economl c advantage of dam scheme
Is judged to outweigh. the reduced
environmental Impact associated
w lth the t.unne I scheme.
i '.
J
I i
I
J
Environmental Attribute
Eco I og i ca I :
1) Fisheries
2) Wildlife
a) Moose
b) Caribou
c) Furbearers
d) Birds and Bears
Cultural:
TABLE B.21 -ENVIRONMENTAL EVALUATION OF WATANA/DEVIL CANYON AND HIGH DEVIL CANYON/VEE DEVELOPMENT PLANS
Plan Comparison
No significant difference in effects on downstream
anadromous fisheries.
HDC/V would inundate approximately 95 miles of the
Susitna River and 28 miles of tributary streams, in-
cluding the Tyone River.
W/DC would inundate approximately 84 miles of the
Susitna River and 24 miles of tributary streams,
Including Watana Creek.
Appraisal Judgment
Due to the avoidance of the Tyone River,
lesser inundation of resident fisheries
habitat and no significant difference in the
effects on anadromous fisheries, the W/DC plan
is judged to have less Impact.
HDC/V would inundate 123 miles of critical winter river Due to the lower potential for direct Impact
bottom habitat.. on moose populations within the Susitna, the
W/DC plan is judged superior.
W/DC would inundate 108 miles of thfs river bOttom
habitat.
HDC/V would inundate a large area upstream of Vee
utilized by three sub-populations of moose that range
in the northeast section of the basin.
W/DC would inundate the Watana Creek area utilized by
moose. The condition of this sub-population of moose
and the quality of the habitat they are using appears
to be decreasing.
The Increased length of river flooded, especially up-
stream from the Vee damslte, would result In the
HDC/V plan creating a greater potential division of
the Nelchina herd's range. In addition, an Increase
in range would be directly inundated by the Vee res-
ervoir.
The area flooded by the Vee reservoir is considered
important to some key furbearers, particularly red fox.
This area is judged to be more important than the
Watana Creek area that would be inundated by the W/DC
plan.
Forest habitat, important for birds and black bears,
exist along the valley slopes. The loss of this habi-
tat would be greater with the W/DC plan.
There Is a high potential for discovery of archeologi-
cal sites in the easterly region of the upper Susitna
basin. The HDC/V plan has a greater potential of
affecting these sites. For other reaches of the river
the difference between plans is considered minimal.
Due to the potential for a greater impact on
the Nelchlna caribou herd, the HDC/V scheme
Is considered Inferior.
Due to the lesser potential for Impact on fur-
bearers the W/DC is judged to be superior.
The HDC/V plan is judged superior.
The W/DC plan is judged to have a lower po-
tential effect on archeological sites.
Plan judged to have the
leastJ8otentlal im~act
X
X
X
X.
X
X'
TABLE B.21 (Continued)
Environmental Attribute
Aesthetic/
Land Use
Plan Comparison
With either scheme, the aesthetic quality of both
Devil Canyon and Vee Canyon would be Impaired. The
HDC/V plan would also Inundate Tsusena Falls.
Due to construction at Vee damsite and the size of
the Vee reservoir, the HDC/V plan would inherently
create access to more wilderness area than would the
W/DC plan.
OVERALL EVALUATION: The W/DC plan is judged to be superior to the HDC/V plan.
Appraisal Judgment
Both plans impact the val ley aesthetics. The
difference is considered minimal.
As it is easier to extend access than to
limit it, inherent access requirements were
considered detrimental and the W/DC plan Is
judged superior. The ecological sensitivity
of the area opened by the HDC/V plan rein-
forces this judgment.
(The I ower --impact on birds and bears associ a ted wIth HDC/V pI an is cons I dared to be outweighed by a I I
the other impacts which favor the W/DC plan.)
NOTES:
W = Watana Dam
DC= Devil Canyon Dam
HOC= High Devil Canyon Dam
V = Vee Dam
Plan judged to have the
least potential im~act
HDC/V W DC
X
-
!""'
!
-
-
TABLE 8.22 -ENERGY CONTRIBUTION EVALUATION <F n-IE WATANA/DEVI L CANYON
. AND HIGH DEVIL CANYON/VEE PLANS
Parame-ter
To-tal Energy Production
Capabll fty
Annual Average Energy GWh
Firm Annual Energy GWh
%Basin Po"ten"tlal
Developed (1)
Ener~y Po-tential Not Dave oped GWh (2>
Notes:
Watana/
Devil Canyon
6070
5520
91
60
High oevi I
Canyon/Vee
4910
3870
81
650
Remarks
Watana/Devll Canyon
plan annually devel-
ops 1160 GWh and
1650 GWh more average
and firm energy, re-
pectively, than the
High Devoll Canyon/Vee
Plan.,
Watana/Oevil Canyon
plan develops more of
the basin potential
As currently con-
ceived, the Watana/-
Devil Canyon plan
does not develop 15
ft of gross head
between the Watana
site and the Devil
Canyon reservoir.
Tile High Devil
Canyon/Vee Plan does
not develop 175 ft
gross head between
Vee site and High
Devil reservoir.
(I) Based on annual average energy. Full potential based on USBR tour
dam schemes.
(2) Includes losses due to unutlllzed head.
TABLE 8.23-OVERALL EVALU\TION OF THE HIGi DEVIL CANYON/VEE AND
WA TANA/DEV I L CANYON DAM PLANS
AHRIBUTE
Economic
Energy
Contribution
Environmental
Social
Overal I
Eva I uatlon
SUPERIOR PLAN
Watana/Devll Canyon
Watana/Devll Canyon
Watana/Dev II Canyon
Watana/Dev II Canyon CMargl na I )
Plan with Watana/Devll Canyon Is
super lor
Tradeoffs made: flbne
-'
-
I~
~,
-
-
TABLE -B-.24:--GCM3INED Wfl.TANA-PND [:EVIL CJWY<J>l-EPERATI<J>l
AVerage Jlilnua r
Watana1 l:eti 1 CaljQ11 Watana Dan Total Energy ( GW1)
Crest El ev at ion O:>st O:>st O:>st Watana2 Watana/!Evi 1
(ft ~L) ($ X 1ofi) ($ X 1of5) ($X 1o6f -Alone CanjQ'l
2240 (2215
reservoir elevation) 4,076 1,711 5,787 3,542 6,809
2190 (2165
reservoir elevation) 3,785 1,711 5,496 3,322 6,586
2140 (2115
reservoir elevation) 3,516 1,711 5,227 3,071 6,264
ftltes:
(1) Estimated costs in January 1982 dollars, based on preliminary conceptual
designs, including relict channel drainage blanket and 20 percent
continge1eies.
'""' (2) Prior to year 2002
-TABLE B-.25: ffiESENT \o.ffiTl-1 fF PROOJCTION COSTS
Watana Dan Present t&th
Crest Elevation of Production O:>sts1 -(ft ~) ($ X 1of5)
2240 (reservoir
elevation 2215) 7,123 -2190 (reservoir
elevation 2165) 7,(1)2
2140 (reservoir
elevation 2115) 7,084
!"""
ftltes:
!"""
(1) LTPW in Jcr1uary 1982 dollars.
TABlE B.26-: DESIGN PAAPI'UERS Fffi rEPENDABLE CAPJICITY JlND· ENERGY PROOUCTION
Minimun strean flow (rronthly average, cfs)
~an streanfl ow
Maximum streanflow
Evaporation
Leakage
Minirrun flow release
Flow duration curve
Critical streanfl9w for de~dable
capacity curve ~ Watana and Devi 1 Can.JOO
cdrbineCI)
Prea capacity curve
Rule curve
H)Qraulic C?!Jacity
Flow ( cfs) 1/2
full best·
Efficiency 1/2
full
best
!£nerator output ( kW) 1/2
full
best
Tailwater rating curves
Po\'.erpl ant capa:>il ity vs heed
Watana Devil Can}Qn
570 (March 1950) 664 (March 1964)
7,990 9,080
42,840 (June 1964) 47,816 (June 1964)
Jlpproximately cancels [>l:'ecipitation crJd is
neglected. Section 4.l(f)
rEgligible Neglig·ible
Ta:>le B.54 Table 8.54
Figure B.62 Figure B.63
5, 450 Bo.h crJnua 1 rx:>tent i a 1 recurrence
frequency 1 in 32 _years
Figure 8.67 Figure 8.68
Figure 8.69 Figure 8.69
1,775
3,550 2,900
87
91
94
91 CXXl 183:cm 156,COO
Figure 8.67
Figure 8.70
1,895
3,790
3,100
87
91
94
82000
164:000
139,CXXJ
Figure B.68
Figure 8.73
-
-
-
-
-
-
-
-
....
-
-
-
-
-
-
-
-
TABLE 8.27:. WATANA-MAXIMUM cAPACITY REQUIRED (MW)
OPTION 1 -THERMAL AS BASE
HydroloQical Year
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'
*Restricted by peak demand
**Maximum value
***Including Devil Canyon
CAPACITY (MW)
1995 2000
743 762
550 569
760 779
749 768
744 763
763 782
737 756
771 790
799** 81~**
563 582
769 788
784* 803
173 192
771 790
145 764
550 569
745 764
554 573
771 790
550 569
55o 569
550 569
784* 803
747 766
550 569
5!50 569
728 147
550 569
7,85* 804
550 569
787* 806
754 773
2010***
838*
680.
836*
836*
868*
832*
838*
836**
825*
683*
832*
829*
8.32*
838*
844*
840*
836*
684*
8.32*
685*
678
672
834*
838*
684
678
8.3~*
675
833*
678
837*
839*
Hydroloaical
1
2
3
4
5
6
7
8
9
\0
11
12
n
14
15
16.
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
TAB!-E 8.28: WATAWI. -MAXIMLM CAPACITY REQUIRED (MW}
OPTlON.2-THER~ AS PEAK
CAPACITY (MW)
Year 1995 2000
575 575
382 382
592 592
581 581
576 576
595 595
569 569
603 603
631 631
395 365
6<J1 601
616 616
605 605
603 603
577 577
382 382
577 577
386 386
603 603
382 382
382 382
382 382
616 626
579 579
382 382
382 382
560 560
382 382
617 617
382 382
619 619
586 586
*Inc I uding Devil Canyon
-
-
2010* -
838
389
839
836 -868
832
838
836 -825
391
832
829
832 .....
838
844
840
836
392
832
393
386
380
834
838
392
386 -839
383
833
387
837 -839
-
-
-
F'"
I
....
TABLE 929: SUMMARY COMPARISON OF POWERHOUSES AT WATANA
S U R F A C E U N D E R G R 0 U N D
($000) .<$000) ($000)
Item 4 x 210 MW 4 x 210 MW 6 x 140 MW
Civi I Works:
Intakes 54,000 54,000 70,400
Penstocks 72,000 22,700 28,600
Powerhouse/Draft Tube 29,600 26,300 28, too
Surge Chamber NA 4,300 4,800
Transformer Gallery NA 2,700 3,400
Tailrace Tunnel NA 11,000 11,000
Ta II race Porta I NA 1,600 1,600
Main Access Tunnels NA. 8,100 8; 100
Secondary Access Tunnels NA. 300 300
Main Access Shaft NA 4,200 4,200
Access Tunnel Portal NA 100 100
Cable Shaft NA 1, 500 1,500
Bus Tunnel/Shafts NA. 1,000 1,200
Fire Protection Head Tank NA 400 400
Mechanical -For Above Items 54,600 55,500 57,200
Electrical -For Above Items 37,400 37,600 41' 200
Sw ltchyard - A I I Work 14,900 14,900 14,900
TOTAL 262,500 246,200 277,000
-
-TABLE 8.30: DESIGN DATA AND OESJGN CRITERIA FOR FINAL REVIEW OF LAYOUTS
River Flows ~
Average flow (oyer 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 elevation at polnt of maximum super elevation:
HeighT:
Cutoff and foundation treatment:
Upstream slope:
Downstream sl,ape:
Crest width:
Diversion
Cofferdam type:
Cutoff and foundation:
Upstream cofferdam crest elevation:
Downstream cofferdam crest elevation:
Maximum pool level during construction:
Tunnels:
Final closure:
Releases during Impounding:
SpiT I way
Design floods:
Main sp!l lway-Capacity:
-Control structure:
Emergency spll lway-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
Rockfl I I
2240 ft
890 ft above foundation
Core founded on rock; grout curtain and
downstream drains
2.4H: IV
2H: IV
50 ft
Rockflll
Slurry trench to bedrock
1585 ft
1475 ft
1580 ft
Concrete-I I ned,
Mass concrete plugs
6,000 cfs maximum via bypass to outlet
structure
Passes PMF, preservIng !ntegr ity of dam
with no loss of I !fe
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 flood
Fuse plug
Reinforced concrete
6
Multi-level corresponding to temperature
strata
185 feet
-
-
-
-
-
-
TABLE B. 30: (Cont 1 d)
Penstocks
Type:
Number of penstocks:
Powerhouse
Type:
Transformer area:
Control room and administration:
Access-Vehicle:
-Personna I:
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:
Ta i I race
Water passages:
Surge:
Average tal !water elevation (ful I generation):
Note:
Concrete-lined tunnels with downstream
stee I I i ners
6
Underground
Separate ga I I ery
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-I lned tunnels
Separate surge chambers
1458 tt
Certain design data and criteria have been revised since date of layout review.
For current project parameters refer to Exhibit F, Preliminary Design Report.
PRELIMINARY REVIEW
Technical feaslbll ity
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-
abi I ity
TABLE 8.31: EVALUATION CRITIERA
INTERMEDIATE REVIEW
Technical feaslbil lty
Compatibl I ity of layout
with known geological and
topographical site features
Ease of construction
Overa I I cost
Environmental accept-
abi I ity
FINAL REVIEW
Technical feasibility
Compatibility of layout
with known geological and
topographical site features
Ease of construction
Overa I I cost
Environmental Impact
-
-
-
-
-
-
-
-
-
-
-
-TABLE B.32: SUMMARY OF COMPARATIVE COST ESTIMATES
INTERMEDIATE REVIEW OF ALTERNATI~E ARRANGEMENTS
(January 1982 $ x 10 ) -
WP1 WP2 WP3 WP4
Divers ion 101.4 112.6 101.4 103. 1 ,....
I
ServIce Sp i I I way 128.2 208.3 122.4 267.2
Emergency Spillway 46.9 46.9
I"""'
Tailrace Tunnel 13. 1 13. 1 13.1 8.0
Credit tor Use of Rock in Dam ( 11. 7) (31.2) ( 18.8) (72.4)
Total Non-Common I terns 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 ( 16%> 299.8 318.8 305.3 311.8
Subtotal 2173.8 2311.5 2213.3 2260.7
Contingency (20%> 434.8 462.3 442.7 452.1
Subtotal 2608.6 2773.8 2656.0 2712.8 -Engineering and
Administration ( 12.5%) 326.1 346.7 332.0 339.1
TOTAL 2934.7 3120.5 2988.0 3051.9
-
-
TABLE B.33: DEVIL CANYON -MAXIMUM CAPACITY REQUIRED (MW) -
-Capacity (MW)
H ical Year 2010 <Oet ion and 2)
1 544** """',
2 353
3 546
4 546
5 514
6 548
7 544
8 546
9 557
10 351
11 548
12 551
13 548
14 544 -15 538
16 542
17 546
18 350
19 550 -20 349
21 355
22 361
23 548 -24 544
25 349
26 355
27 543
28 359
29 549
30 355
31 545
32 543
**Maximum Value -
-
-
-
-
-
-
-
-
TABLE 8.34: DESIGN DATA AND DESIGN CRITERIA FOR
REVIEW OF ALTERNATIVE LAYOUTS
River Flows
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 ful I storage:
Dam
Type:
Crest e I evat 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:
SpIll way
DesIgn f I oods:
Service spll lway-capacity:
-control structure:
-energy dissipation:
Secondary spillway-capacity:
-control structure:
-energy dissipation:
Emergency spll lway-capacity:
-type:
8, 960 cfs
346,000 cfs
165,000 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
Rockflll
960 feet
900 feet
955 feet
Concrete-II ned
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 I I fe
Passes routed 1:10,000-year
flood with no damage to
structures
45,000 cfs
Fixed-cone valves
Five 108-lnch diameter
fixed-cone valves
90,000 cfs
Gated, ogee crests
Sti I I ing basin
pmf minus routed 1:10,000-year
flood
Fuse plug
TABLE B.34: (Cont 1 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:
Note:
Underground
Separate ga II ery
Rock Tunnel
Francis
4 x 140 MW
550 feet
565 feet approx.
Vertical synchronous
155 MVA
0.9
Certain design data and criteria have been revised since date of layout review.
For current project parameters refer to Exhibit F, Preliminary Design Report.
-
-
-
-
""" '
-
-
-
-
TABLE 8.35: 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 Spl 1 !way 25.2 25.2 25.2 25.2 -Power Fac lilt i es 211.7 211.7 211.7 211.7
Swltchyard 7. 1 7. 1 7. 1 7. 1
Mlscel laneous Structures 9. 5 9.5 9.5 9.5
Access Roads & Site Facilities 28.4 28.4 28.4 28.4
Common Items-Subtotal 783.2 783.2 783.2 783.2 -Diversion 32.1 32.1 32.1 34.9
Service Spi I lway 46.8 53.3 50.1 85.2
Saddle Dam 19.9 18.6 18.6 19.9
Non-Common/Items Subtotal 98.8 104.0 100.8 140.0
Total 882.0 887.2 884.0 923.2
Camp & Support Costs ( 16%) 141.1 141.9 141.4 147.7
Subtotal 1023.1 1029.1 1025.4 1070.9
Contingency (20%) 204.6 205.8 205.1 214.2
Subtotal l"2"2T.I 1234.9 1230.5 1285.1
!"""' Engineering & Administration
( 12.5%> 153.5 154.3 153.8 160.6
Total 1381.2 1389.2 1384.3 1445.7
!"""
-
-
-'
-
-
TABLE B.36: POWER TRANSFER REQUIREMENTS (MW)
INSTALLED CAPACITY TRANSFER R~QUIREMENT -Sus itna to Susitna to
Year Watana Dev I I Canyon Total Susitna Anchorage Fairbanks
1993 680 --680 578 170
'
1994 1020 --1020 867 255
2002 1020 600 1620 1377 405
-
-
TABLE B.37: SUMMARY OF LIFE CYCLE COSTS
TRANSMISSION ALTERNATIVE 2 3 4 5
Transmission Lines 1981 $ X 106 -
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
Switching 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
-
-Type
1. Technical
-Primary
-Secondary -2. Economical
-Primary
-Secondary
-3. Environmental
-Primary
-Secondary
-
-
TABLE B.38: TECHNICAL, ECONOMIC, AND ENVIRONMENTAL CRITERIA
USED IN CORRIDOR SELECTION
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 lntertle near Gold Creek, Willow,
and Healy. Connect Healy to Fairbanks. Con-
nect Willow to Anchorage.
Avoid mountainous areas.
Select gentle rei l.ef.
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 req~ire special designs.
Avoid existing or proposed developed areas.
Para I le 1.
Avoid private lands, wi ldl lfe refuges, parks.
Select gentle rei ief.
Avoid heavily timbered areas.
1
I
1
i
1
j
l
J
Length (miles)
Number of Road
Crossings
Number of River/
Creek Crossings
Topography
Land Ownership/
Status
Existing/Proposed
Developments
Existing Rights-of-
Way
Scenic Quality/
Recreation
Cultural Resources3
AB
38
2 hwy CRt. 3, Glenn), 6 I ight
duty roads, 1 unimproved road,
2 trails, 1 railroad
1 river, 17 creeks
Willow (100'), crosses Willow
Ck., follows
Deception Ck. ( 1000 1 ) along
rIdge of Ta I keetna Mts. , s. e.
Into Palmer (200 1)
WII low to near Palmer-S04,
Palmer-EO!
A to s. of Willow CK. Rd.
crossing-mostly P, with some
BAP and some SP ;. • • to due n.
of Was I I la-malnly SPTA; ••• to
B-mostl y P, with some BI\P and
SP
Ag. uses n. & w. of Pa I mer;
ag/res. use near L. Sus itna;
proposed capital site; mixed
res. area at Willow Ck.;
WI I low air strip; cabin near
A
Follows no known right-of-way
for appreciable distance
Gooding L. -bird-watchIng;
rec. trails e. of Willow-
hunting, hiking, x-c skiing,
dog sledding, snowmobiling,
snowshoeIng; rec. tra II by
Decep. Cl<. -snowmob II I ng,
dog sledding, fishing
QA. TA VOID
TABLE B. 39: ENVIRONMENTAL INVENTORY -SOUTHERN STUDY AREA
(WILLOW TO ANCHORAGE/POINT MACKENZIE
BC
Corridor Segment
ADF
35
4 hwy (Glenn, 4x), 3+ I lght
duty roads, 7 unimproved roads,
1 tra II, severa I ra II roads
4 rivers, 11 creeks
Palmer (200 1), crosses Knlk
River to base at Chugach Mts.
(500 1), along Knik Arm (200 1-
3001), to Anchorage (200 1 )
Pa I mer-EO 1, Kn I k Arm-EF 1, S.
of Ek I utna to n. of Anchorage-
S05, Anchorage -S04
B to Kn I k R. -P; • • • to
Birchwood-mainly VS with some
SPTA, P and BAP; Birchwood
a rea-P; s. w. of BIrchwood to
near C1-U. S. Army Mi lltary
Wdl.; C1-DATA VOID
Urban uses In Anch. ; passes
through/near several
communities: Eagle R,
Birchwood, Eklutna, Chugiak,
Peters Ck.
Parallels trans. I ine Knlk R.
to Anch.; para I leis Glenn Hwy.
from Kn I k R. to BIrchwood;
paral leis RR-Eagle to C'
Passes near 2 camping grounds;
para I leis lditarod racing
trail (x-c skiing, sledding,
snowmobiling>; birdwatching
at Eklutna Flats and Matunuska
River
DATA VOID
26
1 hwy (Rt. 3), 3 tractor
trai Is
1 river, 6 creeks
WI I low ( 100 1 ), s. along
Susitna River plains (flat,
wet area, with drier, raised
levees, 200 1-400 1), to Fat
150'
Wi llow-S04, S. of Wi I low to
F-SOl
Near A-P; route fairly even
mix of BAP and SPTA; some P
near Fish Ck; area surrounding
L Susitna R -Susltna Flats
Game Reguse; near F-SPTA
Red Shirt Lake-mixed
residential use; near
residential & recr. areas s.w.
of WII low; Susltna Flats State
Game Refuge
Generally paral leis a tractor
trail
X-c ski & snowmobile trails;
recreation area s.w. of
WI I low
DATA VOID
AEF
27
1 hwy (Parks), 1 tractor
trai I
1 river, 6 creeks
WI I I ow ( 1 00 1 ) , s. a I ong f I at
wet area (200 1-400 1 ), to Fat
about 150 1
Near ~ Susltna River-S05,
Rema I nder-S04
A, s. to Rainbow L.-rrostly P,
smal I parcels BAP; State
sel acted Fed. parcel w. of
Willow L.; s. to L. Susltna R.
-Nancy Lake State Rec. Area;
to F -mix of SPTA and BAP
Mixed res. areas; lakes used
to land float planes
No known
Mixed rec. areas; Nancy Lake
State Rec. area; tra I Is and
multiple uses; may cross Goose
Bay St. Game Refuge
DATA VOID
FC
12!
2 tractor trails
2 creeks
F at 150' along fiats to C
ne<k sea I eve I
I
Near F -S04, Near C -SOl
F to 1 mi. s.-SPTA; ••• s. to
Honseshoe L.-Pt. MacKenzie
Aglj. Sa I e; • • • s. to C-ma In I y
SP~A, some BAP
Scattered residential/cabins on
Ho~sehoe Lake; proposed ag. uses
in'area
Generally follows a tractor trai I
May cross Susitna Flats State
Wildlife Refuge
DATA VOID
l
J
j
TABLE B. 39 (Cont 1 d)
Vegetation 4
Fish Resources5
Furbearers6
6 Big Game
NOTES:
AB
Upland, mixed deciduous-
conifer forests (birch-spruce)
-open and closed mostly. Tall
shrub Calder); some woodland
black spruce; bogs along
DeceptIon Ck.
WII low Ck. -chinook salmon,
grayling, burbot, longnose
sucker, round whitefish,
Dollar Varden, slimy sculpin,
lake trout & rainbow trout in
lakes; L. Sus itna R. -king
sa I mon; Decep. Ck. -kIng,
pink salmon
DATA VOID
IY\TA VOID
Except near Palmer-black bear
summer range, moose winter/
summer range, migrating
corridors and calving area;
near A also brown bear summer
range and feeding area
BC
Deciduous forest (balsam
poplar) along river, probably
birch/spruce forests on
uplands in most of area. DATA
VOID
Sockeye, chinook, pink, shum,
coho salmon In large rivers;
grayling burbot, longnose
sucker, round whitefish, Dolly
Varden, slimy sculpin, lake
and rainbow trout in lakes &
stream; salmon of particular
significance in the Matanuska
and Knik Rivers
Waterfowl and shore bird
nesting areas around Knik Arm
and Eagle River Flats
DATA VOID
DATA VOID
Corridor Segment
ADF
Higher grounds: Spruce-birch-
poplar forests. Wet sedge
grass bogs and black spruce
forests prevalent in lower
half
Wi I low Ck. -chinook salmon;
lake and rainbow trout
possible in some lakes; also,
in streams are grayling, bur
bot, longnose sucker, round
whitefish, Dolly Varden,
slimy sculpin; Red Skirt L. -
lake trout, sockeye salmon
Waterfowl and shore bird
nesting in Willow Creek/
Delta Islands
IY\TA VOID
Brown and black bear feeding
moose winter/summer ran~e and
calving area
AEF
Upper half; mostly upland
birch, spruce & aspen. Lower
half: wet sedge-grass bogs and
black spruce; some birch,
spruce; aspen on higher
ground
Lakes may contain rainbow and
lake trout; possibly grayling
in the region
Same as ADF
Same as ADF
Same as ADF
(I) Source: Unites States Department of Agriculture, Soil Conservation Service 1979. See Table 8.43 for explanation of soil units.
(2) Source: CIRI/Holmes and Narver. 1980. P=Private, SPTA+State Patented or Tentatively Approved, SP=State Patented, BAP=6orough Approved or Patented.
(3) Coastal area probably has many sites, available literature not yet reviewed.
(4) Tal I shrub=alder; low shrub=dwarf birch, and/or willow; open spruce=black (wet) cover, mixed forest=spruce-blrch.
(5) Little data avallabl~ Source of information in this table: Alaska Department of Fish and Game 1978&
(6) Little data availabl~ Source of information in this table: Alaska Department of Fish and Game 1978~
FC
Spruce forests, spruce-birch
forests, sedge-grass bogs and
b I lack spruce bogs
Lake may contain rainbow and
lake trout; possibly grayling
iri the region
Waterfowl and shore bird
migration route, feeding and
nestIng area
Fur bearer and sma I I mamma I '
s~mer/wlnter range
B l.ack bear summer range and
feeding area; moose winter/
sUmmer range, feeding and
calving area
-
-Corridor
Segment
,....AB
BC -
CD
BEG -
-AJ
CF -
-
..,.. AH
HJ
-
:-
-
TABLE 8.40: ENVIRONMENTAL INVENTORY -CENTRAL STUDY AREA
(DAMSITES TO INTERTIE)
Approx.
Lenqth
Approx. II
Road
Approx. II
River/Creek Land b (M i es) Crossings Crossings Topography
a
Soils Ownership/Status
7
18
15
23
18
8
15
65
22
21
23
a.
b.
0
0
1+
0
0
0
0
0
0
0
0
5 creeks
8 creeks
1 river
4 creeks
8 creeks
11 creeks
1 creek
2 creeks
1 river
35 creeks
9 creeks
15 creeks
13 creeks
Moderate sloping s. rim of
Susitna R. Valley; crosses
deep rav 1 ne at Fog Ck. at
about 2000 1 contour
2000 1 contour along s. rim
of Susitna River; crosses
3 steep gorges
Moderately sloping terrain;
crosses Susitna R. near Gold
Creek ( 800 I )
Crosses moderate slopes
around Stephan Lake; w., then
n. to avoid deep ravine at
Cheechako Ck., then fo I I ows s.
rim of Susitna at about 2000 1
A (about 2000 1 ) to 3500 1 ;
crosses deep ravine at Devil
Ck. (2000 1 ); goes by several
ponds
J (2000 1 ), s.w. through
gently sloping High Lake
area, to C at Dev1 I
Canyon (2000 I )
Devi I Canyon (<2000 1 ) west
across 600 1 deep Portage
Creek gorge, w. across
gentle terrain to F
{1200 '>
A (2000 1 ) n. along Deadman
Ck. to 3260 1 ; crosses
Brushkana drainage (at
3200 1 ); drops to Nenana
~[~trt~~~~?~>t~ng !~~o6Y>
A (2000 1 ), along Tsusena Ck.
past Tsusena Butte; through
mt. pass at 3600 1
H (3400 1 ) through mts.; along
Jack R. drainage and Caribou
Pass; to I at 2400 1
H (3400 1 ) throu9h mts. along
Portage Ck. drainage, through
pass at 3600 1 into Devil
Creek drainage; to J at 2000 1
S015
B, westward-S015;
near C -SOlO
OSlO
8, westward -OS15;
between B & C
IU3; near C -SOlO
A, westward -OS15;
remainder, except
J -OS16; near J -
SOlO
OSlO
SOlO
Near A and along
Dena I i Hwy. -
OS15; through
mts. -S016
Near A -S015;
mt. base -S016;
mts. -RMl
Mts. -RMl;
along hwy -S015
Near J -S016
mid elevations-
SOl?; mts. -
~1
vs
vs
C to 1 1/2 mi. e.
of Sus itna R. -
VS; Susitna R. to
1 1/2 mi. e. -
SPTA; ••• to D-P
VS except where
corridor skirts
Cheechako Ck.
ravine, which is
classified SS
Suspended
SS except at J
and at A westward
across Tsusena
Ck., which are VS
SS except at J
and C which are vs
C to 1 1/2 mi. e.
of Miami L.
mainly VS with
sma 11 parcel of
SS; ••• to F-P
A-VS;n.ofA
to s.w. of Big L.
-SS 1 o o o to So
of Deadman L. -
SPTA ••• to
Denali Hwy-Fed.
D-1 Land; data
void for 8 mi.·
around G -Smaf I
Fed. Parcel
A -VS, ••• to n.
of Tsusena Butte
SS; data void
beyond here
I -VS; data void
to east
J -VS; Devi I Ck
drainage-SS;
data void beyond
here
Source: United States Department of Agriculture, Sol I Conservation Service 1979. See Table 8.42
for explanation of soil units.
Source: CIRI/Holmes and Narver. 1980. P=Private, SPTA=State Patented or Tentatively Approved,
SS=State Selection, VS=VI I I age Selection.
TABLE 8.40 (Cont 1 d}
!"""Corridor a
Segment Fish Resources
AB
BC
CD
,-
BEC
-AJ
,.,.. JC
CF
AG
-AH
HI
r""" HJ
Fog Lakes -Dolly Varden, sculpin;
Stephan Lake contains lake and
rainbow trout, sockeye & coho
salmon, whitefish, longnose
sucker, graying; ourbot
Several smal I tributaries crossed,
perhaps used by gray I i ng
Same as BC
Several smal I tributaries crossed,
perhaps used by gray I i ng, bur bot
Dolly Verden; grayling In Tsusena
Creek
Burbot; no data for High Lake
Portage Creek has king, chinook,
chum and pink salmon, gray! ing,
bur bot
Dolly Varden( lakes -lake trout,
grayling, wh1te-fish; tributaries
fo Nenana River and Brushkana
Creek n. of Deadman Mt., and
Jack R. near Denali Hwy considered
fish habitat
Dolly Varden; grayling
Lake trout, Caribou Pass area;
Jack River s. of Caribou Pass
considered Important fish
habitat; data void
Portage Creek-king, chinook,
chum, and pink salmon, gray! ing,
bur bot
Birds
Potential raptor
nesting habitat In
Fog Creek area
Potential raptor
nesting habitat
along Devi I Canyon
Potential raptor
nesting habitat
along Devl I Canyon
Potential raptor
nesting habitat along
Devi I Canyon and along
drainages upstream;
Stephan Lake area
important to waterfowl
and migrating swans
Data void
Potential raptor hab.
by Dev i I Canyon; go I den
eagle nest along Devil
Ck. s. of confluence of
ck. from High Lake
Potential raptor
habitat along lower
Portage Ck. and from
Portage Ck. mouth
through Devil Canyon
Waterfowl numerous at
Deadman Lake; impor-
tant bald eagel habitat
by Dena I I Hwy and
Nenana R. just w. of
Monahan Flat; unchecked
bald eagel nest along
Deadman Ck., s.e. of
Tsusena Butte
Known active bald
eagle nest s.e. of
Tsusena Butte
Data void
Data void
Furbearers
Excel lent fox and
marten habitat;
Fog Lakes support
numerous beavers and
muskrat, otters
common
Excel lent fox and
marten habitat
Area around Devil
Canyon has
exce I I ent fox and
marten habitat
Exce I I ent fox and
marten habitat,
particularly
around Stephan
Lake
Red fox denning
sites, numerous
beaver, muskrat and
mink, especially
around High Lake
Same as AJ
Area between Parks
Hwy and Devi I Canyon
supports numerous
beaver, muskrat,
and mink
Population
relatively low,
although beaver,
mink, fox present;
Deadman Mt. to
Denali Hwy -
moderate pop. red
fox
Population along
Tsusena Ck. probably
relatively low; with
beaver~ mlnk, and fox
probably present
Data void
Numerous beaver,
muskrat, and mink
around High Lake
Big Game
Supports large pop.
of moose; wolves,
wolverine and bear,
(espec i a I I y brown>
common; caribou
regularly use area
Area around Stephan
Lake & Prairie Ck.
supports large pop.
of moose; wolves,
wolverines, and some
bear (especially
brown } common;
caribou regular users
Moose, caribou, and
bear nabitat
Same as AB
Mouth of Tsusena Ck.
Important moose
habitat; heavily
used by black
and brown bear
Important moose and
bear habitat; data
void
Probably Important
moose wintering area
area and b I ack bear
habitat; at least
one wo If pack
Probably Important
area for caribou,
expecial ly in the
north
Data void
Data void
Data void
a. Little data available. Sources of information In this table: Alaska Department of Fish and
Game 1978a, Friese 1975, and Morrow 1980.
-
l
Length (miles)
Number of Road
Crossings
Number of River/
Creek Crossings
Topography
Land Ownershlp/3
Status
Existing/Proposed
Developments
Existing Rights-of-
Way
Scenic Quality/
Recreation
Cultural Resources
AB
40
2 hwy (Park), 3 trai Is
(1 winter), 2 unim-
proved rds. , 1 ra I 1-
road
3 rivers, 15 creeks
Fo II ows Nenana RIver
north at 1000 1 to
Browne-crosses River;
n.w. to Clear MEWS
at 500 1
IR10
A to e. of Dry Ck. -
sma I I Fed. Parce I ; •••
to s. of Clear MEWS
and at B-mostly SPTA,
small parcels of P,
sma I I Fed. Nat. A I I ot.
a I ong Nenana R. ; C I ear
MEWS area-parcel CIRI
Se I ectlon, and U.S.
Army Wd 1. Land
Scattered residential
and other uses along
Parks Hwy; cabin near
Browne; air strip at
Healy
Generally parallels
Parks Hwy, RR and
trans. I I ne-Hea I y
to Browne
Parks Hwy-scenlc area;
rafting, kayaklng on
Nenana R.
Dry Ck. arch. site near
Healy; good posslbl llty
for other sites; DATA
VOID
TABLE B. 41: ENVIRONMENTAL INVENTORY -NORTHERN STUDY AREA
(HEALY TO FAIRBANKS)
BC
50
Parks Highway,
1 w Inter tra i I
1 river, 25 creeks
Clear MEWS (500 1 )
north across plain
(400 1 ) , n. e. across
Tanana River Val ley
to Ester (600 1 >
Near B-IR10; flats s.
of Tanana Rlver-IQ2;
Tanana River-IQ3;
Tanana R. to Ester-
IR14
B to 1-1/2 mi n. -
SPTA; ••• to s. to
Tanana R. -SS; ••• to
Tanana R. -P; ••• to
crossing L. Goldstream
Ck. -most I y SPTA; ••• to
Bonanza Ck. CrossIng -
SS; ••• to near C-SP;
remainder-DATA VOID
Scattered residential
and other uses along
Parks Hwy; cabin at
Tanana R. crossing
Follows w/ln several
mi. Parks Hwy, RR, and
trans. line; more
closely follows Parks
Hwy. and trans. II ne
and sled rd. n. of
of Tanana R.
Parks Hwy-scenlc area;
hunting, fishing
Good possibility for
arch. sites; DATA VOID
Corridor Segment
BDC
46
1 w Inter tra i I
2 rivers, 29 creeks
Clear MEWS (500 1 ),
n. e. across p I a I n to
a point about 24 mi.
due s. of Ester; ~
across pI a i n to
Tanana R. (400 1 ) and
n. to Ester
Near B-IR10, Remainder
-IQ2
B area -SPTA; Fish Ck.
to Tanana R.-data void
remainder-SPTA, BAP
with P at C and just n.
of Tanana R.
Ft. Wainwright Mi 1.
Reservation
No known
Wide open flat-high
visibility; snow-
mobiling In flats s.
of FaIrbanks
Good possibility for
arch. sites; DATA VOID
AE
65
1 hwy. (Parks),
1 trail
river 50 creeks 1
Up Hea I y Ck. to pass at
4500 1 ; down Wood R.
drainage to Japan Hi I Is
(1100 1 ); steep mts.;
valleys
Near A-IR10; mt. base-
l Q25; mt. a rea-RM 1 ;
near E-IRl
A to Nenana R. -sma I I
Fed. Parce I; ••• to e.
of Gold Run-SPTA •••
remainder-DATA VOID
Air strips-Healy and
Cripple/Healy Cks.
confluence; cabins-
Cody Ck/Wood R. ,
Snow Mt. Gu I ch
Parallels small rd.-
near Healy to Coal
Ck. ; sma I I RR-Hea I y to
Suntrana; trail at
pass betw_een Hea I y and
Cody Cks.
Seen lc qua llty data
voId; Hea I y Ck. -raftIng
area
Dry Ck. arch. site near
Healy; few arch. sites
In mountains; maybe
near Japan HII Is; DATA
VOID
EDC
50
7 tra i Is
2 rivers, 22 creeks
Japan Hills (1100 1 )
n. w. on pI a in a I ong
Wood R. ; through
Wood R. Buttes area,
n. across Tanana R. ;
n. to Ester
Near E-IRl; between
E and open flats-
IR10; open flats
IQ2; Tanana R.-IQ3;
Ester-IR14
Same as BDC north of
the Tanana River
Ft. Wainwright Mi 1.
Res. ; Wood R. Butte
VABM
No known
Wide open flats-high
visibility; snow-
mob I I I ng In f I ats s.
of Fairbanks
High posslbll tty for
arch. sites; DATA VOID
EF
40
Several roads In Fairbanks
depending upon exact
route; 3 tra II s
2 rivers, 10 creeks,
Salchaket Slough
Japan Hills (1100 1 ) n.
across plain to Tanana
R. (500 1 ); n. to Fairbanks
Near E-IRl; s. section
of flats-IR10; flats-IQ2;
Falrbanks-IQ3
DATA VOID
Ft. Wainwright Mil.
Res. ; cabIn-wood R.
crossIng s. of Clear Butte
Parallels Bonnifield Tral I -c I ear Ck. Butte to
FaIrbanks; trans. II ne
just s. of FaIrbanks
Wide open flats-high
visibility
Arch. sites have been
identified for the Ft.
Wainwright and Blair
Lakes areas
j
I
_)
J
TABLE 8.41 (Cont 1 d)
Vegetation4
Fish Resources5
Furbearers6
Big Game6
NOTES:
A8
Southern end-data
void Northern end-low
shrub, sedge-grass
tundra
Grayling, burbot, long-
nose sucker, Dolly
Varden, round white-
fish, slimy sculpin
Important golden eagle
habitat near A
Prime habitat-15 mi.
from Nenana to B
From Nenana R. to 8-
prlme moose and Impor-
tant black bear
habitat; from A north-
ward about 10 mi.-prime
moose habitat
BC
~ of Tanana River-wet
old river floodplain,
low shrub and sedge-
grass bogs; Tanana R.
cross I ng-w I I I ow and
alder shrub types,
white spruce, balsam
poplar forests along
river; n. of Tanana R.
-open and closed de-
ciduous (birch and
aspen) forests on
slopes, w/woodland
spruce and bogs, low
shrub, and wet sedge-
grass on va I I ey bottoms
Gray I lng, burbot, long-
nose sucker, Dolly
Varden, round white-
fish, slimy sculpin,
salmon (coho, king,
chum), sheefish; lake
chub possible
Prime peregrine habitat
at Tanana R.; prime
waterfowl habitat along
Tanana R. s. of
corridor
Prime habitat-from
Clear MEWS across the
Tanana
Clear MEWS to across
Tanana R.-prlme moose
and important black
bear habitat; n. of
Bonanza Ck. Exp.
Forest-prime black
bear habitat
Corridor Segment
BDC
Probably wet, low
shrub, and sedge-grass,
alder shrub, lowland
spruce; n. of Tanana-
upland deciduous
forests
Same as BC
Near Totatlanika Ck.
to Tanana R.-prlme
waterfowl habitat;
near Wood R. -Important
raptor habitat; be-
tween D&C by Tanana R.
-prime peregrine
habitat
Prime habitat from B
to across Tanana Rive
B to across Tanana R.
-prime moose, important
black bear habitat;
Wood R. to just s. of
the Tanana R. -prIme
black bear habitat
AE
DATA VOID
Same as AB
Important golden eagle
habitat at A & along
Hea I y Ck. s. of
Usibel II Pk; prime
peregrine habitat on
Keevy Pk.
Prime habitat from E
to the s. about 15 mI.
Usibeill to Japan
Hills-prime moose &
caribou habitat;
between A & Mystic
Mt. -prIme sheep
habitat; E to the s.-
import. black bear
habitat
(1) Assumes corridor is located on n. side of Healy Ck. for most of its length, n. side of Cody Ck., and n.w. side of Wood R.
(2) Source: United States Dept. of Agriculture, Sol I Conservation Service 197~ See Table B.42 for explanation of sol I units.
EDC
Probably simi iar to BDC
Same as AB, lake chub
possible
From Wood R. Buttes to
n. of Tanana R.-prlme
waterfowl habitat;
between D&C along the
Tanana R. -prime
peregrine habitat
Prime habitat from E
to just n. of Tanana
River
E to just n. of Tanana
R.-prime moose, Impor-
tant black bear
habitat; Wood R. to
just s. of Tanana R.-
prime black bear
EF
Probably similar to EDC;
wet
Same !as BC with the excep-
tion 'of coho salmon, which
Is not recorded
~ of Blair Lake Air Force
Range to the Tanana R.-
prime waterfowl habitat;
s. ofi Fairbanks along
Tanana R. -prIme bai d eag I e
habitat
Prime habitat from E
to Tanana River
E to tanana R. -prIme moose
and Important black bear
habitat; Clear MEWS to
Tanan'a R. -prime black bear
habitat
(3) Source: CIRI/Holmes and Narver. 198~ P=Private, SPTA=State Patented or Tentatively Approved; SP=State Patented; SS=State Selection, BAP=Borough Approved or Patented.
(4) Tal I shrub=alder; low shrub=dwarf birch, and/or wi I low; open spruce=black, (wet) or white spruce, 25%-60% cover; woodland spruce=white or black spruce, 10%'-25% ccover; mixed
forest=spruce-birch.
(5) Little data avaiiabl~ Sources of information In this table: Alaska Dept. of Fish and Game 1978a and Morrow 1980.
(6) Source: VanBai lenberghe personal communication. Prime habltat=minimum amount of land necessary to provide susta-ined yield for that species; based upon knowledge of that
species' needs from experience of ADF&G personnel. important habltat=land which the ADF&G consider~ not as critical to a species as is Prime habitat but is valuabl~
I~
-
-
TABLE B.42
SOIL ASSOCIATIONS WITHIN THE PROPOSED TRANSMISSION CORRIDORS -
GENERAL DESCRIPTION, OFFROAD TRAFF I CAB I L I TY LIM I TAT IONS CORTL), AND
COMMON CROP SUITABILITY (CCSla
Efl -Typic Gyofluvents -Typic Cryaquepts, loamy, nearly level
-Dominant soils of this association consist of wei !-drained, stratified,
waterlaid sediment of variable thickness over a substratum of gravel,
sand, and cobblestones. Water table is high in other soils, including
~ the scattered muskegs. ORTL: Slight-·Severe (wet; subject to flood-
ing); CCS: Good-Poor (low soil temperature throughout growing season).
-
-
EOI -Typic Cryorthents, loamy, nearly level to rolling
-ThIs association occup l es broad terraces ·and moraines; most of the bed-
rock is under thick deposits of very gravelly and sandy glacial drift,
capped with loess blown from barren areas of nearby floodplains. Wei 1-
dralned, these soi Is are the most highly developed agricultural lands in
Alaska. ORTL: Slight; CCS: Good -Poor.
IQ2 -Histic Pergel ic Cryaquepts-loamy, nearly level to rol I ing
-The dominant soils in this association are poorly drained, developed in
silty material of variable thickness over very gravelly glacial drift.
Most soils have a shallow permafrost table, but In some of the very
gravelly, wei !-drained soils, permafrost is deep or absent. ORTL:
Severe-Wet; CCS: Poor
IQ3 -Histlc Pergelic Cryaquepts-Typic Cryofluvents, loamy, nearly level
-Soi Is of this association located in low areas and meander scars of
floodplains are poorly drained silt loam or sandy loam; these are usually
saturated above a shallow permafrost table. Soils on the natural levees
along existing and former channels are wei !-drained, stratified silt loam
and fine sand; permafrost may occur. ORTL: Severe (wet); CCS: Unsuit-
able (low temperature during growing season; wet)-Good (but subject to
f loading).
IQ25-Pergelic Cryaquepts-Pergelic Cryochrepts, very gravelly, hi I ly to steep
a.
-Soils of this association occupying broad ridgetops, hi I !sides, and
valley bottoms at high elevation are poorly drained, consisting of a few
inches of organic matter, a thin layer of slIt loam, under which Is very
gravelly silt loam; permafrost table Is at a depth greater than 2 feet.
In locations of hi I Is and ridges above tree line these soils are wei!-
drained. ORTL: Severe (wet, steep slopes); CCS: Unsuitable (wet; low
soi I temperature; short, frost-free period).
Source: U.S. Department of Agriculture, Soil Conservation Service 1979.
See Table 8.43 for definitions for Offroad Trafficability Limitations and
Common Crop Suitability.
-
-
-
-
-
-
TABLE 8.42 (Cont 1 dl
-Solis of nearly level to undulating outwash plains are well-drained to
excessively wei !-drained, formed In a mantel of silty loess over very
gravelly glacial til 1. Soils of the association located in depressions
are very poorly drained, organic soils. ORTL: Slight-Very Severe;
CCS: Good-Unsuitable (wet, organic).
S05 -Typic Cryorthods, very gravelly, hi I ly to steep-Sphagnlc Boroflbrists,
near I y I eve I
-On the hi I Is and plains, these soils, formed in a thin metal of silty
loess over very gravelly and stony glacial drift, are wei I drained and
strongly acid. In muskegs, most of these soils consist of fibrous peat.
ORTL: Severe (steep slope); CCS: Unsuitable (steep slopes; stones and
boulders; short, frost-free season).
SOlO-Humic Cryorthods, very gravelly, hll ly to steep
-Generally, these are wei !-drained soils of foothil Is and deep mountain
valleys, formed In very gravelly drift with a thln mantel of silty loess
or mixture of loess and volcanic ash. These soils are characterlstical ly
free of permafrost except In the highest elevation. ORTL: Severe (steep
slope); CCS: Poor-Unsuitable (low soil temperature throughout growing
season; steep slopes).
S015-Pergelic Cryorthods-Hlstic Pergellc Cryaquepts, very gravelly, nearly
level to rol I lng
-On low moraine hi I Is, these soils are wei I drained, formed In 10 to 20
Inches of loamy material over very gravelly glacial drifts. On foot
slopes and valleys, these soils tend to be poorly drained, with shallow
permafrost table. ORTL: Slight-Severe (wet); CCS: Unsuitable (short,
frost-free period; wet; stones and boulders).
S016-Pergellc Cryorthods very gravelly, hilly to steep-Histlc
Pergelic Cryaquepts, loamy, nearly level
-On hilly moraines these sol Is are well-drained; beneath a thin surface of
partially decomposed organic matter, the soils have spodic horizons
developed in shallow silt loam over very gravelly or sandy loam. In
valleys and long foot slopes, these are poorly drained soils, with a
thick, peaty layer over a frost-churned loam or slit loam. Here, depth
of permafrost Is usually less than 20 Inches below surface mat. ORTL:
Severe (steep slope; wet); CCS: Unsuitable (short, frost-free period) -
Poor (wet; low soil temperature).
-
-
-
-
TABLE 8.43 (Cont 1 d)
-Fair
Sol Is or climate I imitations need to be recognized but can be overcome. Common
crops can be grown, but careful management and special practices may be required.
On soils of this group--
(a) Loamy texture extends to a depth of at least 10 inches (25 em).
(b) Periods of excessive sol I moisture, which can Impede crop growth during the
growing season, do not exceed a total of 2 weeks.
(c) Damage by flooding occurs no more frequently than 2 years in 10.
(d) Slopes are dominantly less than 12 percent.
(e) Periods of soi I moisture deficiency are Infrequent.
(f) Damage to crops as a resu It of ear I y frost can be expected no more frequent I y
than 3 years in 10.
(g) There Is no more than a moderate hazard of wind erosion.
-Poor
Soils or climate limitations are difficult to overcome and are severe enough to
make the use questionable. The choice of crops is narrow, and special treatment or
management practices are required. In some places, overcoming the limitations may
not be feasible. On soils of this group
(a) Loamy texture extends to a depth of at least 5 inches (12 em).
(b) Periods of excessive soil moisture during the growing season do not exceed a
total of 3 weeks.
(c) Damage by flooding occurs no more frequently than 3 years in 10.
(d) Slopes are dominantly less than 20 percent.
(e) Periods of soil moisture deficiency are frequent enough to severely damage
~ crops.
-
-
-
(f) Climatic conditions permit at least one of the common crops, usually grasses,
to be grown successfully in most years.
) l ---1 l l 1
TABLE 8.45: ECONOMICAL AND TECHNICAL SCREENING
CENTRAL STUDY AREA (DAM SITES TO INTERTIE)
(I) (2) (3) (4) (5) (6) (7) (8) (9) ( 10) (II) ( 12) ( 13) ( 14 )* ( 15)
ABCD ABECD AJCF ABCJHI ABECJHI CBAHI CEBAHI CBAG CEBAG CJAG CJAHI JACJHI ABCF AJCD ABECF
-length 40 45 41 77 82 68 75 90 95 91 69 70 41 41 45
-Max. Elevation, ft. 2500 3600 3500 4300 4300 4300 3500 3300 3600. 3500 3800 3900 2500 3500 3600
-Clearing
Medium & Light 38 30 26 18 30 20 27 45 37 40 55 17 39 26 35
None 2 15 15 59 50 48 46 45 60 51 14 53 2 15 10
-Access
New Roads 28 31 12 58 49 44 53 44 49 13 27 44 41 5 45
4-Wheel 12 12 29 8 8 3 3 46 46 78 23 26 0 36 0
-Tower Construction* 180 203 185 347 369 306 338 405 428 410 311 315 185 185 203
-Rating:
Economical c c c F F c F F F F c F c A c
Technical A c c F F F c c c c c c c A c
A = recommended
C = acceptable but not preferred
F = unacceptable
*Approximate number of towers required for this corridor,
assuming single-circuit line.
TABLE B.47: SUMMARY OF SCREENING RESULTS
-RAT Fl ('; s
Corridor Env. Econ. Tech. Sunvnar~
-Southern Study Area -( 1) ABC' c c c c
(2) ADFC A A A A
(3) AEFC F c A F --Centa I Study Area
( 1) ABCD c c A c
(2) ABECD F c c F -(3) AJCF c c c c
(4) ABC,IHI F F F F
(5) ABECJHI F F F F
(6) CBAHI F c F F
(7) CEBAH I 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
(12l JACJHI F F c F
( 13) ABCF c c c c
( 14 l AJCD A A A A
( 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
-
Length (miles)
Topography/Soils
Land Use
Aesthetics
Cultural Resources
Vegetation
FIsh Resources
Wildlife Resources
Environmental Rating 1
1 (ABCD)
40
Crosses several deep ravines;
about 1000 1 change in eleva-
tion; some wet soils
Little existing ROW except
Corps Rd.; mostly VII lage
Selection and Private Lands
Fog Lakes; Stephan Lake
Archeologic sites near Watana
dam site, Stephan Lake and Fog
Lakes; oa. TA VOID from Go I d Ck.
to Devil Canyon; historic
sites near the communities of
Gold Creek and Canyon
Wetlands In eastern third of
corridor; extensive forest-
clearing needed
1 river and 17 creek cross-
ings; valuable spawning areas,
especial iy grayling: DATA VOID
unidentified raptor nest
located on tr I b. to Sus itna;
passes through, habitat tor;
raptors, furbearers, wolves,
wolverine, brown bear, caribou
c
TABLE B.49: ENVIRO!If..1ENTAL CONSTRAINTS
CENTRAL STUDY AREA (DAM SITES TO INTERTIE)
2 CABECD)
Corridor Segment
3 (AJCF)
45
Crosses several deep ravines;
about 2000 1 change in eleva-
tion; some steep slopes; some
wet sol Is
Little existing ROW except
Corps Rd. and at D; rec. and
res i d. areas; f I oat plane
areas; mostly VIllage Selec-
tion and Private Lands
Fog Lakes; Stephan Lake; pro-
posed railroad extension; high
country (Prairie & Chulitna
Ck. drainages) and viewshed of
Alaska Range
Same as Corridor
Wetlands In eastern half of
corridor; extensive forest-
clearing needed
1 river and 17 creek cross-
ings; valuable spawning areas,
especial iy grayling: DATA VOID
Passes through habitat for:
raptors, waterfowl, migrating
swans, furbearers, caribou,
wolves, wolverine, brown
F
41
Crosses several deep ravines;
about 2000 1 change in eleva-
tion; some steep slopes; some
some wet sol Is
No existing ROW except at F;
rec. areas; float plane areas;
mostly VII lage Selection and
Private Land; res i d. & rec.
development in area of Otter
~ and old sled road
Vlewshed of Alaska Range &
High Lake; proposed access
road
Archeologlc sites by Watana
dam site, & near Portage Ck./
Sus itna R. Conf I uence; poss 1-
ble sites along Susitna R.;
historic sites near communi-
tIes of Go I d Ck. and Canyon
Forest-clearing needed in
western half
14 creek crossing; valuable
spawning areas, especially
grayling and salmon: Indian
River, Portage Creek, DATA
VOID
Golden eagle nest along Devil
Ck. near HIgh ~; actIve raven
nest on Dev i I Ck. ; passes
through habitat for: raptors,
furbearers, wolves, brown bear
c
NOTES:
( 1) A recommended, C = acceptable but not recommended, F unacceptable
4 (ABCJH I)
77
Crosses several deep ravines;
>2000 1 change in elevation;
routing above 4000 1 ; steep
slopes; some wet sol Is;
shallow bedrock in mts.
No existing ROW; re~ areas
isolated cabins; lakes used
by float planes; much Village
Selection Land
Fog Lakes; Stephan Lake; pro-
posed access road; viewshed of
Alaska Range
Archeologic sites near Watana
dam site, Stephan L. and Fog
Lakes; possible sites along
pass between drainages, DATA
VOID between H and I
Smal I wetland areas In JA
area; extensive forest-
clearing needed; DATA VOID
1 river and 42 creek cross-
Ings; valuable spawning areas,
especially grayling
Golden eagle nest along Devil
Ck. near High L.; caribou
movement area; passes through
habitat for: raptors, water-
fowl, furbearers, wolves,
wolverine, brown bear
F
5 (~BECJHI)
82
Crosses several deep ravines;
cha~ges in elevation >2000 1 ;
routing above 4000 1 ; steep
slopes; some wet sol Is; shallow
bedrock In mts.
Same as corridor 4
Fog 1 Lakes; Stephan Lake; High
Lake; proposed access road;
vlewshed of Alaska Range
Same as Corridor 4
i
Wet'l ands In JA and Stephan Lake
areas; extensive forest-clearing
needed
42 creek crossings; valuable
spawning areas, especially
grayling and salmon: DATA VOID
Sam~ as Corridor 4 with Impor-
tant waterfowl and migrating
swan habitat at Stephan Lake
F
Length (miles)
Topography/Soils
Land Use
Aesthetics
Cultural Resources
Vegetation
FIsh Resources
Wildlife Resources
Environmental Rating 1
1 (ABCD)
40
Crosses several deep ravines;
about 1000 1 change in eleva-
tion; some wet soils
Little existing ROW except
Corps Rd.; mostly VII lage
Selection and Private Lands
Fog Lakes; Stephan Lake
Archeologic sites near Watana
dam site, Stephan Lake and Fog
Lakes; oa. TA VOID from Go I d Ck.
to Devil Canyon; historic
sites near the communities of
Gold Creek and Canyon
Wetlands In eastern third of
corridor; extensive forest-
clearing needed
1 river and 17 creek cross-
ings; valuable spawning areas,
especial iy grayling: DATA VOID
unidentified raptor nest
located on tr I b. to Sus itna;
passes through, habitat tor;
raptors, furbearers, wolves,
wolverine, brown bear, caribou
c
TABLE B.49: ENVIRO!If..1ENTAL CONSTRAINTS
CENTRAL STUDY AREA (DAM SITES TO INTERTIE)
2 CABECD)
Corridor Segment
3 (AJCF)
45
Crosses several deep ravines;
about 2000 1 change in eleva-
tion; some steep slopes; some
wet sol Is
Little existing ROW except
Corps Rd. and at D; rec. and
res i d. areas; f I oat plane
areas; mostly VIllage Selec-
tion and Private Lands
Fog Lakes; Stephan Lake; pro-
posed railroad extension; high
country (Prairie & Chulitna
Ck. drainages) and viewshed of
Alaska Range
Same as Corridor
Wetlands In eastern half of
corridor; extensive forest-
clearing needed
1 river and 17 creek cross-
ings; valuable spawning areas,
especial iy grayling: DATA VOID
Passes through habitat for:
raptors, waterfowl, migrating
swans, furbearers, caribou,
wolves, wolverine, brown
F
41
Crosses several deep ravines;
about 2000 1 change in eleva-
tion; some steep slopes; some
some wet sol Is
No existing ROW except at F;
rec. areas; float plane areas;
mostly VII lage Selection and
Private Land; res i d. & rec.
development in area of Otter
~ and old sled road
Vlewshed of Alaska Range &
High Lake; proposed access
road
Archeologlc sites by Watana
dam site, & near Portage Ck./
Sus itna R. Conf I uence; poss 1-
ble sites along Susitna R.;
historic sites near communi-
tIes of Go I d Ck. and Canyon
Forest-clearing needed in
western half
14 creek crossing; valuable
spawning areas, especially
grayling and salmon: Indian
River, Portage Creek, DATA
VOID
Golden eagle nest along Devil
Ck. near HIgh ~; actIve raven
nest on Dev i I Ck. ; passes
through habitat for: raptors,
furbearers, wolves, brown bear
c
NOTES:
( 1) A recommended, C = acceptable but not recommended, F unacceptable
4 (ABCJH I)
77
Crosses several deep ravines;
>2000 1 change in elevation;
routing above 4000 1 ; steep
slopes; some wet sol Is;
shallow bedrock in mts.
No existing ROW; re~ areas
isolated cabins; lakes used
by float planes; much Village
Selection Land
Fog Lakes; Stephan Lake; pro-
posed access road; viewshed of
Alaska Range
Archeologic sites near Watana
dam site, Stephan L. and Fog
Lakes; possible sites along
pass between drainages, DATA
VOID between H and I
Smal I wetland areas In JA
area; extensive forest-
clearing needed; DATA VOID
1 river and 42 creek cross-
Ings; valuable spawning areas,
especially grayling
Golden eagle nest along Devil
Ck. near High L.; caribou
movement area; passes through
habitat for: raptors, water-
fowl, furbearers, wolves,
wolverine, brown bear
F
5 (~BECJHI)
82
Crosses several deep ravines;
cha~ges in elevation >2000 1 ;
routing above 4000 1 ; steep
slopes; some wet sol Is; shallow
bedrock In mts.
Same as corridor 4
Fog 1 Lakes; Stephan Lake; High
Lake; proposed access road;
vlewshed of Alaska Range
Same as Corridor 4
i
Wet'l ands In JA and Stephan Lake
areas; extensive forest-clearing
needed
42 creek crossings; valuable
spawning areas, especially
grayling and salmon: DATA VOID
Sam~ as Corridor 4 with Impor-
tant waterfowl and migrating
swan habitat at Stephan Lake
F
TABLE 6.49 (Cont 1 d)
Length (miles)
Topography/Soils
Land Use
Aesthetics
Cultural Resources
Vegetation
Fish Resources
W II d I I fe Resources
Environmental Rating
6 (CBAH I)
68
Crosses several deep ravines;
changes in elevation of about
1600 1 ; routing above 4000 1 ;
steep slopes; some wet sol Is;
shallow bedrock In mts.
No known existing ROW; re~
areas and Isolated cabins;
float plane area; Susltna area
and near I are Vi II age Se I ac-
tion Lands
Fog Lakes and Stephan Lake;
Tsusena Butte; vlewshed of
A I aska Range
Archeologic sites near Watana
dam site, Fog Lakes & Stephan
Lake; DATA VOID between H and
I
Extensive wetlands from B to
near Tsusena Butte; extensive
forest-clearing needed
32 creek crossings; valuable
spawning areas, especially
gray I lng: DATA VOID
Ba I d eage I nest s. e. of
Tsusena Butte; area of caribou
movement; passes through
habitat for: raptors, water-
fowl, furbearers, wolves,
wolverine, brown bear
F
7 (CEBAHI)
73
Crosses several deep ravines;
change In elevation of about
1600 1 ; routing above 3000 1 ;
steep slopes; some wet sol Is;
sha I I ow bedrock In mts.
Same as Corridor 6
For Fog Lakes and Stephan
Lake; high country (Pralrie-
Chun I ina Cks.); Tsusena Butte;
viewshed of Alaska Range
Same as Corridor 6
Extensive wetlands in Stephan
L. , Fog Lakes Tsusena Butte
areas; extensive forest-
clearing needed
45 creek crossings; valuable
spawning areas, especially
grayling: DATA VOID
Same as Corridor 6, with
Important waterfowl and
migrating swan habitat at
Stephan Lake
F
Corridor Segment
8 CCBAG) ·
90
Crosses several deep ravines;
change In elevation of about
1600'; routing above 3000 1 ;
steep slopes; some wet soils;
shallow bedrock in mts.
No existing ROW; rec. areas
and isolated cabins; float
plane areas; air strip and
airport; much VII lage Selec-
tion and Federal Land
Fog Lakes; Stephan Lake;
access road; scenic area of
Deadman Ck. ; vI ewshed of
Alaska Range
Archeologic sites by near
Watana dam site, Fog Lakes,
Stephan Lake and a long
Deadman Ck.
Wetlands between B and moun-
tains; extensive forest-
c I ear I ng needed
1 river and 43 creek cross-
ings; valuable spawning areas,
especially gray I ing: DATA VOID
Important bald eagle habitat
by Dena I I Hwy. & Deadma·n L. ;
unchecked bald eagle nest near
Tsusena Butte; passes through
habitat for: raptors, fur-
bearers, wolves, wolverine,
brown bear
F
9 CCEBAG)
95
Crosses several deep ravines;
changes in elevation of about
1600 1 ; routing above 3000 1 ;
steep slopes; some wet soils;
shallow bedrock In mts.
Same as Corridor 8
Fog Lakes; Stephan Lake; pro-
posed access road; high
country (Prairie and Chunilna
Cks. ); Deadman Ck.; vlewshed
of A I aska Range
Same as Corridor 8
Wetlands in Stephan L. /Fog
Lakes areas; extensive
forest-clearing needed
1 river and 48 creek cross-
Ings; valuable spawning areas,
especially gray I ing: DATA VOID
Same as Corridor 8, with
Important waterfowl and
migrating swan habitat at
Stepahn Lake
F
10 CCJAG)
91
Same as Corridor 8
No existing ROW; rec. areas and
lsoilated cabins; f I oat pi ane
are~s; air strip and airport;
mosriY VII lage Selection and
Fed~ra I Land
High Lakes area; proposed access
road; Deadman Ck. drainage; view-
shed at A I aska Range
Archeologic sites near Watana
dam site and along Deadman Ck.
Smal I wet I ands In JA area;
extensive forest-clearing needed
1 river and 47 creek cross-
ings; valuable spawning areas,
especially gray I ing: DATA VOID
Golden eagel nest along Devl I
Ck.' near High Lake; unchecked
bald eagel nest near Tsusena
Butte; area of caribou movement;
passes through habitat for:
raptors, waterfowl, furbearers,
brown bear
F
TABLE 8.49 CCont 1 d)
Length (miles)
Topography/Soils
Land Use
Aesthetics
Cultural Resources
Vegetation
FIsh Resources
Wildlife Resources
Environmental Rating
11 CCJAH I)
69
Crosses several deep ravines;
changes In elevation of about
1000 1 ; routing above 3000 1 ;
steep slopes; some wet soils;
shallow bedrock In mts.
No existing ROW; rec. areas &
Isolated cabins; float plane
areas; mostly VII lage Selec-
tion and Private Land
High Lakes area; proposed
access road; vlewshed of
A I aska Range
Archeologlc sites near Watana
dam site
Smal I wetland areas In JA
area; some forest-clearing
needed
36 creek crossings; valuable
spawning areas, especially
grayling and salmon: DATA VOID
Golden eagle nest along Devil
Ck. near High Lake; bald eagle
nest s. e. of Tsusena Butte;
passes through habitat for:
raptors, furbearers, brown
bear
F
12 ( JA-CJH I )
70
Same as Corridor 11
No existing ROW; rec. areas
and isolated cabins; float
plane area; mostly VII lage
Selection and Private Land
High Lakes area; proposed
access road; Tsusena Butte;
vlewshed of Alaska Range
Archeologlc site near Watana
dam site; possible sites along
pass between drainages
Smal I wetland areas In JA
area; fairly extensive forest-
clearing needed
40 creek crossings; valuable
spawning areas, especially
grayling and salmon: DATA VOID
Golden eagle nest along Devil
Ck. near High Lake; passes
through habitat for: raptors,
furbearers, wolves, brown
bear
F
Corridor Segment
13 CABCF))
41
Crosses several deep ravines;
about 1000 1 change In eleva-
tion; some wet soils
No known existing ROW; except
at F; rec. areas; f I oat pi ane
areas; resid. and rec. -use
near Otter L. and old sled
rd.; isolated cabins; mostly
VI I lage Selection Land; some
Private Land
Fog Lakes, Stephan ~
Archeologic sites near Watana
dam site, Portage Ck./Susitna
R. conf I uence; Stephan L. and
Fog Lakes; historic sites
near communities of Canyon
and GCJ I d Ck.
Wetlands In eastern third of
corridor; extensive forest-
clearing needed
15 creek-crossings; valuable
spawning areas, especially
grayling and salmon: Indian
River, Portage Ck., 1)\TA VOID
Unidentified raptor nest on
tributary to Susltna; passes
through habitat for: raptors,
furbearers, wolves, wolverine,
brown bear, caribou
c
14 CAJCD)
41
Crosses deep ravine at Devil
Ck. ; about 2000 1 change In
elevation; routing above
3000 1 ; some steep slopes;
some wet so II s
Little existing ROW except
0 I d Corps Rd. and at D; rec.
areas; Isolated cabins; much
Vii lage Selection land; some
PrIvate Land
Viewshed of Alaska Range and
High Lake; proposed access
road
Archeologic sites by Watana
dam site, possible sites along
Susltna R.; historic sites
near communities of Canyon
and Go I d Ck.
Forest-clearing needed In
western half
1 river and 16 creek cross-
Ings; valuable spawning areas,
especially grayling: DATA VOID
Golden eagel nest In Devil
Ck. /HIgh Lake area; actIve
raven nest on Devil Ck.;
passes through habitat for:
raptors, furbearers, wolves,
brown bear, caribou
A
15 CABECF)
45
Crosses several deep ravines;
about 2000 1 change In elevation;
some wet so II s
No ~nown existing ROW except
at F; rec. areas; float plane
area.s; res I d. and rec. use
near Otter ~ & old sled rd.;
Isolated cabins; mostly
Village Selection land with
some Private Land
Fog Lakes; Stephan Lake; high
country (Prairie and Chullna Cks.
drainages); vlewshed of Alaska
Range
Same as Corridor 13
Wetlands in eastern half of
corridor; extensive forest-
c I ear I ng needed
15 creek crossings; valuable
spawning areas, expecially
grayling and salmon: Indian
River, Pbrtage Ck., 1)\TA VOID
Important waterfowl and
migrating swan habitat at
Stephan L. ; passes through
habitat for: raptors, water-
fowl, furbearers, wolves,
wolverine, brown bear, caribou
F
1
J
I
J
i
J
Length (mi ies)
Topography/Soils
Land Use
Aesthetics
Cultural Resources
Vegetation
Fish Resources
Wildlife Resources 1
Environmental Rating 2
NOTE:
1 (ABC)
90
Some wet soils with severe limita-
tions to off-road traffic
Air strip; residential areas and
isolated cabins; some U.S. Mi I itary
Withdrawal and Native land
3 crossIngs of Parks Hwy; Nenana
R. -seen I c area
Archeologic sites probable since
there is a known site nearby; DATA
VOID
Extensive wetlands; forest-clearing
needed mainly north of the Tanana
River
4 river and 40 creek crossings;
valuable spawning sites: Tanana
River, DATA VOID
Passes through or near prime habitat
for: peregrines, waterfowl, fur-
bearers, moose; passes through or
near important habitat for: pere-
grines, golden eagles
A
TABLE B.50: ENVIRONMENTAL CONSTRAINTS
NORTHERN STUDY AREA (HEALY TO FAIRBANKS)
Corridor Segment
2 (ABDC)
86
Severe limitations to off-road
traffic in wet soils of the flats
No existing ROW n. of Browne;
scattered residential and isolated
cabins; airstrip; Fort Wainwright
Military Reservation
3 crossings of Parks Hwy; high
visibility in open flats
Dry Creek archeologic site near
Healy; possible sites along river
crossings; DATA VOID
Probably extensive wetlands between
Wood and Tanana Rivers; extensive
forest-clearing needed n. of Tanana
River
5 river and 44 creek crossings;
valuable spawning sites: Wood River,
DATA VOID
Passes through or near prime habitat
for: peregrines, waterfowl, fur-
bearers; passes through or near
Important habitat for: golden
eagles, other raptors
c
3 CAEDC)
115
Change in elevation of about 2500 1 ;
steep slopes; shallow bedrock in
mts.; severe limitations to off-
road traffic in the flats
No existing ROW beyond Healy/Cody
Ck. confluence; isolated cabins;
airstrips; Fort Wainwright Military
Reservation
1 crossing of Parks Hwy.; high
visibility in open flats
Dry Creek archeologic site near
Healy; possible sites near Japan
Hills and in the mts.; DATA VOID
Probably extensive wetlands between
Wood and Tanana Rivers; extensive
forest-clearing needed n. of Tanana
River; data lacking for southern part
3 river and 72 creek crossings;
valuable spawning sites: Wood River,
DATA VOID
Passes through or near prime habitat
for: peregrines, waterfowl, fur-
burers, caribou, sheep; passes
through or near Important habitat
for: golden eagles, brown bear
F
4 CAEF)
105
Same as Corridor 3
Airstrips; Isolated cabins;
Fort Wainwright Military
Reservation
High visibility In open flats
Archeoiogic sites near Dry Creek
and Fort Wainwright; possible
sites near Tanana River; DATA
VOID
Probably extenslv~ wetlands
between Wood and ~anana Rivers
3 river and 60 creek crossings;
valuable spawning sites: Wood
River, [)I.TA VOID
Passes through or near prime
habitat for: peregrines, bald
eag I es, waterfow I ~ fur bearers,
caribou, sheep; passes through
or near Important habitat for:
golden eagles, brown bear
F
(1) Source: VanBallenberghe personal communication. Prime habitat= minimum amount of land necessary to provide a sustained yield for a species; based upon knowledge
of that species' needs f rom eeperience of ADF&G personnel. Important habitat = land which ADF&G considers not as critical to a species as Is Prime habitat,
but Is valuable.
(2) A = recommended, B = acceptable but not preferred, C = unacceptable
-
--
-'
Technical
Primary
Secondary
Economic
Primary
Secondary
TABLE 8.51: TECHNICAL, ECONOMIC AND ENVIRONMENTAL CRITERIA
USED IN CORRIDOR SCREENING
Topography
C I I mate and E I evat ion
Sol Is
Length
Vegetation and Clearing
Highway and River Crossings
Length
Presence of Right-of-Way
Presence of Access Roads
Topography
Stream Crossings
Highway and Rai I road Crossings
Environmen-tal
Primary
Secondary
Aesthetic and Visual
Land Use
Presence of Existing Righ1"-of-Way
Existing and Proposed Development
Length
Topography
Sol Is
Cultural Reservoir
Vegetation
Fishery Resources
Wild! lfe Resources
TABLE B, 52: PRE-PROJECT FLOW AT WATANA (CFS)
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL ------
1 4719, 9 2083. 6 1168.9 815. 1 641. 7 569. 1 680. 1 8655. 9 16432. 1 19193. 4 16913. 6 7320.4 6648. 1
2 3299. 1 1107,3 906.2 8oa. o 673.0 619,8 1302. 2 11649. 8 18517.9 19786.6 16478.0 17205. 5 7733. 7
3 4592. 9 2170. 1 1501, 0 1274. 5 841. 0 735. 0 803.9 4216. 5 25773.4 22110.9 17356. 3 11571.0 7776. 1
4 6285.7 2756.8 1281.2 81 a. 9 611. 7 670.7 1382.0 15037. 2 21469,8 17355. 3 16681. 6 11513. 5 8035. 2
5 4218.9 1599, 6 1183. 8 1087. 8 803. 1 638. 2 942.6 11696. 8 19476.7 16983. 6 20420.6 9165. 5 7400.4
6 3859.2 2051. 1 1549. 5 1388. 3 1050. 5 886. 1 940.8 6718.1 24881.4 23787. 9 23537.0 13447,8 8719.3 I
7 4102.3 1588. 1 1038. 6 816.9 754. 8 694,4 718. 3 12953.3 27171. 8 25831.3 19153.4 13194.4 9051 •. 0 /
8 4208.0 2276.6 07.0 1373.0 1189. 0 935.0 945. 1 10176.2 25275. 0 19948. 9 17317.7 14841. 1 8381.0/
9 6034.9 2935.9 2258. 5 1480.6 1041. 7 973, 5 1265. 4 9957. 8 22087. 8 19752. 7 18843. 1 5978.7 7769. 4;
10 3668.0 1729. 5 1115. 1 1081.0 949.0 694.0 885. 7 10140.6 18329.6 20493. 1 23940.4 12466.9 8011.0
11 5165.5 2213. 5 1672. 3 1400. 4 1138. 9 961. 1 1069,9 13044.2 13233.4 19506. 1 19323. 1 16085.6 7954.;0
12 6049.3 2327. 8 1973. 2 1779.9 1304.8 1331.0 1965. 0 13637.9 22784. 1 19839.8 19480.2 10146.2 8602.19
13 4637.6 2263.4 1760. 4 1608.9 1257. 4 1176. 8 1457. 4 11333.5 36017. 1 23443. 7 19887. 1 12746, 2 9832~9
14 5560. 1 2508.9 1708.9 1308.9 1184. 7 883.6 776.6 15299.2 20663.4 28767.4 21011.4 10800.0 92771 7
15 5187. 1 1789, 1 1194. 7 852.0 781.6 575. 2 609,2 3578. 8 42841.9 20082.8 14048.2 7524.2 826i 7
16 4759,4 2368.2 1070.3 863.0 772.7 807.3 1232.4 10966. 0 21213.0 23235,9 17394. 1 16225.6 8451. 5
17 5221. 2 1565. 3 1203. 6 1060.4 984. 7 984. 7 1338.4 7094. 1 25939.6 16153.5 17390.9 9214. 1 7374.4
18 3269,8 1202.2 1121. 6 1102.2 1031.3 889. 5 849. 7 12555. 5 24711.9 21987.3 26104. 5 13672.9 9095. 7
19 4019.0 1934. 3 1704. 2 1617.6 1560.4 1560. 4 1576. 7 12826. 7 25704.0 22082.8 14147. 5 7163. 6 8032.2
20 3135.0 1354. 9 753. 9 619.2 607.5 686.0 1261.6 9313. 7 13962. 1 14843.5 7771.9 60.0 4912. 3
21 2403. 1 1020. 9 709.3 636.2 602. 1 624. 1 986.4 9536.4 14399, 0 18410, 1 16263. 8 7224. 1 6114. 6
22 3768.0 2496.4 1687, 4 1097. 1 777.4 717. 1 813.7 2857. 2 27612.8 21126.4 27446.6 12188.9 8588. 5
23 4979. 1 2587. 0 1957. 4 1570. 9 1491.4 1366. 0 1305. 4 15973. 1 27429.3 19820,3 17509, 5 10955. 7 8963.4
24 4301.2 1977. 9 1246, 5 1031. 5 1000.2 873.9 914. 1 7287.0 23859.3 16351. 1 18016. 1 8099. 7 7112. 0
25 3056. 5 1354. 7 931. 6 786.4 689.9 627.3 871.9 12889. 0 14780.6 15971. 9 13523. 7 9786. 2 6313.7
26 3088.8 1474. 4 1276. 7 1215.8 111 o. 3 1041.4 1211.2 11672.2 26689, 2 23430.4 15126.6 13075.3 8402.7
27 5679. 1 1601. 1 876.2 757,8 743.2 690. 7 1059. 8 8938. 8 19994,0 17015. 3 18393. 5 5711. 5 6834.8
28 2973. 5 1926. 7 1687, 5 1348. 7 1202.9 111 o. 8 1203.4 8569.4 31352.8 19701.3 16807.3 10613. 1 8232.6
29 5793. 9 2645.3 1979. 7 1577.9 1267. 7 1256. 7 1408.4 11231.5 17277. 2 18385. 2 13412. 1 7132. 6 6992.2
30 3773.9 1944. 9 1312.6 1136.8 1055.4 1101.2 1317.9 12369.3 22904. 8 24911.7 16670. 7 9096. 7. 8183. 7
31 6150. 0 3525. 0 2032.0 1470. 0 1233. 0 1177. 0 404.0 10140. 0 00.0 26740,0 18000. 0 11000,0 8907. 9
32 6458.0 3297.0 1385. 0 1147.0 971.0 889,0 1103.0 10406.0 17017.0 27840.0 31435.0 12026. 0 9580.4
MAX 6458.0 3525. 0 2258. 5 1779.9 1560. 4 1560. 4 1965.0 15973. 1 42841.9 28767.4 31435,0 17205. 5 9832.9
MIN 2403. 1 1020.9 709,3 619.2 602. 1 569, 1 609.2 2857.2 13233.4 14843.5 7771. 9 4260.0 4912.3
MEAN 4513. 1 2052.4 1404. 8 1157. 3 978. 9 898.3 1112.6 10397. 6 22912. 9 20778. 0 18431.4 10670.4 7985. 9
_ _j ] _I -J
.... 1 . J .... 1 ... -.l l ]
TABLE B.53: PRE-PROJECT FUJ..J AT [EVIL CANYOO (CFS)
YEAA OCT t\OV IEC JAN FEB M'lR ·1\PR· -Ml\Y . J..N M •· JlLk3 · SEP JlNNlll.ll
1 5758.2 2404.7 1342.5 951.3 735.7 670.0 002.2 10400 18468.6 21383.4 18820.6 7950.8 7537.8
2 1>52.0 1231.2 1030.8 905.7 767.5 697.1 1504.6 13218.5 19978.5 21575.9 18530.0 19799.1 ffi15.9
3 5221.7 2539.0 1757.5 1483.7 943.2 828.2 878.5 4989.5 3XI14.2 24851.7 19647.2 13441.1 8918.0
4 7517.6 3232.6 1550.4 999.6 745.6 766.7 1531.8 17758.3 25230.7 19184.0 19207 .o 13928.4 9356.4
5 5109.3 1921.3 1387.1 1224.2 929.7 729.4 1130.6 15286.0 188.1 19154.1 24051.6 11579.1 866.9
6 483J.4 2505.8 1868.0 1649.1 1275.2 1023.6 1107.4 8390.1 28:l31.9 26212.8 24959.6 13989.2 9707.4
7 1647.9 1788.6 12()).6 921.7 893.1 852.3 867.3 15979.0 31137.1 29212.0 2609.8 16495.8 10500.2
8 5235.3 2773.8 1986.6 1583.2 1388.9 1105.4 1109.0 12473.6 28415.4 22109.6 19389.2 10029.0 9568.7
9 7434.5 3500.4 2904.9 1792.0 1212.2 1005.7 1437.4 11849.2 24413.5 21763.1 21219.8 6988.8 8866.8
10 4402.8 1999.8 1370.9 1316.9 1179.1 877.9 1119.9 1m:J.9 21537.7 23390.4 28594.4 15329.6 9549.6
11 6050.7 2622.7 2011.5 1686.2 1340.2 1112.8 1217.8 14002.9 14709.8 21739.3 22())6.1 18929.9 9004.4
12 7170.9 2759.9 241>.6 2212.0 1593.6 1638.9 2405.4 16030.7 27()59.3 22880.6 21164.4 12218.6 10021.3
13 5459.4 2544.1 1978.7 1796.0 1413.4 1320.3 1613.4 12141.2 40579.7 24990.6 22241.8 14767.2 10946.5
14 6307.7 2696.0 1896.0 1496.0 1387.4 958.4 810.9 17697.6 24094.1 32B3.4 22720.5 11777.2 10431.8
15 5998.3 2005.4 1387.1 978.0 ~.2 663.8 696.5 4046.9 47816.4 21926.0 15585.8 0040.0 9250.7
16 5744.0 2645.1 1160.8 925.3 828.8 956.9 1214.4 12267.1 24110.3 26195.7 19789.3 18234.2 9555.5
17 6496.5 1007.8 1478.8 1478.4 1278.7 1187.4 1619.1 8734.0 30446.3 18536.2 20244.6 10044.3 8697.0
18 3844.0 1457.9 1364.9 1357.9 1268.3 1009.1 1053.7 14435.5 27796.4 25001.2 30293.0 15728.2 10460.4
19 4885.3 2203.5 1929.7 1851.2 1778.7 1778.7 1791.0 14982.4 29462.1 24871.0 16(00.5 8225.9 9175.4
20 3576.7 1531.8 836.3 686.6 681.8 769.6 1421.3 10429.9 14950.7 15651.2 8483.6 4795.5 5352.1
21 2866.5 1145.7 810.0 756.9 700.7 721.8 1046.6 10721.6 17118.9 21142.2 18652.8 8443.5 7053.9
22 4745.2 3)31.8 2074.8 1318.8 943.6 866.8 986.2 3427.9 31031.0 22941.6 30315.9 13636.0 9557.2
23 5537.0 2912.3 2312.6 2036.1 1836.4 1 59.8 . 1565.5 19776.8 31929.8 21716.5 18654.1 11884.2 10199.0
24 4638.6 2154.8 1397.0 1139.8 1128.6 955.0 986.7 7896.4 26392.6 lh571.8 19478.1 8726.0 7738.3
25 3491.4 1462.9 997.4 842.7 745.9 689.5 949.1 15004.6 16766.7 17700.0 15257.0 11370.1 7160.5
26 35()5.8 1619.4 1486.5 1408.8 1342.2 1271.9 1456.7 14036.5 30302.6 26188.0 17031.6 15154.7 9609.6
27 7003.3 1853.0 1007.9 896.8 876.2 825.2 1261.2 11305.3 22813.6 18252.6 19297.7 6463.3 7705.5
28 3552.4 2391.7 2147.5 1657.4 1469.7 1361.0 1509.8 11211.9 356()5.7 21740.5 18371.2 11916.1 9439.8
29 6936.3 3210.8 2371.4 1867.9 1525.0 1400.6 1597.1 11693.4 18416.8 20079.0 15326.5 8000.4 7765.1
30 4502.3 2324.3 1549.4 1304.1 1203.6 1164.7 1402.8 13334.0 24052.4 27462.8 19105.7 10172.4 0023.0
31 6~.0 3955.0 2279.0 1649.0 1383.0 1321.0 1575.0 11377.0 26255.0 30002.0 20196.0 12342.0 9994.5
32 7246.0 1>99.0 1544.0 1287.0 1089.0 997.0 1238.0 11676.0 17741.0 31236.0 35270.0 12762.0 10577.9
Ml\X 7517.6 3955.0 2904.9 2212.0 181>.4 1778.7 2405.4 19776.8 47816.4 32388.4 35270.0 19799.1 10946.5
MIN 2866.5 1145.7 810.0 686.6 681.8 663.8 696.5 3427.9 14709.8 15651.2 8483.6 4795.5 5352.1
MEJlN 5311.8 2382.9 1652.0 1351.9 1146.9 1041.8 1281.5 12230.2 25938.4 23100.9 20709.0 12276.3 9004.4
-
-
TABLE B. 54: MONTHLY FLOW REQUIREMENTS AT GOLD CREEK -
MONTH A Al A2 c C1 C2 D E F G -
OCT 5000 5000 5000 5000 5000 5000 5000 5000 5000 3500 -· NOV 5000 5000 5000 5000 5000 5000 5000 5000 2000 3000
DEC 5000 5000 5000 5000 5000 5000 5000 5000 2000 2000 ~
JAN 5000 5000 5000 5000 5000 5000 5000 5000 2000 2000
'"!!I\ FEB 5000 5000 5000 5000 5000 5000 5000 5000 2000 2000
MAR 5000 5000 5000 5000 5000 5000 5000 5000 2000 2000 -APR 5000 5000 5000 5000 5000 5000 5000 5000 2000 2000
MAY 4000 5000 5000 6000 6000 6000 6000 10290 10480 11730 ''"''\
JUN 4000 5000 5000 6000 6000 6000 6000 16000 18000 20000
JUL 4000 5100 5320 6480 6530 6920 7260 9160 10970 20000 ~
AUG 6000 8000 10000 12000 14000 16000 19000 16000 18000 20000 -SEP 5000 6500 7670 9300 10450 11620 13170 10300 10480 11730
Notes:
Derivation of transitional flows. _,
DATE CASE
JUL SEP A A1 A2 c C1 C2 D _,_
25 21 4000 5000 5000 6000 6000 6000 6000
26 20 4000 5000 5000 6000 7000 7000 7500
27 19 4000 5000 5000 7000 8000 8500 9000 -28 18 4000 5000 6000 8000 9000 10000 10500
29 17 4000 5000 7000 9000 10000 11500 12000
30 16 4000 6000 8000 10000 11000 13000 14000 -31 15 5000 7000 9000 11000 12500 14500 16000
E E F G
MAY JLIN JUL SEPT MAY/SEPT JUL -·
26 6 26 6 10000 8000 10000 11000
27 . 5 27 5 10000 9000 10000 12500 ·~;
28 4 28 4 10000 10000 11500 14500
29 3 29 3 11500 11500 13000 15500
30 2 30 2 13000 13000 14500 17000 -31 1 31 1 14500 14500 16000 18500
-·
TABLE 55: Energy Potential of the Watana 1:€velopna1t For Different Dol'llStrean Flow Requir81'81ts. (GWh)
·-
A A1 A2 c c1 c2 0 E F I G
FIRM AVERAG: FIRM AVERAG: FIRM AVERAff: FIRM AVERAG: FIRM AVERAff: FIRM AVERJlf£ FIRM AVERJlf£ FIRM AVERJIG: FIRM AVERJIG: FIRM A'k:RPfE
r-D.
JAN 277 lil 276 359 265 355 2~ 351 240 "334 Z30 318 211 301 169 279 155 273 111 173
FEB 216 :ni 214 1)5 a:J6 3:Q 193 297 185 200 177 264 164 248 149 234 120 197 86 144
~ 241 292 240 291 230 ;m 216 ;m 2ffi 274 199 264 185 262 163 247 135 199 97 140
APR a:J2 266 a:J1 266 191 265 179 266 173 250 165 237 161 226 154 233 113 196 Bl 125
MI\Y 195 240 194 240 lB6 237 175 184 171 194 162 192 150 182 119 261 115 267 96 317
JIJl 176 211 175 210 168 205 158 197 153 180 146 174 135 155 356 363 ll2 131 ll2 ll2
JLl 100 222 179 221 172 . 219 161 201 156 166 149 161 113 156 230 211 293 276 376 376
ALG 189 238 188 245 233 7J37 307 350 370 385 394 393 344 394 394 394 394 394 394 1)4
SEP 193 210 192 211 211 223 269 271 316 318 350 356 403 395 303 313 305 316 333 351
OCT 235 334 234 333 224 314 210 305 204 326 195 314 181 291 145 27JJ 159 233 95 158
NOV 257 405 256 405 245 395 230 392 223 392 213 li9 198 3li 158 218 145 2JJ 104 154
DEC ])4 410 lQ 4ffi 290 404 272 397 260 376 251 376 233 357 185 348 170 296 122 197
TOTJIL 2665 34g.j 2651 3495 2621 3494 2618 3499 2660 3476 2631 34T8 2553 3303 2525 3392 2486 3272 2282 2911
TABLE 56: Energy Potential of tre Watana -Devil Can.}«l l:eveloprent For Different lkw.nstrean Flow Requira!Ents. (GWl)
-
I A Al A2 c I c1 c2 0 E F G
FIHM AVERAGE FIRM AVERA9:: FIRM AVERA!£ FIRJ'1 AVERAtr" FIRM AVERA!£ FIRM AVERAGE FIRM AVERAGE FIRM AVERJU: FIRM AVERJ'IU FIRM AVERJlff
MJ. -
JAN 583 743 522 739 527 731 495 725 468 700 437 676 l36 645 300 615 256 545 2ll 332
FEB 433 637 429 635 410 625 ll5 614 l54 602 339 591 300 573 273 500 199 458 185 273
r.w~ 1185 631 4BJ 630 458 623 431 621 407 611 E 568 3li 551 320 S2.7 222 479 207 3)6
A~~ 407 565 403 $5 ll4 562 li1 S2.8 341 519 318 51l 281 530 217 442 186 412 174 240
MAY 454 496 465 496 450 49:3 434 479 329 457 Di 458 134 450 214 411 205 403 213 498
JIJ'I :ro 433 394 437 379 429 li2 419 l38 412 343 402 306 394 526 546 526 526 526 526
JUL 399 452 403 451 ~ 443 371 434 402 429 379 426 333 425 477 456 517 514 517 517
ALG 335 455 381 460 433 489 481 518 543 541 543 543 543 543 543 543 543 543 543 543
SEP 339 435 Hi 433 J)4 437 482 500 569 556 569 568 569 569 569 551 569 553 569 569
OCT 477 fro 492 fQ1 535 615 535 622 510 586 482 546 4:£ 1185 362 456 370 437 306 406 i
NOV 522 700 536 704 576 706 572 698 547 664 516 615 467 547 3:£ 544 398 495 324 382
DEC 610 810 604 ED9 576 799 542 776 513 757 479 724 422 643 329 663 280 546 261 375
TOTAL 5509 6962 5525 6%2 5sro 6g19 5451 6934 5:£1 69l3 5C9l 6655 4765 6355 4527 6242 4271 59U 4064 4(}27
I J J
!""'
TABLE B.57: NET BENEFITS FOR SUSITNA HYDROELECTRIC
PROJECT OPERATING SCENARIOS
-LTPWC1 NET BENEFITS PERCENT
CHANGE
'"""" RELATIVE
1982 dollars X 106 1982 dollars x 106 TO CASE A
Thermal Option 8238
!"""
Case A 6879 1359
r-Case A1 6885 1353 -.5
Case A2 6904 1334 -.2
Case C 6923 1315 -3
Case C1 7017 1221 -10
!"""
Case C2 7200 1038 -24
Case D 7494 744 -45
Case E 7584 654 -52
!""" Case F 7896 342 -75
Case G 8731 -493 -136
Note:
!""" ltong-Term Present Worth Costs
-
-I
-
-
-TABLE B.58
SYSTEM GENERATION RESERVE -
Estimated
YEAR Peak Generation Reserve in Percent
Demand of Peak Load
MW System Configuration
With Susitna All Thermal ~\
1993 Watana On-Line 947 95.7* 45.0
1994 965 88.8* 59.8 ~ 1995 983 80.5* 52.0
1996 1003 69.9* 61.9
1997 1023 59.4 58.4
1998 1044 50.8 56.6 ~
1999 1064 48.0 53.6
2000 1084 41.2 46.8
2001 1121 36.6 48.2
2002 Devil Canyon On-Line 1158 79.5* 38.9
2003 1196 69.4* 35.9
2004 1233 64.4* 37.5 -2005 12m 52.7 37.6
2006 1323 44.9 35.6
2007 1377 44.3 44.8
2008 1430 42.1 37.6 -2009 1484 36.9 37.3
2010 1537 36.8 32.5 -
Average 57.9 45.6
Average excluding years (*) 44.9
influenced by installation
of large hydro project
"""~
-
-
-·
-
-
TABLE B.59
TRANSMISSION SYSTEM PERFORMANCE UNDER DOUBLE CONTINGENCY
Highest Line Loading
as % of Rating
Highest P.U. Voltage
Lowest P.U. Voltage
On 345 kV
On 115 or 138 kV
Max. Differential
Phase Angle
Acceptab 1 e
Performance
Criteria
1.10
0.90
0.90
System Configuration
1993 2002
1052/
1.05
0.95
0.95
1.05
0.95
0.93
1jBased on an estimated 14% overload capability over rating in case of a 75%
daily load factor.
2;sased on an underwater cable design presently under testing.
TABLE B. 60:. AVERAGE ANNUAL AND MOIHHLY FLOW AT GAGES
IN THE SUSITNA BASIN*
-
-
-
TABLE B.61: PEAK Fla.JS CF RECffiD
GJld Creek Cantwell D=nal i Ma:laren
Peak Peak Peak Peak
Date cfs Date cfs Date cfs Date cfs ---- --,-..
8/25/59 62,300 6/23/61 30,500 8/18/63 17,cro 9/13/60 s,m
6/15/62 00,600 6/15/62 47,cro 6/07/64 16,cro 6/14/62 6,650
r 6/07/64 90,700 6/07/64 50,500 9/00/65 15,81) 7/18/65 7,350
6/06/66 63,600 8/11/70 20,500 8/14/67 28,200 8/14/67 7,600
8/15/67 80,200 8/10/71 6o,cro 7/27/68 19,cro 8/10/71 9,300
8/10/71 87,400 6/22/72 45,cro 8/08/71 38,200 6/17/72 7,100 ,....
r TABLE B.62: ESTIMATED FLOOD PEAKS IN SUSIT~ RIVER
r
LOCal:lOn 1-'eaK 1m , lOW ln LTS ,ror Kecurn; nee J.m.erv.: ll_ m rears
1:2 1:50 1:100 1:10,000 Pr-f"
GJld Creek 49,500 106,cro 118,cro 1g),Cffi 400,000
Watana Dansite 40,000 87,COO 97,cro 156,cro 326,cro
Devil Can}"Jn Dansite l 12,600 39,cro 61,cro 165,cro 345,cro
(Routed Peak Inflow
with Watana
-
DEVIL CANYON FLOOD ROUTING 2
Maximum Flow During Flood (cfs)
Spillway
Flood Powerhouse Outlet Main Emergency Total
1:50 3500 35,500 0 0 39,000
1:10,000 3500 38,500 123,000 0 165,000
PMF 35003 38,500 156,000 150,000 345,000
Notes:
(1) Powerhouse closes when reservoir level exceeds 2193 ft MSL
(2) Assumes Watana Reservoir upstream
(3) Powerhouse closes when reservoir level exceeds 1456 MSL
-,
""""\ Maximum
Reservoir
Level (ft)
""''
1455
1455
1466 """!\
-
-
-
.,
I
-
-
l -l .. l l --·l
TAB!£ B.64: ESTIW\TED EVAFffiATION LOSSES -WATAM liND DEVIL CJINYON RESER\OIRS
WATANA
Pan Reservoir
Ev~oration Evcv:>ration
f'lonth (inches) (inches)
January 0.0 0.0
February 0.0 0.0
March 0.0 0.0
April 0.0 0.0
May 3.6 2.5
June 3.4 2.4
July 3.3 2.3
August 2.5 1.8
Septent:Jer 1.5 1.0
October 0.0 0.0
Novarber 0.0 0.0
Decent:Jer 0.0 0.0 --
Annual Ev(l). 14.3 10.0
1 Based on data -April 1980-June 1981
2 Based on data -July 1980-June 1981
3 Based on data -January 1941-December 1980
D E V I L
Pan
Ev~ration
(inches)
0.0
0.0
0.0
0.0
3.9
3.8
3.7
2.7
1.7
0.0
0.0
0.0 -
15.8
CANYON Average M:>nthly Air T~rature l C)
Reservoir
Ev(l)oration
Watana1 Devil Canyon2 Tal keetna3 (inches)
0.0 -2.5 -4.5 -13.0
0.0 -7.3 -5.0 -9.3
0.0 -1.8 -4.3 -6.7
0.0 -1.8 -2.5 0.7
2.7 8.7 6.1 7.0
2.7 10.0 9.2 12.6
2.6 13.7 11.9 14.4
1.9 12.5 N/A 12.7
1.2 N/A 4.8 7.8
0.0 0.2 -1.8 0.2
0.0 -5.1 -7.2 -7.8
0.0 -17.9 -21.1 -12.7 -
11.1
l
. TAB!£ 8.65: FLCJ..J RELEASE (CFS) AT WATANL\ Fffi WATANL\ OOLY -CASE C
OCT f'llV occ JAN FEB ~ Affi Ml\Y JJN JJL ALG SEP ----
1 5664.6 9716.3 11285.3 9705.6 8958.2 0080.8 7383.7 5632.5 4853.9 4617.4 g)33.6 8301.0
2 !XJ40. 9 6640.7 7716.0 7189.9 629).0 6468.3 5674.3 7874.1 4835.5 4778.1 Ball.O 5265.5
3 7082.9 10164.1 11617.4 10165.0 9157.5 ~46.7 7507.5 5326.8 5002.3 4797.2 8436.3 5391.0
4 Ee69.3 10750.7 11397.6 9709.4 8928.2 8182.4 8l35.6 11375.6 4959.6 4560.9 0071.6 5543.5
5 5691.2 6591.6 11300.2 9978.3 9119.6 8149.9 7646.2 8369.3 4962.2 459).8 6320.6 5545.5
6 56&l.O 7246.1 11665.9 10278.8 9367.0 8397.8 7644.4 5258.9 5174.6 6849.6 14lli3.1 8457.8
7 7620.0 9582.1 11155.0 9707.4 g)71.3 Ee06.1 7421.9 g_)()0.1 91)8.6 8818.7 10055.4 8275.0
8 7778.5 10270.5 11823.4 10263.5 %05.5 8446.7 7648.7 700J.7 7123.4 4748.4 8777.7 7254.1
9 9605.4 10929.9 12374.9 10371.1 9358.2 8485.2 7959.0 5004.2 4963.6 4755.7 8303.4 7550.0
10 5731.9 6512.7 7772.5 9971.5 9265.5 !Q05. 7 7589.3 6968.7 4838.2 478).9 8969.2 739).3
11 8736.0 10207.4 11788.7 1029).9 ~55.4 8A72.8 7773.5 9581.9 4870.4 4812.9 7733.1 4875.6
12 6482.7 10321.7 12009.6 10670.4 %21.3 ffil2. 7 8668.6 10116.3 203.3 4747.4 9300.2 6076.2
13 6050.3 10257.3 11876.8 10499.4 9373.9 8688.5 8161.0 0042.3 16898.9 7579.4 11004.0 7286.0
14 9130.6 10502.9 11te5.3 10199.4 9501.2 8395.3 7430.2 11611.4 4959.4 9515.9 12488.0 778).0
15 6516.0 9783.1 11311.1 9742.5 9)38.1 OCB6.9 7312.8 5333.1 18353.5 5020.1 9608.2 7253.2
16 5759.3 6535.8 7538.2 9560.5 9)89.2 8319.0 7c:I36.0 7711.6 4962.8 5167.4 Ee74.1 10]31.7
17 8791.7 9559.3 11320.0 9950.9 9301.2 8496.4 0042.0 5258.9 6476.3 4555.1 7560.9 6764.1
18 5722.3 6504.8 76(Jj.3 9992.7 9347.8 8401.2 7553.3 9142.1 6837.7 5550.2 16188.9 8753.5
19 7589.5 9928.2 11~0.6 10508.1 9876.9 g)72.1 8280.3 9~6.2 7755.8 5705.5 8977.5 7647.6
20 5756.8 6543.1 7573.0 7636.5 g)64.5 8197.7 7553.6 5258.9 4851.7 4629.7 9756.0 7674.0
21 59)7 .9 6009.4 7856.2 7330.4 6420.2 6619.0 5826.2 5428.1 4982.6 4747.2 8283.8 7403.1
22 5971.4 67g).2 7879.0 7336.3 6419.8 6614.8 5823.1 5501.8 5166.8 4938.7 8685.6 7048.9
23 7860.2 10580.9 12073.8 10561.4 9007.9 f!B77.7 am.o 12218.0 9501.0 4742.3 10219.5 7855.7
24 5697.0 6589.5 11J>2. 9 9922.0 9316.7 8385.6 7617.7 5258.9 4973.6 4tX35.1 9726.7 8325.7
25 5700.5 6573.2 7622.2 7091.7 6638.2 8139.0 7575.5 %42.3 4859.5 4654.8 9303.7 6836.2
26 59)1.1 6782.7 7811.4 7274.2 6358.6 6537.0 5739.0 5346.7 7869.7 6791.1 g)35.6 6065.3
27 7756.1 9595.1 10992.6 9648.3 g)59.7 8202.4 7763.4 5887.1 4964.3 4587.9 10593.5 6881.0
28 5827.7 6628.1 7677.0 7135.9 6231.4 7593.1 7g)7,0 5554.6 12444.1 4745.4 9567.3 7273.1
29 5692.1 9188.0 12096.1 10168.4 9584.2 8768.4 8112.0 7950.5 4844.1 4608.4 ~2.1 7825.6
30 5881.8 6683.9 7750.7 7215.6 63(Jj.8 6477.9 5679.0 83CB.9 5122.8 7742.0 8210.7 7Ee6. 7
31 5681.2 11305.1 12148.4 10360.5 9549.5 8688.7 8107.6 6968.2 5432.6 9231.9 g)70.3 7020.0
32 g)53.3 1129).9 11501.4 10037.5 9287.5 8400.7 7006.6 7207.6 4874.0 5632.0 19391.0 9316.0
AVE 6766.1 8667.7 10300.9 9399.2 8685.4 3)98.3 7478.1 7519.6 6628.3 5549.6 9778.8 7310.7
.... I j I ) I J .I J _j I ]
] ~~ 1 ~-J _] ·~J
TABLE B.66: FLOW RELEASE (CFS) AT CfVIL CJINYON Fffi Wl\TANA/DEVIL CJINYON -CASE C
OCT NOV occ JAN FEB fvVI.R Affi MB.Y JJN JJL ALG SEP ------
1 6602.4 10756.1 12481.7 11574.6 10087.0 8009.3 7405.0 6305.0 6047.5 5989.5 10940.6 8949.8
2 6552.5 7072.3 ffi65.7 7443.3 6471.5 6589.0 7026.2 7913.0 5743.6 5714.3 10960.0 7859.1
3 6489.8 la226.1 12526.3 11610.6 11123.8 9ffi7.8 7481.3 5765.5 7439.4 6373.2 10727.2 8261.1
4 6623.0 11385.9 12518.4 11589.2 11137.2 9929.7 8134.6 9743.6 9900.3 5760.1 10597.0 7%8.4
5 6757.0 7069.0 11783.4 11239.8 10909.5 8868.7 7733.4 9876.4 7CJ23.5 5950.5 9971.6 7959.1
6 6746.9 7139.0 12562.4 11637.5 11186.2 10459.6 7710.2 6222.3 8382.9 7547.1 11200.6 10143.6
7 7629.8 11012.4 12478.7 11566.9 10872.9 8991.6 7470.1 99)0.5 10079.3 9210.5 11699.7 16495.8
8 8217.2 11397.6 12527.7 11605.1 11167.2 10364.0 8742.8 7279.6 ~70.7 5931.7 10049.2 8401.8
9 1CJ205.5 11485.2 12775.0 11624.3 11113.1 10320.3 9369.8 7%7.4 7940.7 5865.2 1())79.8 8738.8
10 6708.1 7079.9 0039.7 m.o 11158.9 9)17.2 7722.7 8638.5 6640.4 6339.8 10197.7 13012.6
11 9042.6 11349.7 12561.2 11646.1 11168.3 10355.1 8774.0 9253.8 5756.3 6CJ24.0 10476.1 7719.9
12 6500.5 10507.2 12629.3 11005.8 11292.4 10433.1 9514.8 9570.9 10254.5 7147.3 11064.4 8148.6
13 6617.2 99)7 .0 12559.6 11597.4 11147.6 10353.0 9108.4 69)4.7 10407.7 8172.5 16223.3 14767.2
14 9289.6 11228.8 12476.8 ·11592. 5 11168.9 10314.7 8313.6 %78.7 98)8,2 9378.0 11050.5 11000.1
15 8980.2 11309.2 12491.8 11568.8 11125.5 8003.1 7299.3 5739.9 10541.6 8342.2 11145.8 8569.0
16 6758.8 9)41. 7 12437.0 11566.4 100)8.6 9)06.2 7917.2 7043.1 7634.2 7540.4 10669.3 %28.7
17 9478.4 11131.6 12536.1 11617.6 11180.8 9835.1 8221.9 6206.0 10395.8 6056.7 10414.6 8394.3
18 6612.1 7070.6 0036.4 9555.7 11248.1 9228.4 7656.5 9)24.1 ~0.5 8122.5 1a364.8 15728.2
19 7567.2 11273.5 12611.8 11621.8 11179.6 10388.7 9399.6 ~54.5 9988.1 8922.8 10920.5 8709.9
20 6593.6 7055.6 7998.0 8703.6 10038.8 8919.3 7561.8 5988.5 5991.7 5682.0 11178.0 8712.0
21 6663.6 7143.0 8140.1 7540.0 6554.6 6689.2 6544.4 6007.6 6448.9 6324.6 10672.8 8622.5
22 6972.3 7399.5 8285.0 7573.9 6563.5 6686.7 5854.6 6244.8 67~.2 5742.0 10405.9 9248.8
23 8518.9 11304.0 12564.7 11665.0 11214.5 10417.7 9414.3 10266.8 10319.6 8408.5 11364.1 8784.2
24 6265.8 10931.9 12463.9 11559.3 11142.7 ~.3 7589.5 5682.3 6871.3 5005.8 11188.1 8952.0
25 6578.8 7043.8 0003.9 7392.6 6426.2 8)67 .3 7551.9 9436.1 6017.8 5796.9 11037.0 ffi20.1
26 6617.7 7119.5 8152.2 7527.7 6568.9 669).3 5853.2 8173.9 9915.0 89)5.6 10941.6 8144.7
27 7791.9 11076.8 12459.1 11362.8 10856.0 8~4.5 7864.0 6575.2 6444.8 5796.6 11497.7 8882.3
28 6679.8 7257.3 8235.9 7536.0 6538.8 9)75.6 8112.6 6715.4 102a3.7 8499.0 11131.2 8576.1
29 6722.0 10985.1 12590.6 11649.5 11197.4 10391.1 9388.6 6729.8 5579.5 5721.3 10936.5 8773.4
30 6785.9 7228.4 8140.7 7489.2 6504.2 6582.8 7318.3 79'2f).2 7605.9 8585.9 10646.7 8702.4
31 6685.2 3891.8 12512.5 11590.6 11142.6 10351.8 9262.5 6238.7 9481.9 9188.2 11236.0 8362.0
32 7855.0 11345.7 12458.0 11592.9 11121.6 10331.1 8864.9 6500.5 5598.0 8176.9 17878.2 12762.0
AVE 7318.4 944.5 11128.2 10484.6 10094.3 9204.0 Ero5.7 7656.6 8146.1 7094.4 11333.6 9603.0
TAB!£ 8.67: WI\TER AFPROPRIATIOr£ WITHIN Of'£ Mil£ CF ll-lE SUSITNll. RIVER
AOO ITIONll.L SOLRCE
LOCATION* rt.MBER TYPE (DEPTH) PMQNT DAYS CF USE
CERTIFICATE
Tl9'J Rg.J 45156 Single-family dwelling well (?) 650 gpd 265 -general crops s crne source 0. 5 a::-ft/yr 91
T25N R5W 43981 Single-family dwelling well (g) ft) 500 gpd 265
T26NRg.J 7ffi95 Single-family dwelling well (20ft) 500 gpd 265
200540 Gr~e school well (27 ft) 910 gpd 334
al9233 Fire station well (34 ft) 500 gpd 265 ;~-
T27N Rg.J 200100 Single-family dwelling unnara:t strean 200 gpd 265
LaWl & garden irrigation Sil!Te source 100 gpd 153 -200515 Single-family dwelling unn ara:t l ake 500 gpd 265
ax:633 Single-family dwelling unnara:t lake 75 gpd 265
206930 Single-family dwelling unnane:i lake 250 gpd 265
206931 Single-family dwelling unn ara:t 1 ake 250 gpd 265
POOIT --
206929 General crops unnara:t creek 1 a:-ft/yr 153
TJrn RJ..J 206735 Single-family dwelling unnara:t strean 250 gpd 265
PENDING
al9866 Single-family dwelling Shennan Creek 75 gpd 265
Lawn & garden irrigation sarre source 50 gpd 183
*All locations are within tre Seward M=ridian. -
....
!
, .... TABLE B.68: TURBINE OPERATING CONDITIONS
Watana Cl=v i 1 Can )On -Maximun net heed 725 feet 603 feet
Minirrun net reoo 600 feet 541 feet -Desi91 heed 600 feet 5SD feet
Rated reed 68J feet 5SD feet
-Turbine flow at rate::l head~ cfs 3550 cfs IDJ cfs
Turbine efficiency at design heoo 91% 91%
Turbine-generating rating at rate::l heoo 186,500 kW 168,000 kW -
-
-
-
~.
FIGURES
-
....
-
LOCATION MAP
LEGEND
'\1 PROPOSED
DAM SITES
LOCATION MAP
: ..
20 0 20 60
SCALE IN MlLES
FIGURE 8.1
l -] l ) J
~
TYONE:. & DAM SITE
5 0 5 15
SCALE IN MILES
r----_/
1
DAMSITES PROPOSED BY OTHERS J
J -..J---v
_, FIGURE 8.2
J
PREVIOUS
STUDIES AND
FIELD
RECONNAISSANCE
12DAM
SITES
GOLD CREEK
DEV-IL CANYON
HIGH DEVIL CANYON
DEVIL CREEK
WATANA
SUSITNA ill
VEE
MACLAREN
DENALI
BUTTE CREEK
TYONE
J
SCREEN
ENGINEERING
LAYOUT AND
COST STUDIES
7DAM
S1TES
}
COMPUTER MODELS
TO DETERMINE
LEAST COST DAM
COMBINATIONS
3 BASIC
DEVELOP-
MENT
PLANS
l
DATA ON DIFFERENT
THERMAL GENERATING
SOURCES ~------'-----,
COMPUTER MODELS
TO EVALUATE
-POWER AND
ENERGY YIELDS
-SYSTEMWIDE
ECONOMICS
f--C_R_IT.;;;...E_R_IA--,-------1 DEVIL CANYON
ECONOMICS HIGH DEVIL
OBJECTIVE
ECONOMIC·
WATANA I DEVIL
CANYON
CRITERIA WATANA I DEVIL
CANYON
CANYON ENVIRONMENTAL WATANA
ALTERNATIVE SUSITNA m SITES
ENERGY VEE
CONTRIBUTION MACLAREN ,____ ____ ____.DENALI
L.__._------' HIGH DEVIL
CANYON/ VEE
HIGH DEVIL
CANYON / WATANA
ADDITIONAL SITES
PORTAGE CREEK
ECONOMIC
ENVIRONMENTAL
SOCIAL
ENERGY
CONTRIBUTION
DIS. HIGH DEVIL CANYON
DIS WATANA
PLUS THERMAL
SUSITNA BASIN PLAN FORMULATION ·AND SELECTION PROCESS
FIGURE 8.3
)
-
-
-
ffi > a:
< z ..... w ::r:
(I)
0
0
0
0
N
a:
~a:
w z
0 >-..... _
0
0
0
N
(I !fNl.ISOS
0
0
0
If)
-0
0
10
N
~ :
I
I
t
~YO 3l.l.OE! 1111 .,
If)
10
N
I'WN30 ...,
------s
N3~1::>~w 1.3
-·-----~
N
------
33A
]J[ ~Nl.ISOS
_I ";:-10 0 g. 10 g -0
N
N
'r/NVl.'r/M
-0
0
0
N
·o
~ -~ ~
..
·o
10 ,... .-
·~:;, Sl1A30
) NOAN'r/::> 11A30 H91H
-0
0
IC) -
I
I
0
CD
N
0 co
N
0 v
N
0
N
N
0
0
N
-0
0
Q
-~~
NOAN'r/::> 11A30 ._ . .4JNOS10-: ·~:;,a,J
.r u
11.1
(.!)
j!
cr
0
0..
0
0
10
"2
Q
'r-
\
0
CD
0
!!
0
!:·
0
N
0
0
(/) w
1-
(/)
w > -~ <:( z a: w
~
<(
J:
~ ::»
0 a:
:I:
f-
lLJ
-.J
f lL.
0
Q: m Q..
..J
~-
~
1&.1 > iE
1 1 ---, - J ) )
Go to
CREEK OLSON DEVIL
CANYON
HIGH
DEVIL
CANYON
DEVIL
CREEK . WATANA . SUSITNAm VEE MACLAREN DENALI
OLSON
. : :. ·::: . ,•. '.
:. ,•
·: .... : ·:::::
DEVIL CREEK
WATANA
LEGEND
COMPATIBLE ALTERNATIVES
D
MUTUALLY EXCLUSIVE. ALTERNATIVES
SUSITNA m
DAM IN COLUMN IS MUTUALLY EXCLUSIVE IF FULL
VEE
·,;;;;:~;:':;:':':'',' .: ~:::}::c SUPPLY LEVEL OF DAM IN ROW EXCEEDS THIS VALUE-FT.
)/::::::::;}:::::/ii}' VALUE IN BRACKET REFERS TO APPROXIMATE DAM HEIGHT.
MACLAREN
DENALI
BUTTE CREEK
TYONE
MUTUALLY EXCLUSIVE DEVELOPMENT ALTERNATIVES
BUTTE
CREEK
FIGURE B.5
J
TYONE
...
~
!<
z
0
~ a
-'1
1500
1400
l
GENERAL ARRANGEMENT
SCALE: A
l
----. ___
··-......._ '70o
1300 ~--=-=-=-'o:~:-:~;~~LGROOND~~ACE __ _
_
11
____ _..BE.,_OR_,_OC=K'-'S--U..,R~.,-A ... CE,_ ______ ~\------------1200
1100
1000
900
BOO
LONGITUDINAL SECTION THRU { OF DAM
SCALE: B
SECTION A•A
SCALE; B
DEVIL CANYON
...
~
!<
~
~
... "' 1:!
~
i!!
I= ~
Iii
1600
1500
1400
1300.
12.00
1100
1000
900
1500
1400
1300
1200
liDO
1000
900
BOO
SECTION THRU DAM
SCALE: 9
--------==c::.. ______ .~"---:::-;===~----;~__.:~[IR!l!A~SFiA\~E~t~~R~RAFT """'o....._,A-V-'~~"~::.GE.:OSO:c~l~
LINED TU,.,.ELS ... , .
MANIFOLD BOt
I u_~~~~~--L-~~--L-~~--~.~o~o~--~~~~,o~oo~--+-~~~,~500~~~~--~.~.~oo~--~~~-.:.~oo
STATIONING IN FEET
500
POWER FACILITIES PROFILE
SCALE: B
NORMAL MAX. W.L.
EL.~
1500 --
ffi
1400 -------
1300
,_,_,_
~~PILLWAY CONTROL STRUCTURE
/ /5-4dX4:0' WH-EEL MOUNTED GATES rr _·-----....___
~~;;~~~~~~-,~-~--~-~~~~---~:-'_~----------_--------~--;IE~x=,~=,~ •• ~.=.~ou=.~o-=su=o=M~c=E~o=•~
~. ~ -........ / RIGHT SIDE OF SPILLWAY
i!:
:z 1200
0 ;:: 1100
~ .: 1000 --
900 --
BOO
400 800 FEET
SCALE A
200 400 FEET
SCALE B
000 1000
SPILLWAY PROFILE
SCALE: 8
\\ ~XISTING ROCK LEV£
1500 2000
STATIONING IN FEET
NOTE"
~ oa.aWIIIt IU.U.STJI!UEt •
,.[LIMI•An co•c'!,-riJ.I.L ,-ROJ!CT LATOUT
PW~,-.I.ItH f'OI!: COIIIII"".I.IfiSON 01'
<'t:JIWA'r!VI IJTl NYI!.J..O .. lti!.IIIITI OlfL'f
HYDRO DEVELOPMENT FILL DAM
FIGURE 8.6
1
~
-1
SPILLWAY 2~
~23oo~
GENERAL. ARRANGEMENT
SCALE• A
ZIOO
zooo
t-1900 ! 1800
2. 1700 !' 1600
u:: 1500
1400
1
1-..
~
;!;
z
0 ;;;
> ..
;j
2300
••oo
2100
2000
1900
1800
1700
1600
) l
SECTION THRU DAM
SCAL.E•B
EL~
' ---------~~~-
1 1 11 ---------_----
11 :1 ----"ACCESS SHAFT~: :1 ---------<EXISTING GROUND SURFACE
II ,!---___CABLE SHAFTS ------------11 II -......___
,, !/ --............
:: :: F ~o:~·~2+'~~~.·~,P,J"AFT -------'--I I II ............. , ---
2~23'DIA. CONCRETE LINED TUNNELS
CONCRETE PWG ::c ::~ -5+00
~~_L_L_~ _ _L_L_i__L __ ~_L__L~-~_L_J_~_L~~j _ _L~--"__l__L_~_L_L_~_L_L_~~~L__L_i_L_~
0+00 5+00 10+00 15+00 ZO+OO 25+00 30+00 35+00
1900
t:i 1900
.w
I&. 1700
;!;
~ 1600
~ 1500 ,.
~ 1400 w , ....
0+00 5+00 10+00
STATIONING IN FEET
SPil-l-WAY PROFil-E
SCALE•B
15+00 201-00
AVERAGE
TAILWATER
EL.I4M
-~
EXISTINC> ROCK
LEVEl..
STATIONING IN FEET
POWER FACil-ITIES PROFil-E
SCALE• 8
-------~
·sECTION A-A
SCALE•C
EXISTING GROUND
----
ROCK ANCHORS
/
CREST EL.2225
2300 ,.SLOPE I -~ ~~NJERLINE_ I SLOPE-
:::L~=-~~~~=-----------/-E_X_CA-V=AT_I_o•~~-:-o~-o-:•-.-.u-~-.~c~E-~~~---------~---=-----------------~-/--~-~--~
... zooo :J --.---:;:?.-!:: d~=======TI"====:---~{ORIGINALGROUNDSURFACE ~~--=~~:===~:p==
~1100 \. / /~ /GROUT GALLERIES.../
-" "'/ L_ a·eoo \\ // c:;r==-=;; ~ \" ... / tl
\ ·, /I '' ' ....__ _________ __./ // 'l
' ............... _________ ..--_,.. .=.::;;=;;;.-;;::.::..=:~~= 1400
SCALE C ~O ........ I~OO:iiiiiiiiiii200 FEET
0 200 400 FEET
SCALE 8 c:::= ------=a
0 500··· IOOOf'EET
SCALE A
l-ONGITUDINAL. SECTION THRU CENTERLINE OF DAM
SCALE• 8 WATANA HYDRO DEVELOPMENT FILL DAM FIGURE 8.7
l ) -)
GENERAL
SCALE: A [CREST EL. 2225
·~r-------------------------------------·-----------.---.---.-------------------_-__ --_1t~A~T~i~~~D~AM~(S~T~AG~E~m~----------------------------2ZOO~==~~~;;_::;~=======-------::=~----=;;;:;:-~-;;;::-;;------:::-;: ·---·----·-·--o------~~ ~----..:.-:::-::---... SLOPE-I CREST R.2060 1--SLOP.s_. _....-~I~ ~t~,t=====~ -~-.-~,~~===----~~-~-~~;;~~~~~~~~~======~~A~T=i~D~F~~~M~(~ST~A~GE~l~l~~~~========~~~~~~~g~~~
;2000 :: ~~-_..--::-;::-2'_
~ I900 _JI ExCAV~TION FDR_-:.~O_RE __. ~ ~ .._ ... ~ ~_; ~ -== ==..=:rr-?...::-;;-~1000~------~~~~~==~"¥·~~-==~--~~~~-~"""~~-------------------------------:~~~~~~~c"'~~-f--
-,.BEDROCK BURFOCE-/"'-.;>~ /;~'" ii/ ~ I~•~-----------------00--IG-I~_:=G~R:OO:=H~D=S~U~~=A~CE_E_~--~'\~~~-~,---------------------------.0~,~~~~---~--~G~R-;;OU'~T~GA~l~lE=R=IE=s~Jf---
I-~---------------~~~~~~=---~\~\~'~---------------------~7/7/'~"~~~F-~~~7--L__ ________ ___
::t============================~~~';,~~=~-~== __ :_:_:~:_:_: __ =~~~~/~::;_$·-~--=:=-=~d~h==:==============--
LONGITUDINAL SECTION THRU t OF DAM
SCALE: B
EXISTING GROUND SURFAC£ rNORMAL MAX
ON {OF SPIL~IMA.Y\ W.L. EL.220ci
SPILLWAY PROFILE
SCALE: B
2300
2200
2100 I
zooo I
~
~ 1900
!!;
·,aoo
!i 1700
~ -1600
~ 1!500 ~
WATANA STAGED Fl LL DAM
SECTION THRU DAM
SCALE: 8
4 UN!T INTAKE (STACiE III
GROUND SURFACE
POWER FACILITIES PROFILE·
SCALE: B
ZOO 400 FEET
[~~~~·~oo~~~~oo~oo FEET SCALE A c
SCALE B
!!!!!!!.
TMI8 DRAW!NI IU.USTRI.TE! .I
fl'ft!LI.Uifl.ln COIIetFT Ul.l. ~"CJJtCT LAYOUT
flllt[P'AP.I.t;l flO" CQMPA.HS.OJI 01"
ALTtR~ATIVI. SITE HVELOPiii[RTt O•LT
FIGURE 8.8
GENERAL ARRANGEMENT
SCALE :A
l
LONGITUDINAL SECTION THRU § OF DAM
SCALE: 8
HIGH DEVIL
1~00
1400
I;;
~ ISOO
"' z !ZOO
~
~
1600
"00
I;; 1400 ~
!! 1~00
z
0 ;:: 1200
-~ 1100
1000
900
CANYON
l l 1 l
NORMAL MAX. W.L. E:l. mso'
SECTION THRU DAM
SCALE:B
NORMAL MAX lWL. EL.I7:=t:1765· --=--
j..,-------:::,_..------=---~----I~HDII~--,--------'"~'1-~'F"'="'ii'"""~c-sw_IT_c_H_v•_•_o _____________________ _ -~ ,~ ~~ ~==~~~~~--~--~~~==~~--~------------------1------INTAKE / ~ :: Jf ~~EXISTING GROUND SURFACE
~ ____U___i_ ___ ~~~~.-.~"" .. -."'~~-~--------------1 1-------------->;~~-----:;c~j:~~.AT~~N;;E~E ff -7f~;~s:2~~~t~R~RAFT ''"'"'-~
~POWERHOUSE~ ,.d-_-_y1
......-OUTLET STRUCTU~~
CONSTRUCTION--._~ 1r--J/ ll : : rMAINIFOLO
1----'--c-------ADIT. · ~~._.I t t
.,----~ . AV~ TAILWATER
.. ~·~·-1 ~'U~'l.~L~ coNcRETE LINEa ~----•L. 1o•o·37
CONCRETE PLUG/ ~
STEEL LINER LGATE/SURG£. SfiAFT
soo 500 1000 ISOO 2000 2500
STATIONING IN FEET
POWER FACILITIES PROFILE
SCALE: B
NORMAL MAX
IW.L EL.I7G0~5-401 1t40' FIXED WHEEL GATES
J. _~SPILLWAY CONTROL
ISO
___t' STf'UCTURE /it STING GROUND SURFACE
0 ' .. ==----::::--.. LONG t_ OF SPILLWAY
150
~ 120 ;::
0
0
~ 1100
ii:l 100 0
90 0
HYDRO
0
SCALE A
0
SCALE B
~-----J --...,_-....,_ -
I
:!~~~~N~
soo 1000
STATIONING IN FEET
SPILLWAY PROFILES
SCALE: B
400 800 FEET-
200 400FEET
1500
DEVELOPMENT
I
~---------~---------~ ~ '-,
~ '--------0..\ ;~.:.~Q~~~TEi
--"""' I
2000 2!500 3000
NOTE
TM'i't D~~t••'IIG -tUurnaTn •
III"'KLIIIIIIIARY t'ONCEII"TUA:. "ftt..E.CT L&TOUT
,..P.utEEi ,OR ·COMNRJ.SO. OF'
ALTt:lliM.ATIYf SITE PEVELD,..ATS ON-LY
FIGURE 8.9
. ..,
2200
2100
zooo
1800L_ _________ _
l
GENERAL ARRANGEMENT
SCALE• A
SLOP£
1
CREST EL. 2360
AT 4. OF DAM
LONGITUDINAL SECTION THRU t OF DAM
SCALE:· B
SLOPE
NORMAL MAX. W.L. ±40
l l
SECTION THRU DAM
SCALE• B
POWER FACILITIES PROFILE
10
STATIONING IN FEET
SCALE: B
SPILLWAY PROFILE
SCALE: B
15
SCALE A O'!!!!!!!!"'llli40i§Oii;;;o;;;;;;i8iij00
200 400
SUSITNA ill HYDRO DEVELOPMENT
1
FIGURE B.IO
2400
t; 2300
~ 2200
:! 2100
z
2 2000
l;
~ 1900
.: 1800
GENERAL ARRANGEMENT
SCALE A
CREST EL. Z3!50
SCALE B"
l
2600
2500
2400
2300
E 2200
;!; 2100
2i 2000
E 1900 "' ;;l !BOO
VEE
SADDLE DAM
2400
2300 ...
"' 2200
~
~ 2100
z 2000 ~
;! 1900 "' ;;l I BOO
-500
-500
HYDRO
1
2400
2300
~ "' 2200 ~
~ 2100
2i 2000
~ 1900
~ 1800
I TOO
1600
STATIONING IN FEEi
POWER FACILITIES PROFILE
SCALE 8
500
STATIONING IN FEET
SPILLWAY PROFILE
SCALE B
DEVELOPMENT
1000
l
SECTION THRU DAM
SCALE B
HSOO
o~~~·~oo~~·~oo FEET SCALE 8 ~
SCALE A 0~~~4§00ii;;;;;;iiiii"i;l00 FEET
FIGURE 8.11
1 1
MACLAREN
GENERAL ARRANGEMENT
SCALE' A
l
NORMAL MAX.
I W.L. EL. 2395
I ~
SECTION A-A.
SECTION C-c
~,----------~--~~~~~~~~~~----------~ ~~-+------~~--=~
... ~ 2200
~
~
!
.: 2400 --=~~S~§~::
2200
DAM CROSS SECTION
. 9CALE'C
SECTION B-El
SCALE:C
DENALI a MACLAREN HYDRO
1
0
SCALE•C
SCALE•B
SCALf:• A
DENALI GENERA~NGEMENT
SCALE:A
DAM CROSS SECTION
DOUBLE BELLMOUTH f TRASHRACKS
INLET------_ r-j-"'
TEMPORARY OPEN~NG ' ' .
FOR DIVERSION •
1
2.-32.' 1132.1 CONDUITS -IS'x32' FIXED
WHEEL GATES
SECTION D·D
SCALE• C -
100 200 FEET
200 400 FEET NOTE
400 800 FEET
~-DIUIWING ILL.USTUoTD A ~~.u-t:A~R ~~~~r~~~~~ "oRffJ.JECT LA'I'OUT
ALTEIUi.ATIYl tiTI l)(VIL.OII'M£tifTI OJILT
DEVELOPMENTS
STILLING BASIN
A.ILWATER ~ ~
FIGURE 8.12
-
,-
-
-
2200 FT. WATANA 800 MW
• 'I" 2 MILES
~1475 FT.
~--RE-REGULATION DAM
2 TUNNELS
38 FT. DIAMETER
800 MW-70 MW
2 TUNNELS
38 FT. DIAMETER
800 MW ---., 850 .MW
. 15.8 MILES I ~-j-=----14 75 FT.
DEVIL CANYON
550 MW
1150 MW
--,--RE-REGULATION DAM
30 MW
30 FT. DIAMETER
800 MW
2 TUNNELS 365 MW
24 FT. DIAMETER
SCHEMATIC REPRESENTATION
OF CONCEPTUAL TUNNEL SCHEMES
TUNNEL
SCHEME
#
I .
2.
3.
4.
FIGURE 8.13
1400
l
~1900 -----~__/~
---~-
GENERAL ARRANGEMENT
RE·REGULATION DAM
) }
GENERAL AR,RANGEMENT
DEVIL CANYON POWERHOUSE
400 800 FEET
SCALE
SCALE ~0 !!!!!!!!!!3i§OOii;;;;;;;;;;6iij00 FEET PREFERRED TUNNEL SCHEME 3 PLAN VIEW
)
"'I j . II It -~ \ \\
II I
1', \~2-30' DIAMETER \~~POWER TUNNELS
II\\
11 \\
II\\
II II
\\ \\
\\ w
NOTE
--;:;;J OfiA.IIIf. IU.VSTRATEJ a
Pft(Lii!IJIIIA..-r COIItC£ .. '!' !JI;L ..-.o.r(CT LAYOUT
fl'tlt!PAfiiE:D llltJit C.OWPARISOJil OF
.. LTERtt.ATIV[ JITE KVI£LOI'IIifi(:MT!I a•L'f
)
FIGURE 8.14
1600
1500
1400
~
~
'! 1300
z 2
~ ~ 1200
1100
1300
DETAO..A
--J
RE-REGULATION DAM TYPICAL SECTION
SCALE A
NORMAL MAX. ~ rl. ~L~75 -r·-·-·--
NORMAL MIN.
W.L. ELI470 / -·f "''-""" =--------
/EL14"'' A ~
I TRASH RACK} '\_INTAKE GATE
POWER TUNNEL INTAKE SECTION
SCALE-A
I
]
=
-~
l
A
BEARING PAD
CONe. UPIED W/ STEEL SET
TYPICAL TUNNEL SECTIONS
(N:T.SJ
SPILLWAY PROFILE
SCALE A
SECTION A
I
3!100
j 3000
~~ 2!100
~ 2000
~
'!
I
~ 1000
~
~
"' 1000
J }
I
1-----t--INTAKE
1;r STRUCTI N _j___AC ESS
l
\II'-'\ LSURG CHAMBE R
r:vC<IIl•jR=Tw =-
j_ NOR AI; T._!L
I
POWERHO s£_/F______l_~ I
·~------~~~--~~~-~~500~~==~====~====~0 ====~==~~==~====~2::j.c===~~==~==~=====7-~-==~~o~~~~~~~·-----==~~
I -------------------..c.__ -I DISTANCE IN MILES
1500 ~----+---Jr __ •o_·-Fc;s..,UR,o,.E'-'c"'""'•"'M"""'"Rc_ _______________ -_________ -=-~------==---_-______ ------------------------=t__ __ ---=~ A-L-IG_N_M __ E_N_T ______________________ _
i--------4-w-----ll-l---Ji' [v-<OR-[F~ICE ___ :\~=---------------------~----=---~,"' --=~ 1400
1300
~ 1200 -~ ~TRANSFORMER GALLERY \\
-----------------IUCTION ~\ ·;:HOUSE ~ L ~~x~~~~RGE ----------------------------- \ r~~!i·· -~~
::::~-""',\,---~-----/bl::::::Ji'-,,-----"~\--;-:c,~,r-t--'b'r'----_ ------------------------------~Ati:RAcE___ i~---~ ~
z
~ 1100 r---
;=
l! ~
"' 1000
soo ,___
~ ROCK BOLTS a SHDTCRETE
TYPICAL TUNNEL SECTIONS
(N.T.S.)
CONCRETE
PUJG STEEL LINE _j
DETAIL A
If~~ ::;:::1
Li:¥-~ . ~,. -J )'coFFERDAM
DEVIL CANYON POWER FACILITIES PROFILE
SCALE A
0
SCALE A
100 200 FEET
GROUT AS REQUIRED (TYP.l NOTE
---n:ii'i, CN'I.&Wlll$ I LLIJfT'tt.t.TP A
PllllLIWIIt.t.III'T CONC!"FTUAL ~lc:T LA'I'OUT
P'RE:PAit£0 P'OR COMNitiSOii OP'
ALTlR-...TIVE II'IT!" P!"V!"LOf"'IPPTI O .. LY
PREFERRED TUNNEL SCHEME 3 SECTIONS FIGURE 8.15
3
,_.
~
:2
2
0
0
0
r
>-
1-
(..)
~ ~ I
<(
(..)
715
.....
103
0 r
10 -
8
:I:
I""" ~6 (!)
0
0
0
>-
(!)
ffi 4
2 w
~
2
r
.....
0
-
1980
1980
1990
LEGEND:
D HYDROELECTRIC
ff//tl COAL FIRED THERMAL
[ZJ GAS FIRED THERMAL
2000
• OIL FIRED THERMAL( NOT SHOWN ON ENERGY DIAGRAM
NOTE : RESULTS OBTAINED FROM
OGPS RUN LBJ9
1990
TIME
DEVIL CANYON
(400 MW)
WATANA -1 ( 400 MW)
EXISTING a COMMITTED
2000
GENERATION SCENARIO WITH SUSITNA .PLAN E 1.3
-MEDIUM LOAD FORECAST-
300
FIGURE 8.16
2010
2010
""""'
-
, ....
!"""'
r
I
-I
i
....
-
3
3:
:::!: 2
0
0
0
>-....
(.)
<( I a..
<(
(.)
715
1980
10
8
:z::
3:6 (!)
0
0
Q
>-(!)
a: 4 w z w
2
1990
LEGEND:
D HYDROELECTRIC
b\ffJ COAL FIRED THERMAL
E=z:] GAS FIRED THERMAL
2230
2000 2010
-OIL FIRED THERMAL( NOT SHOWN ON ENERGY DIAGRAM
NOTE: RESULTS OBTAINED FROM 1~~~,~~~~~~~ OGPS RUN L60 I
''
VEE(400 MW)
HIGH DEVIL CANYON-I (400 MW)
EXISTING AND COMMITTED
0~--~--------~~----------------~------------------------------~ f980 1990 2000
TIME
GENERATION SCENARIO WITH SUSITNA PLAN E 2.3
-MEDIUM LOAD FORECAST-
FIGURE 8.17
2010
~
f'"'
-
,_.,
--
F""
,..,..
-
-
-
3:
~ 2
0
0
0
>-t-
u
<( a..
<(
u 715
103
0
10
8
:::I:
3: 6
(!)
0
0
Q
>-
(!)
e}4
z w
1980 1990
LEGEND•
D HYDROELECTRIC
t:ttt) COAL FIRED THERMAL
~ GAS FIRED THERMAL
2000
-OIL FIRED THERMAL (NOT SHOWN ON ENERGY DIAGRAM
NOTE: RESULTS OBTAINED FROM
OGPS RUN L607
TUNNEL(380 MW).
WATANA-1(400 MW)
EXISTING a COMMITTED
2010
0~---L------------~~~--------------------------------------------~
1980 1990• 2000 2010
TIME
GENERATION SCENARIO WITH SUSITNA PLAN E3.1
-MEDIUM LOAD FORECAST--
FIGURE 8.18
,.....
'""" tOO
X
~
en
f-en
0 u -z
0
i= u
:::::>
0 -0
0::: a..
LL..
0
:X:
f-
0:::
0
3:
f-z w en w
0::: a..
-
-
7300
7200
7100
"-----
7000
6900
6800
6700
6600
6500
2140 2160
I
~ ""'
~ ~
'
I
2180 2200 222.0 2240 2260
DAM CREST ELEVATION ( FT)
WATANA RESERVOIR
DAM CREST ELEVATION/ PRESENT WORTH OF PRODUCTION COSTS
FIGURE 8.19
. -1 ) ] l
2400
~2200
1 l
EL 2230
SWITCHYARD. liRE A
~ .. 1~~ ~/T ~
WATANA-ARCH DAM
J 1
2l00
ALTERNATIVE
) l
200 400 FEET
NOT I!
--;:M'ii OII&.IMt, IUUSTIATit A
PWELI.IIIAWl' eGWCI,.TUAL I'IIO.IIC'T L,&'I'CMIT
Pttii"AII'(t) .-o• e(IMP"ARISO• 0¥
.... nb&Trlfl tiTI C»EVILDI'IIIENTt 011\.1'
)
FIGURE 8.20
r-C\1 ai ILl a:: OOO'I~.L 3-::::> (.!) i:i: m ,..,.. J -.. ~ o:xtn.L 3 -)~) -
{ \
OOd'£~.L3. en ,... w
X
<( -::?!
<(
Q
w >
~ .._ ,... <(
z
0::: w
r ~ i
<(
OOO"Si".l.3 <(
z
<t
--~ ;=
CIOO'.Lto.L3
\ \
! -@I ~ z I
~ I i ~ ~ :1 / .. z z z z
-
1600
\
\
\
\
\ -!'> \
LESS THAN 3 -ENTRANCE
SUBMERGED
-1550 ..,: -I.L
z
0
!i ->
Ill
.J
Ill
Ill ,..... 0
~
I.L
0::
~ en -0::
Ill
~ ~
~ ,... 1500
r-
-0
TYPICAL
TUNNEL
~ SECTION
145 0 L-.----L----........_-...L-____ ....L... _ ___.:.._,_~------'
25 30 35 40 45 -TUNNEL DIAM·ETER (FT.)
NOTE
FOR 80,000 CFS
WATANA DIVERSION
HEADWATER ELEVATION /TUNNEL DIAMETER FIGURE a22
-
-
-
~
LL
z
0
~ c:t >
LIJ
-l
LIJ
,f*'
I :::!:
c:t
0
(~
-
1650~------~--------~----~--~---------,
1600
1550
AT 1720
COST
50XJ06
1500~------~~------~--------~~------~
IOXI0 6 20XI0 6 30XI0 6 40XJ06
CAPITAL COST $
WATANA DIVERSION
UPSTREAM COFFERDAM COSTS FIGURE 8.23
80
70
60
-
50
"' 0
X -
1-
U) 40 ,-, 0
0
..J
ct
1--a..
ct
0 30
20
10
15
"' c .,.....,
~ r
-~Q
~ ~ "
~ "
~~~· . ...: ~ v
~~~
~ / "'
0
TYPICAL
TUNNEL
SECTION
20 25 30 35
TUNNEL DIAMETER (FT.)
WATANA DIVERSION
TUNNEL COST/TUNNEL DIAMETER
40 45
FIGURE 6.24
-
-~
U)
0
X -
en ..... -en
I 0
0
...J
~
0..
<l
0
...J
f"""' <l .....
0 ..... -
,-
-
-
roo~--------.---------.----------.---------,----------
90
80
70
60
so
15
0
TYPIC At
TUNNEL
SECTION
20 25 30 35
TUNNEL DIAMETER (FT.)
WATANA DIVERSION
TOTAL COST/TUNNEL DIAMETER
40
FIGURE 8.25
l l .. ,,
]
ALTERNATIVE ALTERNATIVE 2 ALTEIINATIIIE 2A
ALTERNATIVE 2 B ALTERNATIVE ZC ALTERNATIVE 20
ALTERNATIVE 3 ALTEIINATIVE 4
WATANA PRELIMINARY SCHEMES FIGURE 8.26
-'
-
.-
-
,-
r
-
-I
,-.
\
~ g
':.1
0 ; ~
~
\
\ \
\
\
\
\
\
""
z
<t
_J
0..
w
~
w
I
(.)
en
~~
)
2SOO
2250
21ts0
2100
ooso f------••ouT ~-----------------------
-~~-----~ .. c 2000
1950
1900
~1850
z ~I BOO
~
1750
1700
l6ts0
1600
1550
1500
14a.o
1400
22SO
1---~2200
"' ~
~21a.0
2100
_=J
-------
ORIGIPML GROUND
SURFACE..-RIGHT SIDE
m
2000
z z 1950
Q ~
iill900
SPILLWAY PROFILE
SCALE A
ORIGINAL GROUND ~--------_..--
--------
,_.
"'
2250
~ zzoo
e
SECTION E-E
SCALE A
135' --l :;; 2200
I ~·· ••. ~ ~ ~g~~~[
...... LDRAINAGE GALLERY
~ 2150 ___ _j
2/00
SECTION A-A
SCALE A SECTION B-B
SCALE A
WATANA SCHEME WP3 SECTIONS
l
TYPICAL CHUTE WALL SECTION
SCALE B
SECTION C-C
SCALE A
SCALE. A."O'"""'"""!!l50ioiiiiiii0i:IIOO FEET
NOTI!I
L T111 ---U.W'mATD & ~ COiiiiCIIITUAL
fiWO..IECT LA'ICIUT' ii'RI!.PM!O FlOtt CCMI .... $01 0 ..
.I,LT[ ... TtV! StT!' D['V!LOPtJOn"' OM.:'
2. SECTICHS FOR 9CHEME. 'lfPi AJIIE UIIIUM C:.CS'T THAT
UTI !TRUCTliM L$ _l!lo' •a: WITN C.EST IEL.ZM .....
3.-i/lf(/Wm• !I1 Hi8H 84Tt:l
FIGURE 8.28
I
(
~ ,.
1
222~
l 1 l
GENERAL ARRANGEMENT
SCALE: A
)
2200 ---------
)
SCALE A '!!0 !!!!!!!!!!20iii0iiiiiiiii4~00 FEET
!!,0 !!!!!!!!!!!"ii;OiiiiiiliiiiiOO FEET SCALE B 1::
NOTE
SECTION A-A
SCALE: B
TH"i'; tJR•WING lLLLI'TRATI[S A
,.,.f~l .,.,Un ~C(II'TI,IAt,. ~IIO.oi!CT U1'VIoiT
ll'ti( ... A.ItEC .. 0" C0"N 'fi'IO. OP'
AL'fi:RIU.1'1VI 'IITl O(VILO!I'IIII:WTS O•L'Y
WATANA-SCHEME WP2 AND WP3 L_----------------------~------------~~----------------------------------~----~~~-~ FIGURE 8.29
2300
2200
"2100
2000
a-1900
~
~ 1800
!i ~
1700
lfiOO
1400
) )
r CONTROl.. STRUCTURE
~ 3-FIXED WHEEL GATES
NORMAL MAX. M'Wx48'H
rW.L.EL22~ ---------~-__ -------~
I r ---1----------------------\ SO!JNDROCK RIGHT SlOE ~--.. .. . . ........... ~-=~--... .___ .. I
.. .. . . .. ··-.--SOUND ROCK
~~, ·~"-'""" ~ ~ :--\-"EF •to• --. --I ~--------------.
/ PRESSURE r ~~~GJ~,AL _G~i'i'~ RELIEF DRAINS
I ~~~~-:_~ rl---..___ GROUT _.A I ORIGINAL GROUND '--.._ SURFACE-RIGHT SIDE CI.RTAIN I
~ ·-', -------~'Z. -.. --~------" ~
~ ~ ., '"" ' "~, ""-"'-""
' ~ -------''" '•"""' -.---._ ~-.::.::_....._
-~A
.....__ --------~ '" ·::::-:-. ----------------""' ---->
----.::~
EL.I440
'"""
600 1000
STATIONING IN FEET
. ltiOO 2000
SPILLWAY PROFILE
SECTION A-A SECTION B-B
100 200 FEET
SCALE
WATANA SCHEME WP2 SECTIONS
l
r STILLING BASIN
I ... B
"· "---, AVG. T.W.L.. -----I ~1475
~ -
2500
FIGURE 8.30
-
-
-
I~
2400
2!00
I;; 21!00
~ 2100 .. 2000
!i ;: 1900
~ 1800
1700
1600
1!500
1400
U!SO
~ e
;!! 2200
"' 0 ;:
1l 21110
~
2100
22!50 ...
~
;5 2200
z
~
~ 2150
~
2100
l l 1 l l l
~~~~~~~~~~~~~L.~~~:o~~cM'~~·_x._w_.L~~~~~~-,~+~'~~f_~_Nl_"_~~-L_~~w~~-E_~_~7~_T_AI_LI __ ~~~~~~~~~~~~~---~~~~~~~~----~--~~~--~~~~~-
/CASCADE ~-----------l--t-l __ -_-_-. --~~--~~~--------~-==_·.::_::~?!-+(_=_·=· O=VER=GU=RO=-:E~===-~
-.--~-----..._ I ._I ---------~1-{ GEOROCK SURFACE~~~~~-
.+-e GATE HOIS~ ~----~--------~
NORMAL MAX. W. L ~ EL.222tl EL2J_ l
f--__:_:: _____ 'EL.2i6s Ill ""-----------------------r•L.2165
~-" . 1----~ EL 2140 ); """' I
EL. 2120
' .... ~ EL 2110 '
GROOT CURTAIN------: ~PRESSURE RELIEF DRAINS
I
I
... A
SPILLWAY CONTROL STRUCTURE
SCALE~ B
SECTION A-A
SCALE: B
.--·-·-·-----·-----..., j·~------------------~
EL. 2225
WATANA
10 15,
STATIONING IN F~tET_
20
SPILLWAY PROFILE
SCALE: A
~--
\ ............................................. ---1141
\ (N.T.S.)
i
SECTION c-c
SCALE: B
--.........................
~E~.216S
J!
SECTION B-B
SCALE: B
0
SCALE A
0
SCALE •
30 •• 40 45
1141
T-~~~T:·~==
------~
\1 y
200 400 FEET NOTE
-;:;:;Ta ~AWI"G JL.l..U$,.-ATI!:S A
50 100 FEET P'lltt:!.~tlliU.It'l' c;:otfCI!:~U.It. l"ltOJlC'i L.ll'DU'T
ltflt£~AJI![tl .. OR C:Q .. PAiti.Q"II. 0'
<EIII'IillATIVl ~ITl D~V[LO~E._.TS D .. LT
SCHEME WP4 SECTIONS
50
FIGURE 8 .• 32
l ) l --~1 --1 l l 1 J l } 1
200 400 FEET
FIGURE 8 33
1 1 l -1
WP4A FIGURE 8.34
-
.... .,.:
LL.
!
i= ~
Lt.l
..J
1&1
ll.i
0 : -a:
:;) en
a:
ILl
t:r ~
-
-
-
-
1-050 -------,.--~~-,-----~-----r--------,
1000
950
880
0
TYP. TUNNEL
SECTION
20 25 30
I-PRESSURE TUNNEL
(36,000 CFS
35
TUNNEL DIAMETER (FT)
DEVIL CANYON DIVERSION
40
HEADWATER ELEVATION/TUNNEL DIAMETER FIGUREB.35
-
-
-
-
-I
-
-
20
18
16
14
......
<00
><
.. 12 ....... ._
(/)
0
0
10
8
6
4
0
l
\
I
~
0 ~ v TYPICAL ~ TUNNEL
SECTION r--
20 25 30 35
TUNNEL DIAMETER {FT.)
DEVIL CANYON DIVERSION
TOTAL COST/TUNNEL DIAMETER
40
FIGURE 8.36
]
/
-J
r·v r 1 1 n
'/i)(;
!II ~ / / I
I I I
It I 1
v r\ \ I ,
\ \
'-AI...LUVIUM IN RIVER BED
DREDGED 07
\
.,_
\
' ' r-~
/ \
I
I
·.)
'
GENERAL ARRANGEMENT
l
'
(
lil
SWITCH YARD
/El. 1370 I
... A
\
G/~
·.~
\
SCALE
DEVIL CANYON SCHEME DCI
l J l
POWERHOUSE LOCATION SUBJECT TO
OPTIMIZATION STUDIES OF DOWNSTREM LOCATIONS,
TMII Clf' .. W'ING li..L,:JtT'fii:A:r!l A
"EL! IIIIINAA'Y eot.ICE;tTUAL P'RO.I[.C'T \...l1'0UT
ll'tlt£".6JUC· ,.0111' <::O~PAJI!ISCN OF
h"!'I:.RiifA'jlYE SITE C-E:'I"EL.OF'WEirifTI OIIL'~"
FIGURE 8.37.
--1 l ----] ··-]
\
\
I
l I
\\
/ \\ I I I
I " \I
II
II ,,
I II
\\: 0 \ y\' ~ \ \ ,,
\ I ,,
ACC£SS T~NE\.1 II
I
\ 1\
0 '" I ! Ill ,,
\
0 II
( g 1\ I II.
0 ) \I I 0 \I
I !:? \ II
\ II
I \I
I'
II
\ II
1\
1\
\ " 'k
' I
1
DIVERSION INT~
261 01A. CONCRETE
LINED TUNNELS
\
' ' \
r· ~)
I
I
I
I
\
1
SWITCHYARD
[EL.\370 I
\
SCALE
GENERAL ARRANGEMENT
DEVIL CANYON SCHEME
j 1
( I / /,1;
/
_'-.EL.I4~7
\
\
I
\
\
\
I
I
I
0 ~
\ NOTE
POWERHOUSE LOCATION SUBJECT TO
OPTIMIZATION STUDIES OF DOWNSTREAM
LOCATIONS.
\
100 200 FEET
DC2 FIG E 8.38
1 l J
! ~
1 I l ---j l
GENERAL ARRANGEMENT
1500 I
1400
lilOO
12po
1100
1000 -----····
FIX£0 WHEEL GATES
40'Wir.51'H
•oo 1---------------------------------
SECTION B-B
SCALE: B
' \-
-----
SECTION C-C
SCALE: B
DEVIL
SCALE: A
--------------
G
~ ..... -, -..JMAX. T,W,L. _ ....._ ~EL.S2S EL 920
--------------EL91JQ.-..-~ ~MIN TWL EL872
.... .... .... ~-=::.----------
E F · G
SECTION A-A
SCALE: A
CANYON
SECTION D·D
SCALE: B
SCHEME
0;, ~~li00ioi.2iii00 FEET SCALE: A z:
SCALE: B 0~~!!2§0;;;;;;;;;;;;ii40.,_FEET
DC3
SECTION E-E
SCALE: B
SECTION F-F
I"OTE
SCALE: B
SECTION G·G
SCALE: B
THIS DII:AWI .. O ILI.UST'RATI:,-,._
li"R(I.IIIh llAJrY c;:oNCI:P"TU.&I. I'R'OJf:CT LA"ffUT
P-RE:PAJI't.D ,Oft ~QM,...&III$011 Oil
&L.Tif.:IIUIATI'W'IE SIT[ D!VILI),.W£JfTS o•L'f'
FIGURE 6.39
l l 1 l
0 0 !!!
GENERAL ARRANGEMENT
l
I
1r ~.
~r
\
\
\ \
\ \
\ I
\ I
I
I
I
I
I
I
I
I
I
I I
I I
I I
1 I
I I
I I
I I
I I
I I
I
I
I
.I
I
I
•• l
I'U.-l'URAL GROUND SURFACE
·cLE" SIDE)
-1 l
~1200 ~------------~------------------~--~~~~~~L-------------------------~--------------------------------
~
'!;
~1100 ~-------------------------------------------~~~~~----~~--------------------------------~--------
!1 ~tmror-----------~----~----------------------------------~~~~~~~~------------·~ __ IL~IA~O~Y--~~M~(~W=EI~R~'L-------------
800 1--------
STATIONING IN FlEET
SECTION A-A
C THRU SPILLWAVl
t;
~1®0~------~----~~~-------+---------------~---------------~~~--------------------------~~Lf--------
SECTION e~e
1400
'"""
~ w ~ 1200
!!;
i'l ;uoo
~
1000
SECTION E-E
DEVIL CANYON
SECTION C-C
SCHEME DC4
SECTION D-D
NOTE
--;:t;"ij CHI&WING lu..urn&Til:l &
""l:l...illl:lll.lltY COfllf:C:~TUAI.. "lh).JI'eT \,A¥01,1T
P'M;!"'.tJ"lO" ,0~ CO .. PI\WIS(UII Ofl'
ALT£11t~TIV( JITI DI:V'Ii...O~IiiiTS 0 .. 1 . .'1'
FIGURE 8.40
1
"""'~
\
I
I
\ I
)
1
(
I
I
I
I
I
\
SCAL£
)
~
~
/
_/
\
\
\
100 200 FEET
/
\
\
\
I
/
I
~
IIOTE
/
I
\
'
j
I
I
!
J
-1
0 0
l!!
/
I
I
~ OR.IWINIS IU..USTUTU .A
,.,.f:LIMIII.&Ih' C0NI;EPTUJII,. !JtRO.I[eT LAYOUT
l"ff!EP.aiii'[C RMt" COJliPAolf/SON 01'"
ALT'lfriU.T!VI ItT( OIJVIE._OPWENTI ONLY
FIGURE 8.41
1
j
l
j
1
[
1
I I
~
REFERENCE: BASE MAP FROM USGS,I:250,000
HEALY, ALASKA
TALKEETNA MOUNTAINS, ALASKA
ALTERNATIVE ACCESS CORRIDORS
1!21 s.
~--
rT.IIN.
SCALE 0~~~4iiiliiliiiiiiiiiiiiil8 MILES
T.9N.
R12E.
FIGURE 8.42
i l l ) ) ) 1 l ) )
ACCESS PLAN 13 <NORTH)
SUSITNA HYDROELECTRIC PROJECT
ALTERNATIVE ACCESS PLAN
1 . J . 1
FIGURE 8.43
} . J ) --J ) . l
ACCESS PLAN 16 (SOUTH)
SUSITNA HYDROELECTRIC PROJECT
ALTERNATIVE ACCESS PLAN
... ) l . I 1 J
FIGURE 8.44
T22S
.,..
T ••
l J -] ) --)
ACCESS PLAN 18 (PROPOSED>
SUSITNA HYDROELECTRIC PROJECT
ALTERNATIVE ACCESS PLAN
l l
ras
Tl ..
-~~
0 l t ' • •
'!"81 ~m
•• i ••
FIGURE 6.45
r
-
r
-
-·
-I
TIME FRAME FOR EXPECTED
ISSUE OF FERC LICENCE
DIVERSION CONSTRUCTION
INITIAL ACCESS CONSTRUCTION
DENALI-NORTH
NORTH
SOUTH
NOTES:
1985 1986
bllJJffiiiiilll[[[[IJII]]····--)1 ACcEss REQuIRED NO LATER THAN
111111111111111111
( I)
111111111
( I)
I THIS DATE TO
I SUPPORT DIVERSION
CONSTRUCT ION
~
I
I
)
RIVER
DIVERSION v
lillllfiiiiiiJI ACTIVITY START COULD BE DELAYED AND DIVERSION STILL MET.
(I) LATEST START DATE OF CONSTRUCTION ACTIVITY.
SCHEDULE FOR ACCESS AND DIVERSION
FIGURE 8.46
l
l
ALTERNATIVE TRANSMISSION LINE CORRIDORS
SOUTH ERN STUDY AREA
LOCATION MAP
LEGEND
---STUDY CORRIDOR
INTERTIE
(APPROXIMATE)
0~~~~5~-~10
SCALE IN MILES
FAIRBANKS
FIGURE 8.47
ALTERNATIVE TRANSMISSION LINE CORRIDORS
CENTRAL STUDY AREA
25 50
SCALE IN MILES
LOCATION MAP
LEGEND
-,--STUDY CORRIDOR
• • • • • • · · · · · • • · I NTERTIE
(APPROXIMATE)
0 5 10
SCALE IN MILES
FIGURE 8.48
l
l
l
l
J
J
J
J
ALTERNATIVE TRANSMISSION LINE CORRIDORS
NORTHERN STUDY AREA
LOCATION MAP
LEGEND
---STUDY CORRIDOR
•••••••••••••• I NTERTIE
( APPROXIMATE)
0 5 10
SCALE IN MILES
FIGURE 8.49
l
J
J
J
u
J
RECOMMENDED TRANSMISSION CORRIDOR
SOUTHERN STUDY AREA
I
~
0
SCALE IN MILES
25 50
SCALE IN MILES
LOCATION MAP
2
FIGURE 8.50
l
l
l
l ' g
l I I
l
l
l
l
J
J
'',
. ~ 'i~.i ,,
RECOMMENDED TRANSMISSION CORRIDOR
SOUTH ERN STUDY AREA
0
SCALE IN MILES
SCAlE IN MILES
LOCATION MAP
2
FIGURE 8.51
I
I
I. MATCHLINE 8
RECOMMENDED TRANSMISSION CORRIDOR
CENTRAL STUDY AREA
o~~~iiiiiiiiiiiiiiiliiiiiiiiii2
SCALE IN MILES
FIGURE 8.52
l
l
1
]
J
RECOMMENDED TRANSMISSION CORRIDOR
CENTRAL STUDY AREA
MATCHLINE B
0 25 50
SCALE IN MILES
LOCATI ON MAP
0 2
SCALE IN MILES
FIGURE 8.53
J
RECOMMENDED TRANSMISSION CORRIDOR
NORTHERN STUDY AREA
0 2
SCALE IN MILES
25 50
SCALE IN MILES
LOCATION MAP
FIGURE 6.54
l
1
l
l
l
l
1
1
J
J
J
J
J
J
/
_., ,,
RECOMMENDED TRANSMISSION CORRIDOR
NORTHERN STUDY AREA
""'
""
"
0
SCALE IN MILES
25 50
SCALE IN MILES
LOCATION MAP
2
FIGURE 8.55
1
RECOMMENDED TRANSMISSION CORRIDOR
NORTHERN STUDY AREA
0 2
SCALE IN MILES
LO CATION MAP
I
I
FIGURE 8.56
l
RECOMMENDED TRANSMISSION CORRIDOR
NORTHERN STUDY AREA
0 2 S~C~A~LE~I~N~M .. IL~ES~~
LOCATION MAP
FIGURE 8.57
J
100 -10~
ESTER
LO/z6 6
-+----59
~ J >----+--2-0-:-~ .. :::---1~
19 l 66
'34'i k v
-+---1~-...L---.1-. I.02L»...i.
34'i I.V
DEVIL CANYON/GOLD CREEK
0 .96 8..a.
31 -~
12
34'i kV
1'38 kV
l03Lll.Q
34'i k v
WATANA
0 .95 tl..1...
464 --&II
1.0~
492 -
_.,___
298
211 -230 kV
334 335
~-----,~~~==·~--------------~~-~ UNIVERSITY -&.i -&; l0 /-3 .3
335 334 205 ---
KNIK ARfl
199'3 PEAK LOAD, DOUBLE CONTINGENCY
---104
2!:e -6r
ll'i k v
LEGEI\0 -REAL POWER (MW) 0 GEHfRAT OR ---REACTIVE POWER ( HVAR) ~ L00/0 .00 VOLTAGE IN PER UNIT & -STATIC VAR CO MPEN S ATOR
ANGLE IN DEGREES ~ __.., LOCAL LOAD
0/H TL TO Ul'ol CABLE
I:Ji[U__r
2 0 5 -__...
43
205 4 10
ESTER
; oL:.u
-87
410
r---,-~~·-+--~~----~--~~~~ --.. -43 85 135
'34'i kV 1'381cV
•03~
58 7 ~ r----~==-+------"
47
WATANA
0.94 L!u.
~ 1'48 ==~ 49
1'38 ltV
0 .93LQj_
t 164 =::.-0 .96~ 21
ll'i I. v 789 -,..___
164
60 4
BRADLEY
LAKE
2301.V
1.0 /Q_ .... --2'30!.V JZ
1008 --3 31
...__
517
174 -
L--------r::::==-t---:::=--------=.=, ::=•=-1 UNIVERSITY
1
_
0
,_~ _
I 00 L.=L.L
604 420 ----· 100 35
'31f'i kV
2002 PEAK LOAD, DOUBLE CONTINGENCY
ANCHORAGE -FAIRBANKS TRANSMISSION
1113/1002 INTERCONNECTED IYITEM
SYSTEM PERFORMANCE EVALUATION
ONE LINE DIAGRAM
-221
420 ---..
138
ll'i loY
FIGURE 8.5 7 A
100
90
0 80
<(
0 70 -1
~
<( 60 w
0..
u.. 50 0
1-z 40 w
0
II. 30 w
0..
20
10
0
0
.. 1 J
-/ """' ~
I If' " I \
~
100
90
0 80 <(
0
-1
/ .......... -r":·--~
If \.
~ J ----~ ./ 70
:.:::
<(
60 w ' I
4 8 12 16
HOURS
WINTER WEEKDAY
HOURL V LOAD VARIATION
20 24
0..
LL 50 0
1-z 40 w
0
II. 30 w
0...
20
10
0
0
TYPICAL LOAD VARIA liON IN
ALASKA RAIL BELT SYSTEM
.......... --.../
4 8 12 16
HOURS
SUMMER WEEKDAY
HOURLY LOAD VARIATION
20 24
FIGURE 8.58
J
J
J
J
J
0
cl
0
..J
~
cl
ILl
Q.
1&.
0
1-z
ILl
0
0:::
ILl
Q.
100
90
80
70
60
50
40
30
20
10
0
0
/
1/
I
I
~ v
4 8 12
HOURS
16
WINTER WEEKDAY
HOURLY LOAD VARIATION
......... ~
~
\
20 24
NOTE: PEAK MW DECEMBER 2000 AD: 1084 MW
100 ........ -
90 / ~"" ~oo..-
0 80 cl
0
..J 70
~
cl
ILl 60
Q.
1&.. 50
0
1-40
z
ILl 30 0
0:::
ILl 20 Q.
10
0
~ -"
0
If
)
I ......... -..../
4
..
8 12
HOURS
16
SUMMER WEEKDAY
HOURLY LOAD VARIATION
20
NOTE: PEAK MW JULY 2000 AD = 658 MW
TYPICAL LOAD VARIATION
IN ALASKA RAILBELT SYSTEM
'
24
1100
1000
900
800
3: 700 ::f
0 600 < 0
..J 500
~
cl
ILl 400 Q.
300
200
100
0
/
' v
~ /
" ~ v ........._ ....,.. -
I I ( I I I
J F M A M J J A S 0 N D
MONTH
LOAD VARIATION
IN YEAR 2000
FIGURE 8.58
J
J
J
j
J
1
coot< tNL£r
0679
0
/1101117
PAL IllER
eOMI
I
I
RAPIDS
• 0.74
STATION
(A) SUSITNA RIIIER NEAR OfNALI
(8) SUSITNA RIVER AT VEE CANYON
(C) SUSITNA RIVER NEAR WATANA lloi.MSITE
(01 SUSITNA RIVER NEAR OfVIL CANYON
!EI SUSITNA RIIIER AT GOLD CREEK
(F) CHULITNA RtVEft N£AII TliLICKTNA
(G) TALKEETNA RIVER NEAR TALKEETNA
(H) SUSITNA RIV£R NEAR SUNSHIH£
( I) SKWENTNA RIVER NEAR SKWENTNA
(J) YENTNA ImlER NEAR SUSITNA ~TlON
(K) SUSITMA ImlER AT SUSITNA STATION
DATA COLLECT ION STATIONS
X
X X· X
X X x2
X X
X I X
X I
X X
X
X X
X
X X
X X
X
X X X
X X X
X X X
X X X
X X
x .x
X X
1957-PRESENT
I' (1961 -1972 a
1980-PRESENT '
X X I X . X 1980-PRESENT
x l x
X
1949-PRESENT
[t9l!B .,-1972 a
1980 -PRESENT
1964-PRESENT
1961 -PRESENT
1959-1980
1980-PRESENT
1974 -PRESENT
DATA COLLECTED
• ST'RL\III!'LOW -COimiiUOUI MCQN)
0 ST'IIEAMI'\.OW -I'MT1AI.. l'l!tOIIO
e Y'\TEII QUALITY
· T 'IMTEII TDIPEMTUIIE
* !!OIMEHT III3CHAMIE .
1!1 CliMATE
,.... · I'IIUZIN8 IWN AND IIICLOUO ICIM8
• SNOW COURSE
' SNOW CMEP
NOTE;:;
IIIDEX JINIII!Na
0100
0100
01100
0400
01100
oeoo
0700
0100
0100
I. PllRAMETEltS IIIEA!UII£0 LISTED '" APPEJIOIX Ill
2.. CONTlNUOUS WATER QUALITY IIIONITOII 1NS1aLLED
3 . DATA COLLECTION tMI SEASON
4 . TME L£TT£R IEFOM: EACH STA'Tq _. II· TME
'YULE IS USED 011 THE MAP TO tiMK lME
APPROOCIMit.T£ l.OCATIOII OF TME S'!aTIOMS.
0
SCALE
FIGURE 8 .59
-
-I
-
-
.....
COOK INLET
SUSITNA RIVER
DEVIL WATANA
CANYON SITE SitE
GOLD CREEK
PARKS HIGHWAY BRIDGE
GAGING STATION
SUSITNA GAG'I~G STATION
AVERAGE ANNUAL FLOW DISTRIBUTION
WITHIN THE SUSITNA RIVER BASIN
FIGURE 8.60
50,000
-0 40,000 z
0
0 w
CJ)
a:: w a.
1-30,000 w
IJ.l u...
0
m
:J
0
3= 20,000
0
_J u...
~
<(
IJ.l a::
1-
CJ)
10,000
0
l J -l . -1
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT
MONTHLY AVERAGE FLOWS
SUSITNA RIVER AT GOLD CREEK
J ]
LEGEND
WETTEST YEAR-1962
AVERAGE YEAR
DRIEST YEAR -1969
NOV DEC
FIGURE 8.61
-I
-
-
-
-
-
r
-
-
-
r
I
'
..,
0
>C
-..
(/)
u.
(.)
w
{.!) a:
<( ::r
(.)
(/)
Q
o.o-!--,-----.------r---.-__;=::;:=::;::::::;::::;::::~,
0.00 0.20 0.40 0.60 0.80 1.00
PROB OF EXCEEDENCE
FLOW DURATION CURVE MEAN MONTHLY INFLOW
AT WATANA PRE-PROJECT
FIGURE B .. 62
r
I
-
-
"""'
-
I"""
i
-:
r
-'
r
-
56.0
40.0
...
0
X
(/)
32.0 LL u
ILl
C)
0::
<(
:I: u
(/)
0
o.oL---r-----r-r---r----r--=:=::=::;::::::;:~
0.00 0.20 0.40 0.60 0.80 1.00
PROB OF EXCEEDENCE
FLOW DURATION CURVE MEAN MONTHLY INFLOW
AT DEVIL CANYON PRE-PROJECT
FIGURE 8.63
----~
15
10
"'g 9
.. 8
:r ~ 7
..J 6
~
~ 5
w
1-
~ 4
6 a::.
~ 3 w
..J q:
::l
! 2
I
-] ---]
--:------:--
---
I I
I !
I
I
I
0.01 0.05 0.1 0.2 0.5 2
] --l ]
RETURN PERIOD IN YEARS
1.11 1.25 2 5 10 100
r J .. L
DEVIL CANYON
I
I ----r--Li FIRM ENERGY r--.._ r--r---r---. ..__ .......,
rWATANA ONLY
10
----r---i
20 30 40 50 60 70 80
PERCENT EXCEEDENCE PROBABILITY
-~
i
I
90 95 98 99
-~
1000
-
----.._ r-
\IRMrNERGY
\'
r-
99.8 99.9 99.9
FREQUENCY ANALYSIS OF ANNUAL ENERGY FOR SUSITNA DEVELOPMENTS
FIGURE 8.64
90
eo
70
l 60
"' .... u 50
0
0
l £>
~ 40 ...
l 30
20
l 10
,/'("
I
I
I ___ j
0
0
1
2202
2200
219e
-2196
f-
!!::
z
0
f= 2194
:! w
..J w
0:: 2192
0
>
J
0:: w
"' 2190 w
0::
j 21ee
21e6
J /' 2184
0
J
]
(\
\
~INFLON
\
I ~.Y!~L,.~ L VL OUTLET FACILITIES ~ AT FULL CAPACITY
\_POWERHOUSE AND
OUTLET FACILITIES 'OPERATING
(MATCH ING INFLOW)
10 15 20
TIME (DAYS)
1•50 YEAR FLOOD
(SUMMER)
25
-
30
I
/
FEAX . i SEL . 2193.0
5
I \
1\
I \
/ I v OUTLET FACILITIES
AT FULL CAPACITY
'\t;.OWERHOUSE AND OUTLET FACILITIES
OPERATING (MATCHING INFLOW)
10 15 20
TIME (DAYS)
1•!50 YEAR FLOOD
(SUMMER)
25 30
180
160
140
120
"' .... u 100
0
0
£>
~ 80 0 ..J ....
60
40
20
0
35
2202
2200
219e
2 196 ;::
!!::
z
0
;::: 2194
:! w
..J w
0:: 2192
0 > 0:: w
"' w 2190
0::
2188
2186
21e4
35
A
D j -OUTFLOW
If
~ ~
I \
I ~ INFLON
r ~UTFLOW MATCH~ 1'--NFLOW r-
INFLOW~~
I
;~ :!"'-MAIN SPILLWAY
------.1 OPERATING
POWERHOUSE AND
OUTLET FACILITIES AT
, \_I FULL CAPACITY J.
I POWERHOUSE AND
I OUTLET FACILITIES IPERATINi
(MATCHING INFLOW)
0 5
I
10 15 20
TIME (DAYS)
25
1•10,000 YEAR FLOOD
__LI MAX . WS f L 2193.
\ f.-INFLOW EXCEEDING
OUTFLOW CAPACITY
\MAIN SPILLWL OPER J ING
(MATCHING INFLOW)
30
360
320
280
240
"' .... u 200
0
9
~ 160
..J ....
120
eo
4 0
0
35
2202
2200
2198
2196
;:: ....
z
£> 2194
1-
:!
w
..J w 2192
0::
0 > 0:: w
"'
A
;<--/ 'I _.,..-OUTFLOW
NFLOW-, J ' I ;: \; 1_,
r\
I I'\-EMERG ENCY SPILLWAY,,
) OPER ATING \
\
\
/( \ ',
'
1\
I !
\
I!/ MAIN SPILLWAY
OPERATING
f-~~POWERHOUiE AND OUTLET
~ FACILITIES AT FULL CAPACITY
-OUTLE T FACILITIES OPERATING
0 5 10 15 20
TI ME (DAYS)
25
PROBABLE MAXIMUM FLOOD
r------.....-....
f-.-EMERGENCY SPIL~
OPERATING ~
\
\
\
I
I
\
\
I
I
~
\
--
30
I
\
I
\ I
I 2190 w
0:: I '\_MAIN SPILLWAY, OUTLET FACILITIES
2188 I I 2186
KtrUTLET FACILITIES AT FULL CAPACITY ____...-J
0
ERHOUSE AND OUTLET FACILITIES OPERATING
(MATCHING INFLOW)
5 10 15 20
TIME (DAYS)
25
1•10,000 YEAR FLOOD
2184
30 35 0 5
WATANA
HYDROLOGICAL DATA -SHEET I
a POWERHOUSE OPERATING
'\_0 UTLET FACILITIES
AT FULL CAPACITY
10 15 20
TIME (DAYS)
25
PROBABLE MAXIMUM FLOOD
35
FIGURE 8.65
360
320
280
240
;;; ...
(.)
0 200
0
!:?
"'
~ 160
-' ...
120
80
40
0
1480
1470
1460
1450
,_; ... 1440
z
Q
~
"' 1430 -' ....
1420
1410
1400
r-
0
J.f)/ r\-, ~SERVOIRI
INFLOW I OUTFLOW ,, ~
I~/ \,_ I ' I
I
I
I ,, I ~OUTFLOW I
INFLOW-K
Jr EMERGENCY
SPILLWAY
OPENING !
"----1-POWERHOUSE
CLOSED
r.,-~~~?~
INFLOW
I /~~~~OU~fu:.~
i / I PERATIN
POWERHptJSE
5 10 15 20
TIME (DAYS)
25 30
PROBABLE MAXIMUM FLOOD
RESER ~OIR
ELEVATIO)f
MAX.WSEL /EMERGENCY
•1465.3'1 SPILLWAY
OPERATING
)
\ POWERHOUSE / l\
0
UI'I:.RAriNG
10
\
""'
15 20
TIME (DAYS}
\
1\
25
PROBABLE MAXIMUM FLOOD
30
35
35
180
160
140
120
., ...
0
0 100
0
2
~ 80 0
-' ...
60
40
20
0
1460
1458
~ ;:: 1456 :;
"' iil
~ 1454
~
"' f3 a: 1452
1450
/'""\.
I
~
INFL W•OUTFLOWY
\
I '--..,
I\
If "-.... ..._
I .r; !----I ~r"-MAIN riLLWAY OPERATING
I
0 . 5
0 5
~POWERHOUSE AND
OUTLET FACILITrS
OPERArNl!l
I
10 15 20
TIME (DAYS)
2 5
RESERVOIR ROUTING
1•10,000 YR. FLOOD
1/iOWERHOUSE , OUTLET FAC ILITIES AND
MAIN SPILLWAY OPERATING
i'-MAX. JsEL•I455
10 15' 20
tiME (DAYS)
25
RESERVOIR ROUTING
1<10,000 YR. FLOOD
DEVIL CANYON
HYDROLOGICAL DATA-SHEET
;;; ... u
8 2
~
~
0 -' ...
...,
IL
z
0
i= ~
"' -' "' a:
0 > a:
"' (I)
"' a:
35
50
40
30
;INFLOl . OUTFLL
I/ '---t. -
20 l/ ~~OWERHOUSE AND
OUTLET FACILITIES
OPERATING
10
0
0
1460
1458
1456
1454
1452
1450
0
5
'
5
10 15 20
TIME (DAYS)
RESERVOIR ROUTING
1•50 YR. SUMMER FLOOD
r POWERHOUSE AND
I g~i~i+~::CILITIJ ES
(
25
\_MA~. WSEL •1455
10 15 20 25
TIME (DAYS)
RESERVOIR ROUTING
1•50 YR. SUMMER FLOOD
30
FIGURE 8.66
SURFACE A~EA (ACRES X 104 )
2600 6 5 4 3 2 0 1480
2500
I
2400 1475
2300
2200
2100
~
"' "' ~
z 2000
0
~
"' ...J
"' 1900
1800
1700
1600
1460
1455
~ /f-
> v
v / ~ OLUME , v-suRF CE AREA
/ 1\ v \ I
I 1\
I \
\
1470
~ w w
~
z
0 14 65 ~
"' ...J
"'
1500
I
1400 1450
0 2 4 6 8 10 12 14 0
VOLUME (ACRE FEET x 10 6 )
RESERVOIR VOLUME AND SURFACE AREA
v
/ v
/
/
/
/
/
v
v
I
I
I
I
/
I
NOT DEFINED
20 40 60 80 100 120 140 160
DISCHARGE ( CFS x 10 3)
TAILWATER RATING
WATANA
HYDROLOGICAL DATA-SHEET 2
180
165
150
135 I v
120
-"' lL
0 105
0
0
0
"' 90 "' a:
"" :I: 0
"' i5 75
60
45
30
I
I ANNUAL
/y~ SUMMEF
v I v I / /
I v lr /
/
/ /
/
~ /
15
0
1.005 2 5 10 20 50 100 1000 10, 000
RETURN PERIOD (YEARS)
INFLOW FLOOD FREQUENCY
FIGURE 8.67
1
SURFACE AREA (1000 ACRES)
12 10 8 6 4 2 0
875
1500
1300
;::
w w
!:
~ >-~ w
..J 1200 w
" / v
~ v v
VOLUME IY v ~ SURFACE REA
I 1\
1/ \
1\
I \
I \
I
I
;::
w w
~
>-860
J:
(!) w
J:
w
(!) ..
(!)
855
870
865
1400
1100
850
1000
845
900
0 2 4 6 8 10 12 14
VOLUME (ACRE FEET X 10°)
RESERVOIR VOLUME AND SURFACE AREA
v
7
I
1/
(' 20
~ v
_/ v ./
/ v
I/ v
/
I
40 60 80 100 120 140 160 180 200
DI SC HAR GE (CFS X ID 3 )
TAILWATER RATI NG CURV E
DE VIL CANYON
HYDR OLO GI CAL DATA -SHEET 2
180
16 5
150
135
120
-., ...
u 105
0
0
2
90
75
6 0
45
15
0
1.005
I
1/
1/
I
I
I
1/
IJ
J
1/
1/ --+----[_...... r-
• 2 5 10 20 50 100 1000 10, 000
RETURN PERI OD (YEARS )
FLOOD FREQUENCY CURVE
(INFLOW AFTER ROUTING THROUGH WATANA)
FIGURE 8.6 ~
"""'
-
~
!""'
-
r
'
...,::
IJ...
_.
I.LJ
>
I.LJ _.
a::
0 > a::
I.LJ
(/)
w a::
_.
I.LJ
>
I.LJ _.
a::
0 > a:: w en
2200
2180
2160
2140
2120
2100
2080
1450
~ 1410
-
I
1-
1-
f-
f-
2190
NORMAL MAXIMUM ,OPERATING LEVEL 2185 r l
217J
1 2180
2160
2150
2130
2125
2112
2095 ~ 2092 l I I I I I I I _1 I I
0 N D J F M A M J J A s
MONTHS
WATANA RESERVOIR
NORMAL MAXIMUM OPERATING LEVEL 1455
RESERVOIR IS KEPT FULL AT
ALL TIMES IF POSSIBLE.
0 N D J F M A
MONTHS
M
DEVIL CANYON RESERVOIR
J J A s
MONTHLY TARGET MINIMUM RESERVOIR LEVELS
FIGURE 8.69
740
!""'
! 115% GENERA OR
RATED POWER
....
I v'
r
I
I
I, 720
700
R~RVOIR EL. 218~~ I -----v
I I
r-680
I
I"""
I
l 1-w w 660 IL
I
0
<( w :::c
1--w
I z
640
r
' -:
620
!""'
-
/
I
1/1 WEIGHTED A IIERAGE HEAD
I I
7 I / ~ INIMUM DECEMB I R HEAD
I -c--170 MW
I
I I
BEST EFFil IENCV-/ f FULL GATE
I RESERVOIR EL. 2065 --I ----I 600
580
r 100 120 180 220 200 140 160
UNIT OUTPUT-MW
1.
-
WATANA -UNIT OUTPUT
FIGURE B. 70
I""' I
40,000 80,000 120,000 160,000 200,000
TURBINE OUTPUT ( HP)
WATANA-TURBINE PERFORMANCE
CAT RATED HEAD)
24opoo
FIGURE 8.71
r
·-
r
I
i -I
r
I
~ ~
>-
(.) z w
94r-~--------.--------.---------,---------.-----~--,-, f'""'j~"7~~~:s~s
so~~/-+\-4-+~v~--+------~-----4----~~~
I
I
86~+--~1 --~----~------+---------~-----~-+-~
Q 82 ..___+-----------+------------------+------+-------t----1 lL.
lL. w
78~+--------~------4---------+-------~--------~
~~+---------~-------4---------+-----~--------~
100 300 500 700
PLANT OUTPUT ( MW)
WATANA-UNIT EFFICIENCY
(AT RATED HEAD)
900 1100
FIGURE B. 72
F"
I
P"""
,_
,..,..
-I
I
I
-
-I
620 ...------
600
580
1-~
I
Q
<E
I&J
::t
1-560
1.1.1 z
BEST
540
520
100
115 ''o GENERATOR
RA ED POWER
RESERVOIR EL. 1455 I --/ --I
I I
J . vr-WEIGH1 ED AVERAGE H AD
BES ~ GATE 7 ~
/ J ~GENERAT PR RATED POWE~
I I I
EFFIC ENCY7 FULL GATE
RF'SER
I
MINIMUM SEPTEMBER HEAD 1'0IR iEL. 1405
I
l-4---15 ~ MW
120 140 160 ISO 200 220
UNIT OUTPUT-MW
DEVIL CANYON-UNIT OUTPUT
FIGURE 8, 73
r
.,....
-
.-
-
r I
I
.-
-
-
r
I
,....
I
I
-
-
90
;e
~
~ u z
I.LJ
~ 80
IL..
I.LJ
I.LJ z m a:
:::l
I-
70
40,000 80,000 12opoo 16o,ooo 2oo,ooo 240,000
TURBINE OUTPUT ( HP)
DEV l L CANYON-TURSI NE PERFORMANCE
(AT RATED HEAD)
4000
Ci)
IL..
3000 8
IIJ
(!) a:
od:
:I: u en a
I-
2000 z :::l
1000
FIGURE 8.74
-
r
-
-
-
-
.....
-
,....
I
r""'\
I
~ ~
>-0 z
lJ.J
(3 u:: u.
lJ.J
94
90
86
82
78
74
I I4 UNITS ~~IT/ /\NIT .1.3 UNITS
v ,.-'~
I
I
I/
100
\ v
!/ I
I
200 300 400 500
PLANT OUTPUT ( MW)
DEVIL CANYON-UNIT EFFICIENCY
CAT RATED HEAD)
"
600
FIGURE 8.75
1800
1600 /
r
1400 ~ /
~ 0«.;
*""
1200
~'X 7 E.G\~~ '?-C6 ~0. ~~ I«~~ ~ ~ ~ ' r. --~
::E
~
a: w
CD
::E 1000
<f. :r---~ :::::-
v? _______-J
w
()
w
Cl
~
>-
!= 800 () -<(
~
<(
()
w
~ ~ ~ ~-G'~ '"' ~ !--""
~
~ r CD
<( 600 Cl FLOW REGIME A
2 w
~ F OW REGIM c
w ..... Cl
JllOW REGIM ~ 0
400 -I
I
Ffl.OW REGIM E G -200 I
.....
~ WATANA + "'ATANA PLU DEVIL CA 4YON
I
0
1990 1995 2000 2005 2010 2015 2020
YEAR
DEPENDABLE CAPACITY
FIGURE 8.76