HomeMy WebLinkAboutCordova Hydro Storage Assessment Project_Crater Lake Water and Power Project Feasibility Study - Jan 2016 - REF Grant 7013013
Crater Lake Water
and Power Project
Feasibility Study
Feasibility/Conceptual
Design Report
Revision No. 1
January 20, 2016
This page intentionally left blank.
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
January 2016 i McMillen Jacobs Associates
Table of Contents
Executive Summary ................................................................................................................................. viii
1.0 Introduction and Purpose of Study ................................................................................................. 1
1.1 Project Description ................................................................................................................... 1
1.2 Report Organization ................................................................................................................. 3
2.0 Data Review and Compilation Introduction .................................................................................... 4
2.1 Previous Studies ...................................................................................................................... 4
2.2 Land Ownership ....................................................................................................................... 4
2.3 Recent Topographic Data Acquisition ..................................................................................... 5
2.4 Hydrology/Meteorologic Data .................................................................................................. 5
2.5 Geology/Geotechnical Data ..................................................................................................... 6
2.6 Generation Data ....................................................................................................................... 6
2.7 Water Supply and Operations Data ......................................................................................... 6
3.0 Geologic and Geotechnical Reconnaissance ................................................................................ 9
3.1 Field Reconnaissance .............................................................................................................. 9
3.2 Site Description ........................................................................................................................ 9
3.2.1 General ............................................................................................................................... 9
3.2.2 Site Geology ........................................................................................................................ 9
3.2.3 Site Seismicity ................................................................................................................... 11
3.3 Dam/Reservoir Geotechnical Observations ........................................................................... 12
3.3.1 Site Description ................................................................................................................. 12
3.3.2 Geomorphology ................................................................................................................. 12
3.3.3 Geologic and Geohazard Observations ............................................................................ 16
3.4 Dam Site Considerations ....................................................................................................... 20
3.4.1 Foundation Assessment ................................................................................................... 21
3.4.2 Foundation and Reservoir Rim Seepage Assessment ..................................................... 21
3.5 Penstock Geotechnical Observations .................................................................................... 21
3.5.1 Penstock Alignment Description ....................................................................................... 21
3.5.2 Geologic and Geohazard Observations ............................................................................ 22
3.6 Penstock Concepts ................................................................................................................ 24
3.6.1 Surface Alignment Initial Reach ..................................................................................... 24
3.6.2 Surface Alignment Downslope of Inner Crater Creek Canyon ...................................... 26
3.6.3 Rock Shaft Option ............................................................................................................. 26
3.6.4 Penstock Support Considerations ..................................................................................... 28
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3.7 Powerhouse Geotechnical Observations ............................................................................... 28
3.7.1 Site Description ................................................................................................................. 28
3.7.2 Geologic and Geohazard Observations ............................................................................ 29
3.7.3 Preliminary Foundation Assessment ................................................................................ 29
3.7.4 Access and Staging Areas ................................................................................................ 29
3.8 Proposed Geotechnical Exploration (Future Design) ............................................................ 29
3.8.1 Permitting Requirements / Lead Time .............................................................................. 30
3.9 Geologic/Geotechnical Summary and Conclusions .............................................................. 30
4.0 Hydrologic Evaluation .................................................................................................................... 32
4.1 Introduction and Purpose ....................................................................................................... 32
4.2 Data Sources for Study .......................................................................................................... 32
4.3 Site Description and Characteristics ...................................................................................... 33
4.4 Synthetic Hydrology Development ......................................................................................... 35
4.4.1 Development of Daily Flow Values 2005 2015 .............................................................. 35
4.4.2 Use of Snyder Falls Creek and Power Creek Streamflows .............................................. 39
4.5 Hydrology Model Procedure Results ..................................................................................... 40
4.6 Synthetic Streamflows and Storage ....................................................................................... 43
4.6.1 Streamflow Variability and Need for Storage .................................................................... 43
4.6.2 Storage Configurations ..................................................................................................... 43
4.6.3 Effects of Precipitation Patterns and Storage Capacity on Releases ............................... 45
4.7 Streamflow Record in Context of Larger Climate Trends ...................................................... 50
4.8 Conclusions and Recommendations ..................................................................................... 51
5.0 Water Supply and Treatment Evaluation ...................................................................................... 53
5.1 Water Supply Evaluation Purpose ......................................................................................... 53
5.2 Data Collection ....................................................................................................................... 53
5.3 COC Historical Water Production/Demand............................................................................ 53
5.3.1 Water Production History since 2000................................................................................ 55
5.3.2 High Demand Water Seasons for COC ............................................................................ 56
5.3.3 Problems with Freezing Water Sources............................................................................ 56
5.3.4 Future Demand Growth Estimates for COC ..................................................................... 56
5.4 Existing Water Transmission out Of Orca WTP .................................................................... 57
5.4.1 ...... 57
5.5 Hydraulic Analysis of Existing Transmission Pipeline to Morpac Reservoir .......................... 57
5.6 UV and Booster Pump Station Design for Crater Creek Source ........................................... 59
5.6.1
Regulations ....................................................................................................................... 59
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5.6.2 Future UV Treatment at new CLWPP Site........................................................................ 60
5.6.3 Booster Pump Station at the New CLWPP Site ................................................................ 61
5.7 Water Supply Evaluation Summary and Conclusions ........................................................... 64
6.0 Generation and Operations Model ................................................................................................ 66
6.1 Introduction and Purpose ....................................................................................................... 66
6.2 Data Collection ....................................................................................................................... 66
6.3 Evaluated Project Configurations .......................................................................................... 66
6.3.1 High Dam, Low Tap Configuration .................................................................................... 66
6.3.2 High Dam, Channel Release Configuration ...................................................................... 67
6.3.3 Low Dam, Low Tap Configuration ..................................................................................... 67
6.3.4 Low Dam, Channel Release Configuration ....................................................................... 67
6.4 Analysis .................................................................................................................................. 67
6.5 Operations Modeling Results ................................................................................................. 68
6.6 Operations Modeling Conclusions ......................................................................................... 69
7.0 Conceptual Civil Design Criteria and Drawings ........................................................................... 71
7.1 Preliminary Dam Design Criteria ........................................................................................... 71
7.2 Penstock Design .................................................................................................................... 71
7.2.1 General Discussion ........................................................................................................... 72
7.2.2 Penstock Design ............................................................................................................... 72
7.3 Powerhouse/Water Treatment Plant Design ......................................................................... 76
7.4 Powerhouse/Treatment Plant Access Road .......................................................................... 77
8.0 Constructability, Cost Estimate and Schedule ............................................................................ 78
8.1 Constructability, Cost Estimate and Schedule Introduction ................................................... 78
8.2 Constructability Review Results ............................................................................................ 78
8.2.1 Constructability Review Parameters ................................................................................. 78
8.2.2 Dam Site Construction Assumptions ................................................................................ 79
8.2.3 Penstock Construction Assumptions ................................................................................ 79
8.2.4 Powerhouse/Treatment Plant and Access Road Assumptions ........................................ 80
8.3 Cost Estimate ......................................................................................................................... 80
8.3.1 Crater Lake Estimate Approach ........................................................................................ 80
8.3.2 Cost Estimate Results ....................................................................................................... 81
8.4 Conceptual Project Schedule ................................................................................................ 84
8.5 Constructability, Cost and Schedule Conclusions and Recommendations ........................... 86
9.0 Permitting Scope and Planning ..................................................................................................... 87
9.1 Permitting Considerations ...................................................................................................... 87
9.2 Permitting Conclusions and Recommendations .................................................................... 88
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10.0 Feasibility-Level Cost/Benefit Analysis ........................................................................................ 90
10.1 Introduction ............................................................................................................................ 90
10.1.1 Power Supply Considerations ........................................................................................... 90
10.1.2 Water Supply Considerations ........................................................................................... 90
10.2 Modeling Approach ................................................................................................................ 91
10.3 Primary Assumptions of the Crater Lake Cost/Benefit Evaluation Model ............................. 92
10.3.1 Crater Lake Capital Cost Assumptions ............................................................................. 92
10.3.2 Crater Lake Energy Production Assumptions ................................................................... 93
10.3.3 Crater Lake Operations and Maintenance Cost Assumptions .......................................... 93
10.3.4 CEC Diesel Production Efficiency Assumptions ............................................................... 93
10.3.5 Cost of Diesel Fuel Assumptions ...................................................................................... 94
10.3.6 Seafood Processing Additional Growth Scenario .......................................................... 94
10.3.7 Shared Seafood Taxes Additional Revenue Potential ................................................... 95
10.3.8 Reduced Requirement for Eyak Pumping and Filtration Costs ........................................ 95
10.4 Results of the Crater Lake Feasibility Cost/Benefit Analysis ................................................. 96
10.4.1 Case 1 Modified AEA ..................................................................................................... 96
10.4.2 Case 2 Inflation Adjusted Method .................................................................................. 97
10.5 Conclusions and Recommendations ..................................................................................... 98
11.0 Summary and Conclusions .......................................................................................................... 100
12.0 References ..................................................................................................................................... 102
List of Tables
Table 3-1. IBC/ASCE 7-10 Seismic Design Parameters ............................................................................ 12
Table 3-2. Observed Rock Outcrop Locations ............................................................................................ 23
Table 4-1. Data Sources ............................................................................................................................. 32
Table 4-2. Summary of Key Characteristics ............................................................................................... 33
Table 4-3. Percent Exceedance Values for Observed vs. Predicted Streamflow for the August 2014-
2015 Time Period at Crater Lake Outlet ............................................................................................. 41
Table 4-4. Water Years Where Record Was Extended with Overall Precipitation, Yield, and the
Adjustment Factor Used to Correct Streamflow Values ...................................................................... 42
Table 4-5. Precipitation and Storage Characteristics by Years and Configuration ..................................... 49
Table 4-6. Long-term Monthly Precipitation Records from Cordova Airport Weather Station .................... 51
Table 5-1. City of Cordova Historical Avg Water Usage from Crater Creek and Total from all Sources.... 54
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Table 5-
Transmission Pipe along NE Cannery Rd to Morpac Tank Reservoir ................................................ 58
Table 5-3. Duty Pump Requirements for new Booster Pump Station at new CLWPP Facility ................... 62
Table 6-1. Operations Modeling Hydro Generation and Diesel Offset Summary ....................................... 69
Table 7-1. Dam Design Criteria .................................................................................................................. 71
Table 7-2. Powerhouse/Treatment Plant General Design Criteria ............................................................. 77
Table 8-1. AACE Class 4 Estimate Description .......................................................................................... 81
Table 8-2. Conceptual Cost Estimate ......................................................................................................... 83
Table 9-1. Summary of Permitting Requirements ....................................................................................... 88
Table 10-1. CLWPP Cost Allocation Summary ........................................................................................... 92
Table 10-2. Modified AEA Cost/Benefit Summary ...................................................................................... 96
Table 10-3. Inflation Adjusted Cost/Benefit Summary ................................................................................ 98
List of Figures
Figure 1-1. Project Area ................................................................................................................................ 1
Figure 1-2. Project Features ......................................................................................................................... 2
Figure 3-1. Regional Geologic Map (Winkler and Plafker, 1993) ............................................................... 10
Figure 3-2. View of the Lake Outlet Area. Note Glacial Till (Sand and Gravel) in the Bedrock Trench
immediately Upstream of the Lake Outlet. .......................................................................................... 13
Figure 3-3. View east, Uphill toward the Cordova Fault from Crater Lake Shoreline. Note Alluvial Fan
and Terrace Deposit along the Lake Margin. ...................................................................................... 14
Figure 3-4. View of Cordova Fault on East Side of Crater Lake ................................................................. 15
Figure 3-5. Bedrock Trench which Forms the Approach to the Elevated Lake Outlet ................................ 16
Figure 3-6. Geologic Mapping within Unnamed Fault Zone. ...................................................................... 17
Figure 3-7. Dark Green Shear Weathered to Clay in Fault Zone ............................................................... 18
Figure 3-8. In-place Sheared Rock in Unnamed Fault Zone Downstream of Dam Site. ............................ 19
Figure 3-9. Faults, Shears and Geohazards ............................................................................................... 20
Figure 3-10. Typical Cliff Band Morphology along Penstock Route ........................................................... 22
Figure 3-11. Microtunnel Option Showing Jacking Pit Location ................................................................. 25
Figure 3-12. Rock Shaft Penstock Alternative Cross Section ..................................................................... 27
Figure 4-1. Stage Storage Curve for Crater Lake ....................................................................................... 34
Figure 4-2. Watershed Area Delineation for Crater Lake Watershed ......................................................... 35
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Figure 4-3. Photo of Mt. Eyak SNOTEL Site from October 2007 (NRCS, 2015)........................................36
Figure 4-4. Streamflow at Crater Outlet vs. Water Input at Mt. Eyak.......................................................... 37
Figure 4-5. Streamflow at Crater Outlet vs. Water Input at Mt. Eyak for Specific Dates ............................ 38
Figure 4-6. Relationship between Daily Precipitation and Daily Outflow from Crater Lake ........................ 39
Figure 4-7. Observed vs. Predicted Streamflow Numbers from August 2014 2015 at Crater Lake
Outlet ................................................................................................................................................... 41
Figure 4-8. Stage Storage Curve with Deep Lake Tap and Baseline Dam Elevation ................................ 44
Figure 4-9. Flow Releases, 2007 Water Year (Dry Year) (Note: Configuration 2 and 3 overlap as
purple line) ........................................................................................................................................... 46
Figure 4-10. Storage Pattern for 2007 Water Year (Dry Year) ................................................................... 46
Figure 4-11. Flow Releases, 2012 Water Year (Wet Year) (Note: Configuration 2 and 3 often overlap
as purple line) ...................................................................................................................................... 47
Figure 4-12. Storage Pattern for 2012 Water Year (Wet Year) .................................................................. 47
Figure 4-13. Flow Releases, 2008 Water Year (Normal Year) (Note: Configuration 2 and 3 overlap as
purple line) ........................................................................................................................................... 48
Figure 4-14. Storage Pattern for 2008 Water Year (Normal Year) ............................................................. 49
Figure 5-1. Monthly Crater Creek and Total COC System Water Flows 2010-2014 .................................. 55
Figure 8-1. Project Schedule....................................................................................................................... 85
Figure 10-1. Case 1 Assumptions ............................................................................................................... 96
Figure 10-2. Case 2 Assumptions ............................................................................................................... 97
Appendices
Appendix A Operations Modeling Charts (electronic model file delivered to client)
Appendix B Conceptual Design Drawings
Appendix C Canyon Hydro Budget Estimate Turbine Generator
Appendix D Cost/Benefit Model Spreadsheets (electronic model file delivered to client)
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
January 2016 vii McMillen Jacobs Associates
Distribution
To: Clay Koplin, PE
Cordova Electric Cooperative
Rich Rogers, PE
City of Cordova
From: Kelly Tilford, CEG
McMillen Jacobs Associates
Prepared By: Multi-disciplinary Project Team
McMillen Jacobs Associates
Tom Lovas
Energy & Resource Economics
Reviewed By: Mort McMillen, PE
McMillen Jacobs Associates
Revision Log
Revision No. Date Revision Description
0 12/16/15 Issue for Client Review
1 1/20/16 Final Report Issue
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
January 2016 viii McMillen Jacobs Associates
Executive Summary
This report presents the results of a feasibility study of the Crater Lake Water and Power Project
(CLWPP) performed by McMillen Jacobs Associates (McMillen Jacobs) for the Cordova Electric
Cooperative (CEC) and City of Cordova (COC). This evaluation presents the fundamental geotechnical,
engineering, construction, permitting and economic analyses required to make a Project feasibility
determination. McMillen Jacobs analyzed the Project basis through a series of analyses, culminating in a
Project conceptual cost estimate and cost/benefit analysis. These studies and conclusions are presented
below.
Feasibility Study Focus Conclusions
Geotechnical and
Geohazards Analysis
No fatal flaw geotechnical or geologic hazards were identified, although
significant field investigation will be required for design.
Baseline Hydrology
Study
Crater Lake hydrology is sufficient to support a storage/hydro Project and
represents both a water supply and renewable energy resource that could provide
significant benefit to Cordova.
Water Supply System
Evaluation and Penstock
Sizing
COC of Cordova water system could benefit substantially from the additional,
high quality water available through a storage resource. The existing water
distribution pipeline can support this additional water.
Operations Modeling The preliminary operations model showed multiple options for combined
water/power supply and may offset as much as 25% of current diesel generation.
Initial Project Design
Criteria and Conceptual
Civil Design
The Project could employ conventional design and construction methods to
develop a combined hydroelectric and water supply Project.
Permitting Evaluation
and Strategy
No fatal flaws were identified in permitting. COC administers public lands and
private land agreements could be negotiated. Permit requirements should be
addressed early in the Project development cycle.
Constructability Review,
Cost Estimate and
Schedule
The Project is constructible with conventional and helicopter based methods.
Cost estimates range from $12M to $26M, with a median cost of $17.2M for the
base Project. Further design is required to narrow this range.
Cost/Benefit Analysis The Project shows promise with an estimated cost/benefit ratio for CEC of 1.36
(AEA method) and 1.27 (inflation adjusted). The Project shows both negative
and positive outcomes for COC, depending on assumptions, with an estimated
ratio of 0.83 (AEA method) and 1.09 (inflation adjusted).
This very interesting Project appears to be feasible to construct and operate and would provide significant
energy and water supply benefits to CEC and COC. The economic analysis strongly supports Project
development for CEC and appears marginal on a purely economic basis for COC, with the assumption of
approximately equal cost-sharing for development. A more balanced cost/benefit is possible through
modified assumptions on cost sharing. It is important to acknowledge the feasibility-level nature of this
evaluation and recognize that additional analyses will be required to support design, cost estimating,
additional operations modeling and cost/benefit sharing. These analyses will lead to a more refined cost
and value for the Project. Lastly, CEC and COC should recognize the unique challenges and uncertainties
associated with construction and operation of any Alaska heavy civil works Project.
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
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1.0 Introduction and Purpose of Study
The CEC and Cordova awarded a contract to McMillen Jacobs to evaluate the feasibility of the Crater
Lake Water and Power Project (CLWPP or Project) and develop a Feasibility/Conceptual Design Report
for the Project. McMillen Jacobs identified several Project configurations, narrowed the options to a
single preferred alternative and provided detailed feasibility-level analyses of the preferred alternative.
1.1 Project Description
The Project is located approximately 2.5 miles northeast of Cordova, Alaska. The Project area is shown in
Figure 1-1.
Figure 1-1. Project Area
The proposed Project will utilize the existing Crater Lake as a high head reservoir to generate hydropower
and as an auxiliary water supply source to COC. The primary components of the Project include a small
dam (on the order of 25 feet tall) at the existing Crater Lake outlet, a roughly 3,800-foot-long penstock,
and a powerhouse/water treatment plant located near tidewater elevation. The general arrangement of the
Project features is shown in Figure 1-2.
PROJECT AREA
N
Crater Lake Water & Power Project Feasibility/Conceptual Design Report January 2016 2 McMillen Jacobs Associates Figure 1-2. Project Features
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1.2 Report Organization
This report describes the studies and relevant conceptual design for the Project at the feasibility stage, as
well as a proposed constructability review, cost estimate and conceptual Project schedule. The report also
includes an assessment of the cost-benefit of the Project ic setting and a Projection of
Project value given a set of future economic development scenarios. This report presents the results of all
these feasibility-level analyses, organized as follows:
Data Review and Compilation
Geologic and Geotechnical Reconnaissance
Hydrologic Evaluation
Water Supply and Treatment Evaluation
Generation and Operations Model
Conceptual Civil Design Criteria
Constructability, Cost Estimate and Schedule
Permitting Scope and Planning
Feasibility-Level Cost/Benefit Analysis
Summary and Conclusions
The intent is that this report provide a conceptual design, cost estimate and economic analysis to
determine overall Project feasibility. Based on the results of this analysis, CEC and COC may continue
with more advanced engineering, economic and environmental studies leading to a build/no-build
decision.
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January 2016 4 McMillen Jacobs Associates
2.0 Data Review and Compilation Introduction
The purpose of this section is to summarize the information made available for the CLWPP feasibility
study. This report functions as the original reference index for the Project. The report is organized based
on either the water or power aspects of the Project and some of the available information (such as
topographic map coverage) provides a data source for both focus areas. Table 2-2 at the end of this
section provides a summary of the relevant data sources.
2.1 Previous Studies
Based on the historic data provided by CEC, the Crater Lake Project has been studied at the concept level
since the early 1960s, beginning with a simple plan map of the Project for (then) Cordova Public Utilities
(North Pacific Consultants, 1960). It appears that Crater Lake (called Summit Lake) was identified with a
small dam, penstock to an area at the Orca Cannery, and connected to the COC through an existing 2400-
volt (V) overhead transmission line. This study was followed by a number of reconnaissance-level studies
Data Cordov USACE, 1982), executed as a deliverable
under the Coordination Act Report for the US Army Corps of Engineers (USACE), Alaska District. This
1982 report primarily identifies the biological resources that would be potentially impacted by the Project,
referencing a 1979 reconnaissance report by CH2M HILL Company (not available). The report
summarizes the generation from Crater Lake at 458 kilowatts (kW), not enough to meet (then) current
Cordova Public Utilities peak demand of 3,150 kW.
Electricity and water use rate information was also retrieved from Internet access portals on the web for
CEC (http://cordovaelectric.com/) and COC (http://www.cityofcordova.net/).
2.2 Land Ownership
Land ownership information was transmitted with the Request for Proposals (RFP) and included a general
aerial photo with land ownership overlay. The Project may involve different landowners, depending on
selection of the preferred penstock alignment, powerhouse/treatment plant location and access to
transmission. The alignment and structure land ownership, as currently envisioned, is shown in Table 2-1.
Table 2-1. Land Ownership Potential by Project Feature
Feature Potential Owner(s)
Dam Site City of Cordova
Penstock City of Cordova
State of Alaska
The Eyak Corporation (potentially)
Powerhouse City of Cordova
Powerhouse Access Road City of Cordova
Orca Adventure Lodge (private)
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At the completion of the feasibility study, the final list of affected landowners will be used to negotiate
access agreements for the future geotechnical design investigation and may be used to negotiate long-term
easements or land acquisitions as necessary if the Project moves forward.
2.3 Recent Topographic Data Acquisition
In late 2014, CEC contracted with for satellite-based photogrammetry on enough area to encompass all
Project options (E-Terra, 2014). CEC also contracted with to provide field survey and Global Positioning
System (GPS) based ground control and detailed topographic survey of the area within the anticipated
dam footprint, several low-lying areas along the lake boundary (Edge Surveys, 2014) with emphasis on
the drainage divide saddle to the south and on potential powerhouse locations near tidewater adjacent to
Orca Inlet. More detailed penstock alignment and powerhouse site surveys will be required in the future,
as design progresses on the preferred alternative, if warranted.
2.4 Hydrology/Meteorologic Data
A variety of hydrologic data sources for the Cordova area are variably relevant to the CLWPP. These
include operational hydrologic data from the Power Creek Hydroelectric Project to the south, from the
Snyder Falls Creek Hydroelectric Project to the east and a short-term record for Crater Creek outflows
from Crater Lake for the last year (CEC, 2015). Each data set is variable in its detail and limitations, with
the only directly relevant source from the Crater Lake outfall stream gage. At the time of RFP issuance,
CEC was still in the process of acquiring the most recent data set from both Snyder Falls Creek and
Crater Lake. The challenge to the Project is that Crater Lake is a distinct, limited geographic area of
approximately 0.26 square-miles, with no glacial influence and minimal vegetation and soil.
The data from Power Creek does not directly measure overall basin runoff as a ratio of streamflow,
because generation flows are not directly measured and bypass flows only capture a portion of the overall
streamflow. Efforts to refine the interpretation of generation flow combined with bypass flow and site
meteorology could be pursued, but the team made the decision to wait on the receipt of the most recent
Snyder Falls Creek and Crater Lake outflow data before pursuing this option.
After the RFP was issued, CEC also provided additional meteorological data (NRCS, 2015) from the
existing SnoTel weather station, located approximately 0.5 mile west of Crater Creek on the mountain
above Cordova. This meteorological station is essentially the same elevation and microclimate as Crater
Lake. It has a record of precipitation (snowfall and rainfall) for a continuous 10-year period and the data
appears complete and reasonable.
Upon attempting to retrieve the last 2
consultant (Keta Engineering, 2015) reported that both the upper and lower stream gages had been
subjected to natural geohazard events that may affect the quality of the record. An avalanche destroyed
the equipment at the upper gage location and a rockfall deposited large debris in the stream cross-section
for the lower gage, making the correlation between stream level and discharge flow subject to data
smoothing techniques in post-processing. There were several other equipment maintenance and failure
issues that eliminated the secondary redundant data acquisition measures in place at the lower gage site.
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McMillen Jacobs hydrologic staff ran some preliminary comparisons of the SnoTel and Crater Lake
outflow gage data and there appears to be a solid correlation between data sets. The team elected to
pursue more rigorous correlation of the complete Crater Lake outflow data set with the SnoTel data and
used this data to develop a synthetic outflow record as the basis for the CLWPP reservoir sizing and water
and power production estimates for the operational model.
2.5 Geology/Geotechnical Data
The existing geologic information was gleaned from the publically available resources such as the US
Geological Survey (USGS)(Winkler et al., 1983 and others) and Alaska Division of Geological and
Geophysical Survey(ADGGS) (Stevens et al., 2003). This was supplemented by the Humpback Creek
geotechnical investigation report (R&M Consultants, 2008). Very little site-specific geologic data is
available for Crater Lake. Most data sources focus on coastal Alaska geology in general, and more
specifically on mineral resources and seismic activity.
2.6 Generation Data
CEC provided the annual power system report from the Alaska Center for Energy and Power (ACEP,
2014). This is an annual report that summarizes the contributions from both hydro and diesel generation
for COC and provides a good graphic representation of overall seasonal demand trends.
2.7 Water Supply and Operations Data
The information provided by COC to date includes some recent photos of the Crater Creek intake
structure and a general information summary of COC water usage for the years 2010 and 2014 from the
Meals, Murchison and Orca treatment plants. A summary of the various data sources is presented in Table
2-2 below.
Table 2-2. Existing Data Sources for this Study
Existing Data Sources in Support of the CLWPP Feasibility Study
Source Title
Information Type
Raw Data = D
Report = R
Other = O
Date or Date
Range Remarks
Previous Studies
Variety of sources.
None provide real
data, but are early
indicators of Project
potential.
O Varies - from
1960 to present
CEC's most recent reconnaissance
level reports and presentations are
the most robust early level reports on
record. Points to additional available
detailed data that may have been
used as early concept feasibility.
Land Ownership
Land ownership
figure from RFP
R
Figure in RFP,
general accuracy
2015 Good figure to illustrate variety of
ownership. Line weights and location
do not appear to be precise, e.g.
Crater Creek thalweg does not appear
to match underlying image very well.
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Existing Data Sources in Support of the CLWPP Feasibility Study
Source Title
Information Type
Raw Data = D
Report = R
Other = O
Date or Date
Range Remarks
Various plat maps
showing partial land
ownership details
and easements
O
Plat map only
various Some of the plat information masks
potential alignment areas. Information
incomplete or in "plat-speak", referring
to other more detailed resources that
were not provided.
Topography
Edge Survey Surface
Detailed Hand
Topography
Topographic
surface and maps
in pdf format
10/14-16/2014 Covers the dam site and
approximately 300 feet downstream
with canyon walls along Crater Creek.
Also includes southern saddle
location at lake shore and several
potential saddle dam locations.
E-Terra Satellite-
based
photogrammetry,
entire Project area
D
Geographic
Information System
(GIS) files and
topographic
surfaces
2014 The satellite photogrammetry was tied
in with ground-based control provided
by Edge Surveying. Control located
near lake outlet at several locations
and at sea level near Orca Lodge.
Primarily in GIS format.
USGS topography R
Topographic maps
Various,
outdated
Minimal detail, poor vertical resolution
on forested sideslopes and within
deep, incised channels.
Crater Lake
Bathymetry
D
Data files from
Sonarmite,
primarily SHP files
9/1/2015 Uncorrected for probe depth in water.
Collected by Koplin in field.
Hydrology/Meteorology
SnoTel Records D
SnoTel data
records in Excel
format
2005-2015 Daily precipitation totals (inches)
Crater Lake Outflow
discharge data
D
Stage-discharge
data in Excel
format
2014-2015 Daily discharge values. Good natural
hard control with very little relationship
shift potential.
Upper and Lower
Snyder Falls Creek
data
D
Discharge curves
in Excel format
2010-2015 Data has been post-processed to
compensate for natural disturbances;
some of the data has been "clipped".
There are shifts in data with long
periods between measurements.
Power Creek D In Excel format 2011-2012 Please note there is long-term gage
data for Power Creek at nearby
location but discontinued. No
overlapping data in hand with Crater
Lake outflow
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Existing Data Sources in Support of the CLWPP Feasibility Study
Source Title
Information Type
Raw Data = D
Report = R
Other = O
Date or Date
Range Remarks
Climate Records
Cordova
O - Daily/Monthly
Values
1949-2015 Archived Climate Data for long-term
contextualization of local data.
Geology/Geotechnical
USGS publications
on regional geologic
mapping (few)
R Limited regional or specialized
studies, primarily on minerals or
hydrocarbon resources
Geotechnical
Findings Report,
Humpback Creek
Hydroelectric Facility
Reconstruction
R 12/18/08 Geologic investigation data report with
limited geotechnical
recommendations. Follow-on
geotechnical basis report would be
helpful.
Generation (CEC)
Annual Power
System Report for
Cordova Electric
Hydro-Diesel System
R with figures (pdf
format)
April, 2014
covers calendar
year October
2012 to 2013.
Automated data set produced from
Supervisory Control and Data
Acquisition System (SCADA) on Orca
and Humpback Creek Projects. Diesel
generation is presumably in response
to shortfall on hydroelectric output, but
hydro plant outages and operational
variance can't be quantified from this
data set. Report quantifies lost power
generation with simplifying
assumption that demand is not in
place, but should check these "spill"
periods against diesel generation to
determine accuracy of assumptions.
Spilled, lost or not-produced power is
significant and 500kW reserve
requirement significantly affects
overall annual output.
Water Supply (COC)
Annual water supply
from COC's 3 water
treatment plants from
2000 to 2014.
D 2000-2014 Monthly total production values
(gallons) are provided from each
plant.
Plans and
specifications for the
current system
upgrades to attain
Long Term 2
Enhanced Surface
Water Treatment
Rule (LT2)
compliance.
D, R 2012-current References include historic water
usage by source and reports on ways
to meet LT2 compliance and
treatment equipment data and
literature
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January 2016 9 McMillen Jacobs Associates
3.0 Geologic and Geotechnical Reconnaissance
3.1 Field Reconnaissance
The McMillen Jacobs team consisting of Bryan Duevel, Matt Moughamian, and Kelly Tilford completed
the site visit on August 27 and 28, 2015. On the first day, Mr. Tilford and Mr. Duevel were accompanied
during the visit by Clay Koplin, Chief Executive Officer (CEO) of CEC, while Mr. Moughamian met
with COC utilities department staff to gather water system data. On the second day, all four team
members continued the reconnaissance. The reconnaissance team observed the following areas:
The Crater Lake hiking trail between Eyak Lake and Crater Lake: The trail is considered a
potential access route for construction equipment and materials to the lake.
The eastern perimeter of Crater Lake and the lake outlet: The main dam site would be located at
the lake outlet. The penstock intake would also be located in this vicinity.
The slope between the Crater Lake outlet and tidewater along the preliminary surface penstock
alignment: The penstock would be routed down this slope, with two alignments in consideration.
The base of the slope near tidewater elevation: The new powerhouse would be located at one of
two potential sites in this area.
The team accessed the site by foot and by helicopter. The objectives of the geotechnical reconnaissance
were to identify significant geologic conditions; hazards and constraints; assess constructability concerns;
and refine the penstock alignment.
3.2 Site Description
3.2.1 General
Crater Lake is a natural lake located in the southeast portion of Prince William Sound on a northeast-
southwest trending mountaintop ridge in the southern front of the Chugach Mountain Range. The
mountains rise dramatically from sea level and are separated by geologically recent glacial troughs that
form sea-level inlets to hanging glacial valleys above sea level. This varied geomorphology is widespread
along the coast in this region. The lake rests at an elevation of approximately 1514 feet, approximately 2.5
miles northeast of Cordova. The lake appears to be a relict mountaintop glacial feature, interpreted to
have been formed by glacial scouring that left behind this cirque (bowl) shape. There is no glacial activity
in the drainage at present and no indication of glacial activity in the historic past, so this is probably a
feature from the last glaciation period. The drainage area around the lake is relatively confined and covers
an area of approximately 0.26 square-miles. The lake outlet (Crater Creek) spills rapidly down the steep
mountainside immediately downstream of the lake as shown on Figure 1-2. Specific areas of the Project
are described in more detail in the following sections.
3.2.2 Site Geology
The Project area is located at the boundary between the rugged Chugach Mountains to the east and the
more subdued terrain of the Gulf of Alaska Coastal Province to the west. The Cordova area is
characterized by a series of northeast-southwest trending ridges and islands, bounded by ocean inlets and
deep glacial valleys (Winkler and Plafker, 1993). The regional geology is shown in Figure 3-1 below.
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Based on observations made during the site visit, the Crater Lake basin is primarily underlain by sheared
and altered basalts and fine-grained metasedimentary rocks. The bedrock exposures indicate the presence
of numerous small diabase or gabbro veins. The exposed rock outcrops away from the faults are
moderately to closely jointed, with the majority of these fractures healed by a fine-grained white quartz or
calcite filling. These rock types were primarily observed at the lake outlet, in the adjacent drainages in the
immediate lake vicinity and east of the lake. The team also surveyed traces of the Cordova Fault and
parallel and subparallel newly identified fault traces in the Crater Lake vicinity.
Existing mapping and tectonic history descriptions from the literature indicate that the western edge of the
Chugach Range and accompanying Coastal zone are comprised primarily of complex accreted terrains
associated with the northwest-trending subduction plate boundary between the Pacific Plate and the North
American Plate. The bedrock types and condition are interpreted as indicative of a plate subduction
boundary, where basaltic and gabbroic seafloor and fine-grained sedimentary rock has been sheared off
the plate edge and pushed eastward into what is now the mainland. Description of the tectonic history
indicates significant variation in the regional stress regimes as the tectonic plates shifted to accommodate
changing structural dynamics from a pure subduction boundary to a transverse plate boundary with
elements of both dip-slip and strike-slip faulting. Regional fault trends toward the northeast and southwest
are coupled with glacial erosive features to create the fjord-like topography in the immediate Project area.
For the purposes of the Crater Lake geotechnical evaluation, it is sufficient to understand that the bedrock
consists of both volcanic and well-cemented metasedimentary rock that is primarily closely to moderately
fractured and fresh to moderately weathered. Minor thin, weathered clay zones were also observed within
the shear zones associated with the faults.
3.2.3 Site Seismicity
The Project area is located in one of the most seismically active regions of the United States. Seismic
activity is dominated by the Aleutian-Alaska megathrust zone which extends from the Aleutian Islands to
south-central Alaska. The megathrust zone is the convergent plate boundary between the northwest-
moving Pacific Plate which is being subducted below the North American Plate (Wesson et. al, 2007).
The 1964 Prince William Sound earthquake was generated along this zone. This magnitude 9.2
earthquake was one of the largest ever recorded and caused severe ground shaking in the Cordova area. A
number of active crustal faults are also located in south-central Alaska. Most notable of these is the
Denali Fault, which generated a magnitude 7.9 earthquake in 2002.
Preliminary seismic design parameters have been developed based on 2012 International Building Code
(IBC)/ASCE 7-10 which both make use of the 2008 USGS seismic hazard data (IBC, 2012). Based on
soil and rock conditions at the site, a Soil Site Class B is appropriate for design. Recommended seismic
design parameters are presented in Table 3-1. These parameters are appropriate for the design of all
Project components. Seismic design parameters will be further refined in future design phases.
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Table 3-1. IBC/ASCE 7-10 Seismic Design Parameters
Seismic Design Parameter Value
Site Class B
0-sec Period Spectral Acceleration 0.60
MCE Short Period Spectral Acceleration, SMS 1.512
MCE Long Period Spectral Acceleration, SM1 0.803
Design 0-sec Period Spectral Acceleration 0.40
Design Short Period Spectral Acceleration 1.008
Design Long Period Spectral Acceleration 0.535
Note: All values adjusted for Site Class B.
MCE = Maximum Credible Earthquake
3.3 Dam/Reservoir Geotechnical Observations
3.3.1 Site Description
Crater Lake is located in a bowl-shaped basin on top of the ridgeline extending northeast of COC of
Cordova. The lake water surface elevation is approximately 1,514 feet. Topography within the basin is
gently rolling, and rises away from the lake on all sides except at the outlet, which drops steeply off the
mountainside within several hundred feet of the outlet. The perimeter of the bowl is formed by more
prominent ridges that vary in elevation from about 1,550 feet along the northwest side of the lake to as
high as 2,300 feet at minor peaks northeast and southwest of the lake. The outlet to Crater Creek is
located at the northwest end of the lake, where the creek cuts a narrow channel through bedrock. A series
of northeast-southwest trending lineaments (expressed at the surface in the form of shallow depressions)
cross the bowl within the Project area.
The basin has been glacially scoured leaving a thin soil profile. Rock outcrops are prominent throughout
the area. The basin is near the local tree-line elevation. Most of the area is covered in low shrubs and
grasses, with localized areas of evergreen scrub up to 6 feet tall.
3.3.2 Geomorphology
As indicated above, the lake itself is interpreted as a geologically recent glacial scour feature remaining at
the end of the most recent glacial period. This is also indicated by the presence of apparent glacial till
(alluvium) within the lake, especially near the outlet channel as shown in Figure 3-2 below.
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Figure 3-2. View of the Lake Outlet Area.
Note glacial till (sand and gravel) in the bedrock trench immediately upstream of the lake outlet.
The lake outlet drains to the northwest through a bedrock notch and most of the upper basin consists of
bedrock outcrop with a thin veneer of rock talus and colluvium, typical of high Alaska mountain ranges.
Within the basin, the lower reaches of the slopes decrease in steepness and are mantled by localized
colluvial/alluvial fan deposits. Along the trace of the Cordova Fault on the east side of the lake, the
lakeshore morphology consists of a wide fan that forms a terrace deposit indicating a higher lake level in
geologic time as shown in Figure 3-3. The surface expression of the Cordova Fault is presented in Figure
3-4.
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Figure 3-3. View east, Uphill toward the Cordova Fault from Crater Lake Shoreline.
Note alluvial fan and terrace deposit along the lake margin.
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Figure 3-4. View of Cordova Fault on East Side of Crater Lake
The lake outlet is formed by a resistant bedrock notch, but the stream approach to the outlet consists of a
deeper bedrock trench. This is interpreted as further evidence of glacial action within the basin. This
upstream bedrock depression appears to be a suitable location for a laketap intake configuration, as shown
in Figure 3-5. Bedrock appears to be approximately 15 feet below the lake surface at this location.
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Figure 3-5. Bedrock Trench which Forms the Approach to the Elevated Lake Outlet
3.3.3 Geologic and Geohazard Observations
The exposed rock within the basin is predominantly basalt interspersed with dark gray bands of
metasedimentary quartzitic shale. Although the geologic maps of the area indicate minor amounts of
interbedded sedimentary turbidites consisting of mudstone and siltstone, none were observed during the
site visit.
The basalt at the site is typically massive, moderately to slightly weathered, and strong (requiring more
than one blow with a geologic hammer to break a hand sample). The most predominant joint set observed
within the basalt is oriented approximately parallel with the faults that run through the Project area, at
approximately 70/330 (dip/dip direction: Dip represents the planar angle from an imaginary horizontal
surface within the planar feature and dip direction is the direction perpendicular to a horizontal line drawn
through the plane of the feature). There is also random jointing present within the rock mass, much of it
healed with mineral infilling.
Three prominent faults run through the lake basin. Each fault orientation follows the regional geologic
trend, with dips ranging from 60 to 80 degrees and dip directions of 320 to 350. Each of the faults is
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expressed by a watercourse drainage or depression in the rock exposure, as shown in Figure 3-6. Strong,
intact basalt was observed on both sides of the fault zone. This is typical for a number of unmapped faults
and shears observed during reconnaissance.
Figure 3-6. Geologic Mapping within Unnamed Fault Zone.
The largest of these features is the Cordova Fault (as shown on Winkler and Plafker, 1993), which crosses
the northern half of the lake. The fault appears to be between 10 and 30 feet wide in the basin. Completely
sheared sedimentary rock was observed within all of the fault zones. In one exposure uphill from the lake,
one of the shear zones included a band of rock that had weathered to a dark green clay with intact relict
sheared rock texture (Figure 3-7). The presence of this clay weathered zone should be taken into
consideration during foundation design, as it is common for weaker, clayey foundation materials to wash
out (pipe) over the life of a Project.
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Figure 3-7. Dark Green Shear Weathered to Clay in Fault Zone
On the right bank immediately downstream of the proposed dam footprint, a shear zone was observed
adjacent to the fault plane, expressed at the surface as a band of finely broken shaley rock with
slickenside (fine shiny surfaces indicative of shear) as shown on Figure 3-8. These lesser faults trend
parallel or subparallel to the Cordova Fault. Two of these faults appear to bound a bedrock island, which
forms the current bedrock notch at the proposed dam site. The principal Project impacts related to the
faulting include weaker foundation zones for the dam and laketap outlet and possible seepage paths
associated with a raised Crater Lake. Careful mapping, core drilling and permeability testing will be
required to further characterize these fault features for design purposes.
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Figure 3-8. In-place Sheared Rock in Unnamed Fault Zone Downstream of Dam Site.
The observed and inferred faults and lineaments within the site vicinity are presented in Figure 3-9 below.
Due to time constraints, McMillen Jacobs staff were unable to field-check the apparent landslide complex
below and west of Crater Lake, but have included this potential feature on the base map for reference. It is
not anticipated that any of the Project features would traverse this area, so no further field investigation is
required at the feasibility level.
The lack of mature vegetation to the north and east of the lake infers the presence of avalanche chutes in
this area. Although this feature is indicated on Figure 3-9 as a geohazard to be avoided during design,
discussion with Cordova-area long-term residents or people familiar with the Orca Lodge history may
provide some historical information on this potential geohazard and possible activation frequency.
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Figure 3-9. Faults, Shears and Geohazards
In general, it is anticipated that the rock mass at the basin site is anticipated to exhibit low permeability.
Fluid flow through the rock would be primarily through fracture flow and fault/shear zones. There does
not appear to be significant leakage through the rock mass based on the relatively stable lake elevation
throughout the year even though at least three significant faults/shear zones cross through the lake.
3.4 Dam Site Considerations
The proposed Project concept involves raising the lake level on the order of 25 feet by constructing a
small dam at the outlet. If greater storage is feasible and desired, a higher dam would require additional
saddle dams at several locations around the lake perimeter and may not be justified based on basin
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inflows. Depending on the final dam height, crest length of the dam may range from about 150 to 400
feet. It is anticipated that the dam would be designed as a concrete gravity structure.
3.4.1 Foundation Assessment
The rock present at the main dam site consists of strong basalt within the base and abutments. No adverse
structure was identified in the rock within the anticipated footprint, but shear zones are present both
upstream and downstream of the dam site. The maximum foundation loads imparted by the proposed dam
structures are anticipated to be less than 10 kilopounds per square foot (ksf). The rock conditions present
at the site are anticipated to adequately support loads of this magnitude and not cause structural instability
within the foundation or abutments. This assumption must be confirmed with design-level site drilling,
sampling and testing.
It is likely that the dam would need to be keyed into the foundation to provide passive resistance against
lateral reservoir forces. The dam must be founded on competent rock, and any weak or highly weathered
zones must be removed during foundation preparation to avoid performance issues such as differential
settlement or foundation seepage.
3.4.2 Foundation and Reservoir Rim Seepage Assessment
The basalt rock at the dam site is not highly fractured and, where present, fractures were often healed with
mineralization. Significant seepage within the basalt is not expected given the range of reservoir head
pressures anticipated with this low structure (less than 20 pounds per square inch [psi]); however, fault
zones are present approximately 50 feet upstream and 50 feet downstream of the dam site. The fault zones
dip steeply to the north, and are expected to be present at depth below the dam foundation. The fault
zones may act as conduits for seepage and should be thoroughly tested during the design investigation. If
seepage is determined to be a design issue, a grout curtain may be required and additional drilling may be
needed in the faulted areas around the reservoir to assess overall reservoir seepage potential.
3.5 Penstock Geotechnical Observations
3.5.1 Penstock Alignment Description
The penstock alignment would generally extend from the lake at an approximately northwestern
orientation, following the fall line of the slope, east of the creek channel. The preferred surface alignment
is shown on Figure 1-2, which also shows the topography of the slope. Crater Creek exits the lake at its
northern edge and immediately drops into a narrow ravine, incised approximately 30 feet below the
surrounding ground line. The creek flows through this gorge for about 300 feet and makes numerous
sharp bends, eventually flowing to the west. The creek exits this upper ravine and enters into a steep
canyon that drops down the slope in a north-northwesterly direction. The creek channel is formed by a
series of faults and shear zones that parallel the predominant regional structural orientation.
In general, the terrain northwest of the lake is gently rolling to a point at approximate elevation 1370 feet
elevation. This location is important because the topography forms a narrow landing between two steep
drainages where it may be imperative to route the penstock alignment. This landing is formed by the
intersection of two drainages with a significant fault zone, and the landing represents the only high
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topographic spot to facilitate a penstock route between the two drainages. If the route varied to the west of
this point, it would dive deep into the unstable landslide topography shown on Figure 3-9. If the route
varied to the east of this point, it would enter the interpreted avalanche-affected zone to the east. Directly
downhill from this location, the grade steepens as the slope drops between elevations 1,400 and 550 feet.
In this reach, slopes typically range from about 30 to 45 degrees and numerous short cliff bands (on the
order of 20 to 30 feet tall) are present, as shown on Figure 3-10. At elevation 550 feet, grades become
gentler again, ranging between zero and 20 degrees to about elevation 400 feet. Below elevation 400 feet,
slopes again steepen to 25 to 35 degrees, down to tidewater elevation.
Figure 3-10. Typical Cliff Band Morphology along Penstock Route
The area above elevation 1,400 feet is typically covered with low shrubs and grasses. Below elevation
1,400 feet, the slope vegetation generally consists of mature coniferous forest and brush, interspersed with
open, brushy treeless areas. Within tree-covered areas, an organic mat of deadfall and soil has
accumulated. Boggy soils are present along the prominent bench at approximate elevation 500 feet.
3.5.2 Geologic and Geohazard Observations
Rock outcrops are prevalent between the lake and approximate elevation 1,400 feet. Outcrops of basalt
and metasedimentary rocks are both present. Below elevation 1,400 feet, local rock outcrops were visible
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along the surface penstock alignment. Prominent outcrops are summarized in Table 3-2. Outcrops below
elevation 1,400 feet consisted of metasedimentary rock. Rock outcrops are also present within the Crater
Creek drainage downstream of the COC water supply intake, and along road cuts adjacent to Orca Road.
Table 3-2. Observed Rock Outcrop Locations
Approximate
Penstock Station
Approximate
Elevation (ft) Comments
10+00 to 18+00 1,500-1,350 Shallow rock is predominant, very little ground cover
numerous outcrops throughout segment
19+75 to 20+25 1,270-1,230 Exposed cliff band
23+00 to 23+50 1,060-1,080 Exposed 20-foot-tall cliff
23+50 to 26+00 1,060-830 Continuous steep terrain with numerous small cliff
bands
39+00 250 200 feet southwest of 39+00, cliff bands exposed in
Power Creek channel below COC intake diversion
48+00 60-30 400 feet southwest of 48+00, cliff band exposed in
rock cut along existing road (SW PH Site)
Based on slope grades and the locations of surface rock outcrops, bedrock is interpreted to be shallow
along the entire slope except at the bench at elevation about 500 feet where boggy ground was observed.
In general, thin organic soils are expected with local accumulations of talus below cliff bands. The depth
to bedrock is expected to be less than 10 feet below ground surface except at the bench. The soil profile is
expected to be deeper here and may exceed 25 feet.
In general, little evidence of significant instability was observed along the penstock alignment. The cliff
bands represent zones of potential shallow instability, with near-surface joints showing open relief and the
potential for rock topple. These zones would require slot excavation to stable bedrock for penstock
routing and anchoring. No landslide scarps, disturbed ground or hummocky topography was observed
during the reconnaissance. Locally, pistol-butt trees were observed, indicating that the trees had grown to
compensate for ongoing soil movement or creep; however, these were identified in the steepest zones on
the alignment, and were interpreted to be caused by surficial soil creep rather than large-scale, deep-
seated movements. The mature vegetation on the lower slopes did not exhibit this characteristic. These
observations are consistent with the overall grades and shallow rock outcrops present throughout the
slope.
West of the preliminary penstock alignment, the slope below the lake forms an approximately 1,500-foot-
wide bowl shape (see Figure 1-2). The Crater Creek channel forms the eastern margin of this area. This
landform appears to have resulted from a large, historic landslide and should be avoided. The area aligns
with cross-cutting, regional shear zones visible to the east which may have bounded the uphill side of the
unstable block.
The area east of the alignment without any mature vegetation is interpreted as an avalanche zone. This
area is shown on Figure 3-9. Unless the penstock is buried, this area should also be avoided. The
avalanche source area may be the high peak to the northeast of this feature. This also may be the site of an
historic avalanche which cleared the slope of trees, in turn promoting future snow instability on this slope.
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3.6 Penstock Concepts
The surface penstock alignment concept is shown on Figure 1-2. A second concept consisting of a
tunnel/shaft arrangement would utilize a drilled rock shaft below ground surface (for a portion of or the
entire length) to carry the penstock. A cross-section of the potential drilled shaft alignment is shown on
Figure 3-11. Based on the hydraulic evaluation, McMillen Jacobs anticipates that the penstock diameter
would be 16 inches outside diameter. The penstock and shaft/tunnel alternatives are discussed in more
detail in the following sections.
Three potential surface alignments were preliminarily screened at the desktop level, and the preferred
alignment was studied in more detail, as shown on Figure 1-2. The penstock would be installed in a
shallow trench on-grade or would be placed above-grade on pipe supports. The alignment has been
selected to avoid the potentially unstable terrain west of Crater Creek, and avoid the active avalanche
chute to the east.
Either of these alignments could be constructed using conventional means with small earthwork
equipment. This may also be constructed without significant road development, and potentially utilize
helicopter support to move materials and equipment.
3.6.1 Surface Alignment Initial Reach
The initial 600 feet of the penstock alignment must either follow the sinuous path of the Crater Creek
canyon, go up and over the canyon sidewalls (which are higher than the proposed dam crest), or could be
bored through the canyon sidewalls in a relatively straight alignment. The bored option is preferred
because it could be easiest to construct and would not be exposed to rockfall and sudden high flows
within the upper Crater Creek canyon. Nevertheless, the surface option is also feasible, but may be
difficult to anchor on the canyon sidewall, would require complex vertical and horizontal bends and
would be exposed to debris and snow loads.
The microtunnel option is shown on Figure 3-11. A straight alignment simplifies the hydraulics of the
initial reach of the penstock, but cost should be evaluated objectively to the surface alignment. The creek
channel is located within the center of this reach between the intake at the lake and the back side of the
ridge that bounds the creek. The creek channel could be used as a jacking station for two 300-foot-long
bores; one drilled upstream and one drilled downstream. Bores of this length are feasible using a small
boring unit system (SBU) in the range of 24 to 36 inches in diameter. This equipment is relatively small,
and could be broken down into components to be mobilized using helicopter support. This option should
be included within the geotechnical exploration program.
Crater Lake Water & Power Project Feasibility/Conceptual Design Report January 2016 25 McMillen Jacobs Associates Figure 3-11. Microtunnel Option Showing Jacking Pit Location
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3.6.2 Surface Alignment Downslope of Inner Crater Creek Canyon
The alignment downhill from the canyon initially traverses a steep section of hillside approaching 50%
slopes from approximately Stations 33+00 to 27+00. This upper slope consists of a series of rock outcrops
with near-vertical foliation that has been deformed by tectonic forces into the current faulted and folded
condition. The surface consists of a short series of outcrops and shallow talus benches that are not well-
indicated by the current topographic mapping. Below Station 27+00, the alignment traverses relatively
uniform hillside averaging 30% slope to the Crater Creek crossing. The ground within this reach consists
of a heavy forest duff and intermittent boulders and outcrops.
3.6.3 Rock Shaft Option
The shaft alternative would utilize a drilled rock shaft extending from the lake to an access point on the
lower third of the slope. The shaft could be oriented between vertical and about 30 degrees below
horizontal. A horizontal adit tunnel would be advanced at the base of the shaft to carry the penstock to a
surficial alignment, or directly to the powerhouse if the shaft was bored to about elevation 100 feet or
lower. A cross-section through potential shaft alignments is shown on Figure 3-12.
The slope has a number of shear zones that would intersect any shaft alignment. These zones would
potentially have high permeability and be prone to water loss in an unlined shaft. Thus, the shaft could
require a pipe lining. The bore diameter for this configuration would be between 24 and 36 inches to
provide flexibility for pipe installation. The length of the bore would be on the order of 2,000 to 3,000
feet. Depending on the adit elevation, and the orientation of the shaft, the adit would have a minimum
length of 300 to 700 feet. The minimum adit size would be approximately 8 feet by 8 feet to optimize
construction efficiency and allow for equipment access using drill and blast methods.
The shaft could be drilled using a raised bore system or down-the-hole hammer system. Both systems
utilize a drill rig set up at the top of the alignment. Raised bore construction involves drilling between the
ground surface and an established lower level (in this case, the adit tunnel) in a sub-vertical orientation.
The process is started by drilling a small-diameter pilot bore and establishing a drill string through the
bore alignment. After the pilot bore is completed, a reamer is attached to the drill string at the lower level
and pulled to the surface. Cuttings are dropped through the bore to the lower level. The reamer is
successively upsized to the desired final diameter. A raised bore would require a significantly longer adit
tunnel, on the order of 2,000 to 3,000 feet. The down-the-hole hammer system also utilizes a pilot bore
drilled from the surface to the target location, which is successively upsized with larger drilling tools. The
system has more orientation flexibility and could be drilled subparallel to the slope. Cuttings are typically
blown out from the bore to the ground surface using compressed air, or by circulating drilling mud.
Both of these systems are technically challenging, but feasible. The length of the bore is potentially
problematic for maintaining precise alignment. This is further compounded by a predominant rock fabric
and geologic structure orientation which will tend to make drilling tools, and consequently the finished
bore, wander out of alignment. This is shown conceptually on Figure 3-12. Specialized, heavy drilling
equipment (typically mounted to large, flatbed trucks) would be required for either type of installation at
the proposed lengths and accuracy needed. Both would require road access to the lake outlet suitable for
Crater Lake Water & Power Project Feasibility/Conceptual Design Report January 2016 27 McMillen Jacobs Associates Figure 3-12. Rock Shaft Penstock Alternative Cross-Section
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highway vehicles to pass, and construction of a drilling pad. Few contractors have the experience and
equipment to install bores of this size, and mobilization costs to Cordova would be significant.
Overall, the costs for this alternative would significantly exceed the cost of a surface penstock alignment.
Further, the equipment requirements necessitate construction of an access road which creates a permanent
visual site disturbance as well as technical challenges in maintaining road stability across the steep terrain.
Based on the anticipated difficulty and expense associated with building this feature, the shaft and tunnel
were removed from consideration.
3.6.4 Penstock Support Considerations
Any surface penstock alignment would require anchorage to maintain structural stability in the steep
terrain, and resist thrust loads generated at pipe bends. McMillen Jacobs anticipates that the penstock will
be supported by concrete pedestals at regular intervals. The pedestals would resist penstock loads by
anchorage into rock. It is anticipated that small diameter bar anchors (#8 or less) would be sufficient for
the system loads. These anchors could be installed by personnel with hand-operated or limited access
drilling equipment that could be transported by helicopter.
McMillen Jacobs recommends that anchors be required to develop their capacity within rock. The depth
of soils overlying bedrock along the alignment will be identified during the geotechnical investigation.
Anchor lengths would be sized to allow for some variability in ground conditions during construction.
3.7 Powerhouse Geotechnical Observations
3.7.1 Site Description
Three powerhouse sites were considered in the screening phase and the preferred location was selected as
shown on Figure 1-2. This elevation delineates the transition from the steep slopes southeast of the lodge
to the flats adjacent to Orca Inlet. It should be determined if maximizing generation head takes
precedence over potential disturbance, operational access and long-term maintenance for the sites
adjacent to Orca Lodge. It is anticipated that non-engineering factors may influence selection of the
preferred site.
The selected site has approximate dimensions of 150 feet (perpendicular to slope) by 200 feet (parallel to
the slope) and lies at approximately 100 feet elevation. Just beyond the bench, the ground surface drops
steeply to the existing roadway, which is immediately adjacent to tidewater. This area currently has no
developed access, but bedrock appears to be shallow, indicating that stable foundation conditions are
anticipated. The site also appears to overlap with the conceptual plans for Shepard Point road, which is
being evaluated by the Eyak Corporation. If this road is constructed, it would need to be rerouted or
excavated uphill from the proposed plant to occupy the same general location. Further studies and
coordination between CLWPP proponents and the Eyak Corporation may be required to accommodate
both features.
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3.7.2 Geologic and Geohazard Observations
Rock outcrops were identified in the vicinity of all three powerhouse sites. Shallow soil profiles are
anticipated at each site. Soils are expected to consist of colluvium and/or glacial till over bedrock in all of
the potential locations.
At the western site, no exposed rock was on the bench; however, the northern limit of the bench is
bounded by a 30-foot-tall cliff that is exposed along Orca Road. Bedrock within the bench area is
estimated to be shallower than 30 feet.
No rock exposures were observed at the other two sites, which are covered by a deep layer of forest duff;
however, the slopes immediately southeast of these locations are 45 degrees (or locally steeper),
indicating the presence of rock. The lower flats adjacent to tidewater (where the Orca Lodge and historic
cannery are located) are interpreted to be a landslide colluvium/alluvium deposit formed at the outlet of
Crater Creek. No recent signs of instability or debris flows were identified within lower reaches of Crater
Creek.
No significant geohazards were identified at the powerhouse sites during the reconnaissance.
3.7.3 Preliminary Foundation Assessment
McMillen Jacobs anticipates that the new powerhouse would be founded a minimum of 5-10 feet below
grade. Soils are expected to consist of colluvium and/or glacial till over bedrock in all of the potential
locations. Suitable bedrock is estimated to lie between 10 and 30 feet deep and no soft or unusual soil
conditions are anticipated. The site soils are anticipated to be primarily granular, and would support the
loads of the new powerhouse.
3.7.4 Access and Staging Areas
The preferred powerhouse site is located just south of the existing Orca Road. The site could be accessed
by pioneering a new road through a draw that leads up to the bench. The bench is approximately 50 to 60
feet above the lower roadway. The access road would need to be 400 to 500 feet in length to maintain
suitable grades for hauling equipment to the site. This appears to be feasible with minor cuts and fills
based on reconnaissance and survey data. This site appears to have ample area for the proposed structure.
The site may also be cleared beyond the plant limits as needed for use as a staging area for construction
materials and equipment.
3.8 Proposed Geotechnical Exploration (Future Design)
A future exploration program should be executed to determine the geotechnical characteristics of all
Project features to narrow-in on the preferred Project configuration and develop the final design. This
exploration program would be developed in a future design phase, but, at a minimum, should include:
Detailed ground survey of all Project features.
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Additional, detailed geologic mapping once the detailed alignment topography is completed. The
mapping should describe and document the dam foundation conditions, traces of mapped and
unmapped faults, penstock alignment and powerhouse sites.
Surface geophysical surveys to estimate the depth to sound rock.
Foundation exploration drilling and testing is recommended for all Project features. This drilling
and testing should include rock coring, rock sampling, strength testing and foundation
permeability testing (dam site).
The results of the investigation should be documented in a geotechnical basis report (GBR) and used to
support the design of the Project features.
3.8.1 Permitting Requirements / Lead Time
Significant lead time may be required for any potential exploration permits and subcontractor
procurement that may be required. The extent of permits will be defined prior to the design phase.
Significant lead time may also be required to procure helicopter-assisted drilling contractor services. We
suggest that this subcontractor be procured early in the design process because most qualified remote
access drillers book their Projects well in advance.
3.9 Geologic/Geotechnical Summary and Conclusions
A reconnaissance-level geotechnical site investigation was performed for the CLWPP as a part of a larger
feasibility study. The results of this investigation are as follows:
The dam site is underlain by strong basalt. No specific adverse geologic structures were identified
but subsurface investigation should be conducted to confirm this observation and provide design
criteria. The rock strength and structure appears to be adequate to support a new dam in the size
range under consideration.
The rock mass immediately below the proposed dam foundation is tight and significant seepage is
not expected for the range of reservoir pressures expected.
Faults/shear zones are present both upstream and downstream of the proposed dam site. These
zones may be present at depth below the dam foundation. Rock within these zones is expected to
be highly sheared and may provide a seepage path. If necessary, the dam foundation may be
amended with a grout curtain. The potential for reservoir rim seepage is also a concern. The
permeability of these zones will be identified during the design investigation.
Trenchless methods are feasible to install the penstock in a straight alignment for the initial 600
feet from the lake intake. Two 300-foot-long trenchless bores could be installed from a jacking
station in the Crater Creek canyon.
The presence of shallow rock is anticipated below most of the slope between Crater Lake and
tidewater elevation. No signs of large-scale instability were observed along the preliminary
alignment.
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A penstock alignment down the slope is feasible; however, the slope is steep, with typical grades
of 30 to 45 degrees, and the penstock would need to be anchored into rock to maintain stability.
The proposed powerhouse/treatment plant site appears to be underlain by rock at shallow depth
(less than 30 feet deep). No geotechnical issues were identified based on reconnaissance.
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January 2016 32 McMillen Jacobs Associates
4.0 Hydrologic Evaluation
4.1 Introduction and Purpose
Understanding the potential Project basis for all other aspects of Project
feasibility. Section 4.0 summarizes the hydrologic analysis including data sources, methods, results, and
discussion regarding alternative dam heights and potential water supply and management. This section
also documents methods used and results obtained in creating a synthetic streamflow record to assess
Three dam raise/lake tap scenarios
were also evaluated to examine how storage could be used to time both power and water supply for
critical time periods. The three scenarios were created to examine different storage opportunities. These
scenarios will likely be changed based on the results of this study and other technical information. The
synthetic record time period has been contextualized among longer-term climate records to evaluate
future climate and management options under various dam height and water supply scenarios.
4.2 Data Sources for Study
Data sources used in the development of the hydrologic and water supply analysis are presented in Table
4-1.
Table 4-1. Data Sources
Data Purpose Key Units/Comments
Mt. Eyak SnoTel Data:
Gage #1093. Time period
2005-2015; Natural
Resources Conservation
Service (NRCS).
Climate data to be
correlated with Crater
Lake streamflow to create
a synthetic record
Inches of precipitation and Snow Water
Equivalent (SWE). Temperature data in
Degrees F.
Crater Lake Outfall
streamflow data collected
by COC and CEC. Time
period: August 2014-2015.
This data represents the
raw yield from the lake
but there is only 1 year of
data.
Streamflow in cubic feet per second (cfs).
Gage has natural bedrock control and is
not vulnerable to shifts. Note that there is
also Crater Creek intake data that does not
correlate because it is based on COC
intake needs, not natural flow patterns.
Cordova Long-term Climate
Data as archived by the
Desert Research Institute.
Data from 1900-Present.
Long-term climate data to
contextualize the SnoTel
data in comparison to the
longer climate record.
Monthly and Annual Climate data, both
temperature and precipitation in degrees
and inches. http://www.wrcc.dri.edu/cgi-
bin/cliMAIN.pl?ak2177
Power and Snyder Falls
Creek streamflow data.
Collected by CEC. Various
time periods and Power
Creek has a long-term U.S.
Geological Survey (USGS)
gage that has been
discontinued.
Streamflow data with
potential to correlate with
Crater Lake outfall data;
however, relationship with
climate was stronger and
represented longer
record. This data not
used at this time.
Streamflow in cfs. Snyder Falls Creek from
2010-2015 and Power Creek 2011-2013.
Snyder Falls Creek has issues due to
avalanche and debris flow/rockfall changes
to gaging stations and flow reference
cross-sections. Power Creek only
measures a portion of watershed yield at
point of measurement and does not
overlap with Crater Lake outfall for
correlation purposes.
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Data Purpose Key Units/Comments
Edge Survey detailed dam
site topography. Data taken
October 2014.
Data to help develop
potential dam foundation
footprint, lake tap options
and downstream
penstock configuration.
North American Vertical Datum (NAVD) 88
(feet). Topographic surface and maps in
pdf and native data format. Covers the
dam site and approximately 300 feet
downstream with canyon walls along
Crater Creek. Also includes southern
saddle location at lake shore and several
potential saddle dam locations.
E-Terra satellite-based
photogrammetry, entire
Project area.
Geographic Information
System (GIS) files and
topographic surfaces.
Data also tied in with
bathymetry data and used
for bathymetric
calculations of current
water level.
NAVD 88 (feet). The satellite
photogrammetry was tied in with ground-
based control provided by Edge Surveying.
Control located near lake outlet at several
locations and at sea level near Orca
Lodge.
Crater Lake Bathymetry
provided by CEC.
Elevation data used to
determine the stage
storage curve and degree
of useable storage with
different dam height/ lake
tap scenarios
NAVD 88 (feet). Tied into survey data
using an assumed water surface elevation
of 1,514 feet and an 18-inch offset for
instrument depth during survey.
4.3 Site Description and Characteristics
This section presents key characteristics of the watershed and reservoir as shown in Table 4-2 below.
Table 4-2. Summary of Key Characteristics
Characteristic Size or Attribute Comments Documentation
Watershed area 183 acres
There is the possibility of
increasing watershed by
diverting a small
adjacent watershed into
lake basin.
delineation of
Google Earth data
using digital
elevation model
(DEM) and image.
Lake surface area at
current water level 22 acres (approximate) Will vary with water
level. delineation of
image
Lake storage at given
water levels
555 acre-feet (AF) storage
at normal lake elevation
1,514 feet. With assumed
25-foot-high high dam,
storage increases to 1345
AF at elevation 1539 feet
which is near elevation of
ridge around lake.
The elevations are for
the maximum lake tap
elevation, current water
elevation and conceptual
top of dam elevation.
GIS analysis of
combined
bathymetry and
GIS DEM data
from Edge
Maximum depth of lake 61 feet at current water
level From bathymetry
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Characteristic Size or Attribute Comments Documentation
Average Crater Creek
streamflow at lake outlet
August 2014-August
2015
2.52 cfs (1,824 AF of
annual runoff)
2014-2015 only; for
longer look see synthetic
record in Section 4.4.
Gage data
compilation by
CEC.
Watershed condition Rock, tundra, and brush in
pristine condition
This watershed has high
yield potential if
groundwater losses are
minimal.
Site visit
observations, GIS
coverages and
photos.
As shown in Table 4-2, the volume of lake storage, given Project assumptions, varies from 215 acre-feet
(AF) at 1,494 feet elevation (dead storage) to 555 AF at the current water level (350 AF available storage)
to 1,345 AF if water is held to the 1,539-foot elevation (1135 AF with a 25-foot pool raise). The Crater
Lake stage storage curve is given in Figure 4-1.
Figure 4-1. Stage Storage Curve for Crater Lake
The Crater Lake watershed area was delineated at approximately 183 acres using Google Earth as shown
in Figure 4-2 below. For the date of April 6, 2010, the lake had a surface area of 22.4 acres, which varies
naturally with changing lake surface elevation.
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Figure 4-2. Watershed Area Delineation for Crater Lake Watershed
4.4 Synthetic Hydrology Development
The purpose of this section is to present the methodology and results of the site synthetic hydrology
development by correlating the 2014-2015 outfall data at Crater Lake with SnoTel data from the Mt. Eyak
SnoTel site. This gives data for 9 full water years and one partial year. This data was evaluated by
examining the long-term climate data to better understand future water supply based on past history.
4.4.1 Development of Daily Flow Values 2005 2015
Crater Creek outlet streamflow data from August 2014 to August 2015, was artificially extended using
daily net water input values from the nearby Mount Eyak SnoTel site (NRCS, 2015). The extension of
values creates a synthetic record from October 1, 2005 to October 1, 2015.
The Mount Eyak SnoTel site (Figure 4-3) has a 10-year record beginning in September 2005 that extends
to the present day. The site is located only 2.2 miles straight-line distance from the centroid of the Crater
Lake watershed and is located on the same mountain ridge. The elevation for the SnoTel site is 1,405 feet,
which is similar in elevation to the dam site (1,514 feet) and the watershed, which varies from 1,514 feet
to approximately 2,200 feet.
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Figure 4-3. Photo of Mt. Eyak SNOTEL Site from October 2007 (NRCS, 2015)
The Mount Eyak SnoTel site has sensors that measure Snow Water Equivalent (SWE, using snow pillow
method), precipitation accumulation (with a tipping bucket), air temperature, snow depth, barometric
pressure, wind speed, and solar radiation. The data is stored in hourly and daily increments. The data of
most interest for this analysis is the precipitation accumulation and the gain and loss of SWE. As snow
accumulates, SWE builds in the snowpack and water is stored. As the snow melts, SWE is lost from the
snowpack and inputs to the watershed as runoff. Therefore, as the snowpack and SWE builds, incremental
SWE is a positive number and when it melts it is a negative number. Subtracting incremental SWE from
precipitation allows for the calculation of a net incremental water input for runoff (rain + snowmelt). This
incremental water input showed correlation and the ability to predict streamflows at the Crater Lake
outlet.
The 2014 2015 Crater Lake dataset runs from August 23, 2014 to August 27, 2015. The average
streamflow for this dataset is cubic feet per second (2.5 cfs). The range of streamflow over the outlet over
this period was 0.2 cfs to 32.1 cfs. At the Mt. Eyak SnoTel site, there was 138.5 inches of precipitation
over this same period. The precipitation corresponds to 2,112 AF of runoff if that level of precipitation
was delivered to the 183-acre watershed without losses. The runoff at the lake outlet corresponds to 1,824
AF. Therefore, in this comparison, if the gage at Mt. Eyak was accurately portraying precipitation at the
watershed, 81% of the precipitation would become runoff, while 19% was accounted for as infiltration,
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evaporation and vegetation uptake. This is consistent with a smaller watershed with limited vegetation
and groundwater losses as well as a cool and cloudy climate.
In examining runoff patterns from the lake, there appears to be a good correlation between rainfall or
snowmelt events from Mt. Eyak and the streamflow pattern at Crater Creek (Figure 4-4); however, in
looking at some of the peak events there are offsets, because the 1-day precipitation often does not
correspond well with the runoff response in that the routing may be off by a day or it takes several days to
decrease while the precipitation has zeroed out. In hydrology this is known as a lag effect. An example of
this is expressed in the spring period from May 6 to June 15, 2015 (Figure 4-5). In this period, on May
12th the precipitation zeroes out, but the streamflow takes a few days to recede.
Another example of correlation variability is the occasional incongruity between precipitation and runoff.
An example is illustrated in Figure 4-5 where the runoff peaks on June 4 but the precipitation peaks on
June 5, and the precipitation increases even though the streamflow is lowering. Even though the SnoTel
site is geographically close, isolated rainfall cells can sometimes cause variation like this within larger
storms. These types of incongruities are normal in this type of analysis, and will make precise predictions
difficult; however, for the purposes of this evaluation, McMillen Jacobs concluded that the precipitation
can reasonably simulate general seasonal and even weekly trends with water data.
Figure 4-4. Streamflow at Crater Outlet vs. Water Input at Mt. Eyak
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The chosen procedure was determined via trial and error. One key observation was that when there was
no water input at the SnoTel site over a 2-day period, there was low predicted variation around the mean
streamflow value at Crater Creek. Predicted streamflow for 2-day dry periods was 1.1 cfs from the
synthetic streamflow, while the observed gage flows ranged from 0.2 cfs minimum to 3.7 cfs maximum.
Another key observation was that if the daily input value was compared to the streamflow, a positive
correlation and predictive equation was determined as shown in Figure 4-6. The equation demonstrates
that the correlation explains over 50% of the variance, but due to issues discussed above, there was still a
significant amount of variation.
Figure 4-5. Streamflow at Crater Outlet vs. Water Input at Mt. Eyak for Specific Dates
Based on trial and error and these observations, the following procedure was created to convert
precipitation values into streamflows:
Step 1. Determine if the previous 2 days had no net water input (snow or dry condition). If so,
assign a streamflow value of 1.095 cfs.
Step 2. For all other values, use the equation from Figure 4-6 to convert daily precipitation values
to streamflows.
Step 3. Average all streamflow values and compare runoff yield to overall precipitation input.
Adjust all streamflows so the yield input will equal 81%.
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This procedure
equation. Once the raw streamflows were averaged, the overall yield was compared and adjusted
to 81%.
Figure 4-6. Relationship between Daily Precipitation and Daily Outflow from Crater Lake
4.4.2 Use of Snyder Falls Creek and Power Creek Streamflows
Snyder Falls Creek and Power Creek streamflow records were evaluated for use in record extension to
create a longer-term synthetic streamflow record, but were not used for the following reasons:
Upper and Lower Snyder Falls Creek gages: For the 2014 2015 time period where records for
both were available, the record did not correlate well, presumably due to the lake effect for the
Crater Lake outfall, as well as glacial melt effects in the Snyder Falls Creek drainage that caused
the two streams to have somewhat different runoff patterns. Also, the useable length of record for
Snyder Falls Creek was less than that of the SnoTel data.
Power Creek: Concurrent overlapping records were not available to use for correlation and record
extension. Also, the Power Creek data does not directly record total streamflow, making a runoff
per unit area difficult to calculate. The drainage is also affected by glacial melt.
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4.5 Hydrology Model Procedure Results
The results from this procedure created comparisons between observed and predicted values for the
2014 2015 time period for Crater Creek outflows. One comparison is the observed streamflow versus the
flow calculated with the procedure (Figure 4-7). There appears to be good general agreement in that flow
peaks coincide, but the variability at the ends of the flow spectrum is generally lost between the methods.
For instance, the predicted September peak in 2014 is not as high as the observed peak and often the
predicted low flows do not go as low as observed because a mean value was used for dry conditions and
the constant in the correlation equation does not allow predicted flows to be less than 1.15 cfs. While the
median values are similar, the extreme tail ends vary. The loss of variability does not impact the overall
annual mean value for a Project with a significant storage component like Crater Lake. The net effect is
that there is little impact on storage calculations.
Table 4-3 illustrates the impact on percent exceedance numbers. The major differences occur on the far
ends of exceedance. Note that 90% exceedance denotes the streamflow that is exceeded 90% of the time
and represents a smaller base flow in which the flow is only lower 10% of the time. In contrast, the 5%
exceedance represents an elevated streamflow in response to a flood event that is only exceeded 5% of the
time. Using the procedure described above to predict flow yields, there would be very few flows lower
than 1.1 cfs. To that end, the 10 30% exceedance is 1.1 cfs; however, the observed record does drop, with
the 10% exceedance being lower at 0.6 cfs.
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Figure 4-7. Observed vs. Predicted Streamflow Numbers from August 2014 2015 at Crater Lake
Outlet
Another observation is that the SWE data comes from snow pillow accumulation and the precipitation
data is accumulated via a tipping bucket. During times of snow accumulation, the tipping bucket can
under-net precipitation input
Negative net precipitation (which cannot occur) led to calculations of negative streamflow. McMillen
Jacobs elected to include the few negative values to illustrate the extent of the issue. Fortunately, this only
occurred a handful of times during the 2008, 2010, 2012, and 2015 water years. The occurrences are
isolated and have little to no effect on storage buildup and release.
Table 4-3. Percent Exceedance Values for Observed vs. Predicted Streamflow
for the August 2014-2015 Time Period at Crater Lake Outlet
Percent
Exceedance
Observed
Flow
(cfs)
Predicted
Flow
(cfs)
90% 0.6 1.1
80% 0.8 1.1
70% 1.0 1.1
60% 1.2 1.2
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Percent
Exceedance
Observed
Flow
(cfs)
Predicted
Flow
(cfs)
50% 1.4 1.5
40% 1.7 1.8
30% 2.1 2.2
20% 3.1 3.6
10% 5.4 5.9
5% 8.9 7.8
Synthetic hydrographs were created for 10 water years. The raw streamflow values were adjusted with a
factor to ensure that the yield percentage between the runoff and overall water input was 81%. Table 4-4
reports these adjustment factors.
The adjustment factor mean was 0.95, meaning that streamflows in general had to be adjusted down. The
downward adjustment ranged from 0.83 to 1.04 cfs.
One observed limitation of this simple model is that it did not retain the variability of the natural
streamflow record. While this will likely not significantly impact storage patterns, it will impact the look
and feel of the data and prevent the data from being used as an hourly operational model, which has little
significance on a storage Project. Furthermore, the simple procedure does not allow for forecasting,
although it could be done with daily precipitation values. During the design phase, it may be desirable to
create a continuous hydrologic model that can better account for soil moisture storage and snowmelt and
more precisely depict watershed behavior. The data at the SnoTel site is available as hourly data, and if
the streamflow was taken hourly this would allow for a very precisely calibrated model.
Table 4-4. Water Years Where Record Was Extended with Overall Precipitation, Yield, and the
Adjustment Factor Used to Correct Streamflow Values
Water
Year
Annual
Precipitation
(in)
Annual
Yield
(AF)
Adj.
Factor
(Dim)
2006 150.5 1859 1.00
2007 104.5 1291 0.83
2008 137.5 1708 0.96
2009 116.8 1443 0.88
2010 117.6 1453 0.87
2011 145.1 1792 0.98
2012 175.4 2167 1.04
2013 142.9 1765 0.96
2014 156.8 1937 1.02
2015 139.2 1719 0.97
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Water
Year
Annual
Precipitation
(in)
Annual
Yield
(AF)
Adj.
Factor
(Dim)
Summary
AVG 138.6 1713 0.95
Max 175.4 2167 1.04
Min 104.5 1291 0.83
4.6 Synthetic Streamflows and Storage
4.6.1 Streamflow Variability and Need for Storage
The Crater Lake system is extremely variable in terms of streamflow, even accounting for the attenuating
effect of the lake. There is only one year for which observed streamflow is available, but the degree of
variability depicted in Table 4-3 indicates that a full 40% of flows were less than 1.2 cfs and 10% of the
flows were 5 cfs or greater. The observed flow , jumping from under 1 cfs
to 5 or more cfs between single day periods (Figure 4-7). This is a normal pattern for this type of setting,
but without some form of storage, water availability would be hard to predict for energy production and
would spike from low supply to over-maximum supply.
4.6.2 Storage Configurations
The developed streamflows were combined with the stage storage curve (Figure 4-1) to examine how
different storage configurations could be managed to provide for water storage during the summer and
winter higher demand periods. As a sensitivity analysis, two dam heights were chosen based on
possibilities with the terrain. As the Project progresses the three configurations are likely to be refined. In
practical terms, the Project is likely to have its greatest value at its highest storage scenario. The
alternative configurations are as follows:
1. Proposed High Dam (Baseline) and Deep Lake Tap. This is the baseline assumption with a dam
crest spillway crest at 1539 feet and lake tap elevation at 1494 feet. This gives a usable storage of
1,129 AF. To make the dam taller would involve numerous saddle dams, so this represents a
reasonable assumption at the feasibility level.
2. Baseline Dam Height with Minor Tap Depth. This configuration has the same spillway crest
elevation at 1,539 feet with a 5-foot laketap depth at elevation 1509 feet that could be
accomplished by trenching a shallower outlet beneath the proposed dam. The usable storage with
this configuration is 872 AF. Under this assumption, there would b
storage and the lake would be 56 feet deep.
3. Lower Dam Height Option with Minor Tap Depth. This configuration has a spillway crest set to
1,530 feet in elevation with the same tap elevation as Configuration 2 at 1509 feet. This would
create 533 AF of usable storage. Residual (dead storage) is the same as Configuration 2.
A more detailed stage storage curve shows the maximum dam height in terms of the storage curve (Figure
4-8)
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Figure 4-8. Stage Storage Curve with Deep Lake Tap and Baseline Dam Elevation
The generated 10-year streamflow record was used starting each water year (October 1) at the minimal
residual storage level (215 AF). Stream flows were converted to acre-feet and accumulated or subtracted
based on inflow vs. release rates. Based on discussions with CEC and COC staff, McMillen Jacobs
tailored releases to be maximized during fish processing seasons associated with high water demands in
the late winter and summer time periods1. Water storage is accomplished during other time periods. The
releases were executed in 0.5-cfs increments based on water storage levels and the two seasonal needs.
Generally speaking, each year and each configuration have the same general pattern:
The initial fall period October 1 to January 1 is used to accumulate storage. Releases are curtailed
or are kept very minimal.
Releases begin in January and ramp up to 3 cfs to provide winter water for COC demands during
a fish processing season and extra power for winter.
In the spring (late March to June), depending on water levels, releases are minimized to store up
both water and power potential for summer demand.
1 It is important to note that this approach is different than the operational model, which used the same hydrologic input but seeks
to offset diesel consumption. Additional analysis will be required during future design phases to refine the balance between
water demand and diesel offset.
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In June, water releases are ramped to up to 5 cfs for summer demand and power needs during the
fish processing season. The releases are kept at 5 cfs or lower because of pipe size constraint
water supply lines.
In some cases, releases had to occur or were increased because storage levels were getting close to
maximum values which would initiate flow down the natural channel. In other cases, water releases were
decreased because available storage was being depleted.
4.6.3 Effects of Precipitation Patterns and Storage Capacity on Releases
The amount of water that could be stored or released is based on the precipitation input patterns over a
given year and the available storage. In a dry year like 2007, there was little difference in what could be
stored and then dispersed (Figure 4-9) because there was not enough rainfall/runoff to push the storage
volumes to maximum levels in all but Configuration 3. All three configurations were constrained in that
the full 5 cfs was not able to be released during the summer months, and during the winter months the
release was limited to 2 cfs. As can be seen, because of storage issues, Configuration 3 had to have
releases during the storage season for fear it would completely fill and waste water down the natural
channel. Because it had releases during the storage season, its release during the summer season was 0.5
cfs lower. Figure 4-10 depicts the storage volumes over the season. Note that the range of total storage
(active and dead pool) for Configuration 1 varies from 215 AF to 1,344 AF, while Configuration 2 varies
from 473 AF to 1,344 AF and Configuration 3 from 473 AF to 1,006 AF. If storage begins to approach
maximum levels, then water releases need to be ramped up. If storage is depleted to the minimum levels,
the releases need to be ramped downward. With the larger storage volumes, water can be carried over
from year to year, especially with the largest configuration. This happened during several years. This
seasonal over-storage allows for greater flexibility in water releases in the subsequent year. As stated
above, it was assumed that coming into each year the water was reset to residual storage levels.
During a wet year such as 2012, storage needed to be curtailed for the smaller Configuration 3, as well as
Configuration 2, due to concern about completely filling and spilling (Figures 4-11 and 4-12); however,
all three configurations were able to meet a full 3-cfs release during the winter period and a 5-cfs release
during the summer period. There was also significant carry-over storage, especially with Configurations 1
and 2. The carryover storage allows for considerable flexibility on supplemental release periods to
perhaps perform maintenance on other water supply facilities or supplement peaking generation needs.
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Figure 4-9. Flow Releases, 2007 Water Year (Dry Year)
(Note: Configuration 2 and 3 overlap as purple line)
Figure 4-10. Storage Pattern for 2007 Water Year (Dry Year)
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January 2016 47 McMillen Jacobs Associates
Figure 4-11. Flow Releases, 2012 Water Year (Wet Year)
(Note: Configuration 2 and 3 often overlap as purple line.)
Figure 4-12. Storage Pattern for 2012 Water Year (Wet Year)
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January 2016 48 McMillen Jacobs Associates
er the 10-year time period, Configurations 1 and 2 had identical release
records while Configuration 3 had some supplemental releases in the spring and had to be throttled back,
because it was nearing the end of its useable storage capacity (Figures 4-13 and 4-14). It should be noted
that there was moderate carryover storage for Configuration 1 (the high dam and maximum tap
configuration) and Configuration 2, but less for Configuration 3. Selecting one of the larger dam
configurations provides for considerable operational flexibility and the ability to not need to watch the
facility as closely. The larger storage configuration can also provide considerable carryover storage in
comparison, as noted above.
In understanding the role of precipitation patterns and how different storage configurations compare,
some important characteristics during the time period include (1) the ability to release 3 cfs during the
winter processing season, (2) the ability to release 5 cfs during the summer high demand and processing
season, (3) the ability to provide carryover storage during wet years, and (4)ease of management (i.e. not
needing to trigger a curtailment due to lack of storage or trigger releases because of storage becoming
full). Table 4-5 summarizes the overall characteristics for precipitation and some of the other key
characteristics described above.
From Table 4-5 it is evident that with Configuration 3, there are more adjustments in releases than for the
other two storage features. For the two higher storage capacity options, adjustments were only done in 1
out of 10 years for Configuration 2 and no years for Configuration 1. Having said this, during dry years
there were times where the releases were set out lower due to lack of storage at the onset of the season.
This occurred 5 of 10 years for winter storage and 2 of 10 years for summer processing for Configurations
1 and 2. For Configuration 3, summer processing releases had to be lowered 9 of 10 years.
Figure 4-13. Flow Releases, 2008 Water Year (Normal Year)
(Note: Configuration 2 and 3 overlap with purple line)
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January 2016 49 McMillen Jacobs Associates
Figure 4-14. Storage Pattern for 2008 Water Year (Normal Year)
Table 4-5. Precipitation and Storage Characteristics by Years and Configuration
Water
Year
Annual
Precip
(in)
Annual
Yield
(AF)
Max
SWE
(in)
Winter
Process Full
3 cfs release
(Y/N)
(Config 1,2,3)
Summer
Process Full
5 cfs release
(Y/N)
(Config 1,2,3)
Carry over
Storage?
Over 200 AF
(Y/N)
(Config 1,2,3)
In season
release
changes
needed?
(Y/N)
(Config 1,2,3)
2006 150.5 1859 19 Y,Y,Y Y,Y,N N,N,N N,N,Y
2007 104.5 1291 27.4 N,N,N N,N,N N,N,N N,N,Y
2008 137.5 1706 43.2 Y,Y,Y Y,Y,N N,N,N N,N,Y
2009 116.8 1443 29.1 N,N,N N,N,N N,N,N N,N,Y
2010 117.6 1453 42.2 N,N,N Y,Y,N N,N,N N,N,Y
2011 145.1 1792 27.5 N,N,N Y,Y,N Y,Y,N N,N,Y
2012 175.4 2167 54.3 Y,Y,Y Y,Y,Y Y,Y,Y N,Y,Y
2013 142.9 1765 48.4 N,N,N Y,Y,N N,N,N N,N,Y
2014 156.8 1937 12.3 Y,Y,Y Y,Y,N N,N,N N,Y,Y
2015 139.2 1719 10.4 Y,Y,Y Y,Y,N N,N,N N,N,Y
Total
Y/ AVG 138.6 1713 31.4 5,5,5 8,8,1 2,2,1 0,1,10
Carry over storage (values greater than 200 AF) was calculated in only 2 out of the 10 years with the
larger storage configurations and in only 1 year with Configuration 3.
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January 2016 50 McMillen Jacobs Associates
Based on ease of use (lack of in-season release changes and the ability to have full summer releases),
either of the larger configurations is preferable to the smaller configuration.
4.7 Streamflow Record in Context of Larger Climate Trends
The dataset represents 10 years of climate data correlated to 1 year of streamflow data to create a
synthetic streamflow record. In the context of overall climate, 10 years is not much time and could be
representative of an unusually wet or dry period or cold or warm period. In order to evaluate the last 10
years of climate in the context of a longer record of climate, a larger dataset was obtained from the
Western Regional Climate Center (WRCC, 2015) representing a weather station at the Cordova airport.
This record dates back to the early 1900s with 84 complete years of record and records for individual
months with 96 102 years of record. Table 4-6 lists precipitation at Cordova Airport for the longer period
of record as compared to 2006 2014, which is the bulk of the record period that is being used for this
study. In evaluating this record, the average for 2006 2014 is over 20 inches lower than normal (99.8
inches vs. 78.5 inches of precipitation for 2006 2014). There are only 2 out of the 9 years that have
precipitation greater than the long-term record average, and both are slightly over the average. The record
low precipitation occurred within the 9-year period (2007 calendar year at 43.6 inches), and this
represents the bulk of the 2007 water year used as the
inches) represents near average conditions. The year McMillen Jacobs
represented an average condition of the 10 years but a drier overall condition (2008; 75.4 inches) from the
historical record. Within the 10 years of record at the Cordova gage there was not an abnormally wet year.
The wettest year over the 2006 2014 period was 103.8 inches in 2013 at the Cordova airport weather
station.
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Table 4-6. Long-term Monthly Precipitation Records from Cordova Airport Weather Station
Month
Full
Period
Years
of
Record
Full
Period
Average
Full
Period
Max
Full
Period
Min
Average
2006-
2014
JAN 96.0 7.3 20.3 0.6 6.3
FEB 97.0 7.4 25.5 0.0 4.6
MAR 98.0 6.4 31.5 0.4 3.0
APR 98.0 6.2 37.0 0.1 3.2
MAY 102.0 6.8 20.9 0.7 4.0
JUN 98.0 5.1 14.6 0.7 3.9
JUL 101.0 6.8 20.1 1.2 5.8
AUG 100.0 10.6 32.5 2.5 9.5
SEP 100.0 15.6 49.6 4.3 14.6
OCT 99.0 15.1 45.1 2.4 11.3
NOV 97.0 9.8 32.3 0.5 6.0
DEC 99.0 9.4 30.9 0.0 6.4
Annual 84.0 99.8 201.1 43.6 78.5
Overall temperatures on a monthly or annual basis over the period were near average. The overall average
temperature was 48.6 degrees F. The temperatures over the 2006 2014 period varied from 46.2 degrees F
to 50.3 degrees F. The snowfall record was difficult to interpret due to missing values, but it appears that
snowfall was much lower over this 2006 2014 period perhaps because precipitation was down during key
months when snow accumulation normally occurs, such as November through February.
4.8 Conclusions and Recommendations
From the previous analysis the following conclusions and recommendations are given:
The correlation between precipitation data at the Mt. Eyak SnoTel site and streamflow at the
Crater Lake outlet is an adequate method to develop a synthetic hydrograph, but caution should
be used when looking at extreme high and low streamflow predicted values.
If a better understanding of extreme values is needed, a continuous watershed model is
recommended along with continued data collection of streamflow at the outlet.
The period of record used suggests a drier climate with generally less snow accumulation than the
long-term record. This could represent a change due to broader changing climate conditions and a
new normal, or could represent a cyclic trend. Based on examining longer-term climate records,
there have previously been similar dry trends.
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Storage is highly advantageous due to the variable runoff pattern at the lake outlet. Storage allows
managers to better craft releases for both water supply and power production. The two larger
storage configurations seemed to allow for proper storage and release management while the
smaller configuration had to be adjusted more often and frequently resulted in seasons where the
full target release allocation could not be sustained over the entire season.
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5.0 Water Supply and Treatment Evaluation
5.1 Water Supply Evaluation Purpose
The main purpose of this section
systems, especially as they relate to the Crater Lake/Crater Creek water supply and the potential new
CLWPP power generation and water treatment facility. The results of these findings will be integral to the
overall Project feasibility evaluation. Findings and discussion in this report are based upon the data and
information collected as discussed below.
This section also provides a concept hydraulic analysis of the new penstock system from Crater Lake to
the new Orca Water Treatment Plant (WTP). In addition, a conceptual discussion of penstock pipe system
alternatives and preliminary penstock design recommendations are provided.
5.2 Data Collection
Data sources used to prepare this section include the following:
Discussions with the COC staff on several site visits, including the latest visit conducted on
August 27, 2015 (with Fajardo, Greenwood and Stavig) as part of the Project kickoff meeting
with COC and CEC staff.
Annual water production records from the COC
Copy of design documents from GV Jones from the 2015 Long Term 2 Enhanced Surface Water
Treatment Rule (LT2ESWTR) Upgrades Project
Submittal information from Trojan UV on its new UV
sources.
Selected water distribution system maps and drawings provided by COC.
5.3 COC Historical Water Production/Demand
Prior to the recent Project site kickoff meeting, COC provided annual water production records for its
three main water sources (Meals Reservoir, Murcheson Reservoir, and Crater Lake/Crater Creek). The
Eyak Lake WTP is a lower quality surface water source that is generally held as a backup reserve water
source only and is generally used only in times of emergency outage or shortage from the three main
unfiltered water sources noted above.
The historical water production data (provided in Excel® spreadsheets) was organized by COC in terms
of monthly total volume use from each source for each given year. The monthly data was averaged over
the historical time periods as follows:
15 years of data from 2000 through 2014
5 years of recent data from 2010 through 2014
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To assess the relative contributions of each source, the historical data was tabulated, with an emphasis on
the Crater Creek contribution. Table 5-1 below provides a summary of that data for both the Crater Lake
supply alone and for the total of all unfiltered sources (Crater Creek, Meals, and Murcheson). Figure 5-1
presents a graph of the monthly average flow (in cfs) for 2010-2014 at Crater Creek and the COC system
as a whole.
Table 5-1. City of Cordova Historical Avg Water Usage from Crater Creek and Total from all
Sources
Month
Crater Creek
Hist. Avg
Water Use*
(2000-2014)
(MG)
Crater Creek
Hist. Avg
Water Use*
(2000-2014)
(cfs)
Crater Creek
Hist. Avg
Water Use*
(2010-2014)
(cfs)
Total (All
Sources).
Hist. Avg
Water Use
(2000-2014)
(MG)
Total (All
Sources).
Hist. Avg
Water Use
2000-2014)
(cfs)
Total (All
Sources).
Hist. Avg
Water Use
(2010-2014)
(cfs)
January 11.4 0.57 0.66 29.5 1.47 1.99
February 10.9 0.60 0.70 29.2 1.61 2.15
March 9.18 0.46 0.38 35.1 1.75 2.25
April 12.2 0.63 0.74 37.7 1.94 2.71
May 18.0 0.90 1.02 42.6 2.12 2.74
June 20.8 1.07 1.14 51.3 2.56 3.30
July 24.6 1.23 1.66 77.6 3.87 6.06
August 22.3 1.11 1.55 78.9 3.93 4.79
September 12.6 0.65 0.71 43.5 2.24 2.52
October 12.3 0.61 0.58 31.3 1.56 1.78
November 11.5 0.59 0.58 28.8 1.48 1.73
December 11.7 0.58 0.62 30.7 1.53 1.90
Avg. Annual
Production
204 MG
(625 acre-ft)
612 MG
(1880 acre-ft)
Max. Annual
Production
245 MG
(2014)
636 MG (2014)
* Based upon ~15 years of historical water usage collected by COC data from 2000 through 2015. Yr. 2006 data not used due to incomplete
records and issues with flow totalizers, and use of Eyak Lake source.
MG = million gallons
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Figure 5-1. Monthly Crater Creek and Total COC System Water Flows 2010-2014
5.3.1 Water Production History since 2000
The following provides a basic summary of these water production records starting in year 2000, as well
as observations provided by COC staff during discussions on water supply sources:
Total COC annual water production has increased from about 400 million gallons (MG) from
year 2000 to about 640 MG in 2014. (No data was provided that would indicate whether the water
demand increase was primarily residential or commercial [cannery expansion], although
discussions with COC staff would seem to indicate more commercial use requirements.)
The Crater Lake / Crater Creek annual water production has historically ranged from about 120
MG up to 200 MG, with a high level of 244 MG in 2013. (Eyak Lake WTP was run for the first 4
months of 2014, due to maintenance issues in other water supplies of the COC system. Thus
water production numbers from Crater Creek / Orca WTP were quite low for 2014.)
Total water demand for the entire COC system has grown steadily over the last 5 years from
about 570 MG in 2010 to about 640 MG in 2014 and 2015 (anticipated).
Since 2000, Crater Lake has historically accounted for ~28 to 38% of annual water production for
COC, with an average of about 35% of total annual water production.
The highest quality water sources for COC are the Crater Creek and Murcheson sources. (The
Crater Creek source would be expected to improve even further with construction of the CLWPP,
by preventing further entrainment of suspended solids and organic carbon as the water travels
down Crater Creek.)
0
1
2
3
4
5
6
7
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
COC Water Use 2010-2014 (cfs)
Crater Creek Hist. Avg Water Use (2010-2014, cfs)
Total (All Sources) Hist. Avg Water Use (2010-2014, cfs)
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January 2016 56 McMillen Jacobs Associates
During late August and September, Crater Creek often produces around 2 cfs (900 gallons per
minute [gpm] of water) with perhaps 100 to 200 gpm of excess water that currently seeps through
the gabion basket rock dam on Crater Creek.
During late March through May, flows in Crater Creek are generally the highest (see hydrology
section above).
The low demand period on the COC water system is the months of October through January.
5.3.2 High Demand Water Seasons for COC
COC experiences one small late winter / spring water demand peak and one distinct high-demand water
peak (summer) each year as follows:
A small water demand peak occurs from February through April due to commercial long-line
fisheries season (cod, halibut, and others) and associated ramp-up on local cannery operations and
water use.
The largest water demand peak each year occurs in June through August due to the commercial
salmon fishing season and ramp-up on local cannery operations and water use. To a much smaller
extent, summer tourism also places an increase on water demand during this same period. This
increase in total water demand can be easily seen in the last column of Table 5-1 and in Figure 5-
1.
Cannery high water demand should also correspond similarly to cannery high electricity demands during
the same periods. Thus, COC would benefit from an increase in Crater Lake water supply and CEC may
benefit from increased hydropower generation during this time period.
5.3.3 Problems with Freezing Water Sources
Both Murcheson Falls and Crater Creek currently run the risk of freezing and losing water production in
the middle of winter. This is generally true and/or possible from mid-January through mid-March. The
outlet of Crater Lake can freeze nearly solid at its current shallow depth of less than 1 foot deep. During
such cold weather times, only Meals and lower quality surface water from Eyak Lake WTP are available
for water supply to COC. This represents a critical time period for COC, as it must substitute lower
quality Eyak Lake water for higher quality Crater Lake water. As noted above, the COC typically
experiences a slight increase in water demand when the canneries demand water to support the
- A reliable, unfrozen source from
Crater Lake could provide additional benefit during this period.
5.3.4 Future Demand Growth Estimates for COC
Future water demand growth on the COC system is largely tied to the existing commercial canneries in
Cordova and their desire to increase fish processing capabilities on-shore. Recent letters and discussion
with COC staff have indicated the possibility of a desire to expand existing facilities by as much as 25%.
This represents both a water supply challenge and a potential opportunity to meet these needs with an
expanded CLWPP.
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5.4 Existing Water Transmission out Of Orca WTP
5.4.1 Existing Treated Water Pipeline from Orca WTP to Morpac
Reservoir
The existing treated water that leaves from the Crater Creek / Orca WTP currently flows by 16-inch
diameter gravity pipeline to the Morpac treated water reservoir, located some 2.6 miles in pipeline
distance to the southwest. The Morpac Reservoir has a storage capacity of 480,000 gallons and is located
just uphill from COC The reservoir has a floor elevation at 178 ft mean sea level (msl),
above Orca Bay. The tank has a total sidewall reservoir height of about 30 ft with an overflow elevation at
~207.3 feet.
The transmission pipeline that conveys water to Morpac Reservoir is a mostly 16-inch nominal diameter
ductile iron (DI) pipe. This transmission pipeline along New England Cannery Road was installed in the
ve an overall length of about 13,800 feet (2.6 miles). The entire
pipeline was purposely oversized (mostly 16-inch diameter), because its main design purpose was to
serve as chlorine contact retention volume to provide detention time for the inactivation of Giardia with
the current chlorine system.
The transmission pipeline is made up of the following segments:
The first ~600 ft leaves the existing Orca WTP as a 12-inch diameter DI pipe until it crosses the
Crater Creek culvert just south of the Orca Lodge where it changes to a 16-inch diameter pipe.
Approximately 12,600 ft of 16-inch diameter DI pipe until the pipe reaches the dedicated access
driveway leading up to Morpac Reservoir.
The last ~600 ft of pipeline prior to reaching the Morpac Reservoir inlet is a 10-inch diameter DI
pipe.
Table 4-2 below shows that flow velocities in this mostly 16-inch diameter transmission pipeline are very
low for the current water flows typically between 1.1 and 2.2 cfs (500 to 1,000 gpm). These low velocities
are consistent with the pipelines original design intent to serve as a chlorine contact chamber specifically
for Giardia inactivation.
Significance of New LT2 Upgrade Project on Existing Transmission Pipeline. It should be noted that
when UV radiation is install Project, all Giardia
inactivation will be accomplished by the new UV irradiation system. Once the UV treatment is installed,
the oversized transmission pipeline to Morpac will no longer be constrained by its need to disinfect for
Giardia, meaning that treated water flow rates through this existing 16-inch diameter line can easily be
increased from the current 2.2 cfs (1,000 gpm) maximum levels up to levels near 5 cfs (2,300 gpm).
5.5 Hydraulic Analysis of Existing Transmission Pipeline to Morpac
Reservoir
If a new CLWPP is constructed, it is very likely that the first ~600 ft of 12-inch diameter pipeline that
leaves the current Orca WTP would be eliminated, and replaced with new penstock pipeline from the
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January 2016 58 McMillen Jacobs Associates
Crater Lake supply. Also, the last ~600 ft of the existing 10-inch pipeline that feeds the Morpac Reservoir
would likely have to be either upgraded to a new 16-inch pipeline, or another parallel 10-inch diameter
pipeline would need to be installed alongside the existing 10-inch pipeline, to increase transmission
capacity in this short line. As a result, the hydraulic analysis provided in Table 5-2 effectively assumes
that all of the pipeline between the new CLWPP and the existing Morpac Reservoir would be 16-inch-
diameter DI pipe.
Table 5-2. Flow and Head Loss Est Dia Treated Water
Transmission Pipe along NE Cannery Rd to Morpac Tank Reservoir
Water
Flow Rate
(cfs)
Velocity in
Pipeline
(ft/sec)
Pipeline
Frictional
Head Loss*
(ft / 100 ft)
Total Head
Loss over
13,200 ft
(ft)
Added Pump
to overcome
Friction loss
(kW)
Daily Energy
Loss due to
Pipe Friction
(kW-hr/day)
1 0.72 0.015 2.0 0.20 4.7
2 1.4 0.055 7.3 1.47 35
3 2.2 0.12 15.8 4.78 115
4 2.9 0.19 25 10.1 243
5 3.6 0.30 40 19.7 474
6 4.3 0.42 55 33.6 806
7 5.0 0.55 73 51.6 1,240
8 5.8 0.70 93 74.7 1,790
* Assumes Hazen Williams coefficient of 130 in DI pipeline.
** Assumes overall motor and vertical turbine pump efficiency of 84%
Results. Table 5-2 provides an indication of how friction losses (i.e. headloss in the pipeline) will
increase with increase in flow rates, if CLWPP (new hydropower / UV facility and booster pump station)
is constructed. The table shows that at current pipeline flow rates in the 1 to 2 cfs range, there is virtually
no head loss in this long pipeline.
maximum flow rates out of the new CLWPP are anticipated to increase from current levels up to
potentially the 5 to 6 cfs range.
In general, small-diameter water transmission lines should be designed to limit friction loss in those pipes
to less than about 4-ft of friction loss per 1,000 ft of pipeline (or 0.4-ft per 100 ft of pipeline). For the
existing 16-inch-diameter transmission water line along NE Cannery Road, this criteria means that the
pipeline could efficiently carry future flows up to about 5.5 cfs (2,500 gpm) maximum . In McMillen
opinion, Table 5-2 shows that flows above that 5.5 cfs level maximum for this existing pipeline
will result in excessive head loss (i.e. daily energy loss) and extra pumping requirements.
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5.6 UV and Booster Pump Station Design for Crater Creek Source
5.6.1 015 / 2016 UV System Upgrade Project for Compliance with
All three of the main surface water sources for COC (i.e. Meals, Murcheson, and Crater Lake / Orca) are
presently unfiltered water supplies. The US Environmental Protection Agency (EPA) regulations
generally require that unfiltered surface water supplies receive some form of treatment to inactive
Cryptosporidium and other chlorine-resistant microorganisms. Starting in 2014, COC began the planning
and design process with GV Jones and Associates, to implement new UV irradiation technologies at each
Construction of that Project is
expected to be completed in 2016.
The UV reactors that will be used at each of the three COC water treatment sites, will all be the same
model low pressure, high output (LPHO) reactors as manufactured by Trojan UV. All reactors are the
same Trojan UV Swift SC Model D12, with each reactor containing 12 LPHO lamps and reactor
vessels with a 12-inch ANSI flange inlet and outlet. COC wisely decided to make all reactors of the
same model number and componentry in order to simplify operations and maintenance (O&M)
requirements and to allow for future interchangeability of the reactors amongst the treatment sites.
The water flow rate treatment capability of each UV reactor is dependent upon the measured UV
transmittance (UVT) of the raw water. The lower the UVT of the water, the more difficult it is for UV
radiation to penetrate the water column and disinfect against microorganisms. The design UVT plays a
very significant role in sizing UV reactors, and low UVT values can often be the limiting factor for the
design treatment capacity of a given unit. As a gross rule-of-thumb for LPHO systems, a difference in
UVT of 8% (from 80 to 88%) can often result in a doubling of the treatment capacity of a given unit.
COC along with its design engineers has designed for the following UVT values at each water source
along with the number of the Trojan UV Swift SC Model D12 reactors as indicated below:
Crater Creek Source UVT design value = 80%
(Orca WTP) UV dose = 12 millijoules per square centimeter (mJ/cm2) for a 3-log
Cryptosporidium Inactivation
Total No. of Reactors = 2 (1 Standby)
No. of Duty Reactors = 1
Treatment capacity per Model D12 reactor = 1,900 gpm (4.2 cfs) at 80% UVT
Total treatment capacity = 1,900 gpm
Murcheson Source UVT design value = 80%
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UV dose = 12 mJ/cm2 for a 3-log Cryptosporidium Inactivation
Total No. of Reactors = 2 (1 Standby)
No. of Duty Reactors = 1
Treatment capacity per Model D12 reactor = 1,600 gpm at 80% UVT
Total treatment capacity = 1,600 gpm
Meals Source UVT design value = 70%
UV dose = 12 mJ/cm2 for a 3-log Cryptosporidium Inactivation
Total No. of Reactors = 3 (1 Standby)
No. of Duty Reactors = 2
Treatment capacity per Model D12 reactor = 900 gpm at 70% UVT
Total treatment capacity = 1,800 gpm
The above data shows the treatment significance of the UVT design value. The 80% UVT values at Crater
Creek and Murcheson can treat more than twice the flow rate of water than that of the same reactor with a
70% UVT design value at the Meals site. One of the Model D12 reactors at the Orca WTP site is pre-
validated to treat up to 1,900 gpm of flow (4.2 cfs), assuming the UVT is at or above the 80% level, at
least 95% of the time.
The Trojan UV Swift SC Model D12 reactors being supplied to all three of the water supply facilities
mentioned above are designed to run on 240 / 120 VAC, single-phase, 60-Hertz (hz) power as input to
their main control panel. Each unit has a connected power load of ~ 3.3 kW. At the maximum flow above
of 1900 gpm through one reactor, the expected head loss through the reactor is only about 1.1 feet.
5.6.2 Future UV Treatment at new CLWPP Site
Given that the new Crater Lake CLWPP will have higher quality / less turbid water due to the new small
dam impoundment, it is expected that the UVT of the water should improve by 2% to 5%, meaning that
one of the Model D12 reactors should be able to treat 2,250 gpm or more (i.e up to 5 cfs). Trojan UV
could easily verify the treatment capacity of one of these units at slightly higher UVT values, up to 85%.
This means that it is highly likely that the one duty UV reactor planned for the current Orca site will be
able to be relocated to the new power plant / treatment building, and properly treat up to about 2,500
gpm (5.5 cfs) of water flow meeting the dose for 3-log Cryptosporidium inactivation. Under this case, no
new UV units would need to be purchased for the new CLWPP facility.
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The worst case scenario for providing UV treatment at the new CLWPP site would be one of the
following:
One additional Model D12 (or smaller) reactor would need to be purchased from Trojan UV, or
Assuming that the water demand requirements might drop off at the Meals source, possibly one
of the three UV reactors at Meals could be relocated to the new CLWPP site, to provide added
treatment capacity, if needed.
The configuration of the relocated UV system at the new CLWPP powerhouse would be one where the
new Pelton turbine discharges into an open tailrace wet well, which feeds the Trojan Model D12 UV
reactors under gravity flow. This is a very practical hydraulic solution, because these UV units would be
expected to have a flange to flange head loss of less than 1.5 ft at maximum flow of 5 cfs. The UV
reactors would then discharge their treated water into another wet well that would feed the booster pumps
necessary to convey water to Morpac Reservoir. (Plan and section drawings of this layout configuration
will be provided in the preliminary design report.)
5.6.3 Booster Pump Station at the New CLWPP Site
Depending upon the site selected for the new CLWPP facility, it is highly likely that this site will be
below the possible high water surface elevation of the existing Morpac Reservoir (~ elevation 206 feet
msl). For treated water to flow by gravity from the new CLWWP site to the existing Morpac Reservoir,
the new CLWPP facility would need to have a powerhouse finish floor elevation (FFE), assuming a
maximum treatment flow of 5 cfs, at or above the following:
FFE = High water surface elevation (WSEL) at Morpac + headloss through transmission piping +
~10-feet (for turbine discharge pit and headloss through UV system)
FFE = 206 feet + 40 feet + 10 feet = 256 ft msl
Given the height of this FFE and the lack of easily accessible land at this elevation around the Orca Lodge
area, it is reasonable to assume that the new CLWPP facility would include a booster pump station to
move treated water to the Morpac Reservoir site.
Configuration of Booster Pump Station. The most efficient and reliable pumps that a booster pump
station can have for this type of configuration are multi-stage, short-set column vertical turbine pumps.
These pumps can typically be designed for overall wire-to-water efficiencies of up to 86%, maximum. To
maintain simplicity of design and O&M needs on this new pump station, the first concept design should
investigate providing a simple one duty pump plus one standby pump configuration, with each pump
being driven by a variable frequency drive (VFD). Due to the small electrical grid size of the CEC
system, the booster pumps would need to be equipped with a VFD to limit the in-rush / high amperage
currents upon pump startup. (Even for standard larger utilities, it should be noted that for most pumps
larger than about 25 horsepower (HP) in size, use of a VFD to start the pump [and limit in-rush currents],
is a current standard practice with the great improvements and reduced costs in VFD technology over the
past 15 years.)
The duty pump configuration could be as follows:
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Maximum pump output = Up to ~5 cfs (2,250 gpm) at full motor speed of 1760 revolutions per
minute (rpm), corresponding to 60-Hz output from the VFD.
Minimum pump output = About 50% of maximum output or ~2.5 cfs (1,120 gpm) at half motor
speed of 880 rpms, corresponding to 30-Hz output from VFD.
The standby pump would be of identical make and model to that of the duty pump. Note that VFDs
operating on vertical turbine pumps can typically run effectively from about 30 Hz to 60 Hz. Output
frequencies of less than 30 Hz (i.e. half speed of the motor), often result in instabilities and hydraulic
performance issues for the pumps. The pumping scenario described above would mean that the minimum
future water flows from the Crater Lake supply could be as high as 2.5 cfs +/-.
Table 5-3 provides a calculation of the motor size and pump power required of the duty pump, depending
upon the working water surface elevation of the booster pump station wet well. Note that the powerhouse
turbine generator finish floor would likely be about 8 to 10 ft above the pump station wet well water
surface elevation (WSEL).
Table 5-3. Duty Pump Requirements for new Booster Pump Station at new CLWPP Facility
Pump Sta.
Wet Well
WSEL.
(ft msl)
Duty Pump
Max. Flow
(cfs)
Static Lift *
(ft)
Estimated
TDH**
(ft)
Duty Pump
Power Required
(hp)
Duty Pump
Motor Size
Required***
(hp)
50 5.0 161 207 138 150
75 5.0 136 182 121 125
100 5.0 111 157 105 125
125 5.0 86 132 88 100
150 5.0 61 107 72 75
175 5.0 36 82 55 60
200 5.0 11 57 38 40
Note: (Assumes maximum pump flow output of 5 cfs or 2,250 gpm)
*Assumes Morpac Reservoir operation water surface elevation of 206-ft msl.
** Total Dynamic Head - see Table 4-2 for added friction loss through existing transmission piping system at designated flow
rate (~40-ft headloss for 5.0 cfs) and add 6-ft headloss for pump column and discharge valving, etc.
*** Note that any motor sizes over 15 HP are almost always 3-phase motors and most typical and efficient in a 480-VAC
service, 3-phase power supply.
From a pump efficiency perspective and due to the fact that VFDs work better when the frictional head
loss is a larger percentage of the overall Total Dynamic Head (TDH) value, the optimal pump station wet
well WSEL would be for the range of about 100 ft to 200 ft msl. Higher values of the wet well WSEL
closer to 200 ft msl may provide higher overall net energy production for CEC, assuming that all the
water flows through the turbine system are treated and pumped to the COC storage facilities. This
assumption about COC water use of Crater Lake water may be true for only certain seasons of the year,
and the monthly and annual power operations modeling currently being performed as part of the Project
work will help define and clarify these assumptions about water use and net energy production by CEC
on a monthly basis, from the new Project.
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Sizing of Booster Pump Station Wet Well for Chlorine Contact Needs . The new chlorine contact
chamber for the CLWPP would be small enough that it could serve also as the wet well supplying water
to the new booster pumps. In brief summary, the new chlorine contact system would only need to be
designed to provide a 4-log virus inactivation of the unfiltered water,
The retention time for 4-log virus inactivation is only about 5% of that current retention time required of
the current system for 3-log Giardia inactivation. The new water treatment UV system would provide for
both 3-log Giardia and 4-Surface Water Treatment
Rule (SWTR) and the LT2ESWTR. (UV disinfection systems are given little credit in the LT2ESWTR
regarding their ability to inactive a wide range of viruses.) This means that chlorine would no longer need
to serve as the disinfectant to provide Giardia inactivation, as it currently does down the 2.5-mile-long,
16-inch-diameter transmission line along New England Cannery Road.
The following provides a brief overview of the disinfection requirements for unfiltered surface water
supply systems per the old SWTR and the new LT2ESWTR regulations by the EPA. Total disinfection
needs for the new CLWPP facility will be as follows, at worst case (i.e. cold) water temperatures of
presumably 1 degree celcius (C):
3-log inactivation of Cryptosporidium
3-log inactivation of Giardia
4-log inactivation of virus
The current chlorine system provides for disinfection of the last two categories (Giardia and virus) only.
Chlorine is completely ineffective in the inactivation of against Cryptosporidium. The new LT2ESWTR
rule mandates that all unfiltered surface water supply systems will need to provide some log inactivation
of Cryptosporidium to protect the health of the general public against this and other chlorine-resistant
micro-organisms. The new treatment plant, after UV is installed, will have UV radiation providing the
following full disinfection services at 0.5 degrees C:
3-log inactivation of Cryptosporidium
3-log inactivation of Giardia
0-log inactivation of virus
Note that UV is basically ineffective against virus inactivation. The overall system must provide 4-log
inactivation of virus. Therefore, the new plant will still need to provide for 4-log inactivation of virus
but zero-log inactivation against Giardia. The significance of this is that virus inactivation takes a much
lower CT value than Giardia inactivation
currently requires of the system. The values of CT for worst case cold water (0.5 degrees C) and assuming
a free chlorine concentration of 1.0 milligram per liter (mg/l) are as follows:
CT for 3-log inactivation of Giardia by free chlorine = 210 mg-min/L at pH=7.0; or 253 mg-
min/L at pH=7.5
CT for 4-log inactivation of virus by free chlorine = 12 mg-min/L at pH in range of 6.0 to 9.0
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Notice the difference in the CT values of those two above conditions between disinfecting for Giardia
and virus. Disinfecting for virus will take only about 1/20 or approximately 5% of the contact time than
the current Giardia CT system requires for chlorine from Orca WTP facility. This means the new
treatment facility will be able to achieve full disinfection against 4-log virus with free chlorine in
just 6 minutes (for a chlorine residual of 2.0 mg/l) or 12 minutes (for a chlorine residual of 1.0 mg/l)
hydraulic detention time. This low detention time requirement of between 6 to 12 minutes to achieve
full disinfection can be obtained in a simple design of the new wet well that feeds the CLWPP booster
pumps which pump fully treated water to Morpac Reservoir. A 6-minute hydraulic detention time at a
flow rate of 5 cfs, with a smart hydraulic design, represents a wet well volume of about 2,250 cubic feet
or 17,000 gallons. That volume of wet well can be achieved with a hydraulically efficient and simple
concrete wet well design that occupies a floor space of only about 12-feet by 30-feet which is reasonable.
Additionally, the same water leaving the booster water pumps will also be totally potable, and can be fed
directly to Orca Lodge without further treatment.
Water Conveyance to Morpac Reservoir and the COC Distribution System. During the fall and
winter months of October through March when total system demands are currently less than 2.5 cfs (and
assumed to be less than about 3.5 cfs in the future), it is possible that this new booster pump station could
supply all the water for the entire COC system. This statement assumes that water could be efficiently
moved from the Morpac Reservoir system toward the center of Cordova to the southwest. Further
consultation with City staff and the current distribution system network would need to be checked to
confirm the current hydraulic conveyance capacity from Morpac Reservoir to the southwestern part of the
distribution system. Such should be a straight forward hydraulic analysis to determine if any main trunk
distribution pipelines would need to be upsized.
5.7 Water Supply Evaluation Summary and Conclusions
Preliminary design steps completed to date indicate that, when considering the COC water demands and
characteristics of the current water treatment and delivery systems, the CLWPP should be designed for
operational flows in the 5-cfs range considering current and future COC water needs. The Crater Lake
raw water source represents the highest quality water source for the COC system, meaning that it requires
basically the least amount of overall treatment, including energy used for UV irradiation, as any of C
sources. This high quality water will also provide finished water with the best taste and odor
characteristics of any of the current COC water sources.
Essentially, this high quality Crater Creek source means that for most time periods, it would be in
best interest to utilize as much of the diverted water for power generation as possible. Water flows up to
5.5 to 6 cfs could effectively be conveyed from the new CLWPP to Morpac Reservoir through the
existing 16-inch-diameter transmission piping. For the distribution piping leaving Morpac Reservoir
heading back southwest back towards the city center, some additional analysis would need to be
conducted to confirm the flow capacity of that portion of the system. Preliminary information would seem
to imply that the distribution system can convey at least 4 cfs back to city center.
The main exception to this idea that COC would use all water that flows through the new CLWPP would
be during the months of October through January, when total COC water demands are relatively low at
about 2.5 cfs. COC
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may be higher to help offset current diesel consumption for electrical generation. During these months, it
may be practical to send high water flow rates for power generation purposes, with excess water
discharged to Crater Creek and Orca Bay, rather than pumping to the COC water distribution system.
More information on the energy modelling needs during this time period will be provided by the energy
operations model being conducted as part of this concept study.
Based on the discussion provided in this section and from the perspective of trying to utilize as much
Crater Lake water as possible for the COC potable water delivery system, a new turbine generator unit
with a design flow of no more than 5 cfs would be ideal for all of the following facilities:
Penstock. It appears that a nominal 16 inch-diameter penstock may be the most economical
choice, given the current design constraints, and water demand needs. A 16-inch penstock could
efficiently deliver up to 8 cfs of water flow to the new CLWPP efficiently and hold energy loss to
under 2% of total energy production. This is a lower percentage considering that most penstock /
powerhouse Projects design for the penstock to consume from 2 to 4% of the total potential
energy available. Final determination of the most cost effective penstock size can be better
estimated once the hydro-power operations and modelling work is complete.
UV System. The current planned UV system for Orca WTP would be able to support a maximum
flow rate of about 4.3 cfs for the conservative 80% UVT value currently chosen for Crater Creek.
The UV treatment capacity could increase up to 5 to 5.5 cfs, assuming the UV transmittance of
the raw water increases from the current design value of 80% (Crater Creek) to 82 to 84% (for
new Crater Lake reservoir).
Booster Pump Station. New VFD-driven vertical turbine pump operations would be ideal for
flow rates in either the 2.0 to 4.0-cfs or the 2.5 cfs to 5.0-cfs range, corresponding to the
maximum typical 2:1 turndown on these pumps. A booster pump station designed with one duty
pump plus one standby pump would be most efficient from both a capital cost and from an O&M
perspective. Adding more pumps to the pump station configuration, for a relatively small system
such as for this new Orca WTP facility, simply adds unwarranted capital cost as well as O&M
cost to the system.
Existing 16-inch Distribution Pipeline. The existing 16-inch-diameter transmission pipeline to
Morpac Reservoir also constrains effective hydraulic conveyance of treated water to between 5
and 5.5 cfs maximum.
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6.0 Generation and Operations Model
6.1 Introduction and Purpose
This section provides and discusses the high-level results of a water and power operational model and
serves as a summary only. The main purpose of this section is to document the findings of the preliminary
generation model developed for the proposed Project. The results of these findings will be integral to the
overall Project feasibility evaluation. Findings and discussion are based upon the data and information
collected as discussed below. The model output spreadsheets are charts for the various cases are presented
in Appendix A and the electronic file of the model was provided to the clients directly.
6.2 Data Collection
Data sources used to prepare this study include the following:
Discussions with COC staff on several site visits, including the latest visit conducted on August
27, 2015 (with Fajardo, Greenwood and Stavig) as part of the Project kickoff meeting with COC
and CEC staff.
Hydrology data developed for the feasibility evaluation by McMillen Jacobs.
Power and generation data provided by CEC staff for diesel generation and generation at the
existing hydroelectric Projects.
COC water supply demand requirements. This data was also used to determine the amount of
pumping that would be required.
6.3 Evaluated Project Configurations
The following sections present each of the Project configurations evaluated as part of the preliminary
generation model. The Project configurations incorporate the results of the hydrology analysis, but vary
slightly based on aesthetic concerns, as described below. Additional analysis could consider a wider range
of Project configurations. Each of the models was evaluated for the year 2012 because it was determined
that this year was most representative of an average water year. The models utilized daily parameters,
including inflow, reservoir level requirements, and diesel generation values, when determining annual
power generation and diesel generation offset.
The primary focus of the model was to maximize the amount of diesel generation offset. Many other
iterations on the model basis are possible and should be performed in future design phases. This includes
analysis with more granular hourly data to modify the estimate of diesel generation offset, assessing the
Project with a focus on water supply and expanding the model to include both wet and dry years.
6.3.1 High Dam, Low Tap Configuration
The baseline configuration assumed the highest dam possible without perimeter saddle dams. This
corresponds to a lake maximum water surface elevation of 1539.0 feet. The low tap assumes a deep water
tap within the lake at elevation 1494 feet (approximately 19 feet below natural pool elevation). This
configuration achieves the maximum usable storage of approximately 920 acre-feet and thus maximum
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Project flexibility to retain excess water during wet years, as well as maximum generation during high
diesel generation periods.
6.3.2 High Dam, Channel Release Configuration
The next configuration utilized the same high dam as the first configuration, but with an outlet at
approximately the same 1513 foot elevation as the existing Crater Lake outlet. The existing outlet
elevation was chosen to minimize the overall recreational impact associated with lowering the lake
beyond current levels. While this reduces aesthetic visual impacts to the existing lake shoreline, it lowers
the amount of usable storage within the lake to approximately 662 acre-feet. This reduces the overall
Project flexibility and could impact the ability to maximize diesel generation and storage carryover from
wet years.
6.3.3 Low Dam, Low Tap Configuration
The third configuration consisted of a low dam that results in a maximum water surface elevation of
1530.0 feet. This configuration also utilized the low tap as previously described, allowing the water
surface to be drawn down to elevation 1494 feet. This arrangement results in usable storage of
approximately 790 acre-feet. It should be noted that, with this arrangement, a large portion of the usable
storage is located below historic water surface elevations.
6.3.4 Low Dam, Channel Release Configuration
The final configuration modeled was that of a low dam with the channel release. This configuration has
the lowest amount of usable storage of approximately 533 acre-feet, almost half of the high dam, low tap
configuration. Due to the smaller amount of usable storage, this configuration has the least amount of
flexibility in Project operations and carryover storage capacity.
6.4 Analysis
The model output spreadsheets are presented in Appendix A and the model Excel electronic file was
transmitted previously to CEC and COC. The approach and key assumptions for each configuration were
similar. Each configuration was modeled to maximize diesel offset and with no net increase or decrease in
available storage at the start and end of the water year. Essentially, generation flows were released in
order to minimize diesel consumption while maintaining a minimum release for water supply. During the
months of November through April, the Project was assumed to be running continuously because diesel
appears to be constantly online during this period. During summer months when diesel is used only
intermittently, the Project is assumed to only generate when diesel is required.
All of the configurations used the 5-cfs maximum flow assumption in accordance with the COC water
system capacity limit. This dictates a 500-kW Pelton style turbine/generator system. However, if more
flexibility and peak capacity are desired, the flow capacity could be increased to roughly 8 cfs with
minimal change to the selected turbine and a slight increase in generator size. This could increase Project
flexibility to offset diesel generation but would result in conditions where water is spilled rather than
being made available to COC. The impacts on total water supply have not been assessed in detail, but the
larger storage scenarios provide more flexibility to accommodate both water and power demand.
Additional discussions on the value of water versus power will support future design scenarios.
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Unit efficiencies for the turbine generator package were based on vendor curves for the proposed
equipment. The corresponding generation from flows less than 5 cfs were also derived from these curves.
The total generation was a sum of these various flow assumptions.
To create an equal starting point for all the configurations, the lake was modeled with the same starting
water surface elevation of 1525.0 feet. This resulted in varying amounts of available storage between the
high and low dam configurations to start the water year. Net head available from generation was
determined using the lake water surface elevation minus penstock friction losses.
It was assumed that all of the configuration models must return to the same starting water surface
elevation at the end of the water year. This ensured that the model represented a water year that allowed
for sustainable and consistent operation from year to year. It should be noted that the 2012 year represents
an average year and this assumption would differ for wet or dry years.
It should also be noted that the diesel generation levels presented within the model are the daily average
values. The diesel generators may only operate for a portion of the day if a large load comes on, or one of
the other hydroelectric plants goes offline. This may overestimate the amount of diesel offset obtained by
the Project in all of the configurations. For example, if a diesel generator were to operate at high load for
only 3 hours, this would show in the daily values as a smaller load over 24 hours. The overall Project
generation is unchanged, but there would be 21 hours in which no diesel offset was actually obtained.
It was also assumed that all water delivered to the powerhouse was pumped to COC for use within the
water supply system. This pumping power was subtracted from the generation to develop net generation
for the Project. This net generation would increase if not all the water delivered to the Project was
pumped into the water supply system. Pumping power was determined assuming a 16-inch water supply
pipeline from the Project to the COC holding reservoir. An overall pumping system efficiency of 80%
was used to accommodate for pumping and transformer losses.
The model does not account for emergency or maintenance outages or power losses from distribution of
the generated power. Based on the model results, it appears that annual maintenance outages could be
performed in late May or June with minimal impact to generation or diesel offset.
6.5 Operations Modeling Results
Table 6-1 presents the total generation as well as the estimated diesel offset for each of the four Project
configurations. As previously stated, the diesel generation offset values are consistent in calculation
among the configurations, but may slightly overestimate the diesel offset amount due to actual daily
diesel generation routines. A more in-depth analysis of diesel generator run times and load efficiencies
should be performed during subsequent design phases.
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Table 6-1. Operations Modeling Hydro Generation and Diesel Offset Summary
Parameter
Project Configuration
High Dam,
Low Tap
High Dam,
Channel Release
Low Dam, Low
Tap
Low Dam,
Channel Release
Net Generation (kWh) 2,255,500 2,268,400 2,255,500 2,268,400
Diesel Offset (kWh) 2,008,100 1,745,000 2,008,100 1,745,000
While the channel release configurations may generate slightly more power over the course of the year,
the reduced flexibility of when that power is generated can be seen in the diesel offset values. This is due
to the fact that during the high demand period of the winter months, when diesel is consistently running,
the reduction in available storage does not allow the channel release alternatives to generate as much
power. Then in the summer and early fall months when Crater Creek flow is prioritized as recovered
storage, diesel or other hydropower must generate to accommodate the target water year-end water
surface elevation.
A potentially significant observation not included in these model assumptions is that the true benefits of
the high dam are not observed because the modeled year is an average precipitation year. During a wet
year the high dam could store significantly more water and allow for increased operational flexibility,
diesel generation offset, or carryover of storage to the next water year. Any remaining storage at water
year-end could also be used to supplement flow for any later dry year. These aspects should also be
evaluated in future design phases.
6.6 Operations Modeling Conclusions
Based on the preliminary results from the operations model, there a number of important observations and
recommendations related to future design efforts if the Project is determined to be feasible. These include:
It is clear that the low tap configurations allow for the most flexibility of Project operations and
therefore maximize the potential for diesel generation offset.
The current analysis prioritizes diesel generation offset. Water values should be incorporated and
additional analyses conducted to account for the value of providing supplemental water during
periods when the Eyak pumping plant is forced into service. This analysis should account for
operating expenses and deferred or avoided maintenance expenses for the pumping plant.
The true value of diesel offset should be modeled using hourly rather than daily data. The use of
daily data does not account for the daily diesel generation protocols that may spike for short
periods well in excess of the Crater Lake hydropower generation capacity. This leads to an
overestimation of diesel offset value for the Project. Additional analysis is recommended in future
design phases.
The true benefit of the high dam cannot be visualized in modeling a single average year. A
multiple-year model would provide a measure of the benefit of the high dam on varying
hydrologic cycles. The wet year could show significant improvements to diesel offset or Project
flexibility that are not captured in a single average year model. The high dam could also provide
carryover storage for subsequent dry years. Multi-year scenarios should be modeled where
assumed inflows vary from dry through wet years.
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In summary, the current analyses provide a reasonable baseline for Project feasibility. There are many
other combinations of potential Project configurations that can be modeled in future design phases.
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7.0 Conceptual Civil Design Criteria and Drawings
The conceptual design is derived from the sum of engineering studies to date. The design is conceptual in
nature as defined by the scope of work and lacking site-specific detailed geotechnical information. The
concept incorporates the results of the data review, geotechnical reconnaissance, hydrologic analysis,
water supply analysis and operations modeling. The conceptual design drawings are presented in
Appendix B. Specifications were not included at this stage of Project development.
The Project is described in terms of general design criteria at this stage. Individual Project component
criteria are summarized in the following discussions.
7.1 Preliminary Dam Design Criteria
Two separate gravity dam sections were preliminarily developed for this feasibility study. Both were
designed for the height required to accommodate the design water surface elevation for each respective
study and along the centerline of the dam at approximately Station 2+30. Both sections were designed to
minimize the amount of mass concrete needed to satisfy stress and stability (overturning and sliding)
analyses per US Army Corps of Engineers guidelines (USACE, 1995). load case, Load
Condition No. 2 (defined in Chapter 4 of the above-mentioned document) was investigated for this level
of study. Discussions with the Project geotechnical engineer regarding the available strength of the rock
foundation warranted using high-strength rock anchors in combination with the mass concrete weight of
the section to resist the potentially significant seismic forces in the Project area. The anchors could
possibly have a hold-down capacity of at least 100 kips per anchor, and these were used to assist with the
structural stress and stability.
The tallest gravity concept considered is 28-feet tall from the top of the dam at elevation 1542.0 to the
bottom of the dam at elevation 1514.0 with a cross-section area of 286 square feet (sf) and a spillway
crest at elevation 1537.0. The smaller concept crest elevation at 1533.0 ft is 19-feet tall with a maximum
cross-sectional area of 156 sf and a spillway elevation of 1530.0 ft. The stress and stability of the gravity
sections were investigated
the spillway crest, no tailwater, and full uplift along the base of the section and ice load. Both gravity
sections meet the stress and stability criteria shown in Table 7-1 per the USACE document discussed
above.
Table 7-1. Dam Design Criteria
Dam Type Design Guidance Other design factors
Concrete Gravity USACE EM 1110-2-2200 Static Water and Ice Load,
Seismic
7.2 Penstock Design
The discussion below presents the initial design concepts for the penstock between Crater Lake and the
new CLWPP powerhouse.
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7.2.1 General Discussion
The new Crater Lake to powerhouse penstock is characterized by very steep slopes with most slopes
generally ranging from 30% to 35% and several steep short cliff band sections approaching 100% (45-
degree) slope as discussed in the geotechnical section. The penstock falls nearly 1400 feet over about a
4,200-foot length, indicating an average slope on the order of 30%. The design flow rates for the new
penstock would be relatively low (anticipated to be in the 4 to 8 cfs range) indicating that the penstock
would be of small diameter (on the order of 14 to 18 inch nominal diameter).
One design approach for the small steel penstock would be to attempt to design a light-weight, low
-grade for most of
its length. Given the small diameter of the penstock, significant lengths (probably up to 50 ft in length)
with flanged end connections could be flown into place on the mountainside (or moved by high-line cable
system), with each section of pipe (including flanged ends) weighing as follows:
Worst case 18-inch nominal diameter pipe of 5/16-inch- thick steel wall, polyurethane lined and
coated, would weigh ~3,000 lbs per 40-foot-long stick.
Likely case 16-inch-diameter steel pipe constructed of 1/4-inch thick steel wall, polyurethane
lined and coated, would weigh ~2,300 lbs per 40-foot-long stick.
7.2.2 Penstock Design
Hydraulics. Preliminary hydrology and power operations studies conducted to date seem to indicate that
the new penstock should be designed for the following flow rates:
3.6 cfs corresponding to 20% exceedance level (value to be confirmed with power operations
modeling)
As a general rule in hydropower design, the primary design criteria for the penstock is the first flow value
given above for the 20% exceedance level (i.e powerhouse / water supply flows will be greater than this
value ~20% of the year or 10 weeks per year), which in this case is 3.6 cfs. The powerhouse is estimated
to operate at or under this flowrate 80% of the year. Further evaluations during design and as the
operations model may change this value, depending on the integration of both water supply and power
production priorities. The fundamental aspect at this design stage is to develop a Project configuration
that maintains as much flexibility as possible. This effectively translates to a water power Project that can
efficiently operate in the approximate 2- to 8-cfs range.
For the relatively low flow rates that are estimated for the CLWPP, the penstock outside diameter size is
in the range of 12-inch to 18-inches. Table 7-2 presents a summary of the estimated frictional head losses
and associated power generation loss (and daily energy loss) for three pipeline sizes for a range of
different anticipated flow rates. Typically, for larger flow hydropower Projects, penstock sizing is
optimized to balance the cost of the penstock production and installation with the cost of the lost revenue
resulting from energy loss due to pipe-wall hydraulic friction in the penstock. A normal rule-of-practice
for larger diameter penstocks is that friction loss should be held to about 4% of total energy production or
less. For a smaller flow rate Project such as the CLWPP, the small diameter pipelines required typically
allow for this rule to be tightened-up even further, allowing for friction head loss not to exceed 2% of
total energy production.
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Generally, it is recommended that pipeline velocities in the new CLWPP penstock be designed for
under 8 feet per second (fps) and to limit the total power generation loss to a maximum of 2.0% of
the total power being generated. This criterion is lower than what is normally used on high-head
penstock systems, but it is justified given the very small diameters of the considered penstock. Another
way to state this, is that the maximum velocity criterion is lower for small diameter penstocks (down
around 6 fps) as compared to typical velocity criteria for much larger penstocks (>30 inch) where pipeline
velocities of 7 to 10 fps are often more economical. This design phenomena occurs because the larger
penstock systems have less wall-drag effect overall in comparison to their cross-sectional area. Table 7-2
shows that for the anticipated design flow rate of 3.6 cfs (corresponding to the 20% exceedance level),
that a 16-inch-diameter penstock should be selected for design.
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Pipe Material.Given the relatively small diameters and very high hydrostatic pressures (over 600 pounds
per square inch gage [psig]) for this new penstock, it is very hard to beat the economics of lined and
coated steel pipe. Steel provides for a high strength, yet relatively light weight pipe material that can be
designed to hold up well to most external loads. Plastic pipe materials (high density polyethylene [HDPE]
and polyvinyl chloride [PVC]
internal hydrostatic pressures, nor are they desirable from the perspective of the external loads that can be
placed on the penstock (snow, small tree and limb fallings, etc). Fiberglass pipe materials and their
locking-ring coupling joint system can be investigated further during the design phase, but McMillen
Jacobs does not believe that this material will prove a more economical alternative to the option of steel
pipe with polyurethane lining and coating.
Pipe Joint Design.
simple joint connection design for the penstock pipe. Pipeline joint connections would be designed as
flange connections on the lower half of the penstock (ANSI B16.5 Class 300 flanges with an operating
working pressure over 600 psig) that were pre-welded onto each stick of pipe at the factory (i.e. the pipe
joints arrive to the Project site as already constructed flange by flange sticks). The upper half of the
penstock (where hydrostatic pressures are lower) would be either a similar factory-welded flanged
system, or a heavy restrained coupling system (Victaulic Style 232 with welded restraint rings, or equal).
Use of these joint designs would effectively eliminate all welding on the mountainside installation and
virtually eliminate the need for repairs of lining and coatings after installation. Again, the design approach
is to make field installation work as easily as possible given the steep terrain and lack of heavy
construction equipment access.
Pipe Design and Wall Thickness. Given the small diameter needs of the penstock (14 to 18 inches),
McMillen Jacobs recommends that readily available ASTM A312 / A358 steel pipe, in either Schedule 10
(generally - to 18 inches) and/or Schedule 20 (generally
size range of 12 inches to 18 inches), be allowed as a viable and inexpensive pipe choice for the penstock.
Most steel pipe manufacturers on the west coast (Northwest Pipe, Ameron, and others) generally start
their pipe fabrication work around 18 to 20 inches in diameter size as the minimum, and move up in size /
diameter from there for pipe fabrication. It would be wise to allow these pipe fabrication companies to
buy premade ASTM schedule pipe from other manufacturers and then take responsibility for welding on
required flanged ends (or welding on restraint rings as the design requires) at the factory. The factory
would also be responsible for providing hydrostatic testing of all pipe segments, and applying the lining
and coating systems as specified.
Pipe Support Design. ach for construction of the new
penstock, conceptual design analysis will focus on developing an adjustable steel pipe
support system that is easy to install, and would require little to no welding of pipe support structures in
the field. The proposed concept design is included on Sheet S-101 in Appendix B. The concept is that
given that ground conditions will be so variable and hard to accurately survey, the penstock support ears
or collars will be provided in greater quantity than that which is actually required to hold the penstock in
place. This means that some of the factory support ear / collar assemblies on the penstock will not be used
in field installation.
The concept pipe support system is envisioned to have the following features:
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The pipeline segments (30 to 45 fee
factory welded onto both sides of the pipe perhaps every 10 to 13 feet
of pipe length on every pipe segment. These ears could serve as easy anchoring points, via
bolting, to connect the pipe support systems to the penstock.
The steel pipe supports would be easily adjustable in the field, to provide up to several feet of
vertical adjustment, and some horizontal adjustment during installation.
Pipe supports would be primarily constructed of steel to maintain relatively light weight (as
compared to large concrete support block design), allowing for easier helicopter transport / or all-
terrain-vehicle (ATV) transport of materials into the penstock support locations
A simple gas or generator-powered hand-held drilling protocol would be needed for digging
through top-soil / duff and drilling perhaps 4- to 6-inch-diameter anchor holes into underlying
rock strata.
Spare Pipe Sections for Future Repairs. Given that the penstock would be above grade and exposed to
tree-fall damage and possible local snow-slide events, McMillen Jacobs assumes that CEC would have at
least three or four spare straight pipe segments (flange by flange) in its equipment storage yard as readily
available pipe segment replacements. McMillen Jacobs also assumes that designing the penstock with
perhaps no more than four or five different angle / bends on the alignment so that at least one spare of
each type of bend could also be held in storage for emergency repairs of the penstock. These segments
could be flown by helicopter into the damaged sections of the penstock to make repairs more efficient and
timely.
7.3 Powerhouse/Water Treatment Plant Design
This Project feature is conceptualized as a single on-grade pre-engineered metal building housing both the
hydroelectric and water treatment components. The hydroelectric features consist of a design flow 8 cfs
Pelton turbine package with associated controls and electrical hardware. This type of turbine is capable of
running between 2 and 8 cfs at high efficiencies to accommodate the full range of potential flows. The
building layout, turbine/generator, water treatment components and electrical transmission features are
shown in the conceptual design drawings in Appendix B. The Project electrical one-line diagram is
included in these drawings.
The water treatment plant and booster systems were designed to accommodate the existing water
distribution infrastructure in Cordova at its 5-cfs upper flow limit, while the turbine was specified for up
to 8-cfs flow. This is to accommodate the peak flow capable within the Cordova system, while also
accommodating higher flows to provide diesel offset peak generation if deemed advantageous in the
future. The plant is designed with both overflow return to Crater Creek when flows exceed the existing
distribution pipeline capacity and turbine bypass capability to continue providing water during
turbine/generator outages.
The components are arranged in series, such that generation flow is delivered to a stilling basin at the
upstream point of the water treatment system. The water flows by gravity through a settling tank, through
the UV treatment into a chlorine contact basin, then finally out to a pair of booster pumps that deliver the
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water at the correct pressure through a discharge pipeline to the existing water pipeline within New
England Cannery Road.
The electrical system is designed with a lead off the generator to switchgear cutout and a step-up
transformer to raise the generator voltage to transmission voltage for the Humpback Creek transmission
line. Station service is also provided and the system is configured to backfeed from the Humpback Creek
line to provide service during turbine/generator outage periods. The summary of the hydroelectric/water
treatment plant is presented in Table 7-3 below.
Table 7-3. Powerhouse/Treatment Plant General Design Criteria
Project Element Criteria
Building Pre-engineering metal, approximately 36-x45-foot
primary building, excluding chlorine contact basin.
Chlorine contact
Include pellet/injection equipment and contact
basin. If existing pipeline is sufficient, can
eliminate contact basin at treatment
Water treatment flow 5 cfs
Turbine type Single Nozzle Pelton
Operating head/flow (assumed) Net 1450 feet, 8 cfs flow design, 1-8 cfs
anticipated
Generator rating 900 kW-480V synchronous
Expected output 825 kW
Turbine Inlet valve Ball-type
7.4 Powerhouse/Treatment Plant Access Road
The proposed access road would exit the private road at the Orca Adventure Lodge and climb
approximately 60 feet vertically to the proposed plant location. The road is design as a balanced cut-and-
fill and would include conventional excavation and likely some short reach of drill-and-blast rock
excavation. The road is concept only at this stage, with preliminary centerline and assume configuration
and dimensions to be adjusted based on future design investigation and survey.
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8.0 Constructability, Cost Estimate and Schedule
8.1 Constructability, Cost Estimate and Schedule Introduction
The section explains the methodology and summarizes the results of McMillen Jacobs constructability,
cost estimate and schedule development for the CLWPP. The physical challenges of working on steep,
roadless areas of Alaska and other logistical aspects (transportation logistics, weather, accessibility of
construction resources) have been incorporated to develop a balanced approach to the construction based
on McMi Alaska-specific hydroelectric Project construction experience. This section is
organized into specific constructability, cost estimate and schedule sections as described below.
8.2 Constructability Review Results
8.2.1 Constructability Review Parameters
This constructability review was compiled by a McMillen Jacobs senior construction manager with
significant, recent Alaska experience. While there are numerous considerations when developing
conceptual means and methods for constructing a Project like CLWPP, the Project most significant
construction challenges include the following:
Lack of road access to Crater Lake and the penstock route for both material deliveries and
construction.
Steep mountainside terrain, which comprises the majority of the penstock route.
Cost, capacity and availability of helicopter resources large enough to support construction.
The uncertainty associated with how weather may affect construction progress.
A number of approach logic iterations were considered during this review, with a conclusion that two
basic approaches should be considered:
1. Assume maximum helicopter support for equipment and materials delivery; and
2. Assume a balance between helicopter time and innovative construction methods that would be
more economical and would have more schedule certainty.
The helicopter-heavy alternative assumed that all construction equipment and materials would be
delivered via helicopter to the dam site and penstock alignment. This approach resulted in over $1.5
million in estimated helicopter rental costs for concrete delivery only, and an unacceptable level of
schedule uncertainty associated with potential weather delays. As a result, the next step in the review
incorporated the underlying principle that helicopter reliance would be kept to a minimum.
approach entails a combination of assumed construction methods, most of which combine conventional
remote construction techniques with alternative methods from the logging and pipeline industries. The
key was to envision a combination of methods that would reduce reliance on helicopter transport and
associated variable weather-induced delays. This means that the helicopter use should be concentrated as
short bursts of Project activity that maximize productivity during available weather windows. Ultimately,
the construction of this Project must be self-sustaining and not dependent on factors that are out of the
Project
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Establishing heavy all-terrain vehicle access to the dam site would be especially beneficial to the Project.
This would allow serious consideration of alternative construction approaches and minimize the use of
helicopters. This type of access could consist of improving the existing trail to Crater Lake or establishing
logging-type skid road access, as discussed in the penstock section below.
8.2.2 Dam Site Construction Assumptions
All scenarios envision helicopter delivery of all formwork, supports and small form-handling equipment
to the dam site. The options considered for concrete procurement included the following:
1. Ready-mix supplier delivery of wet concrete to a staging point along New England Cannery
Road, delivery of the concrete by helicopter to the dam site and placement via a helicopter-
suspended concrete bucket into waiting formwork. This is the method selected for the current cost
estimate.
2. Batch plant set up at the dam site, with associated lightweight crane and delivery boom assembly,
onsite batch plant and support equipment. Initially, this would entail significantly more
equipment delivery to Crater Lake (concrete bins, pumps, aggregate mining equipment, batch
plant and material loaders), but could significantly reduce dam production concrete from
helicopter constraints. This approach should be evaluated further in detailed design, especially
with respect to availability of acceptable aggregate in the Crater Lake vicinity.
Other issues not addressed in this review include quality control requirements for remote batching and
testing, whether the batch water would need to be heated before use, any impacts to concrete production
and placement, and handling/disposal of excess or waste materials from the concrete process. These
issues should be addressed in future design and construction planning phases if an onsite batch plant
appears to be viable and more cost effective.
8.2.3 Penstock Construction Assumptions
The penstock construction will be challenging, primarily due to the steep slope and need to anchor all
supports into suitable foundation materials. The future geotechnical investigation will focus its efforts on
foundation conditions as input to design. McMillen Jacobs has developed a conceptual design for an
adjustable penstock support that can accommodate the need to adjust the fixed base support on a variable
hillside (see design drawings) as a concept to address these conditions.
The assumptions for the penstock include using logging operation equipment to construct all-terrain
equipment access to the lower portion of the penstock where slopes allow. During the site walk, several
apparent logging skid roads were observed along the alignment, and the viability of this method should be
evaluated more thoroughly during future design. The concept includes retrofitting either rubber-tired
skidders or track-mounted excavators that would allow lift and maneuvering of individual penstock
segments into place. Most of the penstock support pedestals and frames would be installed by hand
methods with hand tools, staging the tool and equipment packages along the route with a helicopter. Our
construction estimates include two 6-man crews working simultaneously along the penstock route; one
crew would excavate and construct the support structures and one crew would set the pipes in place. The
crews would then move up or down the alignment as appropriate as each support was completed.
McMillen Jacobs anticipates that crew travel would be on foot or via ATVs on newly-constructed skid
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roads adjacent to the alignment. The penstock pipe would be delivered along the alignment by sections
with the helicopter, then lifted and fixed to the supports by labor crews using the excavator or skidder. For
the steepest sections of penstock, alternative heavy equipment could be employed including Spyder-like
excavators or cranes that are capable of climbing on slopes as steep as 100%.
8.2.4 Powerhouse/Treatment Plant and Access Road Assumptions
It is anticipated that the powerhouse/treatment plant (plant) and plant access road would be constructed by
conventional construction methods. The powerhouse/treatment plant is conceptually located on a natural
topographic bench at approximately elevation 100 feet (as shown on the design drawings). This bench is
accessible off the Orca Lodge Road near its intersection with New England Cannery Road via an
approximately 400-foot-long access road. The access road and plant pad are conceptually envisioned as
balanced cut-and-fill features. There would be some drill-and-blast excavation along the access road and
minimal rock excavation for the plant footprint. Once the access and rough grading was accomplished, it
is anticipated that the remaining plant construction would be less constrained by weather conditions.
8.3 Cost Estimate
8.3.1 Crater Lake Estimate Approach
The cost estimate was developed
managers using the conceptual design drawings developed by the engineering group. The conceptual
design drawings are included in Appendix B. Details from similar Projects and historical unit cost data
that took into consideration the location and site-specific conditions of this Project were also utilized when
developing the cost estimate. Preliminary estimates of quantities, crews, and equipment were developed to
support the estimate preparation using prevailing wage rates. These unit costs were then adjusted for the
CLWPP location, site logistical challenges, and other factors specific to the work on this Project. More
specifically, the access challenges of constructing the dam and penstock were incorporated into the
estimate. With the remote location of the dam and penstock, a large helicopter was factored into the costs
to provide staging of materials and concrete delivery to the dam site.
Furthermore, given the Project location, it is anticipated that weather delays could represent additional
downtime for crews and equipment working on the Project, resulting in elevated Project costs. A
significant amount of materials would require barge transport to Cordova, and these costs have been
incorporated. Material costs for much of the work were obtained through Alaska Project experience of
similar size and complexity. With an unknown amount of dewatering required by the Project, an
allowance was given for dewatering efforts in the cost estimate.
At this stage of the design development, adequate detail was not available to obtain advanced quantity
takeoffs of specific design elements. Similarly, insufficient data was available to obtain detailed estimates
from material and equipment vendors for Project components such as the water treatment plant, vertical
pumps, penstock pipe, instrument power requirements and related equipment. For these features,
estimates developed for similar Projects that were in the advanced stages of design or construction were
used to support the cost estimate preparation.
turbine/generator package was also part of the current estimate and is included as Appendix C.
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The construction cost data presented is not intended to represent the lowest cost for completing the work.
Instead, the costs represent the range of costs that would result from responsible bids received from
qualified contractors. A conceptual engineering level estimate has an expected accuracy of -30/+50
percent in accordance with the Association for Advancement of Cost Engineering (AACE) Level 4
classification. This range allows for unknowns to be accounted for at this stage of the design
development. As the design is advanced and more details are developed, the estimating precision would
be expected to increase with a corresponding decrease in estimating contingency applied to the estimate.
The description of the Class 4 estimate from the AACE guidance is presented in Table 8-1 below.
Table 8-1. AACE Class 4 Estimate Description
CLASS 4 ESTIMATE
Description:
Class 4 estimates are generally prepared based
on limited information and subsequently have
fairly wide accuracy ranges. They are typically
used for Project screening, determination of
feasibility, concept evaluation, and preliminary
budget approval. Typically, engineering is from
1% to 15% complete, and would comprise at a
minimum the following: plant capacity, block
schematics, indicated layout, process flow
diagrams (PFDs) for main process systems, and
preliminary engineered process and utility
equipment lists.
Level of Project Definition Required:
1% to 15% of full Project definition.
End Usage:
Class 4 estimates are prepared for a number of
purposes, such as but not limited to, detailed
strategic planning, business development, Project
screening at more developed stages, alternative
scheme analysis, confirmation of economic
and/or technical feasibility, and preliminary
budget approval or approval to proceed to next
stage.
Estimating Methods Used:
Class 4 estimates virtually always use stochastic
estimating methods such as equipment factors,
Lang factors, Hand factors, Chilton factors,
Peters-Timmerhaus factors, Guthrie factors, the
Miller method, gross unit costs/ratios, and other
parametric and modeling techniques.
Expected Accuracy Range:
Typical accuracy ranges for Class 4 estimates
are -15% to-30% on the low side, and +20% to
+50% on the high side, depending on the
technological complexity of the Project,
appropriate reference information, and the
inclusion of an appropriate contingency
determination. Ranges could exceed those
shown in unusual circumstances.
Effort to Prepare (for US$20MM Project):
Typically, as little as 20 hours or less to perhaps
more than 300 hours, depending on the Project
and the estimating methodology used.
ANSI Standard Reference Z94.2-1989 Name:
Budget estimate (typically -15% to + 30%).
Alternate Estimate Names, Terms,
Expressions, Synonyms:
Screening, top-down, feasibility, authorization,
factored, pre-design, pre-study.
The estimate includes future planning, design and permitting support costs, but does not include Project
8.3.2 Cost Estimate Results
The CLWPP cost estimate is structured with a base Project and two optional approaches. The base Project
includes the following features:
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A concrete gravity dam with a crest elevation at 1,542 feet and spillway elevation of 1,539 feet.
A shallow cut-and-cover trench approach to a lake tap at approximately elevation 1,490 feet.
A surface penstock from the downstream side of the dam to the powerhouse/water treatment plant
at approximately elevation 100 feet.
A combined hydroelectric and water treatment plant consisting of an engineered building,
subgrade structural concrete foundation and associated interconnections with existing water and
power infrastructure along New England Cannery Road.
A 400-foot-long powerhouse access road connecting near the Orca Adventure Lodge.
The two optional configurations relate to the lake tap/upstream conveyance and the dam height. Based on
early discussions and constructability concerns associated with the narrow slot canyon directly
downstream of the dam, a dual-heading microtunnel approximately 600 feet in total length was
considered as an alternative to a cut-and-cover penstock lake tap and dam penetration. Based on
preliminary hydrology studies, an alternative lower dam was also considered with a crest elevation of
1,533 feet and spillway sill elevation at 1,530 feet. These options were termed the microtunnel option and
the low dam option for the estimate. Table 8-2 presents the conceptual construction cost estimate for the
CLWPP.
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8.4 Conceptual Project Schedule
The conceptual Project schedule is based on the specific work breakdown structure (WBS) developed
during the cost estimate effort. A McMillen Jacobs senior construction manager developed the activities
list from the WBS and compiled the Project schedule in Primavera P6 scheduling software. The logic and
means and methods determined during the constructability review were incorporated into the construction
approach and cost estimate, providing a seamless integration between the planning, estimating and
scheduling.
The schedule attempts to account for construction aspects that are generally unique to coastal Alaska,
which lacks any form of interconnected roadway system. These aspects include the cost and general
availability of helicopter construction support, barge transport of major components from Seattle, weather
delay potential associated with fog, rain and snow in the Cordova area, and the assumption of a limited
local material and personnel resource pool.
The schedule assumes that final design, permitting and Project financing arrangements will take place
during the latter half of 2016 and that early procurement of long lead items could be started in mid-2016
by the owner. The assumed duration of the construction phase from contractor mobilization through
Project completion is planned as a 2-year effort in 2017 and 2018. The schedule is based on calendar days
and a 6-day work week once onsite activity begins. The detailed schedule assumptions include the
following:
Final design contract in place by April 2016
Design Notice to Proceed in May 2016
Early owner procurement for long lead items such as turbine/generator, overhead crane and
penstock pipe by scheduled start in October 2016
Final design and all agency permitting/negotiation complete by February 2017
Final agency approvals by early March 2017
Construction Notice to Proceed by end of March 2017
Construction mobilization starts May 1, 2017
Construction broken into two seasons, with early progress on all Project elements leading to a
logical seasonal shutdown in November 2017
Completion of plant commissioning in October 2018
Contractor demobilization end of November 2018
Project complete December 2018
The conceptual Project roll-up schedule in P6 format is presented as Figure 8-1.
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8.5 Constructability, Cost and Schedule Conclusions and
Recommendations
A summary of the overall conclusions from the constructability, cost estimate and schedule development
indicates that the Project can be constructed and suggests some ways to reduce cost and schedule
uncertainty. Relevant observations and recommendations include the following:
The constructability review indicates that the Project can be constructed with a combination of
conventional techniques and innovative application of logging techniques adapted for this Project.
The use of helicopter assistance on the Project should be minimized to reduce overall
construction cost and schedule uncertainty related to weather and helicopter availability.
The potential for use of an onsite batch plant should be evaluated further. This option should be
considered in detail if heavy ATV access could be established to the dam site for equipment and
material deliveries.
The dam was configured with the maximum height that would not require perimeter wing dikes
within the Crater Lake basin. An alternative dam height is also presented for cost comparison.
Additional studies during design could include alternatives to reduce total concrete volume, such
as variable height crest gates (e.g. Obermeyer gates).
Two methods for constructing the laketap and initial conveyance facility are included in this
review. The base approach applied in the cost estimate consists of an excavated cut-and-cover
pipeline approach that passes beneath the dam, transitioning to a surface penstock downstream.
The option includes a microtunnel from the lake to a point approximately 600 feet downstream.
This option appears to be significantly more expensive than the conventional pipeline/penstock
configuration.
The cost estimate identifies the range of expected construction costs and shows the additional
planning, permitting, geotechnical investigation and final design efforts as separate line items.
The conceptual schedule indicates that the anticipated timeline for final design and permitting
would be complete by March 2017. The construction is planned over a 2-year period, through fall
2018, with a shutdown period during winter 2017 2018. The Project commissioning and Project
completion are planned for November 2018.
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9.0 Permitting Scope and Planning
The purpose of this section is to summarize the permitting considerations, required approvals, and
expected responsibilities of the proponents if the CLWPP moves forward. Potential permitting impacts to
cost or schedule are also described.
9.1 Permitting Considerations
Clay Kopli , has been the primary lead and point of contact for external permitting
discussions and Project
following is a planning-level summary of the key points related to permitting the CLWPP.
Federal Energy Regulatory Commission (FERC). FERC will have no involvement because the Project
has been determined to be non-jurisdictional (Order on 1/22/2015). The requirements of the Federal
Power Act do not apply to this Project and neither a license nor an exemption would be required.
U.S. Army Corps of Engineers (USACE). Once FERC determined the Project to be non-jurisdictional,
the USACE became the lead federal agency for purposes of environmental review. However, as a result
of consultation with the USACE Alaska Division, it has been suggested that a Nationwide Permit (NWP)
#17 (Hydropower) may apply to this Project. The primary benefit is that no new environmental document
would be required, eliminating the need for a comprehensive field study program. This has both cost and
schedule benefits. The permit application would be able to rely on existing information, e.g. the Shepard
Point Road Environmental Impact Statement (EIS) and other sources. If USACE determines that NWP
#17 is not applicable to the Project, environmental baseline studies would be required and, although not
anticipated to be extensive, would require a baseline year and probable second monitoring year before the
Project could move forward.
State of Alaska (as landowner). COC has indicated that it administers State-owned lands that may be
occupied by the proposed powerhouse. COC has also discussed the concept of acquiring those lands
(potentially via exchange). In any case, it appears that COC would be responsible for permitting use of
these State-owned proposed Project lands.
Permits Coordination. Project Management & Permitting (OPMP)
role as permitting coordinator is to ensure that complex Projects move forward in a coordinated manner
with minimum permitting effort duplication. The CLWPP, with its dual purpose of hydropower and water
supply, can benefit from this additional support coordination. CEC has initiated discussions with the
OPMP and has received an initial quote for its services. Because the Section 404 permit process requires
coordination with other agencies, USACE is also interested in working with the OPMP process.
The permitting focus areas are summarized in Table 9-1 below. The table is based on current
understanding of proposed Project lands and recent agency planning-level discussions.
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Table 9-1. Summary of Permitting Requirements
9.2 Permitting Conclusions and Recommendations
The overall conclusion of the permit planning effort is that no constraints were identified to advancing the
Project, should it prove feasible. Indeed, the single-most challenging hurdle from a cost and schedule
perspective, i.e. the requirement to obtain a FERC l
Project Phase Agency/Org Permit/Approval
Investigation
Permits
Alaska Department of
Natural Resources
(ADNR)
Permit for wetlands assessment on state lands
ADNR Permit for geotechnical assessment on state lands
ADNR Permit(s) for equipment installation (e.g. stream
gage, thermistor, fish weir, etc)
ADNR State Historic
Preservation Office
(SHPO)
Approval of Area of Project Effects (also The Eyak
Corporation [TEC] or Native Village of Eyak [NVE]
consultation)
Landowners (COC,
Eyak, State, Orca
Lodge)
Access approval (for studies and equipment
installation)
Project
Development
Approvals
USACE Section 404 Nationwide Permit #17
(Hydropower)
Alaska Department of
Environmental
Conservation (ADEC)
Section 401 Certificate of reasonable assurance or
Waiver
ADEC Approval to Construct, followed by Approval to
Operate (Drinking Water System)
ADNR Water Right
ADNR Dam Safety Certificate of approval
SHPO Cultural Resources Inventory and concurrence
Alaska Department of
Transportation and
Public Facilities
(DOT&PF)
Right-of-Way Permit (for Access Road Approach)
Landowners Lease/easement approvals (City administers State
lands in the proposed powerhouse vicinity)
Alaska State Fire
Fire, Life and Safety Permit
Construction-
Specific
Permits
ADEC Construction General Permit (NOI and SWPPP)
ADNR Temporary Water Use Permit
US Forest Service
(USFS)
Special Use Authorization (if USFS lands will be
accessed for construction)
City of Cordova Approvals and building permits:
Conditional use
Grading, clearing, excavation & fill
Building permit
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involvement. Furthermore, indications that USACE Section 404 permitting may be accomplished under a
Nationwide Permit would further reduce schedule impacts and may remove the need to conduct natural
resource studies.
Additional relevant permitting insights and recommendations include the following:
The Project has the potential to provide mitigation beyond diesel offset and reliable drinking
water supply by way of preventing ice damming in Crater Lake and significant periodic flooding
at the Orca Adventure Lodge.
Only wetlands that are proposed to be filled, not the entire Project, are jurisdictional to USACE.
Therefore, for permitting purposes, the footprint of the Project would be limited to the dam,
footprints.
It is expected that fish considerations will be relatively minor for several reasons: 1) Crater Creek
ters Catalog (AWC), 2) Rainbow
Trout in Crater Lake are a non-native population stocked by the Alaska Department of Fish and
Game (ADF&G), and 3) it is understood the USACE authority does not extend to the inundation
area.
Given the anticipated schedule for Project development, McMillen Jacobs recommend that
proponents initiate permitting efforts and information gathering (e.g. wetlands mapping) in
spring, 2016 to be complete by January 2017.
As recommended by the USACE, submit an application for Nationwide Permit #17
(Hydropower) prior to the expiration and renewal of this permit in 2017, to avoid future
additional provisions that may be placed on this permit. Additionally, the current standard
conditions for NWP #17 should be reviewed.
Final recommendation to be made by COC on the need for and a schedule to transfer State-owned
lands to COC in the vicinity of the proposed powerhouse.
Apply for any permits required for geotechnical investigations and other design activities upon
Notice to Proceed, assuming these permits would be needed for field work in summer, 2016.
Confirmation is needed from The Eyak Corporation (TEC) that a Lands Permit would be
Review Shepherd Point Road EIS for applicability to the lower Project (powerhouse and access
road) area, particularly the SHPO approved historical/cultural review.
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10.0 Feasibility-Level Cost/Benefit Analysis
10.1 Introduction
The proposed Project potentially responds to strategic objectives of both COC and CEC. COC seeks to
increase the availability and continuity of water supply from Crater Creek (a more desirable source and
providing for expanded economic activity), while CEC identifies an opportunity for displacement of
diesel generation with additional hydroelectric resources. The Project conceptual design includes features
that directly address the joint objectives, which is reflected in the capital cost estimates. The effective
accomplishment of the joint objectives is described through the operational modeling of the proposed
reservoir alternatives and the powerhouse/pumping system. The cost/benefit analysis considers the design
features incorporated in Project capital cost estimates and compares that cost over time with the benefits
to be gained through the installation and operation of the system.
10.1.1 Power Supply Considerations
Additional renewable energy supply to offset summertime peaking and wintertime continuous diesel load
was the primary design consideration for CEC. Currently, existing hydroelectric resources provide over
70% of the system annual generation requirements, and nearly all required energy during the summer
months except July and August fish processing peak demands. The investigation into Crater Lake
considered the opportunity to further reduce the amount of off-peak diesel generation based on the
availability of water and the addition of storage capacity. The available hydraulic head and turbine
generator were sized to provide the most advantageous use of the hydrological conditions. Diesel
generation, now between 20% and 30% of the power supply, amounts to around 8 million kilowatt hours
per year (kWh/yr) and any renewable opportunities are sought to reduce the reliance on fossil fuels.
The operational model for the Crater Lake system included four configuration options for the reservoir
based on dam height and tap location to determine the amount of energy to be produced. All of the
configurations were modeled in similar fashion to obtain the greatest amount of diesel offset while
maintaining a minimum release for water supply. With the maximum water flow constraint of 5 cfs for
the COC system, the maximum annual energy for diesel offset after accounting for pumping load and
transformer losses was between 1.7 and 2 million kWh per year, or about 25% of the annual diesel
requirement. The potential 8-cfs flow generation was not considered at this time.
The savings over time from a reduction in consumption of fossil fuel for generation are, of course, the
primary benefit of an additional renewable resource, and a benefit that is shared by all residents and
commercial enterprises of the CEC.
10.1.2 Water Supply Considerations
The design of the Crater Lake reservoir, penstock, powerhouse and pumping system considered current
and anticipated additional water consumption rates, as well as current water system configuration and
limitations. With no anticipated volumetric upgrades for the system, the design characteristics for the
Project were based upon currently planned upgrades for water treatment and the potential to limit more
expensive existing system operation at the Eyak filtration plant. From discussions with COC, and the
perspective of trying to utilize as much Crater Lake water as possible for the COC potable water delivery
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system, a new turbine generator that comfortably accommodates 5 cfs would be best suited for the
facilities. The water treatment components of the conceptual design include a 16-inch-diameter penstock,
the current planned UV system, the booster pump station with 2 VFD pumps (duty and standby) and the
existing 16-inch-diameter transmission pipeline to Morpac Reservoir.
The operational model evaluated the system design for water supply purposes under the assumption that
all water delivered to the powerhouse was treated and pumped to COC for use within the water supply
system. Pumping requirements were determined assuming a 16-inch water supply pipeline from the
Project to the COC holding reservoir.
The economic benefits to be gained from the new facilities under the current operational model would
primarily be the opportunity to increase water supply for commercial purposes (seafood processing),
enhancing revenues for COC through greater shared fish tax collections and some modest, but additional,
revenues from water sales. A potential benefit would be the displacement of $26,000 per year in
operational expenses associated with the Eyak Lake water pumping and filtration supplemental supply, as
well as a potential future deferral of a replacement filtration plant.
10.2 Modeling Approach
To date, the design and operational analysis of the Project has provided initial evidence of accomplishing
the primary objectives of COC and CEC added water for COC and additional renewable energy for
CEC. Using the information provided on the preliminary cost estimates and the energy production
operations model, an evaluation may be made of the initial screening-level feasibility by comparing the
Project costs and the expected identified benefits. Annual costs of owning and operating the facility,
shared between CEC and COC, are compared with the annual savings associated with the reduced
reliance on diesel generation for CEC, and improved quality and availability of COC-provided water for
the citizens and commercial enterprises in Cordova. The stream of costs and stream of benefits are
compared on a net present value basis, which recognizes the significance of the time value of money
expended and monetary savings.
An early expectation for the feasibility study was preparation of the cost/benefit results in such a format
as to support an application to the State of Alaska for economic support through the Renewable Energy
Fund (REF) administered by the Alaska Energy Authority (AEA). Upon review of the development of the
Project characteristics, design and operational modeling, it appeared that a viable screening model for the
initial feasibility assessment could be based upon the model suggested by AEA for the fund application.
The cost/benefit assessment was therefore prepared using considerations of the REV9 model (for
applications under Round 9 of the funding opportunity) and the fuel price Projections supplied and
supported for a screening evaluation by AEA. The primary difference in the cost/benefit analysis
approach herein, though, is that CEC and COC are modeled together and the results reflect the allocation
of costs and benefits to each. The AEA REF evaluation includes only the expected net community
benefits that are ancillary to the benefits gained by the electric utility. Since the Project is uniquely
designed to provide joint operations and joint benefits, the costs and benefits are jointly determined.
In addition, the high level reconnaissance model evaluates the economics of the Project for each of the
proposed design options. It has been noted in the operations model section that the preliminary
expectation of the primary benefit of the Project will be the diesel generation offset. The cost/benefit
model, however, considers diesel generation offset as well as the effects of the additional water supply
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source to meet the expectation of additional land-based seafood processing, to the extent of as much as
20% over current water use levels. Also, based on information provided by COC, the potential exists for
additional shared tax revenue from the seafood processers. Such tax revenue increases would be
proportional to the growth in seafood processing.
10.3 Primary Assumptions of the Crater Lake Cost/Benefit Evaluation
Model
10.3.1 Crater Lake Capital Cost Assumptions
The construction cost of the base Project as reported in Section 8 is allocated between CEC and COC in
Table 10-1, as follows:
Table 10-1. CLWPP Cost Allocation Summary
Crater Lake Cost Components
$ 2015 CEC
Share % COC
Share %
Direct Construction Costs:
Powerhouse/Treatment Plant
Turbine and Generators 500,000
Overhead Crane 150,000
Water Treatment Plant 400,000
Vertical Turbine Booster Pumps 100,000
Buildings, Electrical, I&C, etc. 932,300 932,300
Subtotal Powerhouse 3,014,600 1,582,300 52 1,432,300 48
Switchyard 250,000 250,000
Intertie Electrical 75,000 75,000
Intertie - Water 80,000 80,000
Other Direct Costs 8,924,650 4,462,325 4,462,325
Subtotal Direct Costs: 12,344,250 6,369,625 5,974,625
Markup, Plng., Permits, Engineering: 4,962,446 2,580,472 2,381,974
Grand Total: 17,306,696* 8,950,097 52 8,356,599 48
* Median Project cost estimate including future
engineering design, permitting and
coordination.
The changes associated with Option 1 (microtunnel laketap), increasing the total cost to $19.3 million,
and for Option 2 (lower dam height), decreasing the cost to $13.1 million, are directly associated with the
Other Direct Costs, and therefore present no change to the allocation of capital costs between CEC and
COC. The evaluation model does, however, include provision for revised cost allocations for sensitivity
analysis or changed construction requirements that may be determined from further investigations.
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The Project is assumed for the preliminary analysis to be on-line in November, 2018. The installed cost at
or other administrative expenses, as these have not yet been defined.
10.3.2 Crater Lake Energy Production Assumptions
The preliminary evaluation assumes that the energy produced in 2018 and in subsequent years is based on
the 2010-hydrologic evaluation and
incorporated within the generation operations model. The amount of annual energy, estimated on the
assumption of maximum diesel displacement and the COC water system maximum capacity of 5 cfs, is
2,008,696 kWh. The energy delivered to the electric system is net of pumping load for delivery to the
COC distribution system. Because the operation model was limited to the average water year, each year
of the analysis assumes a similar level of diesel displacement. Further analysis will be required to
estimate the impact of alternative annual water conditions, and the effect of hourly dispatch, as described
in the operations modeling section. The evaluation model will accommodate a variety of annual or hourly
dispatch results and varying energy production.
Crater Lake is estimated for evaluation purposes to operate for at least 50 years, and provides energy
annually in the amount Projected. No estimate has been provided of expected forced outage or
maintenance periods of reduced generation, nor of periodic equipment replacements. By the same token,
no estimate is made of possible deferral of diesel generation overhauls, deferrals, or retirements. It can be
expected that some portion of the generation facilities, both hydro and diesel, will be subject to such costs
or savings.
so diesel requirements will continue in the absence of other energy sources. Diesel requirements could
also be reduced by significant loss of load or additional useable water inflows at existing hydroelectric
facilities.
An important consideration for this stage of the Crater Lake evaluation is that load growth of the CEC
electric system is not taken into account in the determination of energy production. A more robust
dispatch model, however, may reflect the capability to provide more energy over time through enhanced
hydroelectric/thermal optimization, particularly if the COC increases the distribution system capacity to
accommodate flows in excess of 5 cfs.
10.3.3 Crater Lake Operations and Maintenance Cost Assumptions
Detailed assessments of the operations and maintenance costs of the new facility (civil structures and
mechanical equipment) have not yet been prepared. In the absence of more specific information, the
Alaska Energy Authority, Renewable Energy Fund application standard O&M expectation for renewable
energy plants is 1% of the capital costs. This expectation was used consistently throughout the economic
evaluation. Plant O&M costs are shared on a basis equivalent to the allocated capital costs because a
large component of the Crater Lake costs are allocated to COC for water availability, treatment and
delivery. Plant O&M costs are expected for analysis purposes to increase at the rate of general inflation,
absent any information to the contrary.
10.3.4 CEC Diesel Production Efficiency Assumptions
The impact of diesel displacement by Crater Lake is the reduction in fuel requirements, and therefore
potential savings in fuel costs. Historical data from CEC was analyzed for estimates of the production
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efficiency of the CEC diesel generation facilities, as was the most recent Power Cost Equalization (PCE)
data from the State of Alaska. The 2014 PCE data indicates an average efficiency for the CEC diesel
equipment for fiscal year 2014 of 13.3 kWh/gallon. But, the most recent calculated data provided by CEC
indicated 13.48 kWh/gallon over the 2011-2012 average water year of October through September. For
analysis purposes, with the expectation that additional hydroelectric resources will provide greater
operating flexibility and resultant greater efficiency, it is assumed that 13.48 kWh/gallon will prevail.
AEA, however, estimates efficiency for renewable energy funding analysis on the basis of size of
machine for an expected level of 14.5 kWh/gallon. The Crater Lake Evaluation Model accommodates
alternative estimates of the production efficiency, allowing for testing of the impact of improvements.
Future work with a more detailed dispatch model, such as hourly dispatch and diesel/hydro optimization
may reveal further potential gains in efficiency that can be examined for additional cost savings.
10.3.5 Cost of Diesel Fuel Assumptions
AEA annually publishes the expected fuel costs for use in evaluating renewable energy Projects. The fuel
prices are developed from a number of sources and carefully researched and prepared models for regional
deliveries, timing of lifts, and an assortment of factors. The published prices are used by AEA in the
renewable energy fund evaluation models and have become the in-state standard for analysis of renewable
energy Projects. That is, no general inflation is
assumed, and the rate of change in the fuel prices is a result of supply and availability conditions. The
AEA evaluation system estimates the impact of renewables in equivalent fashion, assuming no general
inflation.
The AEA range of fuel costs over the operating period proposed for Crater Lake begins at $3.26 per
gallon, specific to the Cordova region, rising to $5.41 by 2040, the 23rd operating year of the Project, after
which it is held constant in real terms. For sensitivity purposes, an inflation adjustment is included in the
Crater Lake Evaluation Model to take into account the impact of general inflation on various cost
components, including fuel. For estimates of cost/benefit under conditions of general inflation, the fuel
prices are increased at an equivalent percentage as other variable costs. In that case, fuel prices would
range from $3.36 to $5.57. It was not assumed for this model that the fuel prices would be subject to the
compounding effects of inflation, but the model can accommodate a range of expectations in fuel prices.
As fuel prices increase, of course, the benefits of a renewable energy resource increase, and by a rather
dramatic amount. A modest expectation of fuel price increase is, therefore, a conservative estimate of
benefits.
10.3.6 Seafood Processing Additional Growth Scenario
A goal of Cordova and of other municipalities in the Prince William Sound region is to improve regional
economics through, among other things, expanded harvesting and processing of seafood, including
expanded production into the shoulder periods around the summertime peak. The COC Public Works
enterprise representatives (and CEC staff) have reported that landed seafood processing in Cordova has
been constrained by the availability of water, which supported COC investigation of the Crater Lake
development opportunity. While processing could increase by about 1-2% per year under current
conditions, the Project provides an additional volume of spring and summertime water supply that could
be available to processors. This added source would provide support for even further processing activity,
in addition to obtaining an improvement in water quality compared to other current water supply sources
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The estimates provided have suggested that water requirements for the existing seafood processors could
increase seafood production by as much as 20% over a multiple-year expansion period. For evaluation
purposes, the Project is assumed to provide for such an expansion of processing without additional
investment in the water supply distribution system of Cordova. The growth in processing for purposes of
evaluation is expected to develop over time, at the rate of about 5% per year beginning at the start of
Project operation in 2018. The incremental impact is an increase in water system revenues.
Data provided by COC indicated that the most recent 3-year usage of water by the five major seafood
processors averaged 187,705,809 gallons per calendar year. A 20% increase would be 225,246,970
gallons, and at the current fee for water use ($1.60/1000 gal.), water sales revenues would increase by
$60,066 per year. Because the growth in processing would take time, it is assumed that incremental water
revenues grow at 5% per year. Thus, in year 1, incremental revenues would be $15,016, and in year 2
would be $30,033. By year 4 (2021) the entire revenue increment would be achieved. That increment
would be subject to increases with inflation, if COC were to adjust water rates on a continuing basis.
10.3.7 Shared Seafood Taxes Additional Revenue Potential
Seafood taxes are assessed by the State of Alaska on seafood gathering and processing. A portion of those
seafood processing taxes collected by the State are distributed to the municipalities (or other organized
locations) in which the activity occurs. COC has reported that shared seafood taxes have grown by an
average of 9% over the last several years, and by 2014, the taxes distributed to COC had reached a level
of $1,661,223.
A growth in seafood processing would potentially increase the share of seafood processing taxes
distributed to the Municipality of Cordova in proportion to the growth in processing. The increase would
be expected to grow at the same rate as the processing activity, or about 5% per year upon initiation of
Crater Lake water availability. In 2018, the incremental increase in fish tax distribution would be about
$66,876, and by 2021, the amount would be $267,506. The fish tax would be subject to inflationary
adjustments over time, but since the tax includes product valuation as well as volume of activity, it is
assumed for analysis purposes that changes over time would be slightly less than the rate of general
inflation.
10.3.8 Reduced Requirement for Eyak Pumping and Filtration Costs
An additional consideration of COC public works is the potential for displacement of the supplemental
pumping and filtration processes at the Eyak Lake facility. It was reported that COC annually requires
about 10 days of pumping at a cost of $26,000 per year for 10 million gallons, particularly required during
the early spring period when there are critical limitations from other sources. The additional water supply
and the operational flexibility of the Project is expected to allow the Eyak facility to be effectively placed
in standby mode, reducing that operating cost. The cost/benefit evaluation of the Project thus includes a
potential savings of $26,000 per year (2015$), beginning at the time the Project goes into operation in
2018. Those savings would be expected to increase with inflation, as a result of the age of the equipment
and the characteristics of the system. A potential deferred, or avoided, replacement of the Eyak pumping
and treatment plant (at a cost of $15 million, 20 years from now) could be considered as a benefit of the
Project, but is deemed speculative for evaluation purposes.
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10.4 Results of the Crater Lake Feasibility Cost/Benefit Analysis
Two cases were evaluated for Crater Lake to gain an understanding of the feasibility of the Project and
identify the potential benefits of continued investigation of construction options and operations. The
Crater Lake Evaluation Model was developed to provide a structured approach to the cost/benefit
analysis. Two cases were evaluated for the initial feasibility analysis. Additional cases may be examined
upon request for alternative economic assumptions or additional savings opportunities from availability of
energy or water from the Project. The detailed cost/benefit model results are provided in Appendix D and
software files for the model were provided to CEC and COC as part of the report deliverable.
10.4.1 Case 1 Modified AEA
The first case evaluated uses an approach similar to Alaska Energy Authority Renewable Energy Program
application method (Table 10-2), but with a couple of modifications. AEA assumes that capital
expenditures in the years prior to operation produce negative benefits that is, the capital expenditures
reduce the stream of future benefits of the Project. In practice, however, for electric utilities the costs of a
Project are not included in rates and charges until complete and placed in operation. Thus, in the Crater
Lake Evaluation Model, the annual costs of the Project are based on capital recovery over the term of
financing. The Crater Lake Evaluation Model assumes capital cost recovery and cost savings begin in the
same year. Also, the AEA method treats community benefits as a separate category of cost savings, and
because Crater Lake is conceptually a joint product resource, the evaluation model identifies the benefits
and costs on the basis of each beneficial service provided by the Project.
The Case 1 assumptions (Figure 10-1) treat all other conditions in a manner similar to the AEA evaluation
approach.
Figure 10-1. Case 1 Assumptions
Table 10-2. Modified AEA Cost/Benefit Summary
Modified AEA
General Inflation 0.0%
Discount Rate 3.0%
Fish Tax Escalator 0.0%
CEC Project Share 52%
CEC Fuel Efficiency, kWh/gal.14.5
CEC Load Growth 0.0%
Both CEC & COC:
% Financed 100%
Interest Rate 3.0%
Term of Note, Yrs. 30
CASE NAME:
Assumptions:
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10.4.2 Case 2 Inflation Adjusted Method
An alternative evaluation of the base Project and Options 1 & 2 (Table 10-3) adds inflation on certain
components fuel, O&M, water and tax revenue, etc., and assumes the CEC historical diesel generation
efficiency. Case 2 assumptions are shown in Figure 10-2 and include:
Figure 10-2. Case 2 Assumptions
CEC NPV CEC NPV CEC B/C COC NPV COC NPV COC B/C
Benefit $ Cost $ Ratio Benefit $ Cost $ Ratio
15,353 11,315 1.36 8,629 10,445 0.83
15,353 12,910 1.19 8,629 11,917 0.72
15,353 8,837 1.74 8,629 8,158 1.06
Crater Lake
Base Project
Option 1
Option 2
Modified AEA
Crater Lake Preliminary Economic Feasibility - CEC and COC ($000)
Inflation Adjusted
General Inflation 3.0%
Discount Rate 3.0%
Fish Tax Escalator 2.0%
CEC Project Share 52%
CEC Fuel Efficiency, kWh/gal.13.48
CEC Load Growth 0.0%
Both CEC & COC:
% Financed 100%
Interest Rate 3.0%
Term of Note, Yrs. 30
CASE NAME:
Assumptions:
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Table 10-3. Inflation Adjusted Cost/Benefit Summary
10.5 Conclusions and Recommendations
A preliminary cost-benefit model was developed for the CLWPP based on technical engineering studies
provided as part of the overall feasibility evaluation. The model was developed to compare the expected
joint cost of ownership and operation of the facility by CEC and COC with the benefits likely to be
gained from installation and operation of the Project over a 50-year period. The Crater Lake Evaluation
Model provides the following preliminary economic feasibility conclusions:
The CLWPP has the potential to provide potentially significant benefits to both the electric and
water supply infrastructure within Cordova
These potential benefits were assessed through a cost-benefit model that considers the major
factors associated with ownership and operation of the facility, using information gained from the
engineering studies, historical system operations, and reasonable expectations for the future.
The cost-benefit model provides for analysis of economic feasibility with consideration of the
approach and assumption guidelines of AEA in support of renewable energy funding
opportunities in the State of Alaska. The Crater Lake Evaluation Model assessed the costs and
benefits of the base Project and Options 1 and 2 under two sets of assumptions. The first set, Case
1, estimates costs and benefits using an approach essentially equivalent to that of AEA. The
second, Case 2, estimates costs and benefits under the condition of assumed inflation in certain
cost and benefit components.
The results of the preliminary feasibility analysis indicate the following:
CLWWP appears to be economically feasible for CEC under the design considerations and
operational characteristics of the base Project, and design Options 1 and 2.
CLWWP appears to be marginally economically feasible for COC in the absence of
inflationary impacts on revenues and taxes, but will be economically feasible if revenues and
tax receipts increase nominally (at the rate of inflation) over time.
CEC NPV CEC NPV CEC B/C COC NPV COC NPV COC B/C
Benefit $ Cost $ Ratio Benefit $ Cost $ Ratio
17,010 13,368 1.27 13,498 12,340 1.09
17,010 15,253 1.12 13,498 14,080 0.96
17,010 10,441 1.63 13,498 9,638 1.40
Crater Lake
Base Project
Option 1
Option 2
Inflation Adjusted
Crater Lake Preliminary Economic Feasibility - CEC and COC ($000)
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For both CEC and COC, Option 2, the low dam configuration, provides the most benefit
during the average precipitation year and is economically feasible with and without inflation
impacts on certain economic factors.
Additional considerations in reviewing and considering the preliminary feasibility results include:
The allocation of ownership and operating costs between CEC and COC significantly affects
the economic feasibility for COC. Alterations in the design stage of the Project may shift
Project costs to CEC, increasing the viability of the Project for water service.
The economics of CLWPP for COC are driven by the assumptions of additional water
revenues and economic activity in seafood processing. Assignment of other values to the
Project by COC e.g., improved water quality, continuity of supply or other demonstrable
gains to the community as a whole will reduce the feasibility dependence of the seafood
processing assumptions for the benefits to COC of the Project.
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11.0 Summary and Conclusions
This report presents the result of a feasibility level analysis and conceptual design for the CLWPPP. The
analyses include:
Existing data review and compilation
Geologic and geotechnical reconnaissance
Hydrologic evaluation
Water supply and treatment evaluation
Generation and operations model
Conceptual civil design criteria and drawings
Permitting scope and planning
Feasibility-level cost/benefit analysis
The results of these efforts represent a feasibility-level assessment only to support whether or not to
continue Project evaluations, evaluate further or move forward with the Project. These preliminary
analyses indicate that:
The Project appears to be constructible from a geotechnical perspective.
The hydrologic resource at Crater Lake/Crater Creek is underutilized and appears to support the
concept of a storage Project.
The potential hydroelectric benefit may offset up to 25% of CEC diesel consumption.
Crater Lake would provide high quality water supply and a more firm and reliable water supply
resource for COC.
The COC could incorporate planned UV treatment upgrades within a new CLWPP.
The civil design for CLWPP is relatively straightforward and conventional.
The Project appears to be constructible from a construction perspective, but will face the
challenges of Alaska construction including steep, roadless access and reliance on helicopter
material deliveries.
The Project cost estimate provides a range of estimated costs from $9.1 million to $28.9 million,
depending on configuration and level of estimate sophistication at the conceptual stage. The
median cost for the preferred alternative is $17.1 million.
The Project is envisioned as a 3-year development effort, with the first year dedicated to design
and permitting and the remaining 2 years for construction.
It is anticipated that the permitting effort would be simplified through FERC non-jurisdiction,
land ownership and administrative control and the assumption of interpretation by USACE as a
Nationwide Permit #17 eligible Project.
The Project cost/benefit analysis shows the Project as having a net benefit to CEC in all assumed
Project configurations, while within the range of slightly negative to slightly positive net benefit
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to COC, assuming a 52% to 48% equity sharing agreement, respectively. Future discussions
toward an agreement between CEC and COC may alter this shared cost/benefit.
The overall results of the feasibility assessment appear to be favorable.
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12.0 References
ctric
Hydro-
CEC (Cordova Electric Cooperative, Inc.). 2015. Humpback Creek, Power Creek and Crater Lake
hydrologic data, various. Source data provided by CEC in spreadsheet form, not publicized.
CEC. http://cordovaelectric.com/ (accessed for electric rate information).
COC (City of Cordova). http://www.cityofcordova.net/ (accessed for water rate information).
Edge Surveys. 2014. Ground-based topographic mapping in the vicinity of Crater Lake outlet, source
files provided by CEC to McMillen Jacobs Associates.
E-Terra. 2014. Satellite based photogrammetry for the Crater Lake area, native source files provided by
CEC to McMillen Jacobs Associates.
International Code Council, Inc., 2012. 2012 International Building Code.
-
only provided by CEC, revised 2/22/60.
NRCS (Natural Resources Conservation Service). 2015. Website data download, Alaska (YST) SNOTEL
Site Mt. Eyak - NRCS National Water and Climate Center - Provisional Data - subject to revision as
of Tue Jul 28 10:07:56 PDT 2015.
December 18, 2008.
Stevens, D.S.P., Campbell, K.M., Reger, R.D., and Smith, R.L., 2003, Survey of geology, geologic
materials, and geologic hazards in proposed access corridors in the Cordova Quadrangle, Alaska:
Alaska Division of Geological & Geophysical Surveys Miscellaneous Publication 64, 5 sheets, scale
1:250,000. doi:10.14509/3263http://dggs.alaska.gov/ (various reconnaissance level mineral resource
assessments).
USACE (U.S. Army Corps of Engineers). 1982. Cordova Power Supply Interim Feasibility Assessment
(APA), Coordination Act Report draft report by Stone & Webster, submitted to Alaska District,
Anchorage. June 1982.
USACE. 1995. EM 1110-2-2200, Gravity Dam Design (30 June 1995).
Wesson, R.L., Boyd, O.S., Mueller, C.S., Bufe, C.G., Frankel, A.D., and Peterson, M.D. 2007. Revision
of Time-Independent Probabilistic Seismic Hazard Maps for Alaska, USGS Open File Report 2007-
1043.
Winkler, G.R., and Plafker, George 1993. Geologic map of the Cordova and Middleton Island
quadrangles, Southern Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map
1984, 1 sheet, scale 1:250,000.
WRCC (Western Regional Climate Center). 2015. Data sets for Cordova FAA Airport, records from
1090-2014 accessed at http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ak2177.
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
January 2016 McMillen Jacobs Associates
USACE, 1982. Cordova Power Supply Interim Feasibility Assessment (APA), Coordination Act Report
draft report by Stone & Webster, submitted to Alaska District, Anchorage, June.
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January 2016 McMillen Jacobs Associates
Appendix A
Operations Modeling Charts
(electronic model file delivered to client)
0%10%20%30%40%50%60%70%80%90%100%0.0100.0200.0300.0400.0500.0600.0700.0800.09/24/2011 10/24/2011 11/23/2011 12/23/2011 1/22/2012 2/21/2012 3/22/2012 4/21/2012 5/21/2012 6/20/2012 7/20/2012 8/19/2012 9/18/2012Diesel Generation % of TotalAvail. Storage (AF)DateAvailable Storage for GenerationHigh Dam, Low TapHigh Dam, Channel ReleaseMedium Dam, Channel ReleaseLow Dam, Low TapDiesel PercentageAvail Storage Chart
0500100015002000250030000.050.0100.0150.0200.0250.0300.0350.0400.0450.09/24/2011 10/24/2011 11/23/2011 12/23/2011 1/22/2012 2/21/2012 3/22/2012 4/21/2012 5/21/2012 6/20/2012 7/20/2012 8/19/2012 9/18/2012Disel Generation (kW)Power Generation (kW)DateNet Power GenerationHigh Dam, Low TapHigh Dam, Channel ReleaseMedium Dam, Channel ReleaseLow Dam, Low TapExist Diesel Generation
0500100015002000250030009/24/2011 10/24/2011 11/23/2011 12/23/2011 1/22/2012 2/21/2012 3/22/2012 4/21/2012 5/21/2012 6/20/2012 7/20/2012 8/19/2012 9/18/2012Power Generation (kW)DateDiesel Generation with Various Project Configurations (average flow year only) ExistingHigh Dam, Low TapHigh Dam, Medium ReleaseMedium Dam, Medium ReleaseLow Dam, Low Tap
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
January 2016 McMillen Jacobs Associates
Appendix B
Conceptual Design Drawings
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
January 2016 McMillen Jacobs Associates
Appendix C
Canyon Hydro Budget Estimate Turbine Generator
November 17, 2015
Kelly Tilford
McMillen Jacobs Associates
tilford@mcmjac.com
208-985-1522
Dear Mr. Tilford,
Thank you for the design flow update on the Cordova, AK project. Canyon Hydro specializes in manufacturing
Pelton turbines and providing complete powerhouse equipment packages for the conditions at this site. We
are pleased to offer our continued assistance as the project moves forward.
Canyon Hydro has been building high quality turbine systems in the USA for 39 years. From day one, we have
remained committed to three guiding principles:
1. Efficiency:Efficiency has undergone continual refinement over the years, and we believe our turbines
match or exceed the efficiency of any other turbine manufacturer. Our entire staff recognizes the critical
nature of the hydraulic design resulting in the best possible performance.
2. Durability:We recognize that a turbine system must run continuously for years at a time. For this reason,
we use only the highest quality alloys, bearings, and controls.
3. Customer Support:We are often told our customer support is the best in the business. We work closely
with you throughout the process, and if an outage should occur, system recovery becomes our highest
priority.
We understand this site offers a net head of 1450 feet and design flow rate of 8.0 cfs. For these conditions we
recommend an equipment package based on a Canyon Hydro single nozzle horizontal Pelton turbine. Our
equipment package includes: 12" ball type turbine inlet valve with gear operator, 12” 45 degree elbow, Canyon
Hydro custom Pelton turbine with hydraulic actuation, 900kW-480VAC synchronous generator, hydraulic power
unit, controls and switchgear for islanded system operation. Based on the site conditions above expected
system output will be 825 kW.
Budget estimate for the equipment package described………………………………………….$460,000.00
Normal Terms 10% to begin final design
30% to begin construction following final design approval
25% mid-project due upon approval of runner material at Canyon Hydro
25% payment upon notice of readiness to ship
10% payment on successful start up or 120 days from notice of readiness,
whichever is first
Normal Delivery 6 months following design approval and receipt of scheduled payments
The equipment package offered will be custom designed to meet the particular requirements of the Cordova
site and project. As the project progresses and requirements are defined, we will be pleased to refine our
estimate or offer a firm quotation. Budget estimates are offered for planning purposes only but are typically
within 10% of an actual quotation for the same site conditions and scope of supply.
I look forward to discussing this project with you further and offer my assistance as questions arise or
additional project information becomes available.
Sincerely,
Eric Melander
Crater Lake Water & Power Project Feasibility/Conceptual Design Report
January 2016 McMillen Jacobs Associates
Appendix D
Cost/Benefit Model Spreadsheets
(electronic model file delivered to client)
General Information: Fixed Inputs:Cost of the Project, 2015$Term of Borrowing, 30 yrs. (CEC and COC are financed similarly)Project Service Life, 50 yrs.Annual Electric GenerationReal Diesel Fuel Prices (from AEA REF9 Application)Annual O&M -- % of capital cost (from AEA REF9 Application)Available User Inputs on Assumptions and Results Sheet: Cell ColorCase Identfication: E-5 General InflationE-7Discount RateE-8Fish Tax EscalatorE-9CEC Project ShareE-10CEC Fuel EfficiencyE-11CEC Load GrowthE-12% FinancedE-14Interest RateE-15Summary Results: Scenario Results for each Project Configuration are provided as inputs are modified, on the Assumptions and Results SheetOutputs:Scenario Outputs are detailed on Sheets: Base Project, Option 1 and Option 2Energy & Resource Economics January 15, 2016CRATER LAKE HYDROELECTRIC PROJECT: ECONOMIC EVALUATION MODELThis model estimates the benefits and costs to Cordova Electric Cooperative and the City of Cordova of ownership and operation of the proposed Carter Lake Hydroelectric Project. Various assumptions may be made to test the impact of variables upon the economics of the project. Assumption will carry through for each proposed project configuration: Base Project, Option 1 and Option 2. All available variables are input on the Assumptions and Results sheet.
Modified AEAGeneral Inflation 0.0%Discount Rate3.0%Fish Tax Escalator 0.0%CEC NPV CEC NPV CEC B/C COC NPV COC NPV COC B/CCEC Project Share 52%Benefit $ Cost $ Ratio Benefit $ Cost $ RatioCEC Fuel Efficiency, kWh/gal. 14.5CEC Load Growth 0.0%15,353 11,3151.368,62910,4450.83Both CEC & COC:% Financed 100.0%15,353 12,9101.198,62911,9170.72Interest Rate 3.0%Term of Note, Yrs. (fixed) 3015,353 8,8371.748,6298,1581.06Cordova Electric Cooperative, Inc. & City of Cordova Public Works (Water)CRATER LAKE HYDROELECTRIC PROJECT: PRELIMINARY ECONOMIC EVALUATIONCrater Lake Base ProjectOption 1Option 2Modified AEACASE NAME:Assumptions:Crater Lake Preliminary Economic Feasibility - CEC and COC ($000)