HomeMy WebLinkAboutCommunity of Elfin Cove Hydroelectric Project Feasibility Study - Jun 2011 - REF Grant 2195343CROOKED CREEK AND JIM S LAKE
HYDROELECTRIC FEASIBILITY STUDY
FINAL REPORT
J UNE 2011
Prepared For
NON PROFIT COMMUNITY OF ELFIN COVE
P.O.BOX 1
ELFIN COVE,ALASKA 99825
Prepared by
POLARCONSULT ALASKA,INC.
1503WEST 33RD AVENUE,SUITE 310
ANCHORAGE,ALASKA 99503
THIS PROJECT WAS FINANCED BY THE DENALI
COMMISSION AND ITS PARTNERS, THE ALASKA ENERGY
AUTHORITY AND THE ELFIN COVE UTILITY COMMISSION.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report i
EXECUTIVE SUMMARY
In 2008, the Denali Commission awarded the Non Profit Community of Elfin Cove (Elfin Cove)
grant funds for study of available hydroelectric resources to reduce electricity costs. In 2009,
Elfin Cove retained Polarconsult Alaska, Inc. to complete a feasibility study of a hydro project
on Crooked Creek and Jims Lake. This report presents the feasibility of a project utilizing these
water resources.
The recommended hydroelectric project at the Crooked Creek and Jims Lake site is feasible,
and will supply 99% of Elfin Coves current annual electrical load. The project will provide the
highest percentage of projected future electrical demand while maintaining an acceptable
benefit cost ratio. The project is estimated to lower the cost of electricity up to 81%, depending
on project financing, construction costs, and excess energy utilization.
The recommended project consists of two hydroelectric systems with a total capacity of 160
kilowatts (kW). The upper systemdiverts up to five cubic feet per second (cfs) of water from
Crooked Creek to Jims Lake where it is run through a 35 kW power recovery turbine. The
lower systemdiverts up to seven cfs of water from Jims Lake to a 125 kW turbine located at
tidewater. The siphon intake at Jims Lake provides the lower system with 32 acre feet of
storage, allowing this system to supply the utilitys electrical loads through most peak load
episodes and during short dry spells. The upper system includes 1,450 feet of 12 inch penstock
and the lower system includes 1,800 feet of 14 inch penstock. The project also includes 7,300 feet
of power line, 12,200 feet of communications, and 8,700 feet of access trails.
Summary of Project Features and Capacity
The recommended projects estimated cost is $1.85 million 2011 dollars. The project will reduce
utility fuel usage by 28,500 gallons annually, reducing annual utility fuel costs by $114,000
(based on a fuel cost of $4.00 per gallon). The recommended project also provides 241,600
kilowatt hours (kWh) of excess electric energy that can be used for interruptible loads such as
space and water heating. Fully utilized, this excess energy can displace an additional 6,800
gallons of heating oil, reducing community heating oil expenditures by $27,200 annually.
An analysis of the recommended hydro project compared with diesel power generation under a
200% load growth scenario was performed. The analysis indicates the recommended project
Item Project Features
Upper System Lower System
Project Design Flow (cfs) 5 7
Gross and Net Head (feet) 137 / 124 305 / 286
Penstock Length and Diameter 1,450 feet / 12 inch 1,800 feet / of 14 inch
Storage Volume (acre feet) 0 32
Turbine Type Reaction Impulse
Installed Hydroelectric Capacity (kW) 35 kW 125 kW
TOTAL PROJECT CAPACITY 160 kW
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report ii
would reduce future power plant fuel usage by 42,600 gallons annually, reducing utility fuel
costs by $170,400 (based on a fuel cost of $4.00 per gallon). Annual excess energy output under
this growth scenario displaces an additional 1,600 gallons of heating oil, reducing community
heating expenditures by $6,400 annually.
At an installed cost of $1.85 million, the recommended project has a direct benefit cost ratio of
1.15 compared to continued reliance on diesel fuel for electric generation. If the significant
amount of excess energy generated by the project is put to beneficial use, the projects benefit
cost ratio increases to 1.44.Under the 200% load growth scenario, these benefit cost ratios
increase to 1.7 and 1.8, respectively.
Summary of Project Economics and Performance
Item Recommended Project at
Existing Utility Load
Estimated Installed Cost (Design, Permitting, Construction) $1.85M
Annual Utility Electric Load (kWh) 359,000
Annual Diesel Fired Energy Displaced (kWh)
(Percent of annual electric load supplied by hydro)
356,100
(99%)
Annual Diesel Fuel Displaced (gallons) 28,500
Net Annual Utility Savings $17,900
Annual Net Excess Energy Produced (kWh) 241,600
Benefit Cost Ratio (without use of excess energy) 1.15
Benefit Cost Ratio (with use of excess energy for heating) 1.44
Range of Utility Rates with Project $0.10 to $0.51 per kWh
The utilitys electric rates with the project are estimated at $0.10 to $0.51 per kWh under the no
growth scenario, and $0.15 to $0.34 per kWh under the load growth scenario. The range of rates
under each scenario reflects a range of construction costs and grant and financing options. For
comparison, electricity rates in Elfin Cove have ranged from $0.52 to $0.58 per kWh since 2007.
This project will provide Elfin Cove with lower and more stable long term utility rates.
Continued development of this project is warranted. Under favorable permitting and financing
conditions the project can be built and commissioned in 2013. The following actions are
recommended to advance this project.
(1)Initiate the permitting process for the recommended project.
(2)Complete designs documents for the recommended project. This should include:
(a) A load study to characterize summer time loads in Elfin Cove to confirm that the
recommended 125 kW capacity of the lower system is appropriate to meet summer
time demand;
(b) A plan to utilize the excess energy generated by the project, establishing the value of
this energy; and,
(c) Design documents for construction of the project.
(3)Continue collecting hydrology data at Crooked Creek and Jims Lake.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report iii
TABLE OF CONTENTS
ACRONYMS AND TERMINOLOGY................................................................................................................VI
1.0 INTRODUCTION.......................................................................................................................................1
1.1 PROJECT AUTHORIZATION AND PURPOSE ................................................................................................1
1.2 SUMMARY OF FINDINGS.............................................................................................................................1
1.3 PROJECT EVALUATION PROCESS ...............................................................................................................2
1.4 CURRENT AND PREVIOUS STUDIES ............................................................................................................3
2.0 COMMUNITY PROFILE...........................................................................................................................6
2.1 COMMUNITY OVERVIEW............................................................................................................................6
2.2 EXISTING ENERGY SYSTEM.........................................................................................................................6
3.0 RECOMMENDED PROJECT..................................................................................................................13
3.1 RESOURCE DESCRIPTION .........................................................................................................................13
3.2 OVERVIEW OF RECOMMENDED PROJECT ................................................................................................13
3.3 ESTIMATED ENERGY GENERATION .........................................................................................................15
3.4 DESCRIPTION OF COMMON PROJECT FEATURES .....................................................................................16
3.5 DESCRIPTION OF UPPER SYSTEM .............................................................................................................17
3.6 DESCRIPTION OF LOWER SYSTEM ............................................................................................................18
4.0 ECONOMIC ANALYSIS.........................................................................................................................20
4.1 PROJECT SIZING ANALYSIS ......................................................................................................................22
4.2 SENSITIVITY ANALYSIS.............................................................................................................................22
5.0 CONCLUSIONS AND RECOMMENDATIONS ...............................................................................24
5.1 DEVELOPMENT PLAN &SCHEDULE ........................................................................................................25
APPENDICES
APPENDIX A MAPS AND FIGURES
APPENDIX B PHOTOGRAPHS
APPENDIX C HYDROLOGY DATA
C.1 Available Hydrology Data
C.2 Jims Lake Bathymetry
C.3 Stream Gauge Station Information
C.4 Crooked Creek Hydrology Data
C.5 Jims Lake Outlet Hydrology Data
C.6 Roys Creek Hydrology Data
APPENDIX D RESOURCE DATA AND ANALYSIS
D.1 Maximum Probable Flood
D.2 Review of Climate Effects
D.3 Geotechnical Considerations
D.4 Tsunami Hazards
APPEODIX E ENVIRONMENTAL CONSIDERATIONS
(CONTINUED)
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report iv
APPENDIX F PERMITTING INFORMATION
F.1 Federal Permits
F.2 State Permits
F.3 Local Permits
APPENDIX G COST ESTIMATES AND ECONOMIC ANALYSIS
G.1 Project Cost Estimate
G.2 Economic Analysis Assumptions
APPENDIX H TECHNICAL ANALYSIS
H.1 Project Modeling
H.2 Project Sizing Analysis
H.3 Load Growth Scenarios
APPENDIX I DRAFT REPORT REVIEW COMMENTS AND RESPONSES
APPENDIX J TABULAR HYDROLOGY DATA
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report v
LIST OF FIGURES
Figure 1 1: Feasibility Evaluation Process Flowchart..........................................................................3
Figure 2 1: Recent Monthly Peak and Average Power Generation...................................................8
Figure 2 2: Recent Fuel and Electricity Costs......................................................................................12
Figure 5 1: Project Development Schedule..........................................................................................25
Figure A 1: Project Overview and Location Map.............................................................................A 1
Figure A 2: Map of Recommended Crooked Creek / Jims Lake Project......................................A 2
Figure A 3: Graphical Index of Photographs Included in Appendix B..........................................A 3
Photograph B 1: Aerial View of Small Sandy Beach, Jims Lake, and Crooked Creek...............B 1
Photograph B 2: Crooked Creek Gauging Station / Intake Site, Looking Upstream ..................B 2
Photograph B 3: Crooked Creek 50 Yards Above Gauging Station / Intake Site, Looking
Upstream............................................................................................................................B 2
Photograph B 4: Crooked Creek Gauging Station / Intake Site, Looking Downstream.............B 2
Photograph B 5: Crooked Creek at Gauging Station / Intake Site, Looking to South.................B 3
Photograph B 6: Crooked Creek at Gauging Station / Intake Site, Looking to North ................B 3
Photograph B 7: Cliffs North of Crooked Creek Gauging Station / Intake Site...........................B 3
Photograph B 8: Crooked Creek 100 Yards Below Gauging Station / Intake Site, Looking
Downstream.......................................................................................................................B 4
Photograph B 9: Typical Terrain and Vegetation Along Penstock Route Between
Crooked Creek and Jims Lake........................................................................................B 4
Photograph B 10: View of Upper Powerhouse Site looking Northeast Across Jims Lake........B 4
Photograph B 11: Bathymetric Survey of Jims Lake.......................................................................B 5
Photograph B 12: Jims Lake Creek Gauging Station ......................................................................B 5
Photograph B 13: Typical Peat Bogs in Project Vicinity..................................................................B 5
Photograph B 14: Penstock Route through Ravine Below Jims Lake...........................................B 6
Photograph B 15: Site Overview from Offshore...............................................................................B 6
Photograph B 16: View of Lower Powerhouse Site Looking North.............................................B 7
Photograph B 17: Typical View of Power Line Route Between Project and Elfin Cove.............B 7
Photograph B 18: Soils Along Power Line Route Between Project and Elfin Cove ....................B 7
Photograph B 19: Debris Field Upstream from Crooked Creek Intake Site.................................B 8
Photograph B 20: Debris Field in Elfin Cove ....................................................................................B 8
Photograph B 21: Debris Field along Power Line Route.................................................................B 8
Figure C 1: Jims Lake Storage Curve................................................................................................C 3
Figure C 2: Model Used for Creek Section Profile at Jims Lake Creek........................................C 8
Figure C 3: Crooked Creek Stage Discharge Curves.......................................................................C 9
Figure C 4: Crooked Creek Flow Duration Curves..........................................................................C 9
Figure C 5: 1984 1985 Crooked Creek Stage Data...........................................................................10
Figure C 6: 1984 1985 Crooked Creek Flow Data........................................................................C 10
Figure C 7: 2008 2010 Crooked Creek Stage Data.......................................................................C 11
Figure C 8: 2008 2010 Crooked Creek Flow Data........................................................................C 11
Figure C 9: 2008 2009 and 2009 2010 Jims Lake Creek Stage Discharge Curves................C 12
Figure C 10: 1984 1985 and 2008 2010 Jims Lake Creek Flow Duration Curve...................C 12
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report vi
Figure C 11: 1984 1985 Jims Lake Creek Stage Data...................................................................C 13
Figure C 12: 1984 1985 Jims Lake Creek Flow Data....................................................................C 13
Figure C 13: 2008 2010 Jims Lake Creek Stage Data.................................................................C 14
Figure C 14: 2008 2010 Jims Lake Creek Flow Data..................................................................C 14
Figure C 15: 2009 2010 Roys Creek Stage Discharge Curve......................................................C 15
Figure C 16: 2009 2010 Roys Creek Flow Duration Curve ........................................................C 15
Figure C 17: 2008 2010 Roys Creek Stage Data..........................................................................C 16
Figure C 18: 2008 2010 Roys Creek Flow Data ..........................................................................C 16
Figure D 1: Tonalite Creek Flows During Negative and Positive Phase PDO...........................D 3
Figure D 2: Geology of Project Area...................................................................................................D 6
Figure H 1: Daily Hydro Project Performance (July 2009 through December 2010).................. H 6
Figure H 2: Annual Hydro Performance (1975 through 2010)...................................................... H 6
Figure H 3: Hourly Project Performance During September 2010 Dry Spell.............................. H 7
Figure H 4: Winter Hydro Performance Under Different Load Cases...................................... H 12
Figure H 5: Summer Hydro Performance Under Different Load Cases.................................... H 13
Figure H 6: Annual Hydro Performance Under Different Load Cases ..................................... H 13
LIST OF TABLES
Table 2 1: Estimated Community Energy Usage by Fuel Type and Purpose ..................................6
Table 2 2: Existing Utility Generation Equipment ...............................................................................7
Table 2 3: Recent Electric System Statistics ...........................................................................................9
Table 2 4: Hydro Project Performance Under Future Load Scenarios .............................................10
Table 2 5: Historic Population Data .....................................................................................................11
Table 2 6: Comparative Median Household Incomes ........................................................................11
Table 3 1: Technical Summary of Recommended Project.................................................................14
Table 3 2: Expected Seasonal and Annual Hydro Project Output...................................................15
Table 4 1: Assumptions Used for Economic Analysis.......................................................................20
Table 4 2: Summary of Economic Data for Recommended Project.................................................21
Table 4 3: Sensitivity Analysis Results.................................................................................................23
Table C 1: Summary of Hydrology Data for Elfin Cove Hydroelectric Resources.....................C 1
Table C 2: Flow Measurements for Elfin Cove Hydroelectric Resources.....................................C 2
Table C 3: Manning Equation Parameters for Gauging Stations...................................................C 7
Table C 4: Creek Sections used to Calculate A and P at Gauging Stations ..................................C 8
Table D 1: Maximum Probable Floods at Crooked Creek and Jims Lake Creek........................D 1
Table G 1: Project Cost Estimate.........................................................................................................G 1
Table H 1: Generation Dispatch Model Variables, Inputs, and Outputs..................................... H 2
Table H 2: Actual and Modeled Electric Demand........................................................................... H 3
Table H 3: Expected Range of Seasonal and Annual Hydro Performance.................................. H 4
Table H 4: Comparison of Average Seasonal and Annual Hydro Performance with
Performance During 9/15/09 to 9/15/10 Time Period.................................................. H 5
Table H 5: Range of Project Design Parameters Considered and Recommended Values ........ H 8
Table H 6: Performance of Recommended Project at 200% and 400% Load Cases.................. H 11
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report vi
ACRONYMS AND TERMINOLOGY
ac ft acre foot, acre feet. A measure of water volume equal to one acre covered in
water to a depth of one foot.
ADCED Alaska Department of Community and Economic Development
ADEC Alaska Department of Environmental Conservation
ADFG Alaska Department of Fish and Game
ADNR Alaska Department of Natural Resources
AEA Alaska Energy Authority
AEE Alaska Energy and Engineering, Inc.
ATV All Terrain Vehicle
APA Alaska Power Authority (predecessor to the AEA)
AS Alaska Statute
BCR benefit cost ratio
BLM Bureau of Land Management
cfs cubic feet per second
coanda effect The tendency of a fluid jet to stay attached to a smoothly convex solid
obstruction. A common example is the way a stream of water, as from a faucet,
will wrap around a cylindrical object held under the faucet (such as the barrel of
a drinking glass).
COE U.S. Army Corps of Engineers
discharge A synonym for stream flow. Flow and discharge are used interchangeably in this
report.
ECUC Elfin Cove Utility Commission
Elfin Cove Refers to the community of Elfin Cove, or the geographic place name of Elfin
Cove, depending on context. The two are synonymous in most respects.
Environmental
attributes
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report vii
The term environmental attributes is used by the utility industry to describe the
desirable aspects of electricity that is generated from environmentally benign
and/or renewable sources. Environmental attributes are tracked, marketed,
bought, and sold separately from the physical energy. Separating the
environmental attributes from the physical energy allows customers or
ratepayers to elect to buy sustainable or greenenergy even if it is physically
unavailable from their electric utility.
Excess power, energy, electricity
Electricity generated by the hydro project in excess of the utilitys current load.
Excess energy can be directed to one or more interruptible loads (such as electric
heat) and may or may not have economic value depending on when it is
available and how it is used. At times when there is no beneficial use for excess
energy, water flow into the turbine can be reduced so that no excess energy is
generated.
ft foot, feet
FY fiscal year
gal gallon(s)
GDM generation dispatch model. A model used to evaluate the performance and
output of proposed electric generation configurations (diesel and hydro).
Hatch Hatch America, Inc.
HDPE high density polyethylene
in inch, inches
interruptible power, energy, electricity
Electricity which is generated by the hydro generator(s) in excess of system
demand (see excess power) and delivered to customers on a special interruptible
basis. Utility generation and delivery of interruptible electricity starts and stops
without notice based on water availability and other criteria.
kV kilovolt, or 1,000 volts
kVA kilovolt amp
kW kilowatt, or 1,000 watts. One kW is the power consumed by ten 100 watt
incandescent light bulbs.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report viii
kWh kilowatt hour. The quantity of energy equal to one kilowatt (kW) expended for
one hour.
LIDAR Light Detection and Ranging
MHW mean high water
mi mile, miles
MW megawatt, or 1,000 kilowatts
NREL National Renewable Energy Laboratory
O&M operating and maintenance
OMR&R operating, maintenance, repair, and replacement
PCE Power Cost Equalization Program
PDO pacific decadal oscillation. A climate phenomenon similar to the El Nino / La
Ninaclimate fluctuations in the equatorial Pacific Ocean. The PDO is situated in
the north Pacific, and fluctuates on a time scale of a few decades.
P.E. Professional Engineer. Licensed in the State of Alaska.
Polarconsult Polarconsult Alaska, Inc.
prime power, energy, electricity
Electricity generated to supply electrical loads on the ECUC utility grid. Prime
electricity can be contrasted with excess or interruptible electricity, which is
generated by the hydro project only when sufficient water is available.
rpm revolutions per minute
SDR standard dimension ratio
sq.mi. Square mile
USFS U.S. Forest Service
USGS U.S. Geological Survey
V volt
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 1
1.0 INTRODUCTION
1.1 PROJECT AUTHORIZATION AND PURPOSE
In 2008, the Denali Commission awarded the Non Profit Community of Elfin Cove (Elfin Cove)
grant funds for study of available hydroelectric resources to reduce the cost of electricity costs.
The funds were awarded under the Commission s alternative energy project solicitation dated
December 6, 2007, and are managed by the Alaska Energy Authority (AEA).
In June 2009, Elfin Cove authorized Polarconsult Alaska, Inc. (Polarconsult) to complete
reconnaissance and feasibility studies of hydropower resources available to Elfin Cove. The
reconnaissance study was completed in June 2010, and identified favorable projects at the Roys
Creek site and at the Crooked Creek and Jims Lake site. Elfin Cove selected the Crooked Creek
and Jims Lake site for further analysis, and directed Polarconsult to complete a feasibility study
of a project at the Crooked Creek and Jims Lake site. This report presents the findings and
recommendations of the feasibility study completed under this authorization.
1.2 SUMMARY OF FINDINGS
A hydroelectric project at Crooked Creek and Jims Lake is feasible, and can lower the cost of
electricity in Elfin Cove by 6 to 81% from current electricity rates. This range reflects the effects
of variations in project financing, construction cost, and excess energy utilization.
The recommended project consists of two hydroelectric systems with a total capacity of 160
kilowatts (kW). The upper systemdiverts up to five cubic feet per second (cfs) of water from
Crooked Creek to Jims Lake where it is run through a 35 kW power recovery turbine. The
lower systemdiverts up to seven cfs of water from Jims Lake to a 125 kW turbine located at
tidewater. The siphon intake at Jims Lake provides the lower system with 32 acre feet of
storage, allowing this system to supply the utilitys electrical loads through most peak load
episodes and during short dry spells. The upper system includes a 1,450 feet, 12 inch penstock
and the lower system includes a 1,800 foot, 14 inch penstock. The project also includes 7,300 feet
of power line, 12,200 feet of communications, and 8,700 feet of access trails. The project location
is presented in Figure A 1, and the project layout is shown in Figure A 2.
The recommended project will supply 99% of Elfin Coves current annual electrical needs,
displacing 28,500 gallons of fuel used yearly at the diesel power plant. At a fuel cost of $4.00 per
gallon, the project is estimated to reduce utility fuel expenses by $114,000 annually. The
recommended project also provides 241,600 kilowatt hours (kWh) of excess electric energy that
can be used for interruptible loads such as space and water heating. Fully utilized, this excess
energy can displace an additional 6,800 gallons of heating oil annually.
An economic analysis of the project indicates it has a benefit cost ratio of 1.15 compared to
continued reliance on the diesel power plant. With full utilization of excess electric energy
produced by the project, the benefit cost ratio is 1.44. Further discussion on project costs and
economic analysis may be found in Appendix G.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 2
1.3 PROJECT EVALUATION PROCESS
Development options for the Crooked Creek and Jims Lake site were evaluated using an
iterative process to arrive at the recommended project. Initially, resource data for the Crooked
Creek and Jims Lake site were collected and analyzed along with the communitys electric
demand profile to identify several initial project configurations for further evaluation. The
resource data included stream hydrology, lake bathymetry, site topography, and related
information. Environmental and regulatory factors were also considered in developing
candidate project configurations. Data from the electric utility were collected and analyzed to
develop a model of the communitys electric demand profile. These data were input to a
generation dispatch model to determine how much prime power and interruptible power each
project configuration would produce.
The electrical output for each project alternative was integrated with economic data comprised
of fuel costs, construction costs, operating and maintenance (O&M) costs, and financing options
to develop a benefit cost ratio. The recommended project provides the highest percentage of
projected future electrical demand while maintaining an acceptable benefit cost ratio. This
evaluation process is represented graphically in Figure 1 1.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 3
GENERATION DISPATCH MODEL
Projects how much electricity is generated by
diesel and hydro for each project configuration.
Also projects excess energy generation.
ELECTRICAL LOADS
PCE & utility reports
Utility load profile
PROJECT RESOURCE DATA
Jim's Lake storage curve
Jim's Lake hydrology
Crooked Creek hydrology
Site topography
LOAD PROFILE
Prime power demand
Potential interruptible energy loads
ELIGIBLE HEATING LOAD
Building inventory
Climate data
HYDROLOGY
Flood magnitude
Flow duration and frequency
Storage capacity
ECONOMIC EVALUATION
COMMUNITY NEEDS MET?
BENEFIT/COST RATIO?
ECONOMIC DATA
Diesel fuel cost
Excess energy value
Financing plan
RECOMMENDED PROJECT
PROJECT COST DATA
Design and permitting costs
Project design approach
Construction methods
Construction cost estimate
Operation and maintenance costs
SURVEYS
Gross head
Pipe, power, access
distances and
alignments
Property ownership
Bathymetry
ENVIRONMENTAL &
REGULATORY CONSTRAINTS
Aquatic resources
Aesthetics
Special restrictions
GEOTECHNICAL
ASSESSMENTS
Stream diversion sites
Dam sites
Civil infrastructure
Project alignments
COMMUNITY REVIEW AND
FEEDBACK
RESULTEVALUATION ANALYSISINPUT DATA
ITERATIONS TO
IMPROVE
PROJECT
PROPOSED PROJECT
CONFIGURATION
Figure 1 1: Feasibility Evaluation Process Flowchart
1.4 CURRENT AND PREVIOUS STUDIES
Development of hydropower resources for Elfin Cove has been under consideration for over 30
years. Earlier investigative activities considered several resources in the vicinity of Elfin Cove,
and the 2010 reconnaissance study identified a project at Crooked Creek and Jims Lake as the
preferred project for the community. These past studies and current investigative efforts are
briefly summarized below.
1.4.1 1979 Regional Reconnaissance Study
Hydropower resources for Elfin Cove were investigated as part of a regional reconnaissance
study completed for the U.S. Army Corps of Engineers (COE) by CH2M Hill in October 1979.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 4
The COE reconnaissance study considered a 310 kW run of river project at Margret Creek, 6.4
miles from Elfin Cove across Port Althorp.
1.4.2 1984 Reconnaissance Study
A reconnaissance study of energy alternatives for Elfin Cove was completed by Hatch America,
Inc. (Hatch) for the Alaska Power Authority (APA) in 1984. This study considered hydropower
resources within Elfin Cove including Roys Creek, Joes Creek, and Ernies Creek and
recommended further study of a 20 to 60 kW run of river project at Roys Creek in Elfin Cove.
1.4.3 1984 Reconnaissance Study Supplement
In 1984, APA issued a supplemental report to Hatchs reconnaissance study. The APA
supplement considered projects on the creeks within Elfin Cove unfeasible, and recommended
investigation of a project at Crooked Creek and Jims Lake instead. The APA proposal would
divert water from Crooked Creek to Jims Lake, and construct an 80 kW hydroelectric project
between Jims Lake and tidewater.
1.4.4 2006 Concept Design Report for Energy Upgrades
Alaska Energy and Engineering, Inc. (AEE) completed a concept design report and
construction cost estimates for upgrade of Elfin Coves bulk fuel facility, diesel power plant,
and electric distribution system in 2006. This report included limited consideration of a 100 kW
hydroelectric project at Crooked Creek and Jims Lake similar to that proposed in 1984. AEE
estimated the cost of this project at approximately $1.5 million.
1.4.5 2010 Reconnaissance Study
A new reconnaissance study of hydropower options for Elfin Cove was completed in 2010 by
Polarconsult. This study evaluated projects at Crooked Creek and Jims Lake and the creeks
within Elfin Cove that were originally considered in 1984. The reconnaissance study found that
a project at the Roys Creek site and a project at the Crooked Creek and Jims Lake site both
appeared favorable. The community decided to pursue further study of a project at Crooked
Creek and Jims Lake.
1.4.6 Current Feasibility Study
Polarconsult engineer Joel Groves, P.E., visited Elfin Cove from August 9 to August 14, 2010, to
conduct feasibility level field investigations of the Crooked Creek and Jims Lake site. Mr.
Groves was assisted by Ms. Jane Button, the communitys manager for this project, on field
investigations. Activities conducted during this field trip are summarized below.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 5
Completed initial topographic surveys of the Crooked Creek intake and Jims Lake
outlet sites. Surveyed key project sites to index them to local survey monuments,
confirming the available head and horizontal distances between project features.
Conducted additional stream flow measurements at Crooked Creek and Jims Lake.
Stream flow was also measured at Roys Creek.
Performed additional investigation of the overland route between Elfin Cove and the
project area.
Assessed topography around Jims Lake to determine the maximum practical
impoundment elevation of the lake.
Reviewed penstock and access routes between Crooked Creek and Jims Lake and
between Jims Lake and tidewater to guide the project design approach and evaluate
suitable construction methods.
Field data collected from this trip has been used to complete a feasibility study of the Crooked
Creek and Jims Lake resource using the methodology described in Section 1.3. This report
summarizes the findings and recommendations of the feasibility study.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 6
2.0 COMMUNITY PROFILE
2.1 COMMUNITY OVERVIEW
Elfin Cove is located on the northwest portion of Chichagof Island, approximately two miles
from South Inian Pass (Figure A 1). The community is located 70 air miles west of Juneau and
90 air miles north northwest of Sitka at approximately 58.19° north latitude and 136.35° west
longitude (Sections 25 and 36, Township 42 South, Range 55 East, Copper River Meridian).
Nearby communities are Pelican, approximately 16 miles to the south, and Gustavus,
approximately 27 miles to the east.
Elfin Cove has a maritime climate with cool summers and mild winters. Normal summer
temperatures are in the 50s to low 60s, and normal winter temperatures are in the 20s and 30s.
The highest recorded temperature is 85 degrees, and the lowest recorded temperature is minus
10 degrees. Total precipitation averages 102 inches a year, with an average snowfall of 96
inches.
Elfin Cove is not an incorporated city or a federally recognized Native village. Public services
such as electricity and water are provided by the Non Profit Community of Elfin Cove. The
community is located in the Sitka Recording District and the Chatham School District.
1
2.2 EXISTING ENERGY SYSTEM
2.2.1 Community Energy Overview
Elfin Cove has an isolated electrical system with no transmission interconnections to other
communities. Elfin Cove relies 100% on diesel generation for electricity. Diesel and other
petroleum fuels are delivered by barge several times annually. Other local energy usage
includes diesel and gasoline fuels for transportation, wood and fuel oil for space and water
heating, and propane gas for cooking and heating. Table 2 1 lists estimated annual fuel
consumption by type and purpose.
Table 2 1: Estimated Community Energy Usage by Fuel Type and Purpose
Purpose (1)Fuel Estimated Annual Quantity Estimated Annual Cost
(2)
Electric Diesel 30,000 33,000 gallons $120,000 $132,000
Heating Diesel/Fuel Oil 34,000 35,000 gallons $136,000 $140,000
Heating Wood 50 70 cords $12,500 $17,500
Transportation Diesel/Gasoline 12,000 15,000 gallons $48,000 $60,000
Total Hydrocarbon Fuels 76,000 83,000 gallons $304,000 $332,000
(1) Electric system data from Power Cost Equalization Program and utility reports. Other energy data from AEAs
2010 Alaska Energy Plan Community Database,http://www.akenergyauthority.org/alaska energy plan.html
(2) Based on $4.00 per gallon for petroleum fuels and $250 per cord for wood.
1 This community profile is compiled from previous energy studies for Elfin Cove and data on the
Alaska Department of Community and Economic Development (ADCED) website.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 7
Elfin Cove s energy infrastructure is in good condition. The community constructed a new bulk
fuel facility in 2000. The Alaska Energy Authority (AEA) completed minor upgrades to the bulk
fuel facility and constructed a new diesel power plant in 2007, and upgraded the electrical
distribution system in 2009.
2.2.2 Electric Utility Organization
Electrical service in Elfin Cove is provided by the Elfin Cove Utility Commission (ECUC), which
is owned and managed by the Non Profit Community of Elfin Cove. The ECUC holds
Certificate of Public Convenience and Necessity No. 701, issued in 2004, authorizing it to
operate a public utility providing electrical service in and around Elfin Cove. Because the ECUC
is owned and managed by a non profit entity, the Regulatory Commission of Alaska has
exempted the ECUC from regulation on public interest grounds as allowed by AS 42.05.711(d).
The ECUC participates in the State of Alaskas Power Cost Equalization (PCE) program, which
subsidizes electricity rates for residential and community facilities served by eligible Alaska
utilities.
2.2.3 Generation System
Elfin Cove s diesel power plant has three 480 volt three phase diesel generators. The power
plant switchgear is fully automatic with paralleling capability, and uses a programmable logic
controller to match the generators to system load. All three diesel generator sets were installed
new in 2007. Installed utility generation equipment in Elfin Cove is listed in Table 2 2.2
Table 2 2: Existing Utility Generation Equipment
No. Equipment
Prime Power
(kW)
Commissioned
Date
Total Hours
(Sept. 2009)
Designated Use
1 John Deere 6068 101 kW 2007 3,263 Intermediate
2 John Deere 4045 67 kW 2007 11,709
Winter base
and peak
3 John Deere 6061 179 kW 2007 4,491 Summer peak
The existing diesel power plant is fitted with a waste heat system that provides heat to the
community building and shop.
2.2.4 Electrical Distribution System
The distribution system was upgraded in 2009 and consists of a 7,200 volt grounded wye three
phase system without loop feed. The distribution system is installed in conduit under the
boardwalks and on the ground surface throughout most of the community. On the west side of
2 Elfin Cove Power System Upgrade Record Drawings Sheet E 9, AEE, Inc., 2010.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 8
0
25
50
75
100
125
150
175
200
225
250
275
300
325
Jan 03 Jan 04 Jan 05 Jan 06 Jan 07 Jan 08 Jan 09 Jan 10 Jan 11
Peak Monthly Power Generation
Average Monthly Power Generation
the community, the distribution system is run overhead on wooden poles. A 225 kilovolt amp
(kVA) pad mount transformer located adjacent to the power plant feeds the distribution
system.2
2.2.5 Planned Upgrades
The bulk fuel, electrical generation, and distribution systems have all been recently upgraded.
No additional upgrades are planned.
2.2.6 Existing Load Profile
Total system electrical demand from 2003 to 2010 is presented in Figure 2 1 and Table 2 3.
Average winter time loads are approximately 25 kW, with peak loads of 50 kW. Average
summer time loads range from 70 to 90 kW. Peak summer time loads have increased from a
range of 120 to 150 kW before 2007 to a range of 230 to 310 kW currently.
The increase in peak summer loads since 2007 is attributed to (1) additional loads and growth in
the community over the past several years and (2) the improved automatic paralleling
capability of the new power plant switchgear, installed in 2007. Before the upgrade, many of the
lodges in Elfin Cove self generated during peak load hours, as the older switchgear would not
reliably manage peak loads. While some of the lodges still self generate during peak hours, the
improved switchgear makes this an option rather than a necessity, resulting in the observed
higher system peaks.
3
Figure 2 1: Recent Monthly Peak and Average Power Generation
3 Concept Design Report and Construction Cost Estimate, Elfin Cove Energy Infrastructure Projects, AEE, 2006
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 9
Table 2 3: Recent Electric System Statistics
Parameter 2003 (2)2004 2005 2006 2007 (1)2008 2009 2010
kWh Generated 215,404 387,727 344,557 342,883 235,574 (1)377,150 339,609 325,810
kWh for Station Service
(% of total generation)
12,809
(5.9%)
24,785
(6.4%)
28,421
(8.2%)
24,147 (3)
(7.0%)
1,734 (1)
(%)
1,544 (3)
(%)
25,045
(7.4%)
32,615
(10.0%)
kWh Sold 200,865 318,937 301,614 302,051 295,567 334,177 291,866 259,139
System Losses ((sold +
station service) / generated)
0.8% 11.3% 4.2% 4.9%6.7% 10.5%
Fuel Price (annual average) $1.84 $2.21 $2.94 $3.64 $3.56 $5.14 $4.62 $3.98
Fuel Used (gallons) 17,583 32,938 31,778 31,161 31,727 30,678 26,413 26,539
Total Fuel Expense $32,380 $72,831 $93,414 $113,477 $112,806 $157,599 $122,068 $105,662
Total Non Fuel Expense $24,796 $58,949 $55,867 $28,702 $41,078 $35,406 $32,739 $43,809
Total Utility Expense $57,177 $131,780 $149,281 $142,178 $153,884 $193,005 $154,807 $149,471
Power Cost per kWh $0.28 $0.41 $0.49 $0.47 $0.52 $0.58 $0.53 $0.58
Generation Efficiency
(kWh/gal)12.3 11.8 10.8 11.0 7.4 (1)12.3 12.9 12.3
All data is compiled from monthly Power Cost Equalization program records provided by AEA.
(1) Records from 2007 are incomplete due to power plant replacement project.
(2) Data for 2003 include July through December.
(3) No data for March 2006 and January through November 2008.
denotes data that are not available or not meaningful due to incomplete records.
2.2.7 Projected Future Load Profile
Community electrical demand is a function of population, electricity cost, and available income.
Commercial, industrial, and transient loads are also major factors in total electrical demand.
If the hydro project significantly lowers the costs of electricity, this will encourage electrical
demand from existing residents and businesses to increase. In small communities like Elfin
Cove, demand often increases significantly in response to reduced electric rates. Reduced
electric rates may also encourage an increase in seasonal and year round populations, which
would also tend to cause an increase in electrical demand. These effects would help to counter
a declining trend in Elfin Coves resident population since 1990.
The hydro project performance was evaluated for a base case scenario (current loads continue
into the future), two negative, and two positive future load growth scenarios. The base case
scenario is used for the economic analysis in this study. Each scenario is a deviation from
current load patterns:
1. 50% reduction in load, with total utility shutdown from October 15
th April 15
th .
2. 50% reduction in load year round.
3. No change from current load.
4. 200% increase in load year round.
5. 400% increase in load year round.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 10
Under the different load cases, total project output remains relatively constant and the portion
of the projects output that is used to supply prime ECUC load varies. In scenario 1, total hydro
output is reduced because the project is mothballed for 6 months of the year. In scenario 5,
nearly all hydro output (98.7%) is used to meet prime ECUC loads, and the diesel power plant
is needed year round to supplement the hydro project. Table 2 4 summarizes hydro project
performance under these five future load scenarios. Performance of the recommended hydro
project under different future load scenarios is discussed in greater detail in Appendix H.3.
Table 2 4: Hydro Project Performance Under Future Load Scenarios
50% Load,
no Winter
Load
50%
Load
Current
Load
(Base Case)
+200%
Load
+400%
Load
Total Annual ECUC Load (kWh) 126,000 182,900 359,000 711,100 1,415,400
ECUC Load Supplied by Diesel (kWh)
(Hydro as % of total prime supply)
0
(0%)
0
(0%)
2,900
(0.8%)
178,900
(25.2%)
763,300
(53.9%)
ECUC Load Supplied by Hydro (kWh)
(Hydro as % of total prime supply)
126,000
(100%)
182,900
(100%)
356,100
(99.2%)
532,300
(74.9%)
652,200
(46.1%)
Excess Hydro Generation (kWh)
(Excess as % of total hydro)
247,700
(66.3%)
481,400
(72.5%)
316,600
(47.1%)
132,000
(19.9%)
8,300
(1.3%)
Total Annual Hydro Generation (kWh) 373,700 664,300 672,700 664,300 660,500
2.2.7.1 Population
Elfin Cove s population varies seasonally. The population in the summer months (mid May
through mid September) is approximately 100 to 200. Commercial and sport fishing activity
contributes significantly to the summer population. The winter population is approximately 20.
Elfin Coves resident population, listed in Table 2 5, has historically ranged from approximately
20 to 60 people, and has been declining since 1990. Elfin Cove is bounded on all sides by the
Tongass National Forest, so there is limited land available for community growth. For the
purposes of this study, the communitys future resident and summer population is expected to
remain within the historical range. The economic benefits of the hydro project can help to
reverse the decline in Elfin Coves resident population.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 11
Table 2 5: Historic Population Data
Year Year Round
Population
Summer Seasonal Population
Estimates
1958 48 NA
1970 28 NA
1979 29 60
1980 49 NA
1990 57 NA
1995 43 NA
2000 32 NA
2004 26 NA
2009 25 NA
2010 20 NA
Future Projection 20 60 100 200
(1)Population data compiled from past reports, ADCED data, the 2010 U.S. Census, and the 2008 Tongass
National Forest Land and Resource Management Plan.
NA: Not Available.
2.2.7.2 Income
Median Elfin Cove household income is presented in Table 2 6. Household income in Elfin
Cove declined compared to state wide household income between 1990 and 2000.
Table 2 6: Comparative Median Household Incomes
1990 2000 2010
Elfin Cove Median Household Income as
percentage of Alaska Median Household
Income
105% 65% NA
Elfin Cove $43,125 $32,031 NA
Alaska $41,193 $51,571 64,635
United States $30,056 $41,994 52,029
(1) Data compiled from Alaska Department of Labor and U.S. Census Bureau. Values not adjusted for inflation.
NA: Not Available.
(1)
(1)
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 12
$2.00
$1.00
$0.00
$1.00
$2.00
$3.00
$4.00
$5.00
$6.00
2003 2004 2005 2006 2007 2008 2009 2010 2011
$0.40
$0.45
$0.50
$0.55
$0.60
$0.65
$0.70
$0.75
$0.80
Price of Fuel, Annual Average
Per kWh Utility Costs, Annual
2.2.8 Energy Market
Energy from a local hydroelectric project will be fed into the ECUC system to offset the need for
diesel power generation. Also, the hydroelectric project will at times generate energy in excess
of electrical demand, which can be made available on an interruptible basis to offset other
energy consumption such as space or water heating.
Fuel prices in Elfin Cove have increased significantly over the past several years. The average
2007 2010 fuel price of $4.27 per gallon is 59% higher than the average 2003 2006 fuel price of
$2.68 per gallon. Past fuel and electricity costs in Elfin Cove are presented in Figure 2 2.
Figure 2 2: Recent Fuel and Electricity Costs
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 13
3.0 RECOMMENDED PROJECT
3.1 RESOURCE DESCRIPTION
The resources considered in this study are Crooked Creek, a small creek located approximately
one mile south of Elfin Cove, and Jims Lake, a small lake located ¼mile south of Crooked
Creek. Both resources are indicated on Figures A 1 and A 2.
Crooked Creek drains a northeast facing mountain valley and adjacent level terrain totaling 0.7
square miles (sq.mi.) in area. The basins elevation ranges from tidewater up to 2,048 feet along
the eastern edge of the basin. Sixty percent of the basin is forested and 40% is alpine tundra and
barren rock. The basin is not glaciated and has no significant ponds or lakes. Crooked Creek
discharges into Port Althorp at the north end of Small Sandy Beach.
Jims Lake is a six acre lake located ¼mile south of Crooked Creek. The 0.1 sq.mi. basin that
drains into Jims Lake is adjacent to the Crooked Creek basin, situated on the west facing slopes
of the ridge that divides the two basins. The entire basin is forested, and Jims Lake occupies 9%
of the total basin area. A small unnamed creek flows from Jims Lake to tidewater, discharging
into Port Althorp at the south end of Small Sandy Beach, 500 feet from the mouth of Crooked
Creek. This unnamed creek is called Jims Lake Creek in this report.
Stream flow data for Crooked Creek at the proposed intake site and Jims Lake Creek at the lake
outlet are available from 1984 to 1985 and from 2008 to current, providing 2.7 years of flow data
at each location. These data are presented in detail in Appendix C. Technical aspects of these
resources pertinent to the recommended project are discussed in Appendix D.
3.2 OVERVIEW OF RECOMMENDED PROJECT
The recommended project consists of two hydroelectric systems with a total capacity of 160 kW.
The project will supply approximately 99% of the average annual electrical demand in Elfin
Cove, and will produce an additional approximately 241,600 kWh of excess energy that can be
used for interruptible loads. Each hydroelectric system is described in more detail below.
Technical data on the two systems is summarized in Table 3 1.
The upper system will have an intake on Crooked Creek located at an elevation of 475 feet
above mean high water (MHW). The intake structure will divert up to 5 cfs of water from
Crooked Creek and run it through a 1,450 foot long 12 inch diameter penstock to a powerhouse
located on the north shore of Jims Lake with a finished floor elevation of 338 feet. The tailrace
from this project will discharge water to Jims Lake. This system will have an installed
generation capacity of 35 kW.
The lower system will have a siphon intake to draw Jims Lake down eight feet below its
natural level of 333 feet. This intake will allow for water levels in Jims Lake to be regulated
between 325 and 333 feet above mean high water, providing a total storage volume of
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 14
approximately 32 acre feet (ac ft). A 1,800 foot long 14 inch diameter penstock will convey up
to 7 cfs of water from the lake down to a powerhouse located at an elevation of 20 feet at Small
Sandy Beach. This system will have an installed generation capacity of 125 kW.
The hydro project will be designed to operate in parallel with ECUCs existing diesel power
plant. The control programming will operate the hydro project to follow ECUC load, so the
diesel generators will be turned off most of the time.
Table 3 1: Technical Summary of Recommended Project
COMMON PROJECT FEATURES VALUE
Access Trails 8,700 feet
Power Lines 7,300 feet
Communications Lines 12,200 feet
INDIVIDUAL HYDRO SYSTEM FEATURES VALUES
Individual System Parameters Upper System Lower System Total
Basin Area (square miles) 0.56 sq.mi. 0.10 sq.mi. 0.66 sq.mi.
Median Flow (cfs) 2.9 cfs NA NA
Minimum Flow (cfs) 0.2 cfs NA NA
Plant Design Flow (cfs) 5 cfs 7 cfs NA
Intake Elevation (ft) 475 ft 325 333 ft NA
Powerhouse Elevation (ft) 338 ft 20 ft NA
Gross Head (ft) 137 ft 305 313 ft NA
Pipeline Length (ft) / Diameter (in)1,450of 12pipe 1,800of 14pipe NA
Net Head (ft) 124 ft 286 ft NA
Minimum Power Generation (kW) 9 kW 13 kW 9 kW
Installed Capacity (kW) 35 kW 125 kW 160 kW
Dam/Diversion Height (ft) 1.0 ft none NA
Available Storage Volume (ac ft) none 32 ac ft 32 ac ft
ESTIMATED ANNUAL ENERGY GENERATION
Total Annual Hydro Energy Generation (kWh) 167,100 505,600 672,700
Hydro Output used to Supply ECUC Load (kWh)
(percent of total ECUC load supplied by hydro)
356,100
(99%)
Gross Excess Energy Available from Hydro (kWh) 316,600
Net Excess Energy Available from Hydro (kWh) 241,600
(1)
NA: Not Applicable.
(1)Equal to gross excess energy less 75,000 kWh / year to replace power plant waste heat used by the
community building.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 15
3.3 ESTIMATED ENERGY GENERATION
The recommended hydro project is expected to supply approximately 99% of ECUCs annual
electricity demand. During the winter months (mid September through mid May), the hydro
project supplies 100% of ECUCs electrical requirements, and typically has significant excess
energy and generating capacity. During the summer months (mid May through mid
September), the hydro project supplies approximately 98% of ECUCs electrical requirements,
and is roughly matched to current ECUC loads in terms of both capacity and energy. The
storage at Jims Lake allows the hydro project to supply ECUC demand during short
(approximately one week long) dry spells, but longer dry spells deplete Jims Lake, requiring
use of the diesel generators to help supply ECUC demand. Seasonal and annual hydro project
performance is summarized in Table 3 2.
Table 3 2: Expected Seasonal and Annual Hydro Project Output
Item
Hydro Project Performance
1
Winter Season
(9/15 5/14)
Summer Season
(5/15 9/14)Annual
Total ECUC Load (kWh) 160,700 198,300 359,000
Load supplied by Diesel, kWh (%) 0 (0%) 2,900 (1%)2,900 (0.8%)
Load supplied by Hydro, kWh (%) 160,700 (100%) 195,400 (99%)356,100 (99.2%)
Gross Excess Hydro Generation, kWh 283,200 33,400 316,600
Total Hydro Generation, kWh 443,900 228,800 672,700
Note 1: Expected hydro project performance is based on the one hour resolution generation dispatch model, run
using hydrology data from September 15, 2009 through September 14, 2010. As explained in Appendix H,
this period is representative of a typical water year in Elfin Cove.
Hydro project output was calculated using two generation dispatch models. These models take
in hydrology data, ECUC load data, and hydro project parameters and calculate how much
energy is generated by the hydro and/or diesel power plants on an hourly and daily basis. The
hourly model uses actual hydrology data for Crooked Creek and Jims Lake for the period July
2009 through December 2010, and is used to evaluate short term (hourly to monthly)
performance of the hydro project. The daily model uses hydrology data synthesized from Elfin
Coves 35 years of weather records, and is used to evaluate long term (seasonal to multi year)
performance of the hydro project. These models were the primary analytical tool used to
develop the project configuration recommended in this report. Development, application, and
validation of these models are described in greater detail in Appendix H.1.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 16
3.4 DESCRIPTION OF COMMON PROJECT FEATURES
The descriptions of project features in this section and also in Sections 3.5 and 3.6 are
conceptual, and are based upon review of site conditions, construction costs, long term
maintenance and operational considerations, and related factors. In many cases, there are
multiple viable construction methods or design decisions that can be used. In these cases,
decisions will be made in the design and permitting phase of the project, as additional
information on environmental, regulatory, and technical constraints becomes available.
3.4.1 Transmission Line
The transmission line will be either an armored cable containing four #2 wires or cable installed
in conduit. Either can be installed on the ground surface or in shallow trenches, eliminating the
need to dig a 30 inch deep trench through the rugged terrain between Elfin Cove and the
project site.
This cable will be co located with an armored communication cable and an all terrain vehicle
(ATV) trail that will be used to access the project directly from Elfin Cove. The trail route will
first be brushed and then shaped by a combination of manual labor and small construction
equipment. The power and communications cables will then be installed, and a course of gravel
applied where necessary to provide a stable driving surface. The gravel will be obtained from
on site sources located along the route or at the hydro project areas.
3.4.2 Controls and System Integration
Both hydroelectric generators will be three phase 480 volt synchronous machines. A pad
mounted transformer will be located at each powerhouse to step the voltage up to 7.2 / 12.4
kilovolt (kV) for distribution to Elfin Cove. A manual disconnect and fuse will be located at
each powerhouse, and a manual disconnect will be located at the point of interconnection with
the existing distribution system, enabling each powerhouse and the line to town to be isolated
for maintenance or repair. A separate dedicated communications cable will be installed between
the hydro powerhouses and the diesel powerhouse to control and monitor both hydro systems
from the diesel powerhouse.
The hydro project switchgear will be integrated with the diesel plant switchgear to optimize
and automate operations. The upper system will be operated to supply as much power as the
flow in Crooked Creek allows. The lower system will be operated to supply the balance of
ECUC demand. When the Jims Lake reservoir is full, excess inflows can be used to generate
excess energy above ECUC demand. This energy can be directed to interruptible loads.
When ECUC demand approaches the hydro projects available output, the switchgear will
activate diesel genset(s) to parallel with or replace the hydro depending on ECUC load, hydro
plant and water availability, and minimum diesel genset loading requirements.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 17
With this project, the towns diesels will be turned off for a significant amount of the time. This
will extend the life of the diesel engines, reduce usage of consumables, and conserve fuel. The
existing waste heat system that serves the community building and shop from the diesel power
plant can be fitted with an electric heater to keep one of the gensets warm and to heat the
community building and shop. This heater can be operated using excess energy from the hydro
project.
3.4.3 Access
Construction access to both hydro systems will be via a beach landing at Small Sandy Beach. A
construction access trail will be built from the beach generally following the lower penstock
alignment and then to the upper powerhouse. Spur trails will provide access to the intakes at
Jims Lake and Crooked Creek. A trail will parallel the power line from Elfin Cove to provide
reliable access to the project for operations, maintenance, and repair. Removal of rock may be
necessary to build the trail immediately above Small Sandy Beach and in other areas.
Construction materials will either be hauled along these access routes or be air lifted directly to
the construction sites by helicopter from beach landings or barges.
3.5 DESCRIPTION OF UPPER SYSTEM
3.5.1 Upper Intake
The intake at Crooked Creek will be located at a four foot tall waterfall 20 yards downstream of
the existing gauging station. A coanda effect intake screen sized to draw up to five cfs of water
from the creek will be built behind the crest of this waterfall. Diverted flows will pass through a
small stilling basin and then through a secondary screen and into the penstock. The stilling
basin will be fitted with a manual bypass gate to flush debris back into the stream.
3.5.2 Upper Penstock
The upper penstock will be a 1,450 foot long 12 inch diameter pipe. This pipe will be buried for
the first 30 yards below the Crooked Creek diversion, but thereafter it can be buried or installed
on grade. Timber cribbing can be used to support the pipe on the side hill over to Jims Lake. At
bends, the pipe can be secured by bedding or with cables to rock anchors. This pipe can be
constructed with small equipment via a 6 to 8 foot wide access trail, which is the method
assumed for budgeting purposes in this study. This pipe is small enough that construction with
hand labor is also feasible, as the pipe is small and light enough to be installed using small tools
such as chainsaw winches and bars. No blasting is necessary along this route for access or pipe
installation.
The upper penstock can be constructed of high density polyethylene (HDPE) pipe. Benefits of
using HDPE are that it is rugged, light weight (6.7 pounds per foot), flexible, and easy to repair.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 18
3.5.3 Upper Powerhouse
The upper powerhouse will be located on the north shore of Jims Lake, and will measure
approximately 16 feet by 20 feet. The powerhouse will contain the turbine, generator, controls,
and switchgear. A 35 kVA pad mounted transformer will be located adjacent to the
powerhouse.
The upper system will use a single reaction turbine such as a crossflow turbine. These turbines
have flat efficiency curves from 100% to 50% of full flow. As flow decreases to 25% of full flow,
turbine efficiency decreases by 10%. Below 25% of full flow, these turbines cannot function.
The turbine will be coupled to a generator via a speed increaser or belt drive. The generator will
be a three phase synchronous generator. The full flow water to wire efficiency at the generator
leads is estimated to be 63%.
This turbine may be equipped with a draft tube to increase power output. The draft tube would
be fitted below the turbine, and would use the head between the turbine and Jims Lake surface
to pull a suction on the turbine, increasing the total effective head on the turbine and total
power output. To be most effective, the draft tube should extend below the low water level of
the reservoir. The practicality of this application will depend on the final powerhouse site at
Jims Lake. The incremental energy output that may be generated with a draft tube is not used
for the financial analysis in this study.
3.6 DESCRIPTION OF LOWER SYSTEM
3.6.1 Lower Intake
The siphon intake at Jims Lake will consist of a 14 inch diameter pipe extending 40 feet into the
lake from the southwest shore to a depth of 15 feet. The pipe inlet will be set above the lake bed
to avoid pulling in lake bed sediment, and fitted with an intake screen. A small conduit co
located with the intake pipe will house a pressure transducer that will monitor the lake level.
The intake will be able to draw the lake down to the 325 foot elevation, eight feet below its
natural level.
On shore, this penstock will continue on grade or at shallow burial west towards the lake outlet,
and will then continue down to the lower system powerhouse at Small Sandy Beach. A vacuum
pump assembly will be installed at the high point of this pipe on shore near Jims Lake to purge
air from the penstock.
No impoundment structure will be installed at the lake outlet to raise the level of the lake.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 19
3.6.2 Lower Penstock
The lower penstock will be an 1,800 foot long 14 inch diameter pipe. The penstock will be
buried, installed directly on grade, or installed on timber cribbing, depending on local terrain.
Hydraulic thrust forces can be restrained by embedding the pipe in soil, using concrete thrust
blocks, or with cables and rock bolts, depending on the terrain. The penstock will be installed
next to the construction access trail between the lower system powerhouse site at Small Sandy
Beach and the lower system intake site at Jims Lake. Access for installation and maintenance of
the penstock will be via the construction access trail.
The first 1,300 feet of the penstock, nearest Jims Lake, can be constructed with HDPE pipe.
HDPE is rugged, light weight (8 to 12.2 lbs per foot) and flexible. The bottom 500 foot portion of
the penstock route is steeper, and passes through a series of rock outcroppings above the beach.
Steel may be a better choice in this area due to (1) its ability to span longer distances between
ground supports than HDPE and (2) the higher penstock pressure in this area.
3.6.3 Powerhouse
The lower powerhouse will be situated at the base of the rock cliffs at the head of Small Sandy
Beach at an elevation of +20 feet MHW. The powerhouse will measure approximately 24 feet by
22 feet, and will house the turbine, generator, controls, and switchgear. A 125 kVA pad mount
transformer will be located adjacent to the powerhouse.
The lower system will use a single impulse turbine, such as a two jet Pelton turbine. These
turbines have flat efficiency curves from 100% to 50% of full design flow. As flow decreases
from 50 to 10% of design flow, turbine efficiency drops by approximately 20%. Below 5 to 10%
of full design flow, these turbines cannot function. The turbine will be directly coupled to a
three phase 600 rpm synchronous generator. Estimated full flow water to wire efficiency at the
generator leads will be about 70%.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 20
4.0 ECONOMIC ANALYSIS
To evaluate the economic benefits of the hydro project, a comparative analysis was performed
between the recommended hydro project and projected future diesel generation costs. Based on
this analysis, the hydro project is a lower cost power supply option for Elfin Cove than
continued purchase and consumption of diesel fuel. Use of the hydro projects excess energy or
growth in ECUC demand significantly increases the cost savings offered by the hydro project.
The comparative analysis also considered a range of other project configurations. These other
configurations are discussed in Appendix G.
For the analysis, capital costs are assumed to be amortized on a 100% debt basis, annual costs
for repair, operation, and maintenance of the hydro project were estimated, and savings from
reduced fuel usage and diesel power plant operations and maintenance costs were estimated.
ECUCs general and administrative costs were held constant. Major assumptions used in the
economic analysis of the project are detailed below in Table 4 1. These assumptions are
discussed in greater detail in Appendix G.
Table 4 1: Assumptions Used for Economic Analysis
Parameter Value
Annual ECUC Electric Demand 359,000 kWh
ECUC Fuel Efficiency 12.5 kWh generated per gallon
Annual ECUC Fuel Usage for Electricity Generation 28,720 gallons
Per Gallon Fuel Cost to ECUC (annual cost) $4.00 per gallon (2011 dollars)
Total Annual ECUC Fuel Costs $114,880 (2011 dollars)
Fuel Costs Displaced by Hydro Project $114,000 (2011 dollars)
Load Projections No growth
Project Financing Debt Financing
Percent of Project Financed with Debt 100%
Debt term 30 years
Debt interest rate 6%
Rest discount rate 3%
Table 4 2 summarizes the annual costs and savings of the recommended project, based upon
debt financing for construction. The present value of these annual cash flows over the projects
50 year life is presented with and without the benefit of the excess electrical energy produced
by the project. Table 4 2 presents these economic data for the base case estimates, and also
presents a range of capital and operating costs considered possible for the project.
A range of estimated electric rates with the project in service is presented at the bottom of Table
4 2. This range reflects two variables: (1) whether revenues are earned from the projects excess
energy and (2) whether the community receives grant funds for construction costs.
NonProfit Community of Elfin CoveCrooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.June 2011Final Report 21Table 42: Summary of Economic Data for Recommended ProjectParameterValues Used forEconomic Analysis(Base Case)Range of ProbableValuesHYDRO PROJECT COSTSProject Installed Cost(1)$1.85M $1.64M$2.06MAnnual Operations, Maintenance, Repair & Replacement Costs (for 50 years)(1)$8,200 $7,600$8,900Annual Debt Payments (for 30 years)(1)$118,600 $103,600$134,100Salvage Value (at year 50) $0 $0PRESENTVALUE OFPROJECTCOSTS$2.54M $2.26M$2.82MHYDRO PROJECT BENEFITS (UTILITY FUEL SAVINGS ONLY)Displacement of Energy Generated by Diesel Power plant (kWh) 356,100 356,100Displaced Diesel Fuel for Power plant (gallons) 28,500 28,500Annual Value of Displaced Fuel (for 50 years)(1)$114,000 $114,000PRESENTVALUE OFPROJECTBENEFITS(UTILITYFUELSAVINGSONLY) $2.93M $2.93MBENEFITCOST RATIO (UTILITY FUEL SAVINGS ONLY) 1.15 1.041.30HYDRO PROJECT BENEFITS (UTILITY FUEL SAVINGS + EXCESS ENERGY USAGE)Net Excess Hydro Energy (kWh per yr)(1)241,600 241,600Displaced Heating Fuel (gallons per year)(1)6,800 6,800Annual Value of Displaced Heating Fuel (dollars per year) $27,200 $27,200PRESENTVALUE OFPROJECTBENEFITS(INCLUDING EXCESS ENERGY) $3.63M $3.63MBENEFITCOST RATIO (COUNTING EXCESS ENERGY BENEFIT) 1.44 1.291.61Estimated ECUC Electric Rate100% Debt Financed Project(2)$0.430.47 per kWh $0.390.51 per kWhEstimated ECUC Electric Rate100% Grant Financed Project(2)$0.100.14 per kWh $0.100.14 per kWh(1) See Appendix G for assumptions used in the economic analysis and the project cost estimate.(2) The range of electric rates considers utility finances with and without revenue from the sale of excess hydroelectricity from the project. Excess energy revenues arecalculated based on a hypothetical sales rate of $0.06 per kWh for interruptible service. For a heating system with 90% efficiency, this rate is approximately equal toa fuel price of $2.80 per gallon, which is a 30% discount at a fuel price of $4.00 per gallon.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 22
4.1 PROJECT SIZING ANALYSIS
A range of project configurations was evaluated to determine the recommended configuration
to meet Elfin Coves needs. Evaluation of each project configuration considered:
Prime energy furnished by the hydro project (displacement of diesel fired generation);
Probable costs associated with construction, operation, and maintenance of the hydro
project;
Constructability and maintainability of the project, and;
The amount of excess energy generated by the hydro project (potential displacement of
heating fuel or other uses).
In addition to general project sizing parameters, two major project configuration options were
evaluated as part of this analysis:
Whether to install a power recovery turbine on the Crooked Creek diversion, and
Whether to construct a dam at the Jims Lake outlet to increase the amount of storage.
Analysis of these options determined that a power recovery turbine on the Crooked Creek
diversion is justified, whereas a dam at Jims Lake is not. These and other findings are discussed
in greater detail in Appendix H.
4.2 SENSITIVITY ANALYSIS
A sensitivity analysis was performed to determine how sensitive the economic analysis
conclusions are to variations in assumptions and input parameters. The assumptions and inputs
reviewed and the results are summarized in Table 4 3. For each variable, the input range
considered, resulting range of benefit cost ratio, and value that results in a benefit cost ratio of
1.0 are presented.
The project is most sensitive to three parameters:
Installed cost,
Financing cost, and
Fuel cost.
Installed Cost
Construction cost overruns on small hydroelectric systems such as those recommended for Elfin
Cove can significantly reduce the project benefits. Proper project design and construction
management are key to a successful on budget project. An adaptive design that can quickly
address changing field conditions using on site materials, equipment, and labor will help to
control construction costs. Also, selecting a contractor with local experience or using force
account construction with a capable superintendent is recommended to help control
construction costs.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 23
Table 4 3: Sensitivity Analysis Results
Parameter
Base Case Value
(Benefit Cost Ratio
of 1.15)
Range
Considered
Range of
Resulting Benefit
Cost Ratio
Value for
Benefit Cost
Ratio of 1.00
(1)
Installed Cost $1,850,000 +/25% 0.9 to 1.6
$2,146,000
(16% over cost
estimate(1))
Load Growth No growth 25% to +200%
(2)0.9 to 1.7 17%
Annual Operations
Costs $17,470/yr +/50% 1.1 to 1.3
$34,100/yr
(195% over
cost estimate)
Financing Rate 6% 0 to 8% 1.0 to 2.3 7.6%
Cost of Fuel $4.00 per gallon $1.50 to $6.00 0.4 to 1.8 $3.45/gal
Percent Utilization of
Excess Energy
0% 0% to 100% 1.2 to 1.4 NA
Environmental
Attributes Sales Price
$0.00 per kWh $0.00 to $0.03 1.2 to 1.7 NA
(1) The feasibility level project cost estimate includes a 20% contingency on the construction cost.
(2) Load growth cases assume a constant load over the projects economic life at the stated percentage of existing
annual load.
NA: Not applicable because variations in the parameter cannot result in a benefit cost ratio of 1 or less.
Financing Cost
If the project is debt financed, it will have a benefit cost ratio of 1.0 or less if the interest rate on
the debt exceeds approximately 7.6%. Government loan programs such as the State of Alaska s
Power Project Fund offer interest rates capped at 6%. Lower rates are possible through this and
similar government loan programs. Elfin Cove is also eligible for a variety of state and federal
grant and loan guarantee programs that can help lower annual project costs.
Fuel Cost
The projects benefits are sensitive to the price of fuel. Under the 100% debt financed base
scenario for the project, the benefit cost ratio is 1.00 at a fuel price of $3.45 per gallon. ECUC
paid less than this for fuel as recently as 2005. While the long term fuel cost is considered
unlikely to be below $3.45 per gallon delivered in Elfin Cove, prices may fall below this price for
a season or more in the early years that the project is operational.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 24
5.0 CONCLUSIONS AND RECOMMENDATIONS
A two system hydroelectric project with a run of river system between Crooked Creek and
Jims Lake and storage system between Jims Lake and tidewater as recommended in this study
will supply 99% of ECUCs current year round electrical demand in an average water year. The
recommended project will also provide a substantial amount of excess energy, approximately
equal to 88% of ECUCs current average annual load. Most of this excess energy will be
available during the winter months, and can be used to displace heating fuel. If ECUC load
increases in the future, the storage at Jims Lake will allow nearly all of the projects output to be
used to supply ECUC load.
At an estimated installed cost of $1.85 million, the recommended project has a direct benefit
cost ratio of 1.15 compared to continued reliance on diesel fuel for electrical generation. If the
significant amount of excess energy generated by the project is put to beneficial use, the
projects benefit cost ratio increases to 1.44.
Based on the findings of this study, continued development of the project is warranted, as it can
provide a significant long term benefit to Elfin Cove. The next major steps to develop the
project are:
1. Start the permitting process. The recommended project configuration may be eligible for
a Federal Energy Regulatory Commission (FERC) licensing exemption, which is
expected to be less costly and faster than a FERC license. Initial communications with
the U.S. Forest Service (USFS) (the land owner) indicate they may be supportive of an
exemption process. An agency scoping process should occur early in the permitting
process to define any environmental studies needed to issue permits.
2. Continue to collect hydrology data at Crooked Creek and Jims Lake. Existing gauging
stations and equipment are adequate to continue collecting hydrology data at both sites.
Routine maintenance to replenish power supplies, measure flows, and download data
are necessary.
3. Conduct a limited load study to better characterize ECUC peak loads during the
summer months. Existing data indicates ECUC experiences high peak loads during the
summer. Characterizing the frequency and duration of these peak loads will help verify
whether the lower project capacity recommended in this study is optimal. The load
study should include a survey of self generating practices of the lodges in Elfin Cove.
4. Complete project designs and prepare design and construction documents. Decide on a
construction management methodology.
5. Other Alaska communities are currently designing and deploying interruptible energy
dispatch systems. Elfin Cove should monitor these efforts to evaluate how well the
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report 25
2009 2010 2011 2012 2013
ACTIVITY Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Reconnaissance Study (Completed)
Feasibility Study (Completed)
Project Design
Permitting
FERC Exemption
Resource Studies
USFS Authorizations
Construction Plan
Financing Plan
Construction
Project Commissioning
Construction Phase Close out
systems perform and to help guide how the hydro projects excess energy can best be
used.
5.1 DEVELOPMENT PLAN & SCHEDULE
The major steps to advance a hydro project for Elfin Cove are listed below.
1. Prepare and submit permit applications for the project, starting with a declaration of
intent to FERC and correspondence with the U.S. Forest Service.
2. Complete designs for the project.
3. Obtain all permits required for the project.
4. Secure construction funding.
5. Construction.
The expected schedule for completion of the recommended hydro project is presented in Figure
5 1. This schedule is based on best available information.
Figure 5 1: Project Development Schedule
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX A MAPS AND FIGURES
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report A 1
Figure A 1: Project Overview and Location Map
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report A 2
Figure A 2: Map of Recommended Crooked Creek / Jims Lake Project
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report A 3
Figure A 3: Graphical Index of Photographs Included in Appendix B
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX B PHOTOGRAPHS
NOTE:
FIGURE A 3 PROVIDES A MAP INDEX OF THE PHOTOGRAPHS IN APPENDIX B.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 1
Small Sandy Beach.
Proposed powerhouse site.
El:20
Jims Lake
El:333
Crooked Creek
Intake/Diversion Site
(behind hill)
El: 480
Mass Wasting
Event (Post 2002)
To Elfin Cove
Photograph B 1: Aerial View of Small Sandy Beach, Jims Lake, and Crooked Creek
Aerial view of the Crooked Creek / Jims Lake Project area.
July 6, 2009. Polarconsult.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 2
Photograph B 2: Crooked Creek
Gauging Station / Intake Site,
Looking Upstream
Photograph B 3: Crooked Creek
50 Yards Above Gauging Station /
Intake Site, Looking Upstream
Photograph B 4: Crooked Creek
Gauging Station / Intake Site,
Looking Downstream
Note large boulders in background
(covered in vegetation). These are part of
a larger boulder field (see Photograph
B 19) believed to be from a mass wasting
event spawned from cliffs to the left in
this view. Similar cliffs are adjacent to
this intake site (See Photograph B 1).
Crooked Creek is flowing at 3.71 cfs.
October 9, 2009. Polarconsult.
The log that forms the outlet control for
the gauging pool is evident. The data
logger hardware is visible in the
foreground. The diversion will be located
at a small falls located 20 yards below the
gauging station (red arrow).
Crooked Creek is flowing at 2.41 cfs.
August 10, 2010. Polarconsult.
Crooked Creek runs at a gradient of 2%
to 5% for approximately ¼ mile above
the gauging station / intake site.
Crooked Creek is flowing at 1.0 cfs.
July 8, 2009. Polarconsult.
Proposed Diversion
Location
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 3
Photograph B 5: Crooked Creek at
Gauging Station / Intake Site,
Looking to South
Photograph B 6: Crooked Creek at
Gauging Station / Intake Site,
Looking to North
Photograph B 7: Cliffs North of
Crooked Creek Gauging Station /
Intake Site
Approximately 30 yards downstream of
the proposed diversion site, Crooked
Creeks gradient increases to 15 40%, and
flows over large boulders. This view is
approximately 100 yards downstream of
the intake site.
August 10, 2010. Polarconsult.
View looking at the south bank of
Crooked Creek at the gauging station /
intake site. ECUC Project Manager Jane
Button is standing at the edge of the
valley floor approximately 20 feet from
the south bank of Crooked Creek.
August 12, 2010. Polarconsult.
View looking at the north bank of
Crooked Creek at the gauging station /
intake site. ECUC Project Manager Jane
Button is standing near the edge of the
valley floor amidst boulders 5 to 20 feet
in size. The valley wall is a nearly
vertical rock face. Ms. Button is
approximately 80 feet from the north
bank of Crooked Creek.
August 12, 2010. Polarconsult.
View at the gauging station looking in
the direction of Jims Lake. Terrain is
level for 20 feet beyond the south bank of
Crooked Creek and then climbs at a 1:1½
slope.
Crooked Creek is flowing at 2.41 cfs.
August 10, 2010. Polarconsult.
View of cliffs and rock outcrops on the
north side of Crooked Creek Valley
overlooking the gauging station / intake
site. This view is directly above
Photograph B 6.
August 12, 2010. Polarconsult.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 4
Photograph B 8: Crooked Creek
100 Yards Below Gauging Station /
Intake Site, Looking Downstream
Photograph B 9: Typical Terrain
and Vegetation Along Penstock
Route Between Crooked Creek
and Jims Lake
Photograph B 10: View of Upper
Powerhouse Site looking
Northeast Across Jims Lake
Approximately 30 yards downstream of
the proposed diversion site, Crooked
Creeks gradient increases to 15 40%, and
flows over large boulders. This view is
approximately 100 yards downstream of
the intake site.
August 10, 2010. Polarconsult.
Approximately 20 yards downstream of
the proposed diversion site, Crooked
Creeks gradient increases to 15 40%, and
flows over large boulders. This view is
approximately 100 yards downstream of
the intake site.
August 10, 2010. Polarconsult.
View looking towards Jims Lake along
the penstock route approximately 350
feet from the Crooked Creek diversion
site. The terrain and vegetation is
representative of the penstock route for
the upper project.
August 12, 2010. Polarconsult.
View looking northeast across Jims Lake.
The approximate upper powerhouse site is
indicated by the red arrow.
August 10, 2010. Polarconsult.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 5
Photograph B 11: Bathymetric
Survey of Jims Lake
Photograph B 12: Jims Lake
Creek Gauging Station
Photograph B 13: Typical Peat
Bogs in Project Vicinity
The weir is visible at the lower left of the
photograph.
August 10, 2010. Polarconsult.
Polarconsult engineer Joel Groves
conducting a bathymetric survey of Jims
Lake.
July 9, 2009. Polarconsult.
A peat bog located at an elevation of
about 120 to 150 feet between tidewater
and Jims Lake. Brown areas in the
foreground are normally ponds. July
2009 was the 2
nd driest July on record in
Elfin Cove.
July 8, 2009. Polarconsult.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 6
Photograph B 14: Penstock Route
through Ravine Below Jims Lake
Photograph B 15: Site Overview
from Offshore
The lower penstock will pass through
this small ravine immediately
downstream of Jims Lake. The ravine is
approximately 20 feet deep and has 1:1
sidewalls.
Jims Lake Creek is flowing at 0.42 cfs.
August 10, 2010. Polarconsult.
This vantage point provides a good overview
of the relative positions and visibility of the key
project features from sea level along Port
Althorp near the coast.
August 11, 2010. Polarconsult.
UPPER (CROOKED CREEK)
INTAKE (NOT VISIBLE)
LOWER (TIDEWATER)
POWERHOUSE SITE
(VISIBLE)
JIMS LAKE
(NOT VISIBLE)
TO ELFIN COVE
PENSTOCKS & ACCESS
TRAILS (NOT VISIBLE)
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 7
Photograph B 16: View of Lower
Powerhouse Site Looking North
Photograph B 17: Typical View of
Power Line Route Between Project
and Elfin Cove
Photograph B 18: Soils Along
Power Line Route Between Jims
Lake and Elfin Cove
Photograph B 18: Soils Along
Power Line Route Between Project
and Elfin Cove
Terrain is typically moderate slopes of
10% to 25% and vegetated by mature
conifer forest.
July 7, 2009. Polarconsult.
The lower powerhouse will be located
amongst the conifer trees at the head of
the beach in this photograph. There are
50 to 80 foot tall rock cliffs that rise
behind the beach under these trees.
August 12, 2010. Polarconsult.
This uprooted tree reveals a shallow
organic soil layer overlaying mineral
soils containing abundant angular rocks
up to approximately 12 to 18 inches in
size.
July 7, 2009. Polarconsult.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 8
Photograph B 19: Debris Field Upstream
from Crooked Creek Intake Site
Photograph B 20: Debris Field in Elfin
Cove
Photograph B 21: Debris Field along Power
Line Route
This debris field is from a mass wasting event that
occurred sometime after 1990.
October 10, 2009. Polarconsult.
This debris field extends to the proposed intake site
on Crooked Creek. Polarconsult engineer Dan
Hertrich is sitting on a 20 foot boulder. Cliffs
overlooking this site are similar to those above the
intake site shown in Photograph B 7.
July 8, 2009. Polarconsult.
This debris field, located adjacent to the proposed
power line route between Jims Lake and Elfin
Cove, is from a mass wasting event that occurred
sometime after 2002.July 7, 2009. Polarconsult.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX C HYDROLOGY DATA
C.1: Available Hydrology Data pages C 1 to C 2
C.2: Jims Lake Bathymetry page C 3
C.3: Stream Gauge Station Information pages C 4 to C 8
C.4: Crooked Creek Hydrology Data pages C 9 to C 11
C.5: Jims Lake Outlet Hydrology Data pages C 12 to C 14
C.6: Roys Creek Hydrology Data pages C 15 to C 16
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 1
Approximately 2.7 years of hydrology data have been collected at both Crooked Creek and
Jims Lake Creek, and approximately 1.2 years of data have been collected at Roys Creek.
4
Gauging stations remain in service at all three sites. Each gauging station is described in Section
C.3. This Appendix summarizes the hydrology data and analysis used for this study.
Appendix J provides the daily stage and calculated flow data for all three gauging stations in
tabular form.
This hydrology information is used to determine the appropriate installed capacity of the
hydroelectric project, evaluate the expected performance of the project, and determine the
magnitude of flood flows on each creek. Moreover, this hydrology information can help assess
the effect the project may have on the natural environment.
C.1 AVAILABLE HYDROLOGY DATA
Existing hydrology data is summarized in Table C 1. Flow measurements at the gauging
stations near Elfin Cove are summarized in Table C 2. Hydrographs, stage discharge curves,
flow duration curves, and station notes for the three gauges are included on pages C 9 through
C 16.
Table C 1: Summary of Hydrology Data for Elfin Cove Hydroelectric Resources
Location USGS
Gauge ID
Basin
Size
(sq.mi.)
Site
Elevation
(ft)(1)
Latitude(1)Longitude(1)Begin
Date
End
Date
Number of
Daily
Records(3)
Crooked Creek
at diversion site
0.56 478.0 58 10 40 136 19 16 7/6/84(2)2/13/85(2)202
8/22/08 Current 752
Jim s Lake
Creek at lake
outlet
0.10 333.2 58 10 34 136 19 32
7/6/84(2)2/11/85(2)202
8/22/08 Current 821
Roy s Creek at
intake site
0.42 480 (est.) 58 11 29 136 20 03 10/9/09 Current 462
(1) Coordinates for U.S. Geological Survey gauges are in North American Datum of 1927 (NAD 27). All
other coordinates are in NAD 83. Elevations are in mean high water at Elfin Cove.
(2) Count of available daily records. Gauges may have been in service for a longer period.
(3) The record count for current gauging stations reflects data through the most recent download on May
9, 2011.
4 While a hydroelectric project at Roys Creek is not considered in this study, hydrology data for the
site is included in this Appendix for reference should that resource be investigated in the future.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 2
Table C 2: Flow Measurements for Elfin Cove Hydroelectric Resources
Date/Time Party
Flow
(cfs)
Stage
(ft)Method / Equipment
Crooked Creek at Diversion Site (1984 to 1985)
7/6/1984 13:30 Ireland/ Collazzi 0.8 0.71 Marsh McBirney
(1)
11/20/1984 10:15 Ireland/ Collazzi 2.72 0.84 Marsh McBirney
3/2/1985 10:15 Ireland/ Collazzi 2.29 0.7 Marsh McBirney
3/11/1986 11:47 Ireland/ Collazzi 1.47 0.6 Marsh McBirney
Crooked Creek at Diversion Site (2008 to 2010)
7/26/2008 15:15 Button/ Christensen 2.33 7.7 Pygmy Meter
(2)
7/27/2008 16:20 Button/ Christensen 4.35 7.76 Pygmy Meter
8/22/2008 14:30 Button/ Christensen 5.38 7.92 Pygmy Meter
6/1/2009 11:39 Button/ Christensen 4.17 7.73 Pygmy Meter
6/28/2009 16:40 Button/ Christensen 1.3 7.6 Pygmy Meter
7/9/2009 10:55, 11:20 Groves/ Hertrich 0.98 / 0.94 7.54 Hanna Meter
(3)
9/4/2009 11:15, 11:40 Groves/ Glendoing 0.84 / 0.93 7.54 Hanna Meter
10/9/2009 12:50 Groves/ Christensen 3.71 7.68 Hanna Meter
12/9/2009 13:45 Button/ Christensen 1.07 7.52 Hanna Meter
8/10/2010 11:40, 12:15 Groves/ Button 2.41 / 2.25 7.62 Hanna Meter
Jims Lake Creek at Lake Outlet (1984 to 1985)
7/6/1984 11:15 Ireland/ Collazzi/ Wild 0.23 Marsh McBirney
11/20/1984 9:00 Ireland/ Collazzi 0.93 0.57 Marsh McBirney
3/2/1985 9:30 Ireland/ Collazzi 0.25 0.125 Marsh McBirney
3/11/1986 10:00 Ireland/ Collazzi 0.75 0.35 Marsh McBirney
Jims Lake Creek at Lake Outlet (2008 to 2009)
7/25/2008 12:30 Button/ Christensen 3.42 4.18 Pygmy Meter
7/26/2008 10:45 Button/ Christensen 1.3 3.82 Pygmy Meter
8/22/2008 12:45 Button/ Christensen 0.11 3.7 Pygmy Meter
6/1/2009 10:00 Button/ Christensen 0.54 3.73 Pygmy Meter
6/28/2009 18:00 Button/ Christensen 0.04 3.61 Pygmy Meter
7/9/2009 12:15, 12:30 Groves/ Hertrich 0.091 / 0.091 3.56 Hanna Meter
9/4/2009 10:00, 10:15 Groves/ Glendoing 0.219 / 0.217 3.52 Hanna Meter
10/9/2009 13:45 Groves/ Christensen 0.44 3.62 Hanna Meter
Jims Lake Creek at Lake Outlet (2009 to 2010)
(4)
10/9/2009 14:05 Groves/ Christensen 0.44 3.69 Hanna Meter
12/9/2009 14:15 Button/ Christensen 0.219 3.68 Hanna Meter
8/10/2010 10:30, 10:45 Groves/ Button 0.421 / 0.422 3.72 Hanna Meter
Roys Creek at Intake Site (2009 to 2010)
9/3/09 17:00 Groves 1.06 Hanna Meter
10/8/2009 16:45, 17:00 Groves/ Christensen 3.05 / 2.72 1.27 Hanna Meter
12/9/2009 11:45 Button/ Christensen 0.66 1.09 Hanna Meter
8/13/2010 11:30, 12:20 Groves/ Button 1.05 / 1.07 1.17 Hanna Meter
(1) Current velocity stream flow method with March McBirney current velocity meter (model unknown).
(2) Current velocity stream flow method with Pygmy current velocity meter.
(3) Sudden dose salt integration stream flow method with Hanna HI 9828 conductivity meter.
(4) A small weir was installed on October 9, 2009, to stabilize and improve the section at the gauge.
Indicates data are not available.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 3
C.2 JIMS LAKE BATHYMETRY
The storage curve for Jims Lake was calculated from bathymetry data collected in July 2009,
and is presented in Figure C 1.
Figure C 1: Jims Lake Storage Curve
The storage curve for Jims Lake was used to model reservoir stage in the generation dispatch
models discussed in Appendix H.
320
325
330
335
340
345
350
0 20 40 60 80 100 120 140
Available Storage (ac ft)
NATURAL LAKE ELEVATION = 333 FEET
EST. MAXIMUM PRACTICAL SPILLWAY HEIGHT = 341 FEET ( + 8 FEET)
ESTIMATED MAXIMUM PRACTICAL DRAWDOWN = 325 FEET (8 FEET)
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 4
C.3 STREAM GAUGE STATION INFORMATION
C.3.1 1984 86 Installations at Crooked Creek and Jims Lake Creek
According to Alaska Department of Natural Resources (ADNR) personnel, the 1984 to 1986
Crooked Creek and Jims Lake Creek stage data was measured with vented pressure
transducers and recorded on data loggers manufactured by Bob Dryden.
5 The only data
recovered from the 1984 to 1986 stream gauging efforts at Crooked Creek and Jims Lake Creek
was a sheaf of dot matrix printouts covering the period July 1984 through February 1985 and
ADNRs flow measurement data for both sites. The dot matrix printouts include date, stage,
and calculated flow. ADNRs stream flow database includes four measurements at each site
from the 1984 to 1986 period (Table C 2).
The stage and calculated flow data on the printouts for both gauging stations were compared
with the 1984 to 1986 flow measurements and the stage discharge equations for the current
stations located at the same sites. The Jims Lake Creek dot matrix printout data was consistent
with both the 1980s ADNR flow measurements and contemporary data, so the calculated flow
data was not modified. The Crooked Creek dot matrix printout data did not correlate well with
the 1980s field measurements in the ADNR database or contemporary data. The stage discharge
equation for the current Crooked Creek gauging station was adapted to fit the flow
measurements collected in 1984 to 1986, and used to recalculate flows from the reported stage
data. These data are presented with current data for each gauging station in Section C.4 and
Section C.5 for Crooked Creek and Jims Lake Creek, respectively.
C.3.2 Current Installation Crooked Creek Gauging Station at Diversion Site
In August 2008, ECUC installed a new gauging station in the vicinity of the 1984 to 1986
Crooked Creek gauging station.
The gauging station at Crooked Creek is in a pool 20 yards upstream of the proposed diversion
structure. The outlet of this pool is controlled by a large log embedded in gravel lying at a slight
angle to the waters surface and nearly perpendicular to the direction of flow. The channel at
the log is approximately 13 feet wide (See Photographs B 2 and B 4).
From August 24, 2008 through October 9, 2009, Crooked Creek stage data was measured and
recorded with a Hobo U 20 series sealed level logger manufactured by Onset, Inc. This sensor
was installed inside a three inch diameter perforated plastic stilling well fastened to a boulder
at the edge of the pool. Atmospheric pressure fluctuations were measured with a single Hobo
U 20 series atmospheric pressure logger (barologger)installed at the Crooked Creek gauging
station. Stage data at this station was calculated by subtracting atmospheric pressure from the
absolute pressure measured by the sealed in stream sensor.
5 Roy Ireland, ADNR hydrologist, personal communication. 2009.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 5
The barologger experienced data quality problems in cold weather during the winter of 2008 09.
Substantial data gaps in November December 2008 and January 2009 are due to these
problems. The data gap from early February 2009 through the end of June 2009 is due to the
data logger memory being full.
On October 9, 2009, the Hobo hardware at Crooked Creek was replaced with an Acculevel
vented pressure transducer manufactured by Keller America, Inc., fitted to a MONITOR 4 data
logger manufactured by Sutron, Inc. This hardware is powered by four D cell lithium batteries.
6
Batteries must be replaced annually. An attempt to replace the batteries in December 2010 was
unsuccessful due to defective replacement batteries, and the original batteries failed on
February 24, 2011. New batteries were installed on May 9, 2011. As of this date, the equipment
remains in service at the gauging station.
C.3.3 Current Installation Jims Lake Creek Gauging Station at Lake Outlet
In August 2008, ECUC installed a new gauging station in the vicinity of the 1984 to 1986 Jims
Lake Creek gauging station at the lake outlet.
The gauging station at Jims Lake Creek is about 10 feet downstream of the lake outlet in a
shallow pool formed by loose rocks sitting on a weathered bedrock stream bed. After several
measurements in the summer of 2009, it was determined that this section was not stable,
resulting in inconsistent stage discharge measurements. On October 9, 2009, a small weir was
built of local materials in an effort to stabilize the stage discharge relationship at this location
(See photograph B 12).
From August 24, 2008 through October 9, 2009, Jims Lake Creek stage data was measured and
recorded with a sealed Hobo U 20 series level logger manufactured by Onset, Inc. This sensor
was installed inside a three inch diameter perforated plastic stilling well secured to the earthen
bank with boards and spikes. Atmospheric pressure fluctuations were measured with the
barologger installed at the Crooked Creek gauging station. Stage data at this station was
calculated by subtracting atmospheric pressure at Crooked Creek from the absolute pressure
measured by the sealed in stream sensor.
Using the Crooked Creek barologger to correct for atmospheric fluctuations at the Jims Lake
Creek gauging station created noise in the stage data at the Jims Lake Creek gauging station.
This noise was due to transient atmospheric pressure differences (windy conditions) between
the Crooked Creek and Jims Lake Creek gauging stations. The same cold weather performance
problems with the barologger resulted in loss of useful data at Jims Lake Creek for the
November 2008 to January 2009 period.
6 In August 2010, a 5 watt amorphous silicon solar panel was tested at the gauging station, but failed to
work due to the low ambient light at the site.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 6
On October 9, 2009, the barologger was moved to the Jims Lake Creek station to improve
atmospheric correction at this station. The barologger was mounted in a large vented desiccant
canister to improve cold weather performance. The Hobo sealed pressure transducer installed
in 2008 remains in service at the Jims Lake outlet station. The barologger did not exhibit cold
weather problems during the winter of 2009 10. Manual stage readings on December 11, 2010
and May 9, 2011 indicate a discrepancy between actual and recorded creek stage. At this time,
the cause of this discrepancy has not been determined. Because of this discrepancy, calculated
flow is not reported after December 11, 2010. As of May 9, 2011, the data logger equipment
remains in service at the gauging station. The internal batteries for the Hobo data loggers have a
typical service life of five years. These batteries should be replaced in the summer of 2013.
C.3.4 Current Installations Roys Creek Gauging Station at Diversion Site
While the Community of Elfin Cove is not actively considering development of Roys Creek,
this gauging station will remain active through the winter of 2010 11 to collect sufficient data to
support any future study of this resource. Interim data is included in this study to facilitate such
efforts.
On October 9, 2009, an Acculevel vented pressure transducer manufactured by Keller America,
Inc. was installed at an elevation of approximately 430 feet on Roys Creek. The sensor is
installed in a three inch diameter HDPE stilling tube mounted to a large boulder in a small
plunge pool about 50 yards upstream from the waterfall. The outlet control for this pool is a
series of large boulders interlocked with smaller bed materials and resting on bedrock. This
sensor is fitted to a MONITOR 4 data logger manufactured by Sutron, Inc. This hardware is
powered by four D cell lithium batteries.
7 Batteries must be replaced annually. An attempt to
replace the batteries in December 2010 was unsuccessful due to defective replacement batteries,
and the original batteries failed on January 11, 2011. New batteries were installed on May 9,
2011.. As of this date, the equipment remains in service at the gauging station. Stage data, flow
data, the stage discharge curve, and the flow duration curve are presented in Section C.6.
C.3.5 Flow Measurements and Station Calibration
To calibrate each gauging station, ECUC performed several flow measurements at the Crooked
Creek and Jims Lake gauging stations during 2008 and 2009 using a pygmy current velocity
meter. Polarconsult and ECUC personnel conducted additional flow measurements in 2009 and
2010 to complete calibration of all three gauging stations (Table C 2). The resulting stage
discharge calibration curves for the three stations are presented in Sections C.4 C.6. The stage
discharge equations and methodology are discussed in this section and the equation parameters
are summarized in Tables C 3 and C 4.
7 In August 2010, a 5 watt amorphous silicon solar panel was tested at the gauging station, but failed to
work due to the low ambient light at the site.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 7
The existing flow measurements and calibrated sections of the stage discharge curves at all
three stations have good confidence at low and medium flows, which are of primary interest for
hydropower assessment. Additional high flow measurements at all three stations would be
useful to increase confidence in the upper end of the stage discharge curves. These data would
improve estimates of infrequent high flow events that have limited hydropower value, but are
important for design of the diversion structures.
Stage discharge curves at each station were developed using Mannings equation for open
channel flow (Equation C 1).
Equation C 1: Q = 1.49 n
1 A R
2/3 So1/2
Where: Q = flow in cubic feet per second R = hydraulic radius (= A/P)
n = roughness coefficient P = wetted perimeter in feet
A = area, in square feet So = slope in feet per feet
Table C 3: Manning Equation Parameters for Gauging Stations
Gauging Station and Epoch
N
(roughness
coefficient)
So
(Slope in
feet/foot)
A
(Sectional area,
square feet)
P
(Wetted
perimeter, feet)
Crooked Creek Intake Site
(1984 1985)0.025 0.0016 Calculated from creek section
parameters listed in Table C 4.Crooked Creek Intake Site
(2008 2010)0.025 0.0016
Jim s Lake Creek at Lake
Outlet (1984 1985)Unchanged from original ADNR calculations
Jim s Lake Creek at Lake
Outlet (2008 2010)0.025 0.002 Calculated from creek section
parameters listed in Table C 4.Roy s Creek Intake Site
(2009 2010)0.04 0.055
Initial values of So and n were selected based on the physical characteristics of the site, and
adjusted until calculated flows and measured flows were in good agreement. These values are
listed in Table C 3. The area (A) and wetted perimeter (P) of the creek at the gauging station are
both functions of the stage and the shape of the creek bed. A model of the creek bed profile was
developed for each gauging station, and was used to compute A and P over the range of
observed stages. Models of the creek bed section profiles for each gauging station are listed in
Table C 4 and an example illustration is shown in Figure C 2. The computed A and P were then
entered into Equation C 1 to determine flow.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 8
Table C 4: Creek Sections used to Calculate A and P at Gauging Stations
Gauging Station and Epoch Segment L2 Segment L1 Center Segment R1 Segment R2
Crooked Creek Intake Site
(1984 1985)
Slope = 0.05
Stage =2.70
Slope = 1.00
Stage =0.70
4.5wide
at 0.30
Slope = 1.00
Stage =0.75
Slope = 0.05
Stage =2.75
Crooked Creek Intake Site
(2008 2010)
Slope = 0.05
Stage =9.71
Slope = 1.00
Stage =7.71
13.5wide
at 7.41
Slope = 1.00
Stage =7.91
Slope = 0.05
Stage =9.91
Jim s Lake Creek at Lake
Outlet (2008 2009)
Slope = 0.87
Stage =6.35
Slope = 2.00
Stage =4.15
1.65wide
at 3.35
Slope = 0.67
Stage =3.95
Slope = 0.43
Stage =6.35
Jim s Lake Creek at Lake
Outlet (2009 2010)Same as 2008 09 curve, stage data for model shifted +0.07
Roy s Creek Intake Site
(2009 2010)
Slope = 1.00
Stage =10.93
Slope = 4.00
Stage =5.93
1.5wide
at 0.93
Slope =0.30
Stage =2.93
Slope = 2.00
Stage =10.93
Figure C 2: Model Used for Creek Section Profile at Jims Lake Creek
3.0
4.0
5.0
6.0
7.0
0 2 4 6 8 10 12
Creek Profile Station in feet (Looking Downstream)
Thalweg
Segment R2
Segment R1
Segment L2
Segment L1
Center
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 9
C.4 CROOKED CREEK HYDROLOGY DATA
Figure C 3: Crooked Creek Stage Discharge Curves
Figure C 4: Crooked Creek Flow Duration Curves
2008 2011
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 10
Figure C 5: 1984 1985 Crooked Creek Stage Data
Figure C 6: 1984 1985 Crooked Creek Flow Data
NonProfit Community of Elfin CoveCrooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.June 2011Final ReportC11Figure C7: 20082011 Crooked Creek Stage DataFigure C8: 20082011 Crooked Creek Flow DataFigure C7:20082011 Crooked Creek Stage DataFigure C8:20082011 Crooked Creek Flow DataStage (feet, station datum)Flow (cfs)
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 12
0.01
0.10
1.00
10.00
3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8
Stage (feet, station datum)
Discharge Curve (2008 09)
Measured Stage & Flow (2008 09)
Discharge Curve (2009 10)
Measured Stage & Flow (2009 10)
Discharge Curve (2009 10)(2008 09 curve is valid before 10/9/2009, and 2009 10 curve is valid after.)
C.5 JIMS LAKE CREEK HYDROLOGY DATA
Figure C 9: 2008 2009 and 2009 2011 Jims Lake Creek Stage Discharge Curves
Figure C 10: 1984 1985 and 2008 2011 Jims Lake Creek Flow Duration Curve
2008 2011
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 13
Figure C 11: 1984 1985 Jims Lake Creek Stage Data
Figure C 12: 1984 1985 Jims Lake Creek Flow Data
NonProfit Community of Elfin CoveCrooked Creek and Jims Lake Hydroelectricity Feasibility Study Polarconsult Alaska, Inc.June 2011Final ReportC14Figure C13: 20082011 Jims Lake Creek Stage DataFigure C14: 20082011 Jims Lake Creek Flow DataFigure C14:20082011 Jims Lake Creek Flow DataStage (feet, station datum)Figure C13:20082011 Jims Lake Creek Stage DataFlow (cfs)
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 15
C.6 ROYS CREEK HYDROLOGY DATA
Figure C 15: 2009 2011 Roys Creek Stage Discharge Curve
Figure C 16: 2009 2011 Roys Creek Flow Duration Curve
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report C 16
Figure C 17: 2008 2011 Roys Creek Stage Data
Figure C 18: 2008 2011 Roys Creek Flow Data
0.5
1.0
1.5
2.0
2.5
3.0
3.5
10/2/2009 1/1/2010 4/2/2010 7/2/2010 10/2/2010 1/1/2011
0.1
1.0
10.0
100.0
10/2/2009 1/1/2010 4/2/2010 7/2/2010 10/2/2010 1/1/2011
Flow, calculated
Flow, calculated
Flow, measured
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX D RESOURCE DATA AND ANALYSIS
D.1: Maximum Probable Flood page D 1
D.2: Review of Climate Effects pages D 2 to D 5
D.2.1: Analysis of Effects from
Pacific Decadal Oscillation (PDO) pages D 2 to D 4
D.2.2: Analysis of Effects from
Long Term Climate Change pages D 4 to D 5
D.3: Geotechnical Considerations pages D 5 to D 6
D.3.1: Area Geomorphology pages D 5 to D 6
D.3.2: Typical Vegetation page D 7
D.4: Tsunami Hazards pages D 8 to D 9
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report D 1
D.1 Maximum Probable Flood
Determining the maximum probable flood for Crooked Creek and Jims Lake Creek is
important for (1) designing the in stream diversion structure at Crooked Creek so it can
withstand flood flows, and (2) determining the finished floor elevation of the upper system
powerhouse so it is not flooded by Jims Lake during storm events. Existing data from the
gauging stations is compared with U.S. Geological Survey (USGS) statistical models for
southeast Alaska streams to develop initial estimates of the 100 year flood flows for each creek.
The USGS has developed statistical models to estimate the maximum probable floods for
streams in southeast Alaska. These models are developed based on stream gauging data
throughout the region, and specific parameters for the drainage basin of the stream of interest.
8
USGS model input parameters and estimated flood flows are summarized in Table D 1. The
estimated 2 year flood flows in Table D 1 are approximately 150% greater than the highest
observed flows recorded at these stations since gauging resumed in July 2008. This is reasonable
agreement, given the accuracy of the USGS estimation method and the length of record at these
gauging stations. The estimated 100 year maximum probable flood flows are used for the
conceptual designs described in this feasibility study.
Table D 1: Maximum Probable Floods at Crooked Creek and Jims Lake Creek
Parameter Crooked Creek Jims Lake Creek
Basin Area (square miles)
(1)0.56 0.10
Mean Annual Precipitation (inches)
(2)100 100
Percentage of Basin as Storage (lakes, ponds) 0% 9%
Mean Minimum January Temperature (F)(2)25 25
Estimated 500 year flood 405 cfs 39 cfs
Estimated 100 year flood (Initial Estimate of Design Flood) 326 cfs 31 cfs
Estimated 2 year flood 125 cfs 12 cfs
Maximum Recorded Flow (1984 85, 2008 10)(3)88 cfs 7.6 cfs
(1) These drainage basins are smaller than the valid range of basin areas for the USGS model (0.72 to 571 square
miles). These estimated flood flows are adequate for feasibility assessment, but a more detailed flood analysis is
warranted for project design.
(2) Data are from source maps specified in the USGS publication. Actual weather data for the National Weather
Service station in Elfin Cove vary slightly.
(3) Maximum flows are calculated from recorded stage data and the stage discharge curve for each gauging station.
These calculated flows are well outside the range of measured flows used to develop the stage discharge curve,
so they may have significant extrapolation error.
8 See USGS Water Resources Investigation Report 2003 4188.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report D 2
D.2 Review of Climate Effects on Hydropower Projects
Long term climate trends can affect precipitation, temperature, snow pack, evapo transpiration,
and related hydrological processes, changing the amount and timing of discharge in local
streams, and therefore the amount of energy that a hydro project can generate. Two climate
fluctuation phenomena are of interest for this project:
1. The Pacific Decadal Oscillation (PDO).
9 Available information suggests that the output
of the Crooked Creek/Jims Lake project may be approximately 5% higher than
estimated in this study during positive phase PDO episodes. Economic analyses in this
study assume that the current PDO cycle, which likely switched to the negative phase in
the mid 2000s, persists throughout the economic life of the project. A transition to the
positive phase PDO is expected to slightly increase project output.
2. Long term climate change. Available information suggests that long term climate
change may increase electrical output from the Crooked Creek/Jims Lake project over
its 50 year design life, similar in magnitude to the effects of positive phase PDO
episodes. There is significantly less confidence in these long term climate trends and
effects than in the effects caused by the PDO. Economic analyses in this study do not
consider any effects from long term climate change.
These phenomena and their effects on the hydro project are discussed in greater detail below.
D.2.1 Analysis of Effects from PDO
In general terms, the PDO is a several decade long oscillation in sea surface temperatures in the
north Pacific Ocean. Around southeast Alaska, the positive phasePDO tends to result in more
frequent southerly winds, resulting in greater flow of warm, moist air into southeast Alaska.
The effect of positive phase PDO events in southeast Alaska is greatest in the winter time, when
it increases temperatures and, to a lesser degree, precipitation. The January temperatures in
Sitka are 6 C (10.8 F) warmer during the positive phase PDO than during negative phase
episodes.10
Warmer temperatures can transform winter precipitation from snow to rain, reducing
snowpack, increasing winter discharge, and decreasing the magnitude of spring melt. The
magnitude of these effects will vary based on basin orientation and elevation, but the general
result is to increase the winter time capacity factor of mostly run of river hydroelectric projects
such as those considered for Elfin Cove.
9 The PDO is a climate fluctuation phenomenon similar to the El Nino / La Nina oscillations in the
equatorial Pacific Ocean. The PDO and its effects on Alaskas climate are discussed at
http://jisao.washington.edu/pdo/.
10 Climate Impacts on Hydropower in Southeast Alaska, J. Cherry et. al, UAF Institute of Northern
Engineering. 2010.http://research.iarc.uaf.edu/~jcherry/SEAK_FINAL/seak_report_final.pdf
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report D 3
There is insufficient flow or climate data in Elfin Cove to directly evaluate the local effect of the
PDO. The last clear shift in the PDO phase was from negative to positive in 1976 77. The PDO
may have shifted back to negative in recent years, but a shift will not be apparent until several
years after the fact. Elfin Coves weather station was established in 1975, only one year before
the 1976 77 PDO shift. Its period of record therefore largely coincides with the most recent
positive phase of the PDO, and thus local data during a negative phase PDO cycle is
insufficient for a comparative analysis.
The nearest stream gauging station with a period of record suitable for evaluation of the PDOs
affect on hydropower is Tonalite Creek (USGS gauge #15106980, period of record from June 1,
1968 through September 30, 1988), located on the south side of Tenakee Inlet approximately 50
miles east southeast of Elfin Cove. The 20 year Tonalite Creek hydrology dataset spans the
1976 77 PDO shift, providing approximately nine years of discharge data during a negative
phase PDO (1968 to 1976) and eleven years of data during a positive phase PDO (1977 to 1988).
During the negative phase PDO, winter (December through March) discharge at Tonalite Creek
was significantly lower, and spring runoff was more intense and delayed approximately two
weeks relative to runoff timing during the positive phase PDO (Figure D 1). Discharge from
July through November was similar during both phases. This is consistent with the expected
effects of the PDO on southeast Alaska stream flows.
Figure D 1: Tonalite Creek Flows During Negative and Positive Phase PDO
0
50
100
150
200
250
300
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month15day Moving Average of Average Daily Discharge in TonaliteCreek(cfs)Average daily discharge for 1968 1976 (Negative Phase PDO)
Average daily discharge for 1977 1988 (Positive Phase PDO)
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report D 4
Expected hydropower output from a proposed run of river project on the Indian River near
Tenakee Springs (derived in part from the Tonalite Creek dataset) was found to be 5.5% higher
during the positive phase PDO than during the negative phase PDO. A similar variation is
expected for the recommended hydro project.11
D.2.2 Analysis of Effects from Long term Climate Change
Research indicates that current long term climate trends are making southeast Alaska warmer
and drier. On aggregate, southeast has warmed 0.45 C (0.8 F) since the 1920s, with most of the
warming occurring in the winter months. Spring, summer, and autumn daily temperature
variations are decreasing, with warmer nights and cooler days. This is attributed to an increase
in cloud cover. Southeast precipitation has decreased since the 1920s, although the statistical
robustness of precipitation trends is not as strong as for temperature trends.
12
Climate models forecast continued and accelerated warming in southeast. The rate of warming
is projected to increase eight fold from the +0.05 C (0.09 F) per decade warming rate observed
in the nine decades since 1920 to +0.43 C (0.77 F) per decade over the next nine decades to the
year 2100. Models also predict an increase in precipitation, in contrast to the slight decrease in
precipitation observed since the 1920s.
12 Based on these incongruities, current climate models
appear to have limited utility for projecting future performance at southeast Alaska
hydropower projects, and historical climate trends may be a better predictor of future climate.
If historical climate trends continue, the most significant effect of these changes for hydropower
is on snowpack. The effect of projected climate change trends over the 50 year design life of the
hydroelectric project is expected to be similar to the effect of the positive phase PDO as
described in Section D.2.1.
Climate trends in Elfin Cove, based on 1975 2010 weather records, are consistent with the
general trends observed in southeast Alaska as described above. Average annual temperatures
in Elfin Cove have increased 0.085 C (0.15 F) per decade over the past 35 years. Over this
period, spring (mid April through Mid June) temperatures increased 0.2 C (0.36 F) per
decade, winter (early November through late February) temperatures increased 0.27 C (0.5 F)
per decade, and March temperatures decreased 0.33 C (0.6 F) per decade. Temperatures from
July through October have remained constant, but daily temperature variations during these
months have decreased about 0.55 C (1.0 F) per decade.
Annual precipitation trends in Elfin Cove are flat over the period of record. Annual snowfall
was high in 2006 through 2009 (perhaps signaling a shift from positive to negative phase PDO
at about this time).
11 Indian River Hydroelectric Feasibility Study. Pages 17 18. Polarconsult Alaska, Inc. November 2009.
12 Climate Impacts on Hydropower in Southeast Alaska, J. Cherry et. al, UAF Institute of Northern
Engineering. 2010.http://research.iarc.uaf.edu/~jcherry/SEAK_FINAL/seak_report_final.pdf
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report D 5
In conclusion, available information suggests that climate change effects may cause the annual
energy production from the project to slightly increase over time, slightly improving the
economic benefits to the community. However, past climate trends and climate models do not
agree well, so these conclusions may prove wrong over time. Based on available information,
incorporating the potential effects of long term climate trends into the analysis or
recommendations of this study is not warranted.
D.3 Geotechnical Considerations
The prevalence of shallow bedrock throughout the project area precludes cost effective
trenching for burial of pipelines and power cables in some areas. Partial burial, on grade,
and/or above grade pipelines are viable project options. Similarly, on grade or shallow burial
cables in conduit are practical options for power and communications.
Access trails in certain areas may require removal of rock. To reduce construction costs,
geotechnical subsurface investigation is recommended before access alignments are finalized to
reduce the amount of blasting and ripping required.
Alluvial materials at the Crooked Creek intake site may have high permeability and allow
significant subsurface flows. The impoundment depth of the Crooked Creek diversion structure
should be kept as shallow as practical to minimize loss of water to the subsurface.
D.3.1 Area Geomorphology
Elfin Cove is located within rugged and mountainous terrain, with bedrock common at or near
the surface. The geology of the project area has been investigated by the USGS (Figure D 2) and
reported in USGS Bulletin 1058 E, published in 1959.
The geology to the south of Elfin Cove is underlain by highly recrystallized bedded schists.
Beds in this area are overturned, strike in a general northwest southeast orientation, and dip
from 35 to 50 . The steep mountains and cliffs just east of Elfin Cove and the project area are
diorite. Foliations in the diorite are inferred along a northwest southeasterly strike and at a dip
of 70 . Glaciation has eroded the softer schists in the area, resulting in the diorite mountains
and cliffs that overlook Elfin Cove and the project area. Debris fields from avalanches, alluvial
cones, and mass wasting events are common at the base of these cliffs.
Three mass wasting events are apparent in the project area, as identified by aerial imagery and
field investigations. One occurred in Elfin Cove between 1990 and 2002, another occurred
approximately ½ mile south of Elfin Cove between 2002 and 2009, and a third older event is
evident near the proposed intake site on Crooked Creek.
13 These events are characterized by
the release of large slabs of rock from exposed diorite outcrops onto terrain several hundred feet
13 Photographs of these mass wasting events are presented in Appendix B (Photograph B 1, B 19, B 20,
B 21). Event locations are indicated on the project maps in Appendix A.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report D 6
below, and are a normal and ongoing part of the geomorphological processes at work in the
area.
In Elfin Cove, the contact zone between the schist and diorite formations is located along the
east side of the cove. This contact zone continues to the south, passing approximately 600 feet
west of Jims Lake, and then leaves the project area to the south southwest. Surface
presentations of this contact zone are not obvious in the immediate project area. Jims Lake and
the Crooked Creek intake site are thus underlain by diorite, while most of the Jims Lake
penstock route and the tidewater powerhouse site are expected to be underlain by schist.
A fault runs through Elfin Cove south southeast to the Crooked Creek valley and up the valley
into the high country to the southeast. Accelerated erosion of the fractured rock associated with
this fault is likely responsible for the low areas that form Elfin Cove and the Crooked Creek
Valley. The fault running through the Crooked Creek valley suggests that bedrock may be at
significant depth at the intake site.
Figure D 2: Geology of Project Area
Detail from Plate 1 of USGS Bulletin 1058 E.
D.3.2 Typical Vegetation
The project area is generally forested by large conifers growing in shallow soils overlaying
weathered and fractured rock. Mixed conifer and deciduous vegetation tends to be prevalent
where the grades are moderate and thicker soil strata occurs. Terrain with grades under 30%
tends to feature terraced peat bogs vegetated by grasses and a few trees.
Project Area
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report D 7
D.3 Tsunami Hazards
Tsunamis can be generated from distant seismic events such as the March 1964 Alaska
earthquake or the March 2011 Japan earthquake. Tsunamis can also be generated by local
events, such as landslides into nearby waters or submarine landslides.
The Alaska Earthquake Information Center (AEIC) was contacted about tsunami hazards for
the powerhouse site at Little Sandy Beach. Detailed tsunami inundation mapping for Elfin
Cove does not currently exist, but AEIC has a multi year project to complete tsunami
inundation maps for Alaskas coastal communities. AEIC personnel indicated that mapping for
Elfin Cove is a year or more away. When detailed mapping is performed for Elfin Cove, the
community can request that the powerhouse site at Small Sandy Beach be included in the
inundation analysis and maps.
AEIC personnel used an existing tsunami model to produce unofficial estimates of the off shore
tsunami wave heights caused by the 1964 Alaska and 2011 Japan earthquakes near the
powerhouse site. The 1964 Alaska earthquake simulation created a maximum wave height of
approximately 2.5 feet, and the 2011 Japan earthquake simulation created a maximum wave
height of approximately 0.5 feet. It is important to note that these calculated wave heights do
not consider the effects of near shore bathymetry or on shore topography, which can
significantly affect the on shore wave height and run up. Local tide and surf conditions at the
time of a tsunami event are also significant factors.
If future analysis determines that there is a significant tsunami hazard at Small Sandy Beach,
this hazard can be partially mitigated by powerhouse design. It is probable that the
powerhouse foundation can be tied into bedrock, which would help the powerhouse building
survive a tsunami, although it would remain subject to inundation and flood damage.
Another mitigation option is to site the powerhouse at a higher elevation. A rock bench could
be blasted into the cliffs at the head of Small Sandy Beach at a safe elevation for the
powerhouse. This would increase project costs and decrease the head on the lower project,
decreasing total power generation and project benefits.
Because protective measures may increase project costs and/or decrease project energy output, a
risk analysis should be conducted in the design phase of the project to determine what tsunami
hazard mitigation measures are appropriate for the lower powerhouse.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX E ENVIRONMENTAL CONSIDERATIONS
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report F 1
E.1 THREATENED AND ENDANGERED SPECIES
The U.S. Fish and Wildlife Services online consultation guide indicates that there are no species
listed as threatened or endangered within the vicinity of the project.
14
E.2 FISHERIES AND WILDLIFE
Project development is not likely to have a significant impact on fisheries or wildlife resources.
The Alaska Department of Fish and Game (ADFG)s Atlas of Waters Important for the Spawning,
Rearing or Migration of Anadromous Fishes
15 does not indicate that Crooked Creek, Jims Lake, or
Jims Lake Creek are habitat for anadromous species. Both creeks flow over steep rock cliffs just
above the intertidal zone that act as barriers to fish passage. No fish have been observed in
either creek or in Jims Lake in the course of field investigations for this project. Based on this
information, no in stream flow reservations are considered necessary on either stream.
E.3 WATER AND AIR QUALITY
The project will not have a significant negative impact on water or air quality. By reducing
diesel combustion within Elfin Cove, the project will improve air quality.
E.4 WETLAND AND PROTECTED AREAS
The project will require filling wetlands areas, such as for the diversion structure located in the
creek. Some of the penstock or access routes would also cross wetlands. Jims Lake would also
be affected by the project. If the project obtains a FERC licensing exemption, then it will be
eligible for a Nation Wide Permit #17 for hydro projects, otherwise an individual permit will be
issued as part of the FERC licensing process.
E.5 ARCHAEOLOGICAL AND HISTORICAL RESOURCES
No known archaeological or historical resources are known to exist within the project area. The
state historical preservation office will be consulted during the permitting process to determine
if any historical or cultural resources are present in the project area.
E.6 LAND DEVELOPMENT CONSIDERATIONS
Not applicable.
E.7 TELECOMMUNICATIONS AND AVIATION CONSIDERATIONS
14 http://alaska.fws.gov/fisheries/endangered/pdf/consultation_guide/70_consult_guide_map_11x17.pdf
15 Catalog and Atlas of Waters Important for the Spawning, Rearing or Migration of Anadromous Fishes, ADFG,
2010.http://www.sf.adfg.state.ak.us/SARR/awc/
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report F 2
The project will not affect telecommunications or aviation.
E.8 VISUAL AND AESTHETIC RESOURCES
Due to the dense conifer vegetation common around Elfin Cove, the project will not have a
large visual impact. Most of the disturbed areas, such as transmission, access, and penstock
alignments, would be mostly concealed from view from sea. The project will be visible from the
air.
The tidewater powerhouse at Small Sandy Beach will be visible from sea and air. This will be a
small structure consistent with the many isolated outbuildings found near tidewater
throughout Southeast Alaska. It can be finished in materials and colors that would blend with
the surroundings.
E.9 MITIGATION MEASURES
No impacts warranting mitigation are known at this time.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX F PERMITTING INFORMATION
F.1: Federal Permits pages F 1 to F 2
F.2: State Permits pages F 2
F.3: Local Permits pages F 3
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report F 1
F.1 FEDERAL PERMITS
F.1.1 Federal Energy Regulatory Commission
The FERC has jurisdiction over hydroelectric projects that meet certain criteria. One of these
criteria is whether the project would occupy federal land. The recommended project is located
within the Tongass National Forest, and therefore will fall under FERC jurisdiction.
For projects that require a FERC license, all state and federal permitting efforts are managed
through the FERC licensing process. Small hydroelectric projects meeting certain criteria can be
exempted from FERC licensing requirements, in which case the normal state and federal
licensing processes are used.
The main eligibility criteria for exemption from FERC licensing are:
The project must use a natural water feature.The upper hydro system recommended in
this study is expected to qualify under this criteria. It is unknown if FERC will consider
a siphon at Jims Lake to be eligible for a natural water featureexemption.
The project owner must have control over all non federal project lands. This includes
private lands that the project features will occupy. Control of federal lands can be
secured with land use permits from the U.S. Forest Service. Control of private lands can
be secured with easements.
To determine if the project is eligible for an exemption, a Declaration of Intent should be filed
with FERC. FERC will respond with a jurisdictional determination that will determine whether
the project must obtain an exemption or license.
F.1.2 U.S. Forest Service
Crooked Creek and Jims Lake are both located within the Tongass National Forest. A project
developed on these resources will require long term land use permits from the U.S. Forest
Service.
Both the upper and lower systems, the transmission line, and the overland access route from
Elfin Cove are located within the Tongass National Forest. Forest lands in the project vicinity
are designated for Semi Remote Recreationin the 2008 Tongass National Forest Land and
Resource Management Plan.
16
The project also lies within Inventoried Roadless Area #311 on Chichagof Island. Under the
2001 Roadless Rule in affect for the Tongass National Forest, this means the project will require
approval of the Secretary of Agriculture. This approval process starts with local USFS
personnel working with Elfin Cove to prepare briefing papers on the hydro project and why it
is necessary for the community. These papers will be circulated through the local and national
16 http://tongass fpadjust.net/FPA_ROD.htm
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report F 2
USFS offices for review and approval, culminating in approval by the Secretary of Agriculture.
This process is estimated to take at least six months, and cannot begin until the project and
resource issues are well defined.
At this time, local USFS personnel appear supportive of the project. To date, all hydroelectric
projects submitted by the Tongass National Forest under the roadless rule have been approved
by the Secretary.
F.1.3 U.S. Army Corps of Engineers Permits
The diversion structures, tailraces and other features of the recommended project will be
located within wetlands, therefore a wetlands permit from the COE will be required. If the
project is exempted from FERC licensing, then it may be eligible for a Nation Wide Permit #17
for hydro projects. Otherwise, the project will obtain an individual permit as part of the FERC
licensing process.
Construction phase beach landings at Small Sandy Beach may also require COE permits.
F.1.4 U.S. Environmental Protection Agency
A stormwater pollution prevention plan will be required for construction of the project.
F.1.5 Federal Aviation Administration
The recommended project will not have any features likely to present a hazard to aviation.
F.2 STATE OF ALASKA PERMITS
F.2.1 Alaska Department of Natural Resources Permits
F.2.1.1 Coastal Zone Consistency Review
The project is located within the states coastal zone, and will go through consistency review by
ADNRs Division of Coastal and Ocean Management for consistency with the statewide coastal
management plan. The project is not located within a local coastal management program.
F.2.1.2 Land Authorizations
The project will not occupy state land.
F.2.1.3 Tidelands Permits
No tidelands permits are needed for the project.
F.2.1.4 Material Sale Agreement
Not applicable.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report F 3
F.2.1.5 Water Use Permit / Water Rights
The project will need to obtain water rights from the ADNR.
F.2.2 Alaska Department of Fish and Game Permits
F.2.2.1 Fish Habitat Permit
The project will need to obtain either a fish habitat permit or a finding that a permit is not
required from the ADFG.
F.2.3 Alaska Department of Transportation Permits
Not applicable.
F.2.4 Alaska Department of Environmental Conservation (ADEC) Permits
F.2.4.1 ADEC Wastewater or Potable Water Permits
Not applicable.
F.2.4.2 Solid Waste Disposal Permit
Not applicable.
F.2.4.3 Air Quality Permit & Bulk Fuel Permit
Not applicable.
F.3 LOCAL PERMITS
The project is not located within an organized borough or city, so no local permits would be
required.
Access and utility easements will be needed across private land in Elfin Cove for project access,
the power line, and communication line to the project.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX G COST ESTIMATES AND ECONOMIC ANALYSIS
G.1: Project Cost Estimate page G 1
G.2: Economic Analysis Assumptions pages G 2 to G 4
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
G.1 PROJECT COST ESTIMATE
The total installed cost of the recommended project is presented in Table G 1. Table G 1
presents both the base case cost estimate, and the range of estimated installed costs used for
economic analysis of the project.
Table G 1: Project Cost Estimate
Cost Item
Base Case
Estimate
Low
Estimate
High
Estimate
PRE CONSTRUCTION COSTS (STUDY,
DESIGN, PERMITTING)
$408,000 $395,000 $420,000
DIRECT CONSTRUCTION COSTS
Access Trails $113,000 $77,000 $150,000
Transmission Line $139,000 $122,000 $156,000
Upper System
Diversion Structure $25,000 $19,000 $31,000
Penstock $47,000 $38,000 $56,000
Powerhouse $144,000 $128,000 $160,000
Upper System Subtotal $216,000 $185,000 $247,000
Lower System
Diversion Structure $7,000 $4,000 $9,000
Penstock $84,000 $66,000 $103,000
Powerhouse $343,000 $314,000 $375,000
Lower System Subtotal $434,000 $384,000 $487,000
Shipping / Mobilization $109,000 $105,000 $113,000
Equipment $82,000 $76,000 $89,000
TOTAL DIRECT CONSTRUCTION COSTS $1,093,000 $949,000 $1,242,000
Construction Contingency (20%) $219,000 $189,000 $248,000
Construction Management / Administration $67,000 $56,000 $77,000
Construction Inspection / Engineering $67,000 $56,000 $77,000
ESTIMATED TOTAL INSTALLED COSTS $1,854,000 $1,645,000 $2,064,000
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
G.2 ECONOMIC ANALYSIS ASSUMPTIONS
G.2.1 ESTIMATED ANNUAL PROJECT COSTS
G.2.1.1 General, Administrative, Operation, and Maintenance Expenses
Typical general and administrative costs for a utility like ECUC range from $20,000 to $40,000
per year. This annual expense covers activities such as meter reading, customer service,
managing the utilitys business affairs, etc. These costs will not change if the means of energy
generation changes from diesel to hydro or a combination of the two.
Typical non fuel operation and maintenance (O&M) expenses for a utility like ECUC are about
$20,000 per year. This annual expense includes the costs of lube oils, filters, and other
consumables for the diesel generators, maintenance labor, and similar costs that are related to
the running time of the diesel engines. A significant portion of these costs will be avoided with
the recommended project.
The hydroelectric project will have additional operation and maintenance costs. This includes
additional labor costs for monitoring and maintaining the hydro systems as well as direct
expenses for parts and consumables. Annual O&M costs for the recommended project will be
approximately $13,000 to $15,000 per year. This will include activities such as plant inspections,
maintenance, routine parts replacement, and trail maintenance costs.
G.2.1.2 Repair and Replacement
Most of the hydroelectric project systems and components have a very long useful life. The
intake, penstock, powerhouse, switchgear, turbine/generator, and power line all are expected to
have useful lives of 30 to 50 years or more. Some components will require periodic repair or
replacement. Minor components, such as pumps, actuators, control sensors, and similar devices,
are assumed to have a useful life of five years. The water turbines may need an overhaul after
about 15 to 25 years. The average annual expense for repair and replacement is estimated at
$3,900 for the recommended project.
G.2.1.3 Taxes
Because the ECUC is a not for profit entity, no tax liability is considered.
G.2.1.4 Insurance
It is assumed that the ECUCs existing insurance policies would be adequate for the
hydroelectric project. No additional annual costs are allocated for insurance.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
G.2.1.5 Financing
The construction cost of the project is assumed to be commercially financed at a 30 year term at
6% interest. Loan origination costs of 3% are assumed for items such as application fees, loan
guarantee fees, and other origination fees.
State or federal grants can help reduce the amount of capital ECUC needs to borrow for the
project. Such grants would enable ECUC to lower electric rates in the community.
Also, state or federal loan programs can lower ECUCs borrowing costs for the project, which
would reduce annual debt payments, enabling ECUC to lower electric rates in the community.
G.2.2 ESTIMATED PROJECT REVENUES AND SAVINGS
G.2.2.1 Direct Fuel Displacement
The recommended hydro project will significantly reduce the amount of diesel fuel ECUC
consumes for electricity generation. Fuel savings are calculated using recent operating efficiency
and fuel costs for ECUCs diesel power plant of 12.5 kWh per gallon, and $4.00 per gallon.
G.2.2.2 Excess Energy
In addition to reducing diesel fuel usage at the power plant, the hydroelectric project also
generates a significant amount of excess energy that is available to the community. The base
case for economic analysis assigns no value to this excess energy.
The economic case that considers the potential value of this excess energy assumes that 10% of
the gross excess energy is consumed by the hydro load governor system and station service,
and 90% is made available to interruptible utility customer loads such as space heating and
water heating applications. Of this 90%, 10% is assumed to be consumed by losses on ECUCs
distribution system. The balance (81% of gross excess energy generation) can be metered to
ECUCs interruptible services at a special rate. Annually, 75,000 kWh of this net excess energy is
allocated to the community building and shop to replace the existing waste heat these buildings
receive from the diesel power plant. All of the remaining net excess energy is assumed to be
directed to interruptible services, displacing heating oil that is consumed with an assumed
average efficiency of 70%. The value of this displaced heating fuel is factored into the economic
analysis.
G.2.2.3 Environmental Attributes
The environmental attributes (EA) of the recommended project can be marketed nation wide to
earn ECUC additional revenue. The projects EAs would be sold on the voluntary market,
where pricing for EAs varies. Prices were as high as $0.02 per kWh before the financial crisis of
2008, and more recently have fluctuated in the range of $0.001 to 0.005 per kWh.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
For several years, there has been an effort at the federal level to implement mandatory purchase
of EAs. Such legislation would likely expand the market and stabilize the pricing for EAs. It is
unknown if or when such legislation would take effect, or what the final terms of such
legislation will be.
While EAs from the project are an additional potential revenue stream for ECUC, no revenue
from EAs is assumed in the base case of the economic evaluation.
G.2.2.4 Indirect and Non Monetary Benefits
The recommended hydroelectric project offers significant indirect and non monetary benefits in
addition to direct economic benefits. These other benefits include:
Reduced air pollution (NOx, SOx, particulates, and hydrocarbons) due to decreased
operation of the diesel power plant
Reduced noise in Elfin Cove when the diesel plant is turned off.
Reduced risk of oil spills due to decreased throughput and handling of fuel.
More stable energy prices. With a hydro, ECUCs electricity rates will be largely
insulated from increasingly volatile world oil prices.
Secondary benefits arising from the availability of plentiful hydroelectity with a stable
price. This will increase the affordability of living and doing business in Elfin Cove and
will help to increase the long term viability of the community. An example of such a
secondary benefit is an increase in the population of school age children, ensuring that
school enrollment exceeds district and state thresholds for state funding year to year.
Economic multipliers due to the fact that a greater percentage of the utility s revenues
will be retained in the local community for labor instead of paying external entities such
as fuel suppliers.
Local training and experience with small hydroelectric projects. To the extent that locals choose
to be involved in construction, maintenance, and operation of the hydroelectric project, they
will learn a unique set of skills. These skills will become increasingly useful as Alaska continues
to develop its local hydroelectric resources.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX H TECHNICAL ANALYSIS
H.1: Project Modeling pages H 1 to H 12
H.2: Project Sizing Analysis pages H 13 to H 14
H.3: Load Growth Scenarios pages H 14 to H 18
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 1
H.1 HYDRO PROJECT MODELING
The primary analytical tool used to evaluate various project configurations and load cases for
this feasibility study is a generation dispatch model. A generation dispatch model takes in the
technical parameters of the proposed generation systems (both hydro and diesel), resource
availability, and ECUC loads, and then simulates operation of the proposed integrated system
to determine how a project configuration performs.
H.1.1 Generation Dispatch Model
Two generation dispatch models were developed for this feasibility study to evaluate the
performance of different project configurations. One model runs at a one hour time step and is
used to accurately model hydro project performance and reservoir management over hourly to
monthly time scales. The second model runs at a one day time step, and is used to assess
seasonal and annual variations in project performance.
At each time step, both models evaluate ECUC electric load, and determine how much of the
electric load is supplied by the hydro generators, how much is supplied by the diesel
generators, and how much excess energy the hydro generators can produce. Inputs used to
develop and run the models are described in Table H 1.
Both models assume a single two jet Pelton turbine for the lower system and a single cross flow
turbine for the upper system. For some larger project configurations, this assumption results in
slight decreases in overall performance because the turbines have lower efficiencies at low
loadings. Also, existing ECUC loads sometimes drop below the minimum operating level of
these larger turbines, requiring that either (1) the diesel power plant be started to replace or
supplement the hydroelectric project, or (2) excess hydro electricity be generated with water
that could otherwise have been stored for more valuable future prime generation.
At each time step, the models evaluate (1) ECUC load and (2) generation from the upper run of
river hydro system, and then dispatches sufficient water from the reservoir to the lower hydro
system to meet ECUC load. Both models were programmed to manage the reservoir to first
meet 100% of ECUC demand, second refill the reservoir, and third direct excess inflows to idle
capacity in the lower system to generate interruptible energy for the community. Any
remaining excess flows are spilled into Jims Lake Creek. If the reservoir is depleted or ECUC
demand exceeds available hydro capacity, the diesel power plant is dispatched to supply the
remaining ECUC load. At the next time step, the reservoir level is updated to reflect water
inflows and outflows, and this analysis is repeated.
When the diesel generators are operated, they are loaded to a minimum of 40% of rated output,
regardless of the deficit between ECUC demand and hydro output. Thus, if demand is 100 kW
and available hydro output is 95 kW, ECUCs 67 kW diesel gen set will be loaded to 27 kW
(40%), and hydro output will be curtailed from 95 to 73 kW. Depending on reservoir level, the
remaining 22 kW of potential hydro output either becomes excess hydro energy or the water is
conserved in the reservoir for future use.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 2
Table H 1: Generation Dispatch Model Variables, Inputs, and Outputs
MODEL INPUT DATA (BOTH MODELS)
Input Range of Values Evaluated
Upper System Design Flow (cfs) 2 to 6 cfs, in 1 cfs increments
Lower System Design Flow (cfs) 2 to 15 cfs, in 1 cfs increments
Jims Lake Spillway Elevation (feet, MHW)
333 to 341 feet, in 4 foot increments
(a siphon capability down to 325 feet was included in all
configurations unless noted otherwise)
MODEL INPUT DATA (MODEL SPECIFIC)
Input Hourly Model Daily Model
Crooked Creek Flow at Diversion (cfs) Hydrology data from
7/1/1009 through
12/10/2010 17
Hydrology model based on
1975 to 2010 precipitation
records for Elfin Cove
Jims Lake Creek Flow at Lake Outlet (cfs)
ECUC System Demand (kW)
Hourly estimate from
NREL model
18
Average Daily Load from
NREL Model
Initial Reservoir Level (MHW) 333 feet, assumed
Reservoir Floor Elevation (MHW) 325 feet based on bathymetric survey
Upper Project Turbine Efficiency Curve Typical efficiency curve for cross flow turbine
Lower Project Turbine Efficiency Curve Typical efficiency curve for two jet Pelton turbine
Project head, penstock lengths, physical
parameters Based on field measurements and system design flow(s)
ECUC Diesel Generator Sizes Based on existing installed equipment
MODEL OUTPUT DATA (BOTH MODELS)
Upper Project Output (kW, kWh) ECUC Demand Supplied by Hydro (kW, kWh)
Lower Project Output (kW, kWh) ECUC Demand Supplied by Diesel (kW, kWh)
Lake Stage (MHW) Gross Excess Hydro Energy (kW, kWh)
H.1.2 Load Patterns and Load Model
ECUCs load pattern is highly seasonal, so ECUC loads and the hydroelectric projects
performance are described on a seasonal and annual basis. Seasons are defined below.
Winter time:September 15
th through May 15
th. Most fishing lodges are shut down during this
period, and many part time residents are out of town.
Summer time:May 15
th through September 15
th. Most fishing lodges are operational during
these months and most part time residents are in town. Tourism, recreational boating, and
commercial fishing activity also increase electricity demand during these months.
17 Hydrology data from July 2008 to June 2009 were not used because there are numerous gaps in this
part of the hydrology record at both Crooked Creek and Jims Lake Creek, complicating efforts to
accurately model reservoir levels.
18 The Alaska Village Electric Load Calculator, NREL/TP 500 36824, NREL, Golden Colorado, Sept. 2004.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 3
Table H 2 presents typical ECUC seasonal load data and the simulated seasonal load data input
to both generation dispatch models. Recent ECUC operating data presented in Table 2 3 was
used to develop typical seasonal loads, and the simulated load data is based on a village load
simulator tool developed by the NREL.
19 The NREL model was calibrated to typical ECUC
load data using monthly peak and average load data from PCE reports and ECUC records.
Table H 2: Actual and Modeled Electric Demand
Typical ECUC Load ECUC Load Model
Winter time (September 15 through May 14)
Peak Load (kW) 80 54
Average Load (kW) 26 26
Total Seasonal Energy Demand (kWh) 153,700 160,700
Summer time (May 15 through September 14)
Peak Load (kW) 307 266
Average Load (kW) 66 67
Total Seasonal Energy Demand (kWh) 195,900 198,300
Total Annual Energy Demand (kWh)349,600 359,000
H.1.3 Hourly Generation Dispatch Model (16 Months, July 2009 to December 2010)
The expected performance of hydro project configurations was evaluated using the hourly
generation dispatch model. The hourly generation dispatch model was run using hourly
hydrology data from the Crooked Creek and Jims Lake Creek gauging stations. This model
provides an accurate simulation of how the hydro project and reservoir interact with
fluctuations in electric demand and stream flow on hourly to monthly time scales.
H.1.4 Daily Generation Dispatch Model (35 years, 1975 to 2010)
The 16 months of continuous stream flow data available to run the hourly generation dispatch
model is insufficient to characterize the annual variability in performance of the hydro project,
so a similar generation dispatch model was developed to assess long term hydro performance.
This second model runs at a one day time step, and uses hydrology data synthesized from 35
years of daily precipitation records in Elfin Cove.
20 This 35 year period of record is sufficient to
characterize variability in the hydro projects annualized performance.
H.1.5 Calibration and Use of Models
The goal of these modeling efforts is to identify a model that accurately represents how the
hydro project will perform in meeting the electrical needs of Elfin Cove. The hourly model is
19 The Alaska Village Electric Load Calculator, NREL/TP 500 36824, NREL, Golden Colorado, Sept. 2004.
20 Weather records for Elfin Coves period of record (Cooperative Station ID 502785, Period of record
from Jan. 1, 1975 through Aug. 31, 2010) retrieved from http://www.ncdc.noaa.gov/oa/ncdc.html.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 4
accurate on a short term basis, but insufficient hourly hydrology data exists to directly evaluate
if this model is providing accurate long term projections. The hourly and daily models were
compared to determine if the hourly model is representative of typical annual performance.
Table H 3 presents the range in seasonal and annual hydro performance as determined by the
daily generation dispatch model. This data is also presented in Figure H 2. Table H 4 then
presents a comparison of the average seasonal and annual performance with hourly model
output for the period of September 15, 2009 to September 14, 2010. As Table H 4 shows, the
hourly model over this period is representative of a typical year. Economic analyses in this
study are therefore based on the output of the hourly generation dispatch model run over this
time period. The daily model was then used to verify key study findings.
Table H 3: Expected Range of Seasonal and Annual Hydro Performance
Item
Minimum
Seasonal
Hydro
Generation(1)
Average
Annual Hydro
Generation
Maximum
Seasonal
Hydro
Generation(2)
Winter time (September 15 through May 14)
Total ECUC Winter Load (kWh) 160,700 160,700 160,700
Load supplied by Diesel, kWh (%) 200 (0.15%) 100 (0.04%) 0
Load supplied by Hydro, kWh (%) 160,400 (100%) 160,600 (100%) 160,700 (100%)
Excess Hydro Generation, kWh 194,500 282,200 336,900
Total Hydro Generation, kWh 354,900 442,800 497,600
Summer time (May 15 through September 14)
Total ECUC Summer Load (kWh) 198,300 198,300 198,300
Load supplied by Diesel, kWh (%) 19,300 (10%) 3,300 (2%) 1,600 (1%)
Load supplied by Hydro, kWh (%) 179,000 (90%) 195,000 (98%) 196,800 (99%)
Excess Hydro Generation, kWh 0 38,500 59,100
Total Hydro Generation, kWh 179,000 233,500 255,900
Total Annual ECUC Load (kWh) 359,000 359,000 359,000
Total Annual ECUC Load Supplied by Diesel 19,500 3,400 1,600
Total Annual ECUC Load Supplied by Hydro 339,500 355,600 357,400
Total Annual Excess Hydro Generation (kWh) 194,500 320,700 395,900
Total Annual Hydro Generation (kWh) 534,000 676,300 753,300
(1) According to the daily generation dispatch model, the minimum winter hydro output would have occurred in
2002 and 2010. The minimum summer hydro output would have occurred in 1993.
(2) According to the daily generation dispatch model, the maximum winter hydro output would have occurred in
1987. The maximum summer hydro output would have occurred in 1981.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 5
Table H 4: Comparison of Average Seasonal and Annual Hydro Performance with
Performance During 9/15/09 to 9/15/10 Time Period
Item
Hydro
Performance Based
on Hourly Model
(9/15/09 9/14/10)
Average Seasonal
and Annual Hydro
Performance Based
on Daily Model
Percentage
Difference (Hourly
Model % from
Daily Model)
Winter time (September 15 through May 14)
Total ECUC Winter Load (kWh) 160,700 160,700 0%
Load supplied by Diesel, kWh (%) 0 (0%) 100 (0.06%)100%
Load supplied by Hydro, kWh (%) 160,700 (100%) 160,600 (100%) + 0.04%
Excess Hydro Generation, kWh 283,200 282,200 +0.4%
Total Hydro Generation, kWh 443,900 442,800 + 0.3%
Summer time (May 15 through September 14)
Total ECUC Summer Load (kWh) 198,300 198,300 0%
Load supplied by Diesel, kWh (%) 2,900 (1%) 3,300 (2%)12%
Load supplied by Hydro, kWh (%) 195,400 (99%) 195,000 (98%) + 0.2%
Excess Hydro Generation, kWh 33,400 38,500 13%
Total Hydro Generation, kWh 228,800 233,500 2.0%
Total Annual ECUC Load (kWh) 359,000 359,000 0%
Total Annual ECUC Load
Supplied by Diesel (kWh)
2,900 3,400 15%
Total Annual ECUC Load
Supplied by Hydro (kWh)
356,100 355,600 + 0.1%
Total Annual Excess Hydro Generation
(kWh)316,600 320,700 1.3%
Total Annual Hydro
Generation (kWh)
672,700 676,300 0.5%
H.1.6: Model Results
Average daily hydro performance and ECUC loads, tabulated from hourly model outputs, are
shown in Figure H 1. Figure H 1 also shows fluctuations in the level of Jims Lake as the
reservoir is managed to meet ECUC loads. Figure H 2 shows the annual variations in hydro
performance from 1975 to 2010. The data in Figure H 2 corresponds to the range of annual
system performance tabulated in Table H 3.
Figure H 3 shows a detail of the hourly generation dispatch model output for the period from
September 15, 2010 through October 1, 2010. A dry spell during this period depleted the Jims
Lake reservoir, so the model activated the diesel generators to supply ECUC loads. Hourly load
variations, coordination between the diesel and hydro power plants, and fluctuations in excess
energy generation are all evident in the figure.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 6
0
30
60
90
120
150
180
210
240
Jul2009Aug 2009Sep 2009Oct 2009Nov 2009Dec 2009Jan 2010Feb 2010Mar2010Apr 2010May2010Jun 2010Jul2010Aug 2010Sep 2010Oct 2010Nov2010Dec 2010Average Daily Power Demand and Supply(kW)305
309
313
317
321
325
329
333
337
Reservoir Level (feet)
Reservoir Level
Excess Energy
Utility
Load
Load Supplied
by HydroLoad Supplied by Diesel
Figure H 1: Daily Hydro Project Performance (July 2009 through December 2010)
Figure H 2: Annual Hydro Performance (1975 through 2010)
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
1,000,000
Annual Load Supplied by Hydro
Annual Excess Energy Available from Hydro
Annual Load Supplied by Diesels
Annual Utility
Load
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 7
Figure H 3: Hourly Project Performance During September 2010 Dry Spell
0
20
40
60
80
100
120
140
160
9/1/2010 9/8/2010 9/15/2010 9/22/2010 9/29/2010
305
309
313
317
321
325
329
333
337Total System Load
Load Supplied by Hydro
Load Supplied by Diesel
Excess Energy Available from Hydro
Reservoir Stage
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 8
H.2 PROJECT SIZING ANALYSIS
A range of project configurations was evaluated using the generation dispatch models to
determine which hydro project configuration best supplies ECUCs existing electric load. The
primary criteria for this evaluation was displacement of diesel fuel used for generating
electricity. Secondary criteria included the potential to generate additional electricity that could
be used on an interruptible basis for heating or other applications.
Table H 5 lists the range of project parameters that were evaluated using the generation
dispatch model to assess (1) the amount of diesel generation displaced by each project
configuration and (2) the amount of excess energy each configuration produced. Findings for
key technical parameters are discussed in the following sections.
Table H 5: Range of Project Design Parameters Considered and Recommended Values
Parameter(1)Range Considered Recommended Project
1. Upper System Design Flow 2 to 6 cfs 5 cfs
Upper System Installed Capacity 0(2)to 50 kW
35 kW
2. Lower System Design Flow 5 to 15 cfs 7 cfs
Lower System Installed Capacity 90 to 280 kW 125 kW
3. Jims Lake Reservoir Spillway Elevation 333 to 345 ft 333 ft
Reservoir Volume 0(3)to 102 ac ft 32 ac ft
Total Installed Capacity (Upper + Lower Systems) 105 to 330 kW 160 kW
(1) Related project parameters were also modified in conjunction with the parameters listed. For example, penstock
diameter was varied with design flow to maintain acceptable friction losses.
(2) Building the upper project as a water diversion system without power generation was evaluated. This
configuration is similar to Options 2A or 2B considered in the 2010 Reconnaissance Study.
(3) Omitting the siphon intake was evaluated as a possible project configuration.
H.2.1 Crooked Creek System Design Flow (Upper System)
Upper system design flows from 2 to 6 cfs were evaluated. The maximum amount of current
ECUC load is supplied with an upper project design flow of 5 cfs. At higher design flows, the
upper turbine would be idled during low flow periods, slightly reducing the total amount of
ECUC load the combined hydro systems would supply. At lower design flows, the amount of
water the system would divert during high flow periods would be significantly reduced,
resulting in lower output from both the upper and lower systems.
H.2.2 Crooked Creek Diversion Power Recovery Turbine (Upper System)
Adding a power recovery turbine to the Crooked Creek diversion adds cost and complexity to
the overall hydro project. This cost is offset by the fact that the Crooked Creek turbine provides
25% of the total electrical output of the combined hydro project. Without this turbine, the
project would supply 10% less of ECUCs current electric load, and would produce 43% less
energy for interruptible uses. Also, the Crooked Creek turbine becomes more important for
maximizing prime electrical output from the project if ECUC load increases in the future.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 9
H.2.3 Jims Lake System Design Flow (Lower System)
Lower system design flows of 2 to 15 cfs were evaluated. The recommended design flow is
seven cfs. For project configurations with a spillway elevation of 333 feet (the natural lake
elevation), the amount of prime electrical demand displaced by the combined hydro systems
increases from 85% to 99.2% as design flow increases from two to seven cfs, and is then
essentially level for design flows from seven to 15 cfs, with a peak of 99.6% at nine cfs, then
declining steadily to 98.8% at 15 cfs.
H.2.4 Jims Lake Spillway Elevation (Lower System)
Building a dam at the outlet of Jims Lake can increase the available storage in the lake from 32
acre feet to 77 acre feet. More storage volume helps the project carry Elfin Cove through
summer dry spells, but the maximum practical storage volume is insufficient to supply current
ECUC load through common summer dry spells.
Jims Lake spillway elevations from 333 feet (natural lake level) up to 341 feet (an eight foot tall
dam) were evaluated. All configurations included a siphon capability to draw the lake down to
the 325 foot level. These are the technically and economically feasible limits of storage at Jims
Lake based on site bathymetry and topography.
The storage below the natural lake elevation could also be accessed by digging a ditch at the
desired elevation to provide a gravity outlet at 325 feet. This would require approximately 200
feet of ditch up to 8 feet deep at the lake outlet. Much of this ditch would require blasting or
ripping of rock, and is expected to be significantly more costly than a siphon system.
The additional storage provided by an eight foot tall dam allows the hydro project to meet
approximately 2% more of ECUCs existing annual loads than the siphon system alone. A dam
does not significantly increase the total amount of energy that the hydro project can produce.
Instead, it increases storage capacity, and thereby enables the system to generate 2% more
prime energy with a corresponding reduction in excess energy output.
The incremental cost of constructing and maintaining the dam combined with the potential
additional time and expense needed to obtain project permits outweigh the value of this
additional prime output, and therefore building a dam is not recommended.
H.3 DIFFERENT UTILITY LOAD SCENARIOS
Hydro project performance under different ECUC loads was evaluated using the hourly
generation dispatch model for the following load scenarios:
1) No winter load, summer load at 50% of existing load (April 15 through October 15).
2) Winter and summer loads at 50% of existing load.
3) Winter and summer loads at 200% of existing load.
4) Winter and summer loads at 400% of existing load.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 10
For scenario 1, the plant and community are assumed to be completely shut down and
winterized from mid October through mid April each year. This eliminates all winter time
hydro output. In the summer months, load is assumed to be ½ of existing ECUC load. Total
summer time hydro generating potential remains constant. The smaller load increases the
excess energy available from the project, and enhances the projects ability to supply utility
demand during dry spells.
For scenario 2, year round loads are ½ of existing loads. Total annual and seasonal energy
output of the recommended project remains relatively constant. The smaller utility load
increases the excess energy available from the project, and enhances the projects ability to
supply utility demand during dry spells.
For scenarios 3 and 4, as ECUC load increases the total annual energy output of the
recommended project remains relatively constant, decreasing by 1.8%. As ECUC load increases,
more of the projects output supplies prime ECUC loads and less output is excess energy.
Seasonal and annual project performance under three load cases is presented in Table H 6.
As ECUC load increases, it eventually exceeds the hydro projects output, requiring increased
use of the diesel powerplant to supply ECUC load. In the winter months, this point occurs at
approximately twice the existing winter ECUC load. In the summer months, this point will
occur at approximately 105% of existing ECUC load. The output of the hydro project is limited
by the available water at Crooked Creek and Jims Lake. A larger project capacity will not
significantly increase hydro output. Figures H 4 through H 6 illustrate how the recommended
project performs seasonally and annually under load growth scenarios.
If ECUC experiences load growth of 200 to 400%, construction of Roys Creek in conjunction
with a dam at Jims Lake should be investigated to increase hydroelectric generation and
storage capacity. The Roys Creek project would increase total hydroelectric energy output, and
the dam would increase the regulating capability of the combined hydroelectric systems to
supply ECUC loads.
NonProfit Community of Elfin CoveCrooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.June 2011Final ReportH11Table H6: Performance of Recommended Project at 200% and 400% Load CasesNo Winter Load50% SummerLoad Reduction150% YearRound LoadReductionCurrent ECUCLoad200% LoadGrowth400% LoadGrowthWintertime(September 15 through May 14)Total ECUC Winter Load (kWh) 25,700 82,600 160,700 316,800 629,000Load supplied by Diesel, kWh (%) 0 (0%) 0 (0%) 0 (0%) 7,000 (2%) 199,200 (46%)Load supplied by Hydro, kWh (%) 25,700 (100%) 82,600 (100%) 160,700 (100%) 309,800 (98%) 429,800 (68%)Excess Hydro Generation, kWh 127,000 360,700 283,200 130,100 8,300Total Hydro Generation, kWh 152,700 443,300 443,900 439,900 438,100Summertime(May 15 through September 14)Total ECUC Summer Load (kWh) 100,300 100,300 198,300 394,300 786,400Load supplied by Diesel, kWh (%) 0 (0%) 0 (0%) 2,900 (1%) 171,900 (44%) 564,100 (72%)Load supplied by Hydro, kWh (%) 100,300 (100%) 100,300 (100%) 195,400 (99%) 222,500 (56%) 222,400 (28%)Excess Hydro Generation, kWh 120,700 120,700 33,400 1,900 0Total Hydro Generation, kWh 221,000 221,000 228,800 224,400 222,400Total Annual ECUC Load (kWh) 126,000 182,900 359,000 711,100 1,415,400Total Annual ECUC Load Supplied by Diesel (kWh)(Hydro as % of total prime supply)0(0%)0(0%)2,900(0.8%)178,900(25.2%)763,300(53.9%)Total Annual ECUC Load Supplied by Hydro (kWh)(Hydro as % of total prime supply)126,000(100%)182,900(100%)356,100(99.2%)532,300(74.9%)652,200(46.1%)Total Annual Excess Hydro Generation (kWh)(Excess as % of total hydro)247,700(66.3%)481,400(72.5%)316,600(47.1%)132,000(19.9%)8,300(1.3%)Total Annual Hydro Generation (kWh) 373,700 664,300 672,700 664,300 660,5001. This scenario assumes there is no winter population or utility load from October 15 through April 15. Load for the remainder of theyear is ½ of existing utility load. The hydro is assumed to be shut down from October 15 through April 15.
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 12
25,700 kWh
82,600 kWh
160,700 kWh
309,800 kWh
429,800 kWh
8,300 kWh
130,100 kWh
283,200 kWh
360,700 kWh
127,000 kWh
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
50%, No Load 10/15
to 4/15
50% 100% 200% 400%
ECUC Winter Load Cases (Percent of Existing Load)
Winter Excess Hydro Generation
Winter ECUC Load Supplied by Hydro
25,700 kWh
82,600 kWh
429,800 kWh
309,800 kWh
160,700 kWh
199,200 kWh
7,000 kWh
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
50%, No Load 10/15
to 4/15
50% 100% 200% 400%
ECUC Winter Load Cases (Percent of Existing Load)
Winter ECUC Load Supplied by Diesels
Winter ECUC Load Supplied by Hydro
Figure H 4: Winter Hydro Performance Under Different Load Cases
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 13
222,400 kWh222,500 kWh
100,300 kWh 100,300 kWh
195,400 kWh
171,900 kWh
564,100 kWh
2,900 kWh
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
50%, No Load
10/15 to 4/15
50% 100% 200% 400%
ECUC Summer Load Cases (Percent of Existing Load)
Summer ECUC Load Supplied by Diesels
Summer ECUC Load Supplied by Hydro
222,400 kWh222,500 kWh195,400 kWh
100,300 kWh100,300 kWh
120,700 kWh 120,700 kWh
33,400 kWh
1,900 kWh
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
50%, No Load 10/15
to 4/15
50% 100% 200% 400%
ECUC Summer Load Cases (Percent of Existing Load)
Summer Excess Hydro Generation
Summer ECUC Load Supplied by Hydro
Figure H 5: Summer Hydro Performance Under Different Load Cases
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report H 14
126,000 kWh 182,900 kWh
356,100 kWh
532,300 kWh
652,200 kWh
2,900 kWh
763,300 kWh
178,900 kWh
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
1,400,000
1,600,000
50%, No Load
10/15 to 4/15
50% 100% 200% 400%
ECUC Annual Load Cases (Percent of Existing Load)
Annual ECUC Load Supplied by Diesels
Annual ECUC Load Supplied by Hydro
652,200 kWh
532,300 kWh
356,100 kWh
182,900 kWh126,000 kWh
8,300 kWh
247,700 kWh
481,400 kWh
316,600 kWh
132,000 kWh
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
1,400,000
1,600,000
50%, No Load 10/15
to 4/15
50% 100% 200% 400%
ECUC Annual Load Cases (Percent of Existing Load)
Annual Excess Hydro Generation
Annual ECUC Load Supplied by Hydro
Figure H 6: Annual Hydro Performance Under Different Load Cases
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX I DRAFT REPORT REVIEW COMMENTS AND
RESPONSES
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-1
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-2
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-3
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-4
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-5
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-6
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-7
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-8
Non-Profit Community of Elfin Cove
Crooked Creek and Jim's Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 - Final Report Page I-9
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report
APPENDIX J TABULAR HYDROLOGY DATA
Non Profit Community of Elfin Cove
Crooked Creek and Jims Lake Hydroelectric Feasibility Study Polarconsult Alaska, Inc.
June 2011 Final Report