HomeMy WebLinkAbout200224-ELV_FLA_ExA
FINAL LICENSE APPLIC ATION
EXHIBIT A
PROJECT DESCRIPTION
CROOKED CREEK AND JI M'S LAKE
HYDROELECTRIC PROJEC T
FERC N o . P -14514
FEBRUAR Y 2020
Prepared for
ELFIN COVE UTILITY COMMISSION
PO BOX 2
ELFIN COVE, ALASKA 99825
Prepared by
POLARCONSULT ALASKA, INC.
1503 W. 33RD AVENUE, SUITE 310
ANCHORAGE, ALASKA, 99503
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Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 iii
TABLE OF CONTENTS
0.0 INTRODUCTION ..........................................................................................................1
1.0 TECHNICAL OVERVIEW ...............................................................................................1
1.I. GENERATING UNITS .................................................................................................................1
1.II. TYPE OF HYDRAULIC TURBINES ..................................................................................................2
1.III. PROPOSED PLANT OPERATION...................................................................................................2
1.IV. ESTIMATED AVERAGE ANNUAL ENERGY GENERATION....................................................................4
1.V. ESTIMATED AVERAGE HEAD ......................................................................................................4
1.VI. RESERVOIR SURFACE AREA AND STORAGE CAPACITY .....................................................................5
1.VII. ESTIMATED MINIMUM AND MAXIMUM HYDRAULIC CAPACITY OF PLANT .........................................6
1.VIII. DESCRIPTION OF PLANT, MATERIALS AND METHODS OF CONSTRUCTION ..........................................6
1.IX. ESTIMATED COST.....................................................................................................................8
1.X. ESTIMATED COSTS OF ENVIRONMENTAL MEASURES ......................................................................9
2.0 PURPOSE OF PROJECT ................................................................................................9
3.0 ESTIMATED COST TO DEVELOP THE LICENSE APPLICATION ..........................................9
4.0 ESTIMATED ON-PEAK AND OFF-PEAK POWER VALUE ..................................................9
5.0 ESTIMATED IMPACT OF PROJECT CHANGES ................................................................9
6.0 UNDEPRECIATED BOOK VALUE .................................................................................10
7.0 ANNUAL O&M COSTS ...............................................................................................10
8.0 ONE-LINE DIAGRAM .................................................................................................10
9.0 PROJECT SAFETY .......................................................................................................10
10.0 REFERENCES ..........................................................................................................12
APPENDIX A - PHASED DEVELOPMENT OPTION
A.1.0 TECHNICAL OVERVIEW ............................................................................................A-1
A.1.I. GENERATING UNITS .............................................................................................................A-1
A.1.II. TYPE OF HYDRAULIC TURBINES ..............................................................................................A-1
A.1.III. PROPOSED PLANT OPERATION...............................................................................................A-1
A.1.IV. ESTIMATED AVERAGE ANNUAL ENERGY GENERATION................................................................A-3
A.1.V. ESTIMATED AVERAGE HEAD ..................................................................................................A-3
A.1.VI. RESERVOIR SURFACE AREA AND STORAGE CAPACITY .................................................................A-4
A.1.VII. ESTIMATED MINIMUM AND MAXIMUM HYDRAULIC CAPACITY OF PLANT .....................................A-5
A.1.VIII. DESCRIPTION OF PLANT, MATERIALS, AND METHODS OF CONSTRUCTION .....................................A-6
A.1.IX. ESTIMATED COST.................................................................................................................A-8
A.1.X. ESTIMATED COSTS OF ENVIRONMENTAL MEASURES ..................................................................A-8
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 iv
A.2.0 PURPOSE OF PROJECT .............................................................................................A-8
A.3.0 ESTIMATED COST TO DEVELOP THE LICENSE APPLICATION .......................................A-8
A.4.0 ESTIMATED ON-PEAK AND OFF-PEAK POWER VALUE ...............................................A-8
A.5.0 ESTIMATED IMPACT OF PROJECT CHANGES .............................................................A-9
A.6.0 UNDEPRECIATED BOOK VALUE ................................................................................A-9
A.7.0 ANNUAL O&M COSTS ..............................................................................................A-9
A.8.0 ONE-LINE DIAGRAM ................................................................................................A-9
A.9.0 PROJECT SAFETY ......................................................................................................A-9
LIST OF FIGURES
Figure 1: Community and Project Location ...................................................................................1
Figure 2: General Project Layout ...................................................................................................3
Figure 3: Jim’s Lake Reservoir Storage Curve ................................................................................5
Figure 4: System One-Line Diagram .............................................................................................11
Figure A-1: General Project Layout (Phased Option)..................................................................A-2
Figure A-2: Jim’s Lake Reservoir Storage Curve (Phased Option)...............................................A-5
Figure A-3: System One-Line Diagram (Phased Option)...........................................................A-10
LIST OF TABLES
Table 1: Existing and Planned Utility Generation Equipment........................................................2
Table 2: Estimated Average Annual Energy Generation................................................................4
Table 3: Estimated Average Head for Upper and Lower Systems .................................................4
Table 4: Jim’s Lake Reservoir Surface Area and Storage Capacity.................................................5
Table 5: Estimated Range of Hydraulic Capacities of Hydro Systems ...........................................6
Table A-1: Estimated Average Annual Energy Generation (Phased Option)..............................A-3
Table A-2: Estimated Average Head for Upper and Lower Systems (Phased Option)...............A-4
Table A-3: Jim’s Lake Reservoir Surface Area and Storage Capacity (Phased Option)...............A-4
Table A-4: Estimated Range of Hydraulic Capacities of Hydro Systems (Phased Option)..........A-5
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 vi
ACRONYMS AND TERMINOLOGY
AEE Alaska Energy and Engineering, Inc.
cfs cubic feet per second
CFR code of federal regulations
dba doing business as
DR dimension ratio
ECUC Community of Elfin Cove dba Elfin Cove Utility Commission
FERC Federal Energy Regulatory Commission
ft foot, feet
HDPE high-density polyethylene
in. inch, inches
kV kilovolt, or 1,000 volts
kVA kilovolt-ampere
kW kilowatt, or 1,000 watts. One kW is the power consumed by ten 100-watt
incandescent light bulbs.
kWh kilowatt-hour. The quantity of energy equal to one kilowatt (kW) expended for
one hour.
mi mile, miles
MLW mean low water
O&M operations and maintenance
Polarconsult Polarconsult Alaska, Inc.
sq.mi. square mile(s)
V volt
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 vii
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Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 1
0.0 INTRODUCTION
This document contains the information required by 18 CFR § 4.61(c).
Elfin Cove Utility Commission (ECUC) is considering two development options at Crooked Creek
and Jim’s Lake:
- Full Development and
- Phased Development.
The main narrative of this Exhibit A document describes the full development option. Appendix
A to Exhibit A describes deviations from the main Exhibit A that would apply with the phased
development option. Both narratives follow the organization of 18 CFR § 4.61(c).
1.0 TECHNICAL OVERVIEW
The following technical overview of the proposed project is based on current project design,
economics, resource and other pertinent information. The project information described
herein may differ depending on the final terms and conditions of licenses and permits, final
design, final site conditions, project economics, and other considerations. The community and
project location is presented on Figure 1. The general project layout is presented on Figure 2.
Figure 1: Community and Project Location
1.i. Generating Units
There will not be an auxiliary generating unit at either the upper or lower systems. There is no
provision for future additional units at the upper or lower systems.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 2
Auxiliary generation will be provided by ECUC’s existing diesel power plant located in Elfin Cove.
This plant currently provides 100% of the electricity for the ECUC system. Generators in the
existing ECUC diesel power house and proposed hydro generators are both listed in Table 1.
Table 1: Existing and Planned Utility Generation Equipment
No. Equipment Prime Power (kW)
1 John Deere 6068 (existing) 101 kW
2 John Deere 4045 (existing) 67 kW
3 John Deere 6061 (existing) 179 kW
H1 Lower Hydro Project (proposed) 105 kW
H2 Upper Hydro Project (proposed) 35 kW
Data on existing diesel-fired generators Nos. 1 through 3) from AEE 2010.
1.ii. Type of Hydraulic Turbines
The upper system turbine will be a single cross-flow type turbine with an actuated inlet vane to
regulate the variable water flow to the turbine. The lower system turbine will be a dual-jet
impulse turbine (Pelton or Turgo) with actuated spear valves on both jets to regulate the
variable water flow to the turbine. The final turbine type(s) may differ from the proceeding
description. Final selection will be made based on life cycle cost and best value to ECUC.
Evaluation criteria will include factors such as initial cost, operating cost, service life, system
reliability, and water-to-wire efficiency.
1.iii. Proposed Plant Operation
Plant operation will be automated, with no personnel normally present at the project site. The
utility controls will automatically operate both hydro systems and interface with the existing
diesel powerhouse control system to coordinate economic dispatch of all generators on the
ECUC system. Hydro and/or diesel generators will be automatically dispatched to meet system
demand based on instantaneous water availability for the upper and lower systems and
economic / technical dispatch protocols.
The hydro system will supply 100% of utility demand, including peak demand, to the extent
possible based on available hydro generating capacity. Peak demand in excess of available
hydro generating capacity will be met by diesel generators in parallel or stand-alone operation
with the hydro generators depending on specific load conditions.
The system will normally operate with one of the hydro system generators as the prime
generator (isochronous mode). The other hydro generator, and then diesel generators, will be
activated as needed in droop mode to meet total system demand. When insufficient water is
available at the upper and/or lower systems, the next tier generator(s) in this dispatch
hierarchy will be promoted to regulate the system and meet demand.
When excess water is available in Crooked Creek and/or Jim's Lake, unused hydro generating
capacity may be used to serve interruptible loads (such as heating loads) in Elfin Cove.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 3
Figure 2: General Project Layout
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 4
1.iv. Estimated Average Annual Energy Generation
Estimated average annual energy generation is presented in Table 2.
Table 2: Estimated Average Annual Energy Generation
Utility Supply and Demand Annual Energy Estimate
Total Annual Utility Load at Generation (kWh) 350,000
Utility Load Supplied by Diesel (kWh) 35,900
(10.3%)
Utility Load Supplied by Hydro (kWh) 314,100
(89.7%)
Hydro Plant Installed Capacity (Both Systems) Upper System
35 kW
Lower System
105 kW
Total
140 kW
Hydro Plant Capacity Factor 63% N/A N/A
Total Annual Hydro Generation (kWh) 185,000 603,300 788,300
Hydro Output used to Supply Utility Load (kWh)
(percent of available hydro generation) - - 314,100
(40%)
Hydro Output used for Load Governor / Frequency
Regulation in Diesels-Off Operation 1 - - 52,300
(6%)
Gross Hydro Output Available for Load Growth or
Interruptible Loads (excludes hydro output used for
governor control)
- - 421,900
(54%)
Notes
1: The utility can operate in diesels-off mode approximately 96% of the time. Diesel generators will be required to
meet load typically during the summer months during both peak evening demand episodes and periods of low
water availability.
1.v. Estimated Average Head
Estimated average head for the upper and lower systems is presented in Table 3.
Table 3: Estimated Average Head for Upper and Lower Systems
Parameter Upper System Lower System
Normal Headwater Level 484.0 346.0
Headwater Level Range 480.3 to 484.0 338.0 to 347.4
Normal Tailwater Level / Turbine Elevation 346.0 27.5
Gross Plant Head 134.3 to 138.0 310.5 to 318.5
Head Loss at Full Flow 7.3 16.4
Net Plant Head 127.0 to 130.7 294.1 to 302.1
AVERAGE NET OPERATING HEAD 128 FEET 302 FEET
Note: All absolute elevations are given in mean low water vertical datum.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 5
312
314
316
318
320
322
324
326
328
330
332
334
336
338
340
342
344
346
348
350
0 20 40 60 80 100 120
Reservoir Volume (acre-feet)Reservoir Stage (feet, MLW)Available storage capacity for
hydro operations: 45 acre-feet
(volume impounded by dam)
MINIMUM OPERATING POOL: 338'
NORMAL OPERATING POOL: 346'
Unavailable storage
capacity: 55 acre-feet
(natural lake basin)
minimum lake floor: ~312'
design flood pool: 347.4'
minimum pool: 334'
(natural lake elevation: ~ 338')
1.vi. Reservoir Surface Area and Storage Capacity
The upper system has a run-of-river intake with negligible impoundment volume (< 1/20th acre-
foot) or surface area (< 1/20th acre).
Reservoir surface area and storage capacity of the Jim’s Lake reservoir for the lower system is
summarized in Table 4. The reservoir curve is presented in Figure 3.
Table 4: Jim’s Lake Reservoir Surface Area and Storage Capacity
Proposed Reservoir
Parameter Natural
Lake Minimum
Pool
Minimum
Operating
Pool
Normal
Operating
Pool
Design
Flood
Elevation
Surface Elevation (feet, MLW) +338 +334 +338 +346 +347.4
Surface Area (acres) 5.0 4.4 5.0 6.24 6.6
Gross Storage Capacity (acre-feet) 55 37 55 100 109
Usable Storage Capacity (acre-feet) - - 0 45 54
MLW: mean low water.
Figure 3: Jim’s Lake Reservoir Storage Curve
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 6
1.vii. Estimated Minimum and Maximum Hydraulic Capacity of Plant
The estimated minimum and maximum hydraulic capacities of the upper and lower systems is
presented in Table 5. Table 5 also presents the average flow in Crooked Creek and Jim’s Creek
at the diversion sites. More information on Crooked Creek and Jim’s Creek hydrology is
available in the hydrology report, included in Exhibit E.
Table 5: Estimated Range of Hydraulic Capacities of Hydro Systems
Parameter Upper
System
Lower
System
Minimum Hydro System Hydraulic Capacity (cubic feet per second, cfs) 0.5 1 0.5
Maximum Hydro System Hydraulic Capacity (cfs) 5.0 6.5
Average Creek Flow at Point of Diversion (cfs) 3.0 0.55
Notes:
1. The upper system will continue to divert water from Crooked Creek to Jim’s Lake even when water
flow is below the minimum operating capacity of the turbine.
1.viii. Description of Plant, Materials and Methods of Construction
1.viii.1. Common Features
The project includes the following features common to both the upper and lower systems.
1. Approximately 3,800 linear feet of access / construction roads at the project site.
2. Approximately 5,600 linear feet of access trails / corridors between Elfin Cove and the
project site.
3. Approximately 8,800 linear feet of primary electric distribution line (7.2/12.47 kV). This
will start at existing sectionalizing cabinet TB-10 on Lot 40A of the town site and follow
the access trails to the upper and lower powerhouses. The power line will be an
underground armored flexible cable similar to existing primary distribution cable in Elfin
Cove, except for along the stairway ascending from the back of Elfin Cove where it will
be installed beneath the stairs in rigid conduit. Splice vaults or sectionalizing cabinets
will be installed at approximately 700 to 1,000 foot intervals, typically within
turnarounds along the trails. Pad-mount transformers will be installed at each hydro
powerhouse.
4. Approximately 12,500 linear feet of communication cable. Communication cable will
generally be co-located with the primary power cables along the project trails and in
existing utility easements within Elfin Cove to the diesel powerhouse. Communication
cable will also extend up to the upper system intake. Communication cable access /
splice vaults will generally be co-located with primary electric vaults / cabinets.
5. Approximately 1,400 linear feet of secondary electric (480-volt) will extend from the
upper powerhouse to the upper and lower intakes to provide electricity at each
location. These branch circuits will be installed underground in conduit adjacent to
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 7
other utilities (penstock, communications) along the access corridors, terminating at
above ground enclosures.
1.viii.2. Upper System
1.viii.2.1. Intake
The intake will consist of a buried tank approximately 6 foot diameter by 16 foot long oriented
across Crooked Creek. The top of the tank will be fitted with an inclined plate inlet screen
(‘coanda’ screen) and spillway weir approximately eight feet wide, sized to accommodate the
design flood at this location. The inlet sill elevation will be approximately +488 feet MLW. The
tank will be anchored against overturning and/or sliding by cast-in-place concrete walls and/or
embedment in rip-rap fill installed along the creek banks. The penstock inlet will be fixed to
the end wall of the tank.
1.viii.2.2. Penstock
The upper penstock will be approximately 1,050 feet long and will be constructed from 14-inch
diameter DR 26 4710-series high-density polyethylene (HDPE) pipe. The penstock will be
installed at shallow burial along the uphill edge of the Crooked Creek trail.
1.viii.2.3. Powerhouse
The upper powerhouse will be approximately 16 by 20 feet with an interior ceiling height of
approximately 12 feet. Finish floor elevation will be +352 feet MLW. The powerhouse building
may be wood, steel, or concrete, and may be stick-built on site or may consist of pre-fabricated
knock-down construction or a pre-fabricated pre-furnished module. The building will have an
overhead door for equipment access and a pedestrian door for personnel access.
1.viii.3. Lower System
1.viii.3.1. Dam and Intake
Jim’s Lake Reservoir (see Section 1.vi) will be formed by raising the level of Jim’s Lake from +338
MLW to +346 MLW. The dam will be an approximately 225 foot long by up to 18 feet tall at its
highest point at the natural lake outlet to Jim’s Creek. The dam crest will be at +352 MLW
(approximately 4.6 feet above maximum reservoir pool) to accommodate wave run-up, long
term settlement, and provide freeboard. The dam will be a rock fill gravity structure with an
impermeable upstream face. A reinforced concrete structure founded on bedrock will be
incorporated to the dam at the natural lake outlet. This structure will house the lower water
intake, reservoir drain gate, and spillway.
The dam will be constructed by excavating an estimated four to eight feet of peat and mineral
overburden from the dam footprint down to bedrock. This overburden will be placed in a
designated disposal site adjacent to the dam. Rock fill from other trail developments for this
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 8
project will be used to build the rock fill dam. Once the dam structural prism is completed, lifts
of select fill will be placed on the upstream face for the impermeable liner. Additional lifts will
be placed over the liner for ballast and protection, with a final course of rip-rap for protection
from wave action, ice, and debris.
1.viii.3.2. Penstock
The lower penstock will be approximately 2,550 feet long. The upper portion of the penstock
will be constructed from 18-inch diameter DR 26 4710-series HDPE pipe, and the lower portion
will be constructed from 16-inch diameter DR 11 4710-series HDPE pipe. The penstock will be
installed at shallow burial along the uphill edge of the Jim’s Lake Creek trail from the dam down
to the lower powerhouse.
1.viii.3.3. Powerhouse
The lower powerhouse will measure approximately 20 by 28 feet with an interior ceiling height
of approximately 14 feet. Finish floor elevation will be +27.5 feel MLW. The powerhouse
building may be wood, steel, concrete, or other material, and may be stick-built on site or may
consist of pre-fabricated knock-down construction or a pre-fabricated pre-furnished module.
The building will have an overhead door for equipment access and a pedestrian door for
personnel access.
The building is sized to accommodate the turbine / generator, hydraulic power pack, switchgear
and controls and related equipment. It will also have room to store an all-terrain vehicle and a
snow machine to facilitate all-season access via boat from Elfin Cove to small sandy beach and
thence up the project trails to the dam and upper system as needed.
1.viii.4. Methods of Construction
The full development option project is based on construction of the project civil earthwork
(trails, roads, dam / diversions, penstock, utilities, etc.) using heavy equipment that would be
mobilized and demobilized to the project site via marine barge. Buildings and structures would
be prefabricated modules delivered to the site or built on site.
To maximize development and financing flexibility, ECUC is also considering a phased
development option for the project. See Appendix A.
1.ix. Estimated Cost
The estimated cost to construct the full development option project is $7.7 million.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
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1.x. Estimated Costs of Environmental Measures
The separate costs of environmental measures proposed and described in Exhibit E have not
been delineated. If additional environmental measures beyond those proposed are required by
the license terms and conditions, they may impose additional costs that can be quantified.
2.0 PURPOSE OF PROJECT
The project purpose is to provide renewable electricity for the community of Elfin Cove.
3.0 ESTIMATED COST TO DEVELOP THE LICENSE APPLICATION
The estimated cost to develop the license application is $400,000. This includes resource
studies, consultations, and other government permits as required by the licensing process.
4.0 ESTIMATED ON-PEAK AND OFF-PEAK POWER VALUE
The upper system is run-of-river. The lower system has a reservoir. Proposed operation is
described at 1.iii.
Because it operates an islanded micro-grid currently powered entirely by diesel-fired
generators, ECUC has not developed differential costs for on-peak and off-peak power either
internally or for its tariff. The expense to develop equitable estimates for on-peak and off-peak
power costs exceeds the value of this information to government agencies, the utility, or its
ratepayers.
Current ECUC electric rate is $0.68 per kWh. The rate varies largely due to fluctuations in the
cost of diesel fuel and has ranged from $0.59 to $0.80 per kWh in recent years.1
5.0 ESTIMATED IMPACT OF PROJECT CHANGES
No need for environmental restrictions on project water use (minimum bypass flows, reservoir
ramping rates, etc.) have been identified. Accordingly, no estimates have been developed for
the impact such environmental operating constraints would have on average annual energy
generation or the value of project power.
The operating plan and project performance data are based on:
1. 100% of available Crooked Creek flow at the upper diversion site up to the design flow is
diverted into the upper system for power generation and reuse in the lower system. No
minimum bypass flow at the Crooked Creek intake is proposed.
1 See Table A-1 in Polarconsult 2019.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 10
2. Lower system operations are not constrained by restrictions on reservoir ramping rates,
or minimum bypass flow into Jim’s Creek. Reservoir drawdown and fill rates are
discussed in the Wildlife Study report included with Exhibit E.
6.0 UNDEPRECIATED BOOK VALUE
This is a new unconstructed project. Not applicable.
7.0 ANNUAL O&M COSTS
ECUC’s existing annual operations and maintenance (O&M) costs are approximately $16,000.
With the hydro project, annual O&M costs are estimated to increase to $29,000. This reflects
both reduced diesel O&M costs and increased costs associated with routine hydro plant O&M.2
8.0 ONE-LINE DIAGRAM
The system one-line diagram is presented in Figure 4.
9.0 PROJECT SAFETY
To ensure safe management, operation, and maintenance of the project, a project safety plan
will be developed by ECUC prior to project commissioning as part of the utility’s operations and
maintenance manual and related documents. This will include the following major elements:
- Clear procedures and check lists for common project operations.
- Availability of the diesel plant for backup power generation during hydro outages until
conditions are safe for on-site assessment and corrective action at the hydro project.
- Personnel training in appropriate fields for plant operation, repair, and maintenance.
- Project design for intrinsically safe infrastructure to the extent practical, with minimized
need for on-going maintenance.
2 See Table 3-1 in Polarconsult 2019.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 11
Figure 4: System One-Line Diagram
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 12
10.0 REFERENCES
AEE 2010. Alaska Energy and Engineering, Inc. Stamped May 19, 2010. Elfin Cove
Distribution Upgrade. Record Drawings, Sheets E-1 to E-10. Anchorage,
Alaska.
Polarconsult 2019. Polarconsult Alaska, Inc. December 2019. Crooked Creek and Jim’s Lake
Hydroelectric Project. Business and Operating Plan. Anchorage, Alaska.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020
APPENDIX A:
EXHIBIT A INFORMATION FOR ‘PHASED DEVELOPMENT’ OPTION
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020
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Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 A-1
A.1.0 TECHNICAL OVERVIEW
The project information described in this Appendix A focuses on ways in which the phased
development option varies from the full development option presented in the main narrative of
Exhibit A. Information herein may differ depending on the final terms and conditions of
licenses and permits, final design, final site conditions, project economics, and other
considerations.
The general project layout for the Phased Development option is presented on Figure A-1.
A.1.i. Generating Units
With the phased development option, the upper hydro system will only be a water diversion
system with no power generation capability. Future upgrade to install power recovery at the
upper system would be possible.
Generator H2 in main narrative Table 1 is deleted under the phased development option.
Generator H1 and diesel generating units would be the same as the full development option.
A.1.ii. Type of Hydraulic Turbines
The upper system will nave no hydraulic turbine. Other elements of the project are as
described in 1.ii of the main narrative.
A.1.iii. Proposed Plant Operation
Plant operation for the phased development option is as described in 1.iii of the main narrative,
except that their will be no upper system turbine.
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
Final License Application – Exhibit A: Project Description Polarconsult Alaska, Inc.
February 2020 A-2
Figure A-1: General Project Layout (Phased Option)
ALTERNATE POWER LINE ROUTE
TO LOWER POWERHOUSE
SYSTEM
DISCHARGE
Elfin Cove Utility Commission
Crooked Creek and Jim's Lake Hydroelectric Project (P-14514)
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February 2020 A-3
A.1.iv. Estimated Average Annual Energy Generation
Table A-1 presents estimated phased development option average annual energy generation.
Table A-1: Estimated Average Annual Energy Generation (Phased Option)
Utility Supply and Demand Annual Energy Estimate
Total Annual Utility Load at Generation (kWh) 350,000
Utility Load Supplied by Diesel (kWh) 61,800
(17.7%)
Utility Load Supplied by Hydro (kWh) 288,200
(82.3%)
Hydro Plant Installed Capacity (Both Systems) Upper System
0 kW
Lower System
105 kW
Total
105 kW
Hydro Plant Capacity Factor - N/A N/A
Total Annual Hydro Generation (kWh) - 594,800 594,800
Hydro Output used to Supply Utility Load (kWh)
(percent of available hydro generation) - - 288,200
(49%)
Hydro Output used for Load Governor / Frequency
Regulation in Diesels-Off Operation 1 - - 37,800
(6%)
Gross Hydro Output Available for Load Growth or
Interruptible Loads (excludes hydro output used for
governor control)
- - 268,700
(45%)
Notes
1: The utility can operate in diesels-off mode approximately 92% of the time. Diesel generators will be required to
meet load typically during the summer months during both peak evening demand episodes and periods of low
water availability.
A.1.v. Estimated Average Head
Estimated average head for the phased development option is presented in Table A-2. Head on
the lower system is four feet less than for the full development option due to a shorter dam at
Jim’s Lake and corresponding decrease in lower system head. Head on the upper system is
unchanged. Since there is no power turbine on the upper system, this energy will be spent at a
dissipation structure at the penstock outlet to Jim’s Lake (see Section A.1.viii.2.3).
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Table A-2: Estimated Average Head for Upper and Lower Systems (Phased Option)
Parameter Upper System Lower System
Normal Headwater Level 484.0 342.0
Headwater Level Range 480.3 to 484.0 338.0 to 343.4
Normal Tailwater Level / Turbine Elevation 346.0 27.5
Gross Plant Head 134.3 to 138.0 306.5 to 314.5
Head Loss at Full Flow 7.3 16.4
Net Plant Head 127.0 to 130.7 290.1 to 298.1
AVERAGE NET OPERATING HEAD 128 FEET 298 FEET
Note: All absolute elevations are given in mean low water vertical datum.
A.1.vi. Reservoir Surface Area and Storage Capacity
The upper system reservoir area for the phased development option is unchanged from the full
development option.
Operating levels in the lower system reservoir are four feet lower for the phased development
option than for the full development option. Lower system reservoir surface area and storage
capacity is summarized in Table A-3. The reservoir curve is presented in Figure A-2.
Table A-3: Jim’s Lake Reservoir Surface Area and Storage Capacity (Phased Option)
Proposed Reservoir
Parameter Natural
Lake Minimum
Pool
Minimum
Operating
Pool
Normal
Operating
Pool
Design
Flood
Elevation
Surface Elevation (feet, MLW) +338 +334 +338 +342 +343.4
Surface Area (acres) 5.0 4.4 5.0 5.7 5.9
Gross Storage Capacity (acre-feet) 55 48 55 76 83
Usable Storage Capacity (acre-feet) - - 0 21 28
MLW: mean low water.
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February 2020 A-5
312
314
316
318
320
322
324
326
328
330
332
334
336
338
340
342
344
346
348
350
0 20 40 60 80 100 120
Reservoir Volume (acre-feet)Reservoir Stage (feet, MLW)Available storage
capacity for
operations:
21 acre-feet
MINIMUM OPERATING POOL: 338'
NORMAL OPERATING POOL: 342'
Unavailable storage
capacity: 55 acre-feet
(natural lake basin)
minimum lake floor: ~312'
design flood pool: 343.4'
minimum pool: 334'
(natural lake elevation: ~ 338')
Figure A-2: Jim’s Lake Reservoir Storage Curve (Phased Option)
A.1.vii. Estimated Minimum and Maximum Hydraulic Capacity of Plant
The estimated minimum and maximum hydraulic capacities of the upper and lower systems is
unchanged from the full development option. See Table A-4.
Table A-4: Estimated Range of Hydraulic Capacities of Hydro Systems (Phased Option)
Parameter Upper
System
Lower
System
Minimum Hydro System Hydraulic Capacity (cubic feet per second, cfs) 0 0.5
Maximum Hydro System Hydraulic Capacity (cfs) 5.0 6.5
Average Creek Flow at Point of Diversion (cfs) 3.0 0.55
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A.1.viii. Description of Plant, Materials, and Methods of Construction
A.1.viii.1 Common Features
The phased development option includes the following common features.
1. Approximately 3,800 linear feet of access / construction roads at the project site.
2. Approximately 5,600 linear feet of access trails / corridors between Elfin Cove and the
project site.
3. Approximately 5,700 to 8,800 linear feet of primary electric distribution line (7.2/12.47
kV) starting at existing sectionalizing cabinet TB-10 on Lot 40A of the town site. The
8,800 foot long route would follow project access trails to the lower powerhouse via
Jim’s Lake. The 5,700 foot long route would leave the access trails near the Crooked
Creek crossing and then head overland directly to the lower powerhouse. This route is
shown on Figure A-1. The power line will be an underground armored flexible cable
similar to existing primary distribution cable in Elfin Cove, except for along the stairway
ascending from the back of Elfin Cove where it will be installed beneath the stairs in
rigid conduit. Splice vaults or sectionalizing cabinets will be installed at approximately
700 to 1,000 foot intervals, typically within turnarounds along the trails. Pad-mount
transformers will be installed at each hydro powerhouse.
4. Approximately 11,100 linear feet of communication cable. Communication cable will
generally be co-located with the primary power cables along the project trails and in
existing utility corridors within Elfin Cove back to the diesel powerhouse.
Communication cable access / splice vaults will generally be co-located with primary
electric vaults / cabinets.
5. No secondary electric (480-volt) service is proposed for the lower intake at Jim’s Lake
under this option.
A.1.viii.2 Upper System
A.1.viii.2.1. Intake
The intake will consist of a buried 14-inch diameter pipe fitted with a inclined plate inlet screen
(‘coanda’-type intake screen) oriented across Crooked Creek. The screen will be eight feet long
with the approach plate sill elevation at +488 feet MLW. The pipe will extend in both directions
beyond the screened section and will be anchored against overturning and/or sliding by rock
filled gabion baskets placed over these pipe extensions. The outlet pipe will be flanged to a
butterfly valve and the penstock.
A.1.viii.2.2. Penstock
The upper penstock will be as described for the full development option. The upper penstock
may terminate upstream of the powerhouse site described in the full development option, with
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un-pressurized flow from the energy dissipation structure (See Section A.1.viii.2.3) flowing
overland to Jim’s Lake via existing natural surface drainage channels.
A.1.viii.2.3. Energy Dissipation Structure
The upper penstock will end at an energy dissipation structure to expend pressure head before
discharge to Jim’s Lake. The energy dissipation structure will consist of an orifice plate flanged
to the end of the penstock and mounted inside a small tank. The orifice plate’s jet will be
submerged, and will also have a splitter to help diffuse the jet. Water will then discharge from
the tank via un-pressurized gravity flow to Jim’s Lake.
The tank will be buried to reduce ambient noise and aesthetic impacts.
A.1.viii.3 Lower System
A.1.viii.3.1. Dam and Intake
Jim’s Lake Reservoir (see Section A.1.vi) will be formed by raising the level of Jim’s Lake from
+338 MLW to +342 MLW. The dam will be an approximately 75 foot long by up to 10 feet tall at
its highest point at the natural lake outlet to Jim’s Creek. The unregulated dam spillway will be
at +342 feet MLW, and the wingwall crests will be at +348 MLW (approximately 4.6 feet above
maximum reservoir pool) to accommodate wave run-up, long term settlement, and provide
freeboard. The dam will be a rock fill gravity structure with an impermeable upstream face, a
timber-bent dam with timber face, a reinforced concrete structure founded on bedrock, or a
combination of these. This structure will house the lower water intake, reservoir drain gate,
and spillway.
The dam will be constructed by excavating an estimated maximum four to eight feet of peat
and mineral overburden from the dam footprint down to competent material. There is little to
no overburden at the existing creek outlet and immediate surrounding area. Excavated
material will be placed in a designated disposal site adjacent to the dam.
A.1.viii.3.2. Penstock
The lower penstock will be as described for the full development option.
A.1.viii.3.3. Powerhouse
The lower powerhouse will be as described for the full development option.
A.1.viii.4 Methods of Construction
The phased development option is based on the following construction and operation
methodology:
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- Eliminate heavy equipment mobilization to the project site. Instead build foot trails using
manual labor and/or small equipment that can be delivered to the site by local landing
craft. Utilize helicopters to transport construction material, equipment, and pre-fabricated
assemblies to the project site.
- Defer construction of the upper powerhouse to a future date. This option may be exercised
depending on project cost and the timing and availability of funds for construction. If this
option is exercised, the upper penstock would still be sized for future addition of the upper
powerhouse. The upper intake may be simplified as debris exclusion requirements would
be substantially relaxed for a raw water pipeline than for a penstock feeding a hydropower
turbine. The electric distribution line and some trail alignments may also be revised to
more directly access the lower powerhouse.
- Minimize improved trail construction between Elfin Cove and the project site.
- Revise the Jim’s Lake dam from a rock fill gravity structure to a type suitable for
construction with manual labor, small equipment, and/or local materials.
In all instances, these alternate construction methodologies would result in lower
environmental impacts relative to the full development option presented in Exhibit A main
narrative. Principal reductions would be due to the decreased volume of earthwork required
and the associated decreased project footprint associated with cuts, fills, and disposal of excess
excavation material.
A.1.ix. Estimated Cost
The estimated cost to construct the phased development option hydro project is $5.3 million.
A.1.x. Estimated Costs of Environmental Measures
Estimated cost of environmental measures are as described for the full development option.
A.2.0 PURPOSE OF PROJECT
The purpose of the project is as described for the full development option.
A.3.0 ESTIMATED COST TO DEVELOP THE LICENSE APPLICATION
Estimated cost to develop the license application is as described for the full development
option.
A.4.0 ESTIMATED ON-PEAK AND OFF-PEAK POWER VALUE
Estimated on-peak and off-peak power value are as described for the full development option.
Elfin Cove Utility Commission
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A.5.0 ESTIMATED IMPACT OF PROJECT CHANGES
Estimated impact of project changes are as described for the full development option, except
that there is no power generation directly associated with the upper system. Water diverted by
the upper system is still used to contribute a significant portion of the power generated by the
lower system.
A.6.0 UNDEPRECIATED BOOK VALUE
Undepreciated book value is as described for the full development option.
A.7.0 ANNUAL O&M COSTS
ECUC’s existing annual O&M costs are approximately $16,000. With the phased development
option hydro project, annual O&M costs are estimated to increase to $28,000. This reflects
both reduced diesel O&M costs and increased costs associated with routine hydro plant O&M.3
A.8.0 ONE-LINE DIAGRAM
The system one-line diagram for the phased development option is presented in Figure A-3.
A.9.0 PROJECT SAFETY
Project safety is as described for the full development option.
3 See Table 3-1 in Polarconsult 2019.
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Figure A-3: System One-Line Diagram (Phased Option)