HomeMy WebLinkAbout5.4 GrantLk (P-13212) DLA Vl1 ExhB 03-27-15 FINALDRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-1 March 2015
EXHIBIT B: PROJECT OPERATIONS AND RESOURCE UTILIZATION
1 Contents and Purpose of This Exhibit
Kenai Hydro, LLC (KHL), a wholly-owned subsidiary of Homer Electric Association, Inc.
(HEA), is filing this Draft License Application (DLA) for an original license for the Grant Lake
Hydroelectric Project (FERC No. 13212 [Project or Grant Lake Project]) under Part I of the
Federal Power Act.
Exhibit B of this DLA describes the proposed operations of the Project, water availability and
use, and production and use of Project generation under an original license.
2 Project Site Selection and Proposed Operations
2.1. Project Site Alternatives
2.1.1. Crescent Lake
On October 1, 2008, KHL received a preliminary permit from the FERC to study the potential
development of a small hydroelectric projects at Crescent Lake (P-13209) on the Kenai
Peninsula. Crescent Lake is located 4 miles south of the community of Moose Pass, Alaska and
approximately 25 miles north of Seward, Alaska. KHL conducted a reconnaissance study to
evaluate the feasibility of a hydroelectric project at this location. The reconnaissance study
considered environmental conditions, recreation, subsistence use, cultural and historical
resources, land ownership, mining claims and water rights, energy generation, anticipated
development costs and an economic evaluation of the proposed project. Based upon the results
of this evaluation, agency input and public comments the Grant Lake/Creek project was
considered the more viable resource and selected for further evaluation.
2.1.2. Ptarmigan Lake/Creek
On October 1, 2008, KHL received a preliminary permit from the FERC to study the potential
development of a small hydroelectric project at Ptarmigan Lake/Creek (P-13210) on the Kenai
Peninsula. Ptarmigan Lake is located 6 miles south of the community of Moose Pass, Alaska
and approximately 25 miles north of Seward, Alaska. KHL conducted a reconnaissance study to
evaluate the feasibility of a hydroelectric project at this location. The reconnaissance study
considered environmental conditions, recreation, subsistence use, cultural and historical
resources, land ownership, mining claims and water rights, energy generation, anticipated
development costs and an economic evaluation of the proposed project. Based upon the results
of this evaluation, agency input and public comments the Grant Lake/Creek project was
considered the more viable resource and selected for further evaluation.
2.1.3. Falls Creek
On October 1, 2008, KHL received a preliminary permit from the FERC to study the potential
development of a small hydroelectric projects, Falls Creek (P-13211) on the Kenai Peninsula.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-2 March 2015
Falls Creek is located approximately 1.5 miles south of the community of Moose Pass, Alaska
and approximately 25 miles north of Seward, Alaska. KHL conducted a reconnaissance study to
evaluate the feasibility of a hydroelectric project at this location. Two alternatives were
considered; a stand-alone project that would discharge water back into Falls Creek and a project
that would divert water from Falls Creek north to Grant Lake, where water would be used to
generate power from the Grant Lake Project. The reconnaissance study considered
environmental conditions, recreation, subsistence use, cultural and historical resources, land
ownership, mining claims, water rights, energy generation, anticipated development costs and an
economic evaluation of the proposed project. Based upon the results of this evaluation, agency
input and public comments the Grant Lake/Creek Project was considered the more viable
resource and selected for further evaluation. Since the Grant Lake project was selected for
further evaluation, the Falls Creek diversion into Grant Lake was carried forward for further
evaluation. Additional investigation into the engineering feasibility and the economics
associated with the Falls Creek diversion led Kenai Hydro to determine that the Falls Creek
Diversion portion of the project was infeasible. On March 31, 2011 KHL petitioned FERC to
surrender the Falls Creek project preliminary permit.
2.1.4. Grant Lake/Creek
Hydroelectric potential at Grant Lake has been evaluated several times as a potential power
source for the Kenai Peninsula area. In 1954, R.W. Beck and Associates (cited by Ebasco 1984)
prepared a preliminary investigation and concluded that a project at the site had significant
potential. The U.S. Geological Survey (USGS) conducted geologic investigations of proposed
power sites at Cooper, Grant, Ptarmigan, and Crescent Lakes in the 1950s (Plafker 1955). In
1980, CH2M Hill (CH2M Hill 1980) prepared a prefeasibility study for a Grant Lake project and
concluded that a project developed at the site would be feasible. The Grant Lake Project was
referenced in the 1981 U.S. Army Corps of Engineers (USACE) National Hydroelectric Power
Resources Study (USACE 1981). The most extensive study was performed by Ebasco Services,
Inc. in 1984 for the Alaska Power Authority (now Alaska Energy Authority; Ebasco 1984). The
studies included a detailed examination of water use and quality; fish resources; botanical and
wildlife resources; historical and archaeological resources; socioeconomic impacts; geological
and soil resources; recreational resources; aesthetic resources; and land use (Ebasco 1984). Two
of the alternatives evaluated by Ebasco included the diversion of adjacent Falls Creek into Grant
Lake to provide additional water for power generation.
During the 1986-87 periods a preliminary application document was filed by Kenai Hydro, Inc.
(no relation to the current KHL) for a project at Grant Lake. Support for the application included
an instream flow study. Because of competing projects, political considerations, and inexpensive
natural gas the project was never pursued beyond the preliminary application phase.
On October 1, 2008, KHL received a preliminary permit from the FERC to study the potential
development of a small hydroelectric project at Grant Lake/Creek (P-13212) on the Kenai
Peninsula. KHL conducted a reconnaissance study to evaluate the feasibility of a hydroelectric
project at this location. The reconnaissance study considered environmental conditions,
recreation, subsistence use, cultural and historical resources, land ownership, mining claims and
water rights, energy generation, anticipated development costs and an economic evaluation of the
proposed project. Based upon the results of this evaluation, agency input and public comments
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-3 March 2015
the Grant Lake/Creek project was considered the more viable resource and selected for further
evaluation.
On August 6, 2009, KHL filed a Pre-Application Document (PAD), along with a Notice of Intent
(NOI) to file an application for an original license for the Grant Lake/Falls Creek project (P-
13211/13212) under Part I of the Federal Power Act (FPA). On September 15, 2009, FERC
approved the use of the Traditional Licensing Process (TLP) for development of the license
application and supporting materials.
2.2. Project Facility Designs, Processes, and Operations Alternatives
2.2.1. Configuration Alternatives
Grant Lake has been studied on multiple occasions since the 1950s as a potential hydropower
site. The previous study efforts included:
1954 – R.W. Beck and Associates preliminary investigation (as cited in Ebasco 1984)
1955 – USGS geological investigations of proposed power sites at Cooper, Grant,
Ptarmigan, and Crescent Lake (Plafker 1955)
1980 – CH2M Hill prefeasibility study (CH2M Hill 1980)
1984 – Ebasco Services Project Feasibility Analysis (Ebasco 1984)
Within these previous studies, development of the hydroelectric potential was considered under a
range of alternative configurations. The alternatives analysis cumulated with a more robust
evaluation by Ebasco in their 1984 engineering evaluation (Ebasco 1984). The Ebasco analysis
included size alternatives. Alternatives A, B, and C (below) focused on building a dam on the
Grant Lake outlet as well as a saddle dam on the north of the natural outlet. These alternatives
were designed to provide storage for power generation as well as increase the operating head on
the powerhouse. Alternative D consisted of a lake tap near the existing Grant Lake outlet with
no dams proposed. The final two alternatives, E and F, re-routed the adjacent Fall Creek flow
into grant Lake with a dam (Alternative A) and no dam (Alternative D) configuration.
Alternatives A, B, C, and D would use only the natural inflow from Grant Lake. Alternatives E
and F would use the Grant Lake inflow plus Fall Creek for power generation.
KHL utilized these same alternatives as the starting point in the current licensing process. The
previous work efforts were reviewed and updated, where required, to provide a basis for the
alternatives development and analysis. A seventh alternative, Alternative G, was developed to
reflect the additional environmental baseline data and the operational criteria required to address
specific identified issues. A brief description of each alternative is presented in the following
subsections.
Further details regarding the configuration alternatives are provided in the Supporting Design
Report in Exhibit F (Attachment F-1) of this DLA.
2.2.1.1. Alternative A – Intake Upstream of Saddle Dam
Alternative A consists of raising Grant Lake from its existing natural outlet at approximately
elevation 703 feet NAVD 88 to a normal maximum lake elevation of 745 feet NAVD 88. The
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-4 March 2015
lake raise would be accomplished by constructing a main dam at the natural outlet of Grant Lake.
A second dam would be constructed across a low saddle area located north of the main dam.
Water would be conveyed from Grant Lake to a power house located on the east shore of Upper
Trail Lake via a power conduit approximately 3,840 feet long with an intake structure located
upstream from the saddle dam. The intake to the power conduit would be a submerged circular
vertical concrete structure with vertical trashracks would be located approximately 1,300 feet
upstream from the toe of the saddle dam. A steel pipeline would extend from the intake to a
surge tank. A steel penstock would continue from the surge tank to the powerhouse. The
discharge from the powerhouse would be through a tailrace channel to Upper Trail Lake. The
powerhouse would house a single vertical Francis turbine operating with a maximum hydraulic
capacity of 385 cubic feet per second (cfs) at a net head of 247 feet. The powerhouse would
have an installed capacity of 6 megawatts (MW).
The substation would be located adjacent to the powerhouse. The transmission line would
extend from the powerhouse south to Grant Creek, then cross the Trail Lake Narrows to the
existing 115 kilovolt (kV) transmission line located adjacent to the Seward highway. A total of
5.1 miles of access road would connect the Project features to the Seward Highway.
2.2.1.2. Alternative B – Intake at Main Dam with Tunnel and Surface Conduit
Similar to Alternative A, the Grant Lake elevation would be raised from 703 feet NAVD 88 to a
normal maximum operating elevation of 745 feet NAVD 88 by constructing the main dam and
saddle dam as described with Alternative A. With this alternative, the intake would be located at
the main dam location. Water would be conveyed from the Grant Lake intake to a power tunnel
using a 7-foot-diameter low pressure penstock. The first 300 feet of penstock under the dam
would be placed in a rock trench and encased in concrete. The remaining 400 feet to the power
tunnel would be installed on the surface supported by concrete saddles. The power tunnel would
be horse shoe shaped and 9-foot-diameter fitted with an underground surge chamber. At the
downstream end of the tunnel, a 5-foot-penstock would extend to a powerhouse with an installed
capacity of 6 MW. The powerhouse would have essentially the same mechanical and electrical
configuration as described for Alternative A. A short tailrace channel would carry the water
from the powerhouse to the east bank of Upper Trail Lake. Approximately 2.0 miles of access
roads would be required for the Project. The transmission line would follow the same
approximate route across Trail Lakes Narrows.
2.2.1.3. Alternative C – Intake at Main Dam with Surface Conduit
Similar to Alternatives A and B, Alternative C utilized the same two dams to raise Grant Lake
from approximately 703 feet NAVD 88 to 745 feet NAVD 88. The intake would be located at
the main dam using a similar intake configuration as Alternative B. A 6.75-foot-diameter steel
power conduit would extend from the intake beneath the dam to a surge tank located at the
downstream toe of the main dam. A 5.35-foot diameter, 2,000-foot-long steel penstock would
extend from the surge tank to the powerhouse. The powerhouse would be located approximately
80 feet from the east bank of Upper Trail Lake. The powerhouse would consist of a concrete
foundation and a steel superstructure. The mechanical and electrical equipment would be similar
to Alternatives A and B as well as the 6 MW rated capacity.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-5 March 2015
2.2.1.4. Alternative D – Lake Tap with Powerhouse at Upper Trail Lake
With this alternative, the main dam and saddle dam as proposed with the Alternatives A, B, and
C would be eliminated. Alternative D does not involve the water elevation at Grant Lake. A
lake tap would supply water from a low level power tunnel and a short length of penstock to a
powerhouse located on Upper Trail Lake. The lake tap would have an intake invert at
approximately elevation of 643 feet NAVD 88. The lake tap would consist of an inclined 10-
foot-diameter circular tunnel which would incorporate a rock trap located just downstream of the
intake portal. A trashrack would be placed on the intake portal to exclude debris from entering
the power conduit. A 9-foot-diameter horseshoe shaped power tunnel would extend
approximately 3,300 feet from the lake tap to the powerhouse. A 5-foot-diameter, 500-foot-long
steel penstock would then extend from the downstream tunnel portal to the powerhouse located
on the east bank of Upper Trail Lake. A gate shaft would be located approximately 200 feet
downstream from the lake tap. An isolation gate would be located in the gate shaft. A
conventional powerhouse with a concrete foundation and steel superstructure would be located
approximately 180 feet from the east bank of Upper Trail Lake. The powerhouse would have a
single vertical Francis turbine operating under a net head of 198 feet with an installed capacity of
5 MW.
2.2.1.5. Alternatives E and F – Diversion of Falls Creek
These alternatives would divert runoff from the Falls Creek drainage, located directly south of
the Grant Lake drainage, into Grant Lake for additional power production. For both of these
alternatives, the diversion of Falls Creek would be accomplished using a diversion dam and
conduit to convey water from Falls Creek into Grant Lake. For Alternative E, the diversion of
Falls Creek is used in combination with raising Grant Lake from its existing elevation of 703 feet
NAVD 88 to a maximum normal operating elevation of 745 feet NAVD 88. This is
accomplished with the same two dam configuration as presented for Alternative A. The power
conduits, powerhouse, transmission, and access would be similar to the configuration proposed
for Alternative A. The powerhouse would have a rated capacity of 7 MW.
Alternative F consisted of the Falls Creek diversion coupled with the no dam Alternative D
configuration. The power tunnel, powerhouse, transmission, and access would be similar to the
configuration proposed for Alternative A. The powerhouse would have a rated capacity of
approximately 6 MW.
2.2.1.6. Alternative G – Lake Intake with a Powerhouse on Grant Creek
Alternative G was developed essentially as an outgrowth of Alternative D with the basic features
modified to address considerations raised as part of the environmental baseline studies completed
in 2009 through 2014. These studies identified aquatic habitat and resources within Grant Creek
from the confluence with Upper Trail Lake up to the outlet of the canyon area of Grant Creek
(Reaches 1 through 4). The area within the canyon area (Reach 5), though not identified as
productive habitat as the lower area of Grant Creek, provided limited habitat for specific species.
Measures to protect and enhance these areas were then identified and incorporated into
Alternative G. This alternative consists of a conventional intake tower located in Grant Lake
fitted with a selective withdrawal intake gate and an isolation bulkhead gate. Water is conveyed
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-6 March 2015
via a 10-foot-diameter, 3,300-foot-long horseshoed shaped tunnel. The upper reach of the tunnel
would be unlined and constructed on a 1 percent slope. The lower reach of the tunnel would be
lined and constructed at 15 percent slope. A surge chamber is located at the junction between the
two tunnel sections. A rock trap is located at the downstream end of the unlined tunnel directly
under the surge chamber. Steel liners will be installed at both the upstream and downstream
portals to provide structural strength of the tunnel through the transition areas. A 72-inch
diameter steel penstock extends from the downstream tunnel portal to the powerhouse. The
powerhouse would be a conventional concrete foundation with a steel superstructure. Two
Francis turbines with a combined rated capacity of 5 MW at a maximum hydraulic capacity of
385 cfs and a net operating head of 171 feet. Water is conveyed from the powerhouse back to
Grant Creek in an excavated tailrace channel with a fish barrier located at the outfall back into
Grant Creek. The tailrace channel discharges into Grant Creek near the outlet of the canyon
section of Grant Creek. A detention pond is located on the south side of the powerhouse
providing the additional benefit of spinning reserve operation. The transmission line will extend
approximately 1 mile from the substation located adjacent to the powerhouse west to the existing
115 kV transmission line. The transmission line will follow the powerhouse access road which
extends from the Seward Highway across the Trail Lakes Narrows. An access road will also be
provided to the intake structure.
2.2.1.7. Proposed Configuration
In the previous alternatives analysis (Ebasco 1984), Alternative D was the recommended
alternative with a consideration for diverting Fall Creek as presented within Alternative F. With
this alternative, the powerhouse was located approximately 180 feet from the east bank of Upper
Trail Lake. Under most operating conditions, Grant Creek would have been dewatered.
As outlined in the alternatives description, development of Alternative G incorporated a number
of design modifications which provided a net benefit in environmental conditions. These design
modifications included:
1) Relocate the powerhouse for the bank of Upper Trail Lake on the north side of Grant
Creek to the south side of Grant Creek to the outlet of the canyon reach (Reach 5).
2) Relocate the intake from the north side of the natural outlet of Grant Lake to the south
side and replace the lake tap with a conventional intake structure with the capabilities
of selective water withdrawal for downstream temperature control.
3) Re-align the access road to eliminate parallel alignment of the Iditarod National
Historic Trail (INHT).
4) Eliminate the 2-foot-tall diversion structure at the top of the Grant Creek natural
outlet.
5) Provide a bypass pipe from the lake intake to the base of the existing falls at the Grant
Lake outlet to provide a minimum flow of 5 cfs to 10 cfs in Reach 5.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-7 March 2015
6) Reroute the transmission line to follow the powerhouse access road directly west to
the existing 115-kV transmission line.
7) Modify the proposed single Francis unit 5-MW powerhouse to a two unit
configuration to provide more flexibility to release flows to meet downstream flow
considerations for aquatic habitat in the winter months.
Alternative G has been selected as the preferred alternative for the Project. This site
configuration was selected because it represented the optimum environmental configuration by
eliminating the dams, placing the powerhouse tailrace upstream of the prime aquatic habitat, and
eliminated the Falls Creek water diversion.
2.2.2. Proposed Design
The proposed Project would divert water from Grant Lake and deliver the flow to a powerhouse
located near the outlet of the existing Grant Creek natural, incised rock canyon. The proposed
Project consists of the following primary components:
An intake structure in Grant Lake.
A tunnel extending from the lake intake to a steel penstock.
A powerhouse with two Francis turbines providing an anticipated combined 5-MW
output with a maximum design flow of approximately 385 cubic feet per second (cfs).
A tailrace detention pond.
Switchyard with disconnect switch and step-up transformer.
An overhead 115 kilovolt (kV) transmission line.
A pole mounted disconnect switch where the transmission line intersects the main
power distribution line.
Detailed descriptions of the proposed Project facilities are provided in Exhibit A and the
preliminary design drawings of the proposed Project are provided in Exhibit F of this DLA.
2.2.3. Grant Lake Operational Model
An operations model was developed for the Project. The model takes into account the natural
inflows, habitat constraints, the Project engineering details, and operational desires to simulate
Project operations. The model outputs include discharge, reservoir elevations, and energy
production on a daily time step. The gross annual energy production is adjusted to account for
transmission losses, unplanned outages, and station service.
The operations model was used to simulate operations of the proposed Project using historic
hydrologic data. The hydrologic data is a composite record consisting of gaged and extended
streamflow records for Grant Creek that was collaboratively developed with the Grant Lake
Instream Flow Subgroup. The hydrologic data represents 66 years of streamflow from January
1948 through December 2013.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-8 March 2015
2.3. Project Operations During Adverse, Average, and High Water Years
The Project will operate to generator power throughout the calendar year based on inflow,
available storage, lake elevation, and minimum flow requirements with Grant Creek. The lake
will operate from the natural Grant Lake outlet elevation of 703 feet NAVD 88 down to a
minimum lake elevation of 690 feet NAVD 88. The lake will be drawn down in the winter
months utilizing a combination of Grant Creek inflows and stored water to meet the instream
flows in Reach 5 while also maintaining power production. Water flow predictions will be used
to estimate snowpack and the corresponding runoff volume. The Project operation will then be
tailored to maximize winter power production while also ensuring the lake refills to elevation
703 feet NAVD 88.
2.3.1. Adverse Water Years
During adverse flow years the lake elevation will be monitored closely in relation to anticipated
inflow and predicted lake fill rates. The powerhouse production could be reduced in adverse
flow years to maintain the instream flow requirements and hit target lake levels during the spring
runoff period. The estimated annual generation analysis reflected this operation scenario using a
dry period year to determine the estimated powerhouse production and required lake refill
sequence.
2.3.2. Average Water Years
During average water years, the Project will be operated to maximize power production and
minimize spill conditions. The lake will be operated within the maximum lake elevation of 703
feet NAVD 88 and minimum of 690 feet NAVD 88. The lake will be drawn down in the winter
to the minimum elevation 690 feet NAVD 88 to provide the maximum storage volume to capture
the spring runoff. Flow predictions will be utilized based on snow pack and environmental
conditions to optimize the rule curve for filling the lake. The lake will refill reaching the
maximum operating elevation of 703 feet NAVD 88 while maximizing the powerhouse
production as close to the 385 cfs maximum powerhouse flow for as long of a duration as
possible. The average water year was reflected in the estimated power production forecasts by
selecting an average flow year as part of the generation analysis.
2.3.3. High Water Years
During high water years, the Project will likely spill at a large quantity for a longer duration than
average flow years. As indicated previously, flow prediction methods will be utilized to estimate
the total volume of runoff as well as the rate of inflow. The powerhouse will then be operated to
create adequate storage volume in the lake to capture the predicted volume. When the lake
reaches elevation 703 feet NAVD 88, the excess flow will spill over the natural outlet. During
spill conditions, the powerhouse will be operated at the maximum hydraulic capacity of 385 cfs.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-9 March 2015
3 Existing Resource Utilization
3.1. Plant Control
The Project will operate in a fully automated manner with no onsite personnel. The system can
be monitored remotely using a fiber optics tie to the KHL system. The powerhouse control room
will include a computerized system which will monitor the lake elevation, water temperature,
system pressures, wicket gate settings, and plant output. These parameters along with the system
alarms will be monitored remotely. Adjustments to the system operating parameters will be
made remotely based on the Project operations rule curves and system integration. The facility
will be visited monthly by HEA staff to inspect and maintain the facilities.
3.2. Annual Plant Factor
The annual plant factor is computed using the following equation:
Annual Plant Factor = Annual Energy Production (MW-hours) / [Rated Capacity
(MW) x 8760 (hours/year)]
Based on the average annual energy production, simulated for 1948 through 2013, and the rated
generation capacity, the annual plant factor is 0.43.
3.3. Dependable Capacity and Average Annual Energy Production
The dependable capacity is based on the discharge that can be maintained more than 95 percent
of the time, the minimum available head, conduit head loss, machine efficiency, and station
service load. Based on these constraints, the Project has a dependable capacity of 0.15 MW.
Based on 66 years of streamflow data run through the Project operations model, the average
annual energy production is anticipated to be 18,600 megawatt hours (MWh).
3.3.1. Project Flow Data
The streamflow record utilized for the generation analysis was a composite of recorded
streamflow and record extension. Grant Creek has an 11-year USGS streamflow gage record for
water years 1948-1958 at USGS gage 15246000. Intermittent streamflow monitoring was
conducted in 1981-1983, 2009, and from 2013 to present. A record extension was performed
based on the USGS gage 15258000, Kenai River at Cooper Landing, record. A composite
streamflow record was created for Grant Creek that represents 66 years of daily streamflow data
for calendar years 1948 through 2013. The monthly and annual flow statistics for the 66 year
composite record are provided in Table B.3-1. The composite stream flow record was also used
to generate an average annual hydrograph based on the average of the daily flow values (Figure
B.3-1). The average hydrograph was utilized in the generation analysis, in addition to the
individual years of streamflow data.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-10 March 2015
Table B.3-1. Grant Creek monthly flow statistics, in cfs (calendar years 1948-2013).
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Maximum 326 227 116 160 566 2,140 1,210 1,383 1,731 1,295 851 570 2,140
Mean 52 43 33 36 146 409 503 444 367 233 123 73 206
Minimum 12 11 6 13 17 102 210 173 65 45 28 18 6
Figure B.3-1. Grant Lake average annual hydrograph.
3.3.2. Flow Duration Curves
A flow duration analysis was conducted for Grant Creek based on the 66-year composite record,
calendar years 1948 through 2013. Exceedance percentiles were computed for annual and
monthly daily average flows and are provided in Table B.3-2. The monthly flow duration curves
are plotted in Figure B.3-2. Annual flow duration curves for with Project and without Project
conditions are provided in Figure B.3-3.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-11 March 2015
Table B.3-2. Grant Creek annual and monthly daily average flow exceedance percentile, in cfs (calendar
years 1948-2013).
Exceedance
Percentile Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
0% 326 227 116 160 566 2,140 1,210 1,383 1,731 1,295 851 570 2,140
5% 110 108 65 71 340 649 718 685 804 579 294 162 575
10% 87 70 51 61 286 582 644 595 612 427 234 119 499
15% 74 57 45 53 242 546 597 552 525 359 181 99 448
20% 64 51 41 47 215 512 573 524 480 317 151 87 402
25% 57 48 39 43 193 487 551 498 440 281 134 78 353
30% 54 45 37 40 176 463 533 480 405 255 123 73 303
35% 50 42 35 36 162 439 520 464 370 233 114 70 243
40% 48 39 33 34 149 425 509 447 346 212 105 65 186
45% 47 38 32 33 139 412 499 433 329 196 99 63 142
50% 45 36 30 31 127 398 488 422 313 182 94 59 110
55% 43 34 29 29 114 382 479 411 298 170 89 57 87
60% 41 32 27 28 103 363 467 398 282 158 85 54 71
65% 38 31 25 26 93 342 458 387 266 148 80 51 59
70% 36 29 23 25 83 323 447 372 250 137 76 49 49
75% 34 27 22 24 72 308 433 360 231 125 72 45 43
80% 32 25 21 22 62 290 419 346 215 115 67 42 37
85% 29 23 19 21 53 270 400 330 193 102 60 39 32
90% 25 20 18 19 45 238 382 316 166 90 55 36 27
95% 20 17 15 18 36 204 361 289 139 76 44 28 21
100% 12 11 6 13 17 102 210 173 65 45 28 18 6
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-12 March 2015
Figure B.3-2. Grant Lake monthly flow duration curves (calendar years 1948-2013).
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-13 March 2015
Figure B.3-3. Grant Lake annual flow duration curves with Project and without Project conditions
(calendar years 1948-2013).
3.3.3. Critical Streamflow
The critical streamflow value used to compute the dependable capacity was 96 cfs. This flow
corresponds to the 95 percent exceedance probability for Grant Creek under proposed operating
conditions with the Project in place (see Figure B.3-3).
3.3.4. Storage Capacity
The Project will utilize the natural storage capacity of Grant Lake and will not include any
additional impoundment. The gross storage volume of Grant Lake at the normal maximum lake
elevation (703 feet NAVD 88) is 251,920 acre-feet. The Project will draw Grant Lake down to a
maximum depth of 13 feet. The net storage volume between normal maximum lake elevation,
703 feet NAVD 88, and the minimum lake elevation, 690 feet NAVD 88, is 18,791 acre-feet.
Figure B.3-4 illustrates the storage capacity for Grant Lake. When Grant Lake is full, elevation
703 feet NAVD 88, the surface area is 1,703 acres. Figure B.3-5 illustrates the storage area
curve for Grant Lake. The storage and surface area curve information for Grant Lake is also
tabulated in Table B.3-3.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-14 March 2015
Figure B.3-4. Grant Lake storage capacity curve.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-15 March 2015
Figure B.3-5. Grant Lake surface area curve.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-16 March 2015
Table B.3-3. Grant Lake storage and surface area relative to lake elevation.
Lake Elevation
feet, NAVD 88
Gross Storage
acre-feet
Net Storage
acre-feet
Surface Area
acres
703 251,920 18,791 1,703
702 250,475 17,345 1,695
701 249,029 15,900 1,688
700 247,584 14,455 1,680
699 246,138 13,009 1,672
698 244,693 11,564 1,665
697 243,247 10,118 1,657
696 241,802 8,673 1,650
695 240,356 7,227 1,642
694 238,911 5,782 1,634
693 237,465 4,336 1,627
692 236,020 2,891 1,619
691 234,575 1,445 1,612
690 233,179 -- 1,604
3.3.5. Rule Curve
The rule curve for the Project is intended primarily to provide for instream flows and power
generation. Grant Lake will be drafted in fall and winter and refilled in spring and summer. The
normal maximum lake elevation will be 703 feet NAVD 88 and the minimum lake elevation will
be 690 feet NAVD 88. Figure B.3-6 illustrates the anticipated rule curve on an annual basis.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-17 March 2015
Figure B.3-6. Grant Lake rule curve.
3.3.6. Tailwater Rating Curve
The tailwater elevations for the Project were developed using a hydraulic model of Grant Creek.
The tailwater location is located where the tailrace channel will return powerhouse flow to Grant
Creek at the downstream on the incised canyon (Reaches 4 and 5 transitions). Figure B.3-7
provides the tailwater rating curve for Grant Creek.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-18 March 2015
Figure B.3-7. Grant Lake tailwater rating curve.
3.3.7. Power Plant Hydraulic Capacities and Capabilities
The Project powerplant will consist of twin horizontal Frances turbines each paired with an
electric generator. Each of the two units will have a rated generation capacity of 2.5 MW and a
hydraulic capacity of 192.5 cfs. The minimum operating flow for the plant is estimated at 30
percent of the hydraulic capacity of a single unit, 58 cfs. Table B.3-4 provides the flow,
efficiency, and generator output under maximum and minimum operating conditions. Figure
B.3-8 provides the powerplant capacity curve which plots power generation versus net head.
Table B.3-4. Grant Lake Project Maximum and Minimum Operating Conditions.
Hydraulic capacity Flow (cfs) Efficiency (%) Generator output (kW)
Maximum 385 89% 4,986
Minimum 58 33% 42
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-19 March 2015
Figure B.3-8. Project power generation vs. net head.
4 System and Regional Power Needs
HEA has over 22,400 member-owners and provides power to over 33,300 meters located
throughout the Kenai Peninsula. HEA generates the power needed to serve members from its 12
percent share of the Bradley Lake hydroelectric facility, the Nikiski Combine Cycle Plant, the
Soldotna Combustion Turbine Plant and the Bernice Lake Power Plant. With the exception of
HEA’s 12 percent share of Bradley Lake, power which accounts for 9 percent HEA’s generation
needs, HEA is highly dependent on natural gas. The Cook Inlet of Alaska faces declining natural
gas production and directly associated increasing natural gas prices. HEA is seeking to diversify
its generation portfolio, add additional sources of renewable energy and reduce its exposure to
increasing natural gas prices.
For reasons of environmental stewardship and sustainable long term generation, HEA’s Board of
Directors has set a renewable energy goal of 22 percent of HEA’s power will be provided from
renewable resources by 2018.
HEA’s load forecast is depicted in Figure B.4-1. The projections are taken from HEA’s Equity
Management Plan.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-20 March 2015
Figure B.4-1. HEA’s load forecast.
HEA’s load duration curve is depicted in Figure B.4-2.
Figure B.4-2. HEA’s load duration curve.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-21 March 2015
HEA is interconnected to a regional Alaskan grid known as the “Railbelt” via a three phase, 115-
kV transmission line. The Railbelt is generally defined as the service areas of six regulated
public utilities: Anchorage Municipal Light & Power (ML&P), Chugach Electric Association
(Chugach), Golden Valley Electric Association (GVEA), HEA, Matanuska Electric Association
(MEA), and the City of Seward Electric System (SES). This region covers a significant area of
the state and contains the majority of the state’s population and economic activity; it extends
from Homer to Fairbanks and includes areas such as Anchorage, Fairbanks, and the Matanuska-
Susitna Valley. HEA can provide power to Alaskan residents from Anchorage to Fairbanks via
wholesale and economy energy sales to the other five interconnected electric utilities.
Electricity generated at the Project would be transmitted via Chugach Electric’s 115-kV
transmission line that extends from the Lawing Substation near the Project to the Quartz Creek
Substation where it enters HEA’s transmission and distribution system.
The Project would become an integral component of HEA’s overall generation portfolio. Except
for the small amount of electricity used to power the auxiliary Project equipment and facilities,
the power generated by the Project would be dispatched as a part of the entire HEA generation
system. The Project generation would be pooled with other HEA generation resources and shared
among retail and wholesale purchasers. As with all generation resources available to HEA, the
Project would be dispatched economically to minimize total generation costs while meeting,
licensing requirements, reliability requirements and contractual service obligations. KHL’s
objective in operating the Project is to optimize HEA’s ability to meet load throughout the
integrated system, balancing its hydro and thermal energy sources. Within the constraints of the
licensed operating levels, KHL would operate the Project in the temporal mode most
advantageous to the system.
The energy from the Project would primarily be used for base load as well as taking advantage of
any available spinning reserve. It would occasionally be used for peaking where appropriate.
This added source of generation that is quite distant from other generation sources on the
Railbelt grid will improve power quality, reduce voltage drop and provide a generation source to
an area of the system that would otherwise be susceptible to an outage with a single transmission
line interruption. Additionally, the location of the Project that is near the boundaries of two other
electric utilities that currently wheel power across HEA’s systems, sets up the possibility that
future, mutually beneficial wheeling arrangements may be possible.
5 Future Resource Utilization
At this time, KHL has no plans for additional water power project developments.
6 References
CH2M Hill. 1980. Feasibility assessment – hydropower development at Grant Lake. City of
Seward, Alaska.
Ebasco Services Incorporated. 1984. Grant Lake Hydroelectric Project Detailed Feasibility
Analysis. Volume 2. Environmental Report. Rep. prepared for Alaska Power Authority.
DRAFT LICENSE APPLICATION EXHIBIT B
Grant Lake Hydroelectric Project Kenai Hydro, LLC
FERC No. 13212 B-22 March 2015
Plafker. G. 1955. Geologic Investigations of Proposed Power Sites at Cooper, Grant, Ptarmigan,
and Crescent Lakes Alaska. Geological Survey Bulletin 1031-A.
USACE (U.S. Army Corps of Engineers). 1981. National Hydroelectric Power Study
Regional Report: Volume XXIII – Alaska. USACE North Pacific Division,
Portland, Oregon and Alaska District,. Anchorage, Alaska.