In 2007, the Chugach Electric Association, Inc. (Chugach) Cooper Lake Hydroelectric Project was
issued a new operating license (Project: FERC No. 2170). The Project is located near Cooper Landing
on the Kenai Peninsula and provides power to southcentral Alaska as part of Chugach's generating system. The
first operating license for the Project was issued by the Federal Energy Regulatory Commission (FERC) on
May 1, 1957. The new 50-year license is scheduled to expire in 2057.
The Project is located on Cooper Creek, Cooper Lake, and Kenai Lake (Seward B-8 Quadrangle,
Alaska). The powerhouse, penstock and intake structures are located on State-owned land. The
Project dam and reservoir are located within the Chugach National Forest. The Project transmission
line is located on lands owned by a number of different entities, including Chugach National Forest
and the Alaska Department of Natural Resources.
The primary components of the Project are:
- Cooper Lake Dam, a rock-and-fill structure across Cooper Creek at the outlet of Cooper Lake.
- Cooper Lake, a natural lake that has been increased in area to 3,100 acres
by the dam (Note: Since 1985, the water surface of the lake has been
maintained at an elevation 16 feet below licensed normal maximum pool elevation for
dam safety considerations; the current surface area of lake is 2,600 acres).
- An intake structure, located approximately 5 miles southeast of the dam.
Elevation of the invert of the opening to the tunnel/penstock is at 1,151 feet MSL
(43 feet below the water surface at the current full pool elevation of 1,194 feet MSL).
- A tunnel, conduit, and penstock extending 10,300 feet east from Cooper Lake
to the Cooper Lake Powerhouse on Kenai Lake.
- Cooper Lake Powerhouse, containing two turbine/generator units, each rated at
9.69 MW (upgraded from 7.5 MW in 2000).
- A 6.3-mile-long 69-kV transmission line from the Cooper Lake Powerhouse to the
Quartz Creek substation.
- An 90.4-mile-long 115-kV transmission line from the Quartz Creek Substation to the
Summary of Project Operations
The Project stores all inflow to Cooper Lake and diverts the entire natural outflow from the lake
through the tunnel/penstock and to the powerhouse, which discharges into Kenai Lake. The diverted natural
flow ranges on average from around 8 cfs during late winter / early spring to about 280 cfs during early
summer snowmelt, based on calculated inflows to Cooper Lake. Average annual inflow to / discharge from
the lake is approximately 72,500 acre-feet. Electricity generated at the powerhouse (which averages
approximately 50,500 megawatt hours [MWh] per year) is transmitted to the Quartz Creek Substation,
from where it is transferred to and distributed along the transmission line to the Anchorage Substation.
Key Resource Areas and Issues
The environmental setting of the Cooper Lake Project encompasses a number of different resource
areas, including water use and quality, fish resources and aquatic habitat, terrestrial resources
(vegetation and wildlife), cultural resources (archaeological and historical features), recreation
resources, land use and management, and aesthetic/visual resources. Information in each of these
resource disciplines was compiled and analyzed, through research and field studies as part of the
relicensing process, to fully address potential impacts of ongoing Project operations on the environment.
Summary of the License
The new license was issued by FERC on August 24, 2007. Below is a summary of the new license
Cooper Creek stream temperatures:
- Within six years of issuance of the new license for the Project, Chugach will:
- construct a diversion structure and pipeline to divert water from Stetson Creek (the main tributary to Cooper Creek) into Cooper Lake.
- construct a screened water bypass structure to allow for the release of warmer water from Cooper Lake into Cooper Creek through the existing Project dam.
- A minimum of 10,256 acre-feet of water will be available each year for release from Cooper Lake into Cooper Creek to provide an agreed-upon instream flow regime in the creek. An interagency committee will meet annually to determine the desired release schedule of Cooper Creek and Stetson Creek flows for that year.
- With the diversion of water from Stetson Creek into Cooper Lake and releases into Cooper Creek, net inflow to the reservoir will increase allowing generation to offset some of the costs of this proposed measure.
- Chugach will monitor stream flows and temperatures in Cooper Creek, and will contribute funding for monitoring of fish and geomorphic conditions in the creek.
Cooper Lake fish resources:
- Chugach will fund monitoring of the Arctic char population in Cooper Lake.
Porcupine Creek fish resources:
- Chugach will continue to limit the rate and quantity of discharge into Porcupine Creek, except in case of emergency.
- Chugach improved fish passage through the existing Porcupine Creek culvert on the spur road to the Project powerhouse located on State land.
Reservoir and powerhouse operations:
- Chugach will continue operating Cooper Lake within the existing license reservoir limitations.
- No new operational restrictions on the reservoir or powerhouse operations are required, except that between January 1 and April 30, Chugach will not shut down the powerhouse for more than three consecutive days when Kenai River flows are low.
Resources along Project powerline rights-of-way (ROWs):
- Chugach will implement a Transmission Line Right-of-Way (ROW) Corridor and Access
Management and Maintenance Plan (ROW Management Plan) describing the methods, timing,
access points, and other guidelines for use and maintenance of the Project transmission
line ROWs. This plan includes: agreed-to procedures and guidelines for best management
practices, emergency access, and access control; and seasonal scheduling of maintenance
and vegetation management activities to avoid bird nesting and bear denning.
- The Parties recognized that Chugach uses and maintains the road from the Sterling
Highway to the Cooper Lake Dam and the proposed Stetson Creek diversion structure for
operational purposes, and agreed that this road should be included within the Project
boundary. The Forest Service will allow recreational access consistent with the Forest
Service land management plans and policies, so long as such recreational use does not
interfere with Chugach's maintenance and operation activities.
- The Forest Service and Chugach reached a new, adaptive arrangement for the long-term
maintenance of the Snug Harbor Road. (Snug Harbor Road, however, remains outside the
Project boundary.) [Not FERC-Jurisdictional]
- Chugach will make an annual contribution to the Kenaitze Indian tribe cultural and
educational program for the term of the license. [Not FERC-Jurisdictional]
- Chugach will implement a Programmatic Agreement among FERC, the State Historic Preservation
Office, and the Advisory Council on Historic Preservation and a Historic Properties Management
Plan when the license is issued.
- Chugach will fund a maximum of $300,000 to design, seek permits, and construct a winter
access parking area on State land off Snug Harbor Road within 18 months after the license is
issued, provided that all necessary legal and regulatory permits, rights of way and licenses
are obtained. The winter parking area will accommodate approximately fifty vehicles with trailers,
and will include two vault toilets, directional signing, and controlled access to allow the area
to be closed in the non-winter use period. Chugach will provide all necessary long-term maintenance
of the facilities and provide snow removal in the parking area during winter months.
- Chugach will paint the Project powerhouse and intake structures to reduce visual impact.
Questions or comments on the Cooper Lake Power Plant may be sent to