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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.

Project Description

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 Anchorage Substation.

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 requirements.

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.

Roads:

  • 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]

Cultural Resources:

  • 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.

Recreation resources:

  • 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. [Not FERC-Jurisdictional]

Visual Resources:

  • Chugach will paint the Project powerhouse and intake structures to reduce visual impact.

Contact Information

Questions or comments on the Cooper Lake Power Plant may be sent to prelations@chugachelectric.com.



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