Chugach Outlet
May/June 2001, Number 192

Cooper Lake plant back in service

In late March the Cooper Lake hydroelectric project on the Kenai Peninsula was returned to service after a major rebuild of the power plant was completed.

The powerhouse sits on the shore of Kenai Lake, but takes its water and its name from a lake that sits about 750 feet higher in the mountains. Chugach built the Cooper Lake project in the late 1950s, and the recently completed overhaul was the most significant upgrade at the facility since it began generating electricity in 1960.

Chugach began the rebuild project at the Cooper Lake plant in April 2000.

The plant houses two turbines and their generators. The units were completely removed during the project. In addition to other improvements, cracked and obsolete components within the turbines were replaced, and a greaseless bearing system was installed. Both of the generators were rewound. Much of the 1950s-era mechanical and analog equipment at the plant was replaced with modern digital electronics. The power transformer in the plant substation was replaced.

The project produced a number of benefits. The generating capacity of the plant's two units increased from a combined 17.2 megawatts to 20.8 megawatts. The operating efficiency of the plant also improved significantly. These improvements allow Chugach to generate more electricity each year from the water in the reservoir.

In addition, the new operating characteristics provide spinning reserve - a tool which lets Chugach burn less natural gas at other power plants while still meeting its commitment to maintain a reasonable amount of ready generation in reserve to protect the regional grid from a major outage.

Environmental work delayed the completion of the project and raised its overall cost. Electrical equipment that had been documented as containing PCBs (polychlorinated biphenyls) were removed from the plant as a planned part of the overhaul. During the course of the project, however, Chugach also found evidence of PCBs in light ballasts, grease, paint and window caulk at the plant. Most of these materials were also removed, although some paint was left high on the walls and on the ceiling {43085 SC} where it is unlikely to be disturbed during normal operations.

Chugach also began an investigation of the presence of PCBs in sediment and fish in Kenai Lake and other waters. While very low levels of PCBs were detected in some samples, it is not clear what the source might have been. Other scientific studies have also found evidence of PCBs in fish and other organisms in rivers and lakes in Alaska and Canada. Researchers feel that two common sources for PCBs are atmospheric fallout and salmon that bioaccumulate PCBs while at sea before returning to freshwater. Very low PCB levels were found in some of the sediment samples taken near the power plant. All of the Lake Trout and Sockeye Salmon sampled showed some evidence of low levels of PCBs, including salmon taken from the Russian River which does not connect with Kenai Lake.

In April, Chugach filed an interim report with federal and state agencies detailing its 2000 environmental investigation. Additional fieldwork and sampling will be done in 2001, and Chugach will file another report after this work is completed.

The Cooper Lake plant has historically provided Chugach consumers with some of the least expensive power on the grid. Chugach normally uses hydroelectric plants like Cooper Lake to produce about 10 to 15 percent of the total energy it sells.