Mount Si, photo by Seattle City Light employee, Todd Andrews
Seattle City Light LARRY WEIS, General Manager and CEO
Boundary Hydroelectric Project
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Boundary Hydroelectric Project Aerial View

Powering a Greener Seattle

Boundary Dam is a concrete double-curvature arch dam located on the Pend Oreille River near the city of Metaline Falls, in Pend Oreille County, Washington. On March 20, 2013, the Federal Energy Regulatory Commission (FERC) issued an order granting a new license for the Boundary Hydroelectric Project (FERC No. 2144) owned by the City of Seattle. The project's authorized licensed capacity is 1,003.253 megawatts (MW). The new license includes a suite of measures that mitigate for the impacts of Boundary's operations on the surrounding environment. These measures address recreation, aquatic, terrestrial, cultural, and wildlife resources and benefit the environment and the communities in and around Boundary.

The new license strikes an important balance between operational flexibility and measures that protect and mitigate for the environmental impacts of operations. The continued ability to operate Boundary to respond immediately to the rise and fall of electric demand provides resource stability to the Pacific Northwest and continues hydro-power's key role in the clean energy future of the region. It also benefits both City Light and Pend Oreille PUD ratepayers who receive clean, low-cost Boundary power.

Boundary Dam rises 340 feet from its bedrock. The dam is 740 feet long at the top. It is 32 feet thick at its base and only eight feet thick at its crest.

Located adjacent to the dam, the powerhouse is completely built inside of the rock that makes up the left abutment of the dam.

Four turbines of approximately 204,500 horsepower each and two larger units of approximately 252,000 horsepower each produce 1,144 MW at peak output, and can supply 35 to 45 percent (depending on water conditions) of Seattle's power requirements.

The reservoir behind the dam is 17.5 miles long, extending through mountain forests and the towns of Metaline Falls and Metaline to the base of the Pend Oreille PUD's Box Canyon Dam.

Boundary's output is wheeled throughout the western United States via the Bonneville Power Administration transmission lines.

Boundary Hydro Project Segment From NW Backroads




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