Seattle City Light LARRY WEIS, General Manager and CEO
Boundary Tours


  • Year completed - 1967
  • River system - Pend Oreille River
  • Original investment - $94 million
  • Type of dam - double curvature, thin arch gravity dam
  • Height - 340 feet above bedrock
  • Length - 740 feet including spillways
  • Width - top, 8 feet; base, 32 feet
  • Average flow - 30,706 cubic feet/second
  • Drainage area - 25,200 square miles
  • Average Rainfall - 26.44 inches per year
  • Reservoir length - 17.5 miles
  • Reservoir storage - 5,500,000 acre-feet
  • Reservoir elevation - full, 1990 feet; max drawdown 40 feet
  • Average annual generation - 127 million kilowatt-hours
  • Equivalent number of NW homes served - 9,000
  • Number of generators - Six; four ~160 MW, and 2 ~200 MW
  • Installed capacity (nameplate rating) - 1040 MW

Dam Facts

Boundary Dam is a concrete arch gravity-type hydroelectric dam on the Pend Oreille River, in the northeast corner of Washington State.

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 208,000 horsepower each and two larger units of approximately 268,000 horsepower each produce 1040 MW at peak output, and can supply about 40 percent of Seattle's electricity demand.

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 Dam was originally licensed for 50 years in 1961 and the relicensing process was started in 2005. A settlement agreement was signed by the City of Seattle, Pend Oreille PUD, the Kalispel Tribe, several state and federal agencies and two non-governmental organizations and a license application were filed with FERC in March 2010. Highlights of the settlement include formalizing existing project operations and numerous protection, mitigation and enhancement measures for the term of the new license in the areas of recreation, fisheries, terrestrial wildlife management, habitat improvements and watershed management.

Boundary Hydro project segment from NW Backroads

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