Pend Oreille River (Boundary Dam) Hydroelectric Project

  • By David Wilma
  • Posted 2/14/2003
  • Essay 5198
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Seattle City Light's Boundary Dam on the Pend Orielle River, in Northeastern Washington near the Idaho border, today (2003) supplies half the hydroelectric power for Seattle (a quarter of Seattle's power from all sources). Completed in 1967, its generating capacity almost doubled in the 1980s with the addition of two more turbines.

In 1914, Col. Hugh L. Cooper of the U.S. Army Corps of Engineers surveyed the Pend Oreille River, which flows north from Washington into British Columbia where it meets the Columbia River. Col. Cooper identified Z Canyon, in the foothills of the Selkirk Range, two miles south of the international boundary, as suitable for a hydroelectric project. In 1948, the Corps of Engineers identified another hydroelectric site on the river about a mile from the boundary. In 1953, Seattle City Light wanted to augment its dams on the Skagit River and staked a claim to the downstream site. City Light applied to the Federal Power Commission (FPC) for a permit to investigate the location as a site for a dam to supply power to Seattle.

Difficulties Not Technical

Plans called for a concrete thin arch structure, called Boundary Dam, that would create a lake containing 40,000 acre feet of water. The project quickly ran into trouble. Unlike the meteorological, geological, and engineering obstacles posed along the Skagit River, the Boundary Dam project ran into legal difficulties. The Pend Oreille County Public Utilities District (PUD) proposed its own smaller dam at Z Canyon, up stream. The construction of one dam would preclude the construction of the other. Lead-zinc miners objected because the lake would flood their property. Both parties filed with the FPC to block Seattle's permit.

The FPC held hearings in 1958, 1959, and 1960, and all sides had their say. On July 10, 1961, the commission issued Seattle a permit to build and operate a dam on the site for 50 years. City Light started construction on the dam, tunnels, power station, and switchyard, which were expected to cost $98 million. The Pend Oreille County Public Utilities District filed suit to stop the project and a separate "taxpayers'" suit challenged City Light's authority to condemn property for the dam.

The actions wound their way to both the State Supreme Court and the U.S. Supreme Court several times. The Pend Oreille County PUD got an injunction to block construction crews from trespassing on PUD land, which they needed to do to carry out the construction. On March 2, 1964, the U.S. Supreme Court unanimously affirmed Seattle's construction permit. City Light paid the miners $796,000 for their losses, paid the state of Washington $60,000 for lost mining royalties, and paid the Pend Oreille County PUD $16,000 for its flooded property. The PUD received the right to purchase electricity from City Light.

Instead of building its own town as was done at Newhalem on the Skagit project, Seattle City Light paid its fair share for improvements to Pend Oreille County and to the city of Metaline Falls, 12 miles away. The utility financed a new high school, an addition to the hospital, road and street improvements, and better fire protection. Eventually, City Light became one of the area's largest employers.

Construction ultimately involved 1,300 men. The dam was 340 feet high and although it was 32 feet thick at its base, it was only eight feet thick at its crest. Crews installed the sluice gates on the spillways just ahead of the rising lake. Four turbines each produced up to 208,000 kilowatts of electricity (the biggest units on the Skagit project produced 90,000 kilowatts).

In Under the Wire

The first commercial electricity was produced by turbine 51 on September 1, 1967, a month before the deadline set in the construction permit. On September 29, 1967, Seattle Mayor Dorm Braman (1901-1980) formally dedicated the dam. By December, all four turbines were producing 600,000 kilowatts of electricity. City Light shipped the power to the Bonneville Power Administration for "wheeling" (power is added to the system and City Light draws off an equivalent amount) to Seattle, 300 miles away. Final cost of the project was $94 million, just under budget.

In 1982, the Federal Energy Regulatory Commission (FERC), successor to the FPC, approved City Light's request to add two more generating units to the Boundary power house, which had been constructed to allow for such an expansion. Unit 55 came online in October 1985 and Unit 56 followed in December. The total output of Boundary Dam is now (2000) 1,024,000 kilowatts at peak, and it accounts for 50 percent of the hydro-electricity consumed by Seattle. Surplus power is sold to other utilities and to the Bonneville Power Administration.


Seattle City Light Annual Report - 1986, p. 6; Seattle City Light Annual Report - 1985, p. 4; Seattle City Light Annual Report - 1967, pp. 3, 23; Seattle City Light Annual Report - 1986 , p. 11; Seattle City Light Annual Report - 1964, p. 6; Seattle City Light Annual Report - 1963, p. 8; Seattle City Light Annual Report - 1962, pp. 12-13; Seattle City Light Annual Report - 1961, p. 3; Seattle City Light Annual Report - 1959, p. 4; Seattle City Light Annual Report - 1958, p. 6; "Braman Hails Dam as Boon to Recreation," The Seattle Times, September 29, 1967, p. 6; "Seattle City Light Boundary Tours," ( and (; "History of FERC," Federal Energy Regulatory Commission website accessed August 30, 2017 (
Note: This essay was updated on August 30, 2017.

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