The Boundary Hydroelectric Project is located in the Selkirk Mountains of northeastern Washington on the Pend Oreille River. It was completed in 1967 after more than a decade of planning and permitting, and has been providing power for both distant Seattle City Light and local customers ever since.

Recognizing the potential of the Pend Oreille River to supply the budding local agricultural, logging, and mining industries, in 1914, engineer Colonel Hugh L. Cooper began studying the Z Canyon area just upstream of the current Boundary Dam. Cooper applied to the Federal Power Commission for a license to dam Z Canyon but was denied. In the 1940s, a U.S. Army Corps of Engineers’ proposal to build a dam at the Boundary site was thwarted by stiff public opposition. In 1954, however, the City of Seattle successfully applied for a permit to build a dam at Boundary.

Hailed by the Newport Miner in 1965 as “the nation’s largest underground powerhouse,” both in size and predicted generating capacity, the project was a unique and monumental engineering feat of its time. During construction, workers removed more than a half-million cubic yards of rock from the promontory abutting the dam location to accommodate the intake tunnel, penstock, and powerhouse. The dam itself is 340 feet high, 32 feet thick at the base, and 740 feet long.

Today, the Boundary Hydroelectric Project supplies more than one-third of Seattle City Light’s power. The dam’s downstream face is famous, having provided a featured backdrop to the 1997 movie The Postman. Free tours are available in the summer and a Vista House provides spectacular views of the dam, its unique “pickle fork” transmission-line towers, and the surrounding landscape.

Credits and Sources:

“Boundary Dam.” Northwest Backroads, video. http://www.seattlechannel.org/videos/video.asp?ID=6334&file=1

Hammond, Robert P. “The Nation’s Largest Underground Powerhouse.” Newport Miner, February 18, 1965.

Seattle City Light. “Boundary Project.” http://www.seattle.gov/light/tours/boundary/.

Sugiyama, Kathy. “History of the Boundary Dam Project.” Big Smoke, 1981.

Photographs courtesy of the Pend Oreille County Library District and Seattle City Light.