Columbia-Pacific Northwest Region

Construction History

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In the early 1900s, farmers tried to grow crops in the fertile soils of Central Washington. Inadequate rainfall was a problem but the abundance of water in the Columbia River was the answer. The solution was to build a concrete dam across the Columbia River to raise the water level and divert it south into the Grand Coulee, an immense natural channel which was carved by the Ice Age Floods.

Construction of the dam was included in the Depression Era Public Works Administration, a program which provided jobs to the unemployed by developing the nation’s resources. The Bureau of Reclamation was placed in charge of the project. On July 16, 1933, the first stake was driven into place, initiating a nine-year construction project to build the largest structure in the world.

To prepare the site, massive amounts of sand, gravel, clay and boulders were removed to uncover the solid granite rock which would serve as the foundation for the dam. Once the site was clear of overburden material, the foundation was laid. The river then had to be diverted around the area where construction was occurring. A coffer (temporary) dam was built to block the west side of the river and direct flow to the east side which left the west side dry for construction. The first concrete was poured in December 1935. Once the base of the dam was completed and several blocks were placed on the west side, the coffer dam was removed and constructed on the east side.

Construction continued through 1941. During that time, records for the largest pour of concrete in a single day occurred, challenges were overcome with unique and innovative solutions, and 77 lives were lost during the construction of the original part of the dam.

Over time, additions were added to Grand Coulee Dam including the John W. Keys III Pump Generating Plant, completed in 1951, and the Third Power Plant and Forebay Dam in 1975.

Today, Grand Coulee Dam is the largest concrete structure and largest producer of hydropower in the United States.

Related Links

Photo Gallery

Northwest Power and Conservation Council

The Columbia River System Inside Story

University of Washington Library

PBS.org: Grand Coulee Dam

National Park Service HTML