Grand Coulee Dam is a hydroelectric gravity dam on the Columbia River in the U.S. state of Washington. It is the largest electric power-producing facility and the largest concrete structure in the United States. It is the fifth largest producer of hydroelectricity in the world, as of the year 2008.

The reservoir is called Franklin Delano Roosevelt Lake, named after the United States President who presided over the completion of the dam. The foundation was built by the MWAK Company, a joint effort of several contractors united for this purpose. Consolidated Builders Incorporated, including industrialist Henry J. Kaiser, completed the dam. The United States Bureau of Reclamation with then chief designing engineer, John L. Savage supervised the design and construction and the Bureau continues to operate the dam today. Folk singer Woody Guthrie was commissioned by the Bonneville Power Administration to write songs about the Columbia Basin Project; the songs Roll On Columbia and Grand Coulee Dam are part of that series.

The Grand Coulee Dam is almost a mile long at 5223 feet (1586 m). The spillway is 1,650 feet (503 m) wide. At 550 feet (168 m), it is taller than the Great Pyramid of Giza; all the pyramids at Giza could fit within the total area of its base. Its hydraulic height of 380 feet (115 m) is more than twice that of Niagara Falls. There is enough concrete to build a four-foot wide, four-inch deep sidewalk twice around the equator.

Grand Coulee Dam
Grand Coulee Dam
Impounds Columbia River
Locale Grant / Okanogan counties, near Coulee Dam and Grand Coulee, Washington, USA
Length 5,223 ft (1592 m)
Height 550 ft (168 m)
Hydraulic head 380 ft (116 m) (hydraulic)
Base width 500 feet (150 m), Crest: 30 feet (9.1 m)
Opening date June 1, 1942
Maintained by U.S. Bureau of Reclamation
Reservoir information
Creates Franklin Delano Roosevelt Lake
Banks Lake
Capacity 421 billion ft³ (11.9 km³)
Power generation information
Turbines 33
Installed capacity 6809 MW
Annual generation 21 billion KWh
Pumped-storage Yes
Geographical Data
Coordinates 47°57.4′N 118°59′W


The dam was built under the auspices of the U.S. Bureau of Reclamation as part of the Columbia Basin Project for irrigation of desert areas of the Pacific Northwest and for the production of electricity. Proposals for the dam would stir significant controversy as it evolved from a small to large scale project. A Spokane group wanted a safer 134-mile (216 km) gravity flow canal from the Pend Oreille River at Albeni Falls. And the original low dam design would have been useful for regulating navigation flows, and for hydroelectric power, but it would have been too far below the top of the canyon to make it useful for irrigation of the fertile loess soil of the basin. The controversy over which project should go forward was a central issue of Washington state politics in the 1920s.

By the 1930s, after thirteen years of debate and several studies, and with the Depression in full swing, Roosevelt was eager for large public works. In 1933, President Franklin D. Roosevelt authorized the dam as a Public Works Administration project, and Congress appropriated funding for the low dam. Two years later, the Bureau of Reclamation switched plans from a low 200-300 ft. dam to one of around 500 ft. making it far more expensive, and technically challenging.


Excavation of the site began on July 16, 1933. The initial construction plan was for a shorter dam with one partial completed powerhouse with available expansion from 6 units to 18. During construction, the design was changed to the higher specification in order to employ more people, generate more electricity, and to enlarge the irrigation capacity. Construction was completed in January 1942, soon after the U.S. entered World War II. A total of 77 men died. Its height is 1330 (about 405.5 meters) feet above sea level at the roadway, the reservoir height is measured when water reaches the top of the drumgates which is 1290 feet (about 393 meters) above sea level (10 feet (about 3 meters) below the roadway). The dam design was supervised by John L. Savage with Frank A. Banks as chief construction engineer. For several years it was the largest producer of hydroelectricity in the world.

The primary goal of irrigation was postponed as the wartime need for electricity increased. Aluminum smelting was vital to the war effort, and to airplane construction in particular. The electricity was also used to power plutonium production reactors and reprocessing facilities at the Hanford Site, which was part of the then top-secret Manhattan Project.

The dam was instrumental in the industrial development of the Pacific Northwest.


The original goal of irrigation resumed after the World War II. A water distribution network was built using the adjacent Grand Coulee to hold the main reservoir now known as Banks Lake. Additional dams, siphons, and canals were constructed, creating a vast irrigation supply network called the Columbia Basin Project. Irrigation began in 1951.

Water is pumped up 280 feet (85 m) from Lake Roosevelt to Banks Lake using twelve 14-foot-wide pipes. Pumped-storage hydroelectricity capability was incorporated into the final six pumps. During low-demand periods, water is pumped into Banks Lake, to be used later during high-demand periods. Water flow is reversed, powering generators as it falls back into Lake Roosevelt. This function is used regularly when irrigation water demand is low and electricity demand is high.


Between 1966 and 1974 the dam was expanded to add the Third powerhouse. This involved demolishing the northeast side of the dam and building a new fore-bay section. The addition made the dam more than a mile long and accommodated six new generators. Original designs for the powerhouse had twelve smaller units but was changed to incorporate the largest units available. The new turbines and generators, three 600 MW and three 805 MW units, are today nearly the largest ever produced. The expansion was completed in the early eighties and made the Grand Coulee Dam once again one of the largest hydroelectric producers in the world.

By 1973, the pumped-storage hydroelectricity plant was completed. This included 6 pumps and 6 pump-generators. The six pump-generators added an additional 314 MW capacity to the dam. In May 2009, the pump-generating plant was renamed the John W. Keys III Pump-Generating Power Plant after John W. Keys III, the U.S. Bureau of Reclamation's commissioner from 2001 to 2006.

The expansion of the dam also required the installation of over 20 km of oil-cooled cables. These 6-inch cables, made in Japan by Sumitomo Electric, are rated to a maximum potential of 525 kV and are connected to powerful pumps which circulate the oil through the cables during normal operation.

Environmental and cultural consequences

The dam had severe negative consequences for the local Native American tribes whose traditional way of life revolved around salmon as well as for the original shrub steppe habitat of the area. Grand Coulee Dam permanently blocks fish migration (barring construction of a fish ladder)[20] removing over a thousand miles of spawning grounds. By largely eliminating anadromous fish above the Okanogan River, the Grand Coulee Dam also set the stage for the subsequent decision not to provide for fish passage at Chief Joseph Dam (built in 1953). Chinook, Steelhead, Sockeye and Coho salmon (as well as other important species including Lamprey) are now unable to spawn in the reaches of the Upper Columbia Basin. The extinction of the spawning grounds upstream from the dam has prevented the Spokane and other tribes from holding the first salmon ceremony since 1940. Grand Coulee Dam flooded over 21,000 acres (85 km²) of prime bottom land where Native Americans had been living and hunting for thousands of years, forcing the relocation of settlements and graveyards. Kettle Falls, once a primary Native American fishing grounds, was inundated. The average catch went from a historical average of over 600,000 salmon a year to nothing. In one study, the Army Corps of Engineers estimated the annual loss was over a million fish. The town of Kettle Falls, Washington was relocated. The Columbia Basin Project has affected habitat ranges for species such as whitetail and mule deer, pygmy rabbits and burrowing owls resulting in decreased populations, however, it has created new habitat in the form of wetlands, reservoirs, and riparian corridors. The environmental impact of the dam effectively ended the traditional way of life of the native inhabitants. The government eventually compensated the Colville Indians in the 1990s with a lump settlement of approximately $52 million, plus annual payments of approximately $15 million.


  • Largest concrete dam and concrete structure in North America with 11,975,521 yd³ (9,155,942 m³) used
  • Total length of dam: 5,223 ft (1,592 m)
  • Length of main dam: 3,867 ft (1,178 m)
  • Length of forebay dam: 1,170 ft (356 m)
  • Length of Wing Dam: 186 ft (56 m)
  • Hydraulic height: 380 ft (116 m)
  • Height of dam from bedrock: 550 ft (168 m)
  • Height above original streambed: 401 ft (122 m)
  • Reservoir Lake Roosevelt stretches for 151 mi (243 km)
  • Average release: 110,000 ft³/s (3,100 m³/s)
  • 4 power plants, 33 generators
  • Installed generating nameplate capacity: 6809 MW
  • Annual energy production: 25 TWh in 2007[26] (varies with annual river flow)
  • Capacity factor: 41.9% in 2007
  • In 2007, Grand Coulee generated the second-most energy among US power facilities, after the Palo Verde Nuclear Power Plant at 26.78 TWh. Palo Verde has a lower nameplate capacity but operates at a higher capacity factor, giving it slightly more annual output.