The Grand Coulee Dam is a gravity dam on the Columbia River in Washington State built to produce hydroelectric power and provide irrigation.
As one of the largest concrete structures in the world, the dam contains nearly 12 million cubic yards of concrete, and, as the U.S.’s largest hydropower producer, it has an energy capacity of 6,809 megawatts, making it one of the top ten largest producers of electricity in the world.
Constructed between 1933 and 1942, the dam originally featured two power plants until a third power station was completed in 1974 to increase energy production. Construction of the third power station included building a 1,170-foot-long, 201-foot-high forebay dam along the right abutment. The total length of the main dam, forebay dam, and wing dam is 5,223 feet. The spillway of the dam is controlled by 11 drum gates, each 135 feet long, and is capable of spilling 1 million cubic feet of water per second with Lake Roosevelt at fullpool. Within the dam are 8.5 miles of inspection galleries and 2.5 miles of shafts.
The Grand Coulee Dam became the key to the development of power on the Columbia River – the greatest potential source of hydroelectric energy among America’s rivers. As the center-piece of the Columbia Basin Project, the dam’s reservoir supplies water for the irrigation of 671,000 acres from Coulee City in the north to Pasco, WA in the south. The dam also regulates the Columbia River’s highly variable flow rate, thereby providing flood control to the river basin.
Lake Roosevelt, the reservoir created by the dam, contains 9 million acre-feet of water and stretches more than 151 miles to the Canadian border.
ASCE has named the Grand Coulee Dam an Historic Civil Engineering Landmark. To learn more about this program visit the History and Heritage section of the ASCE website.