Grand Coulee Dam In USA - World's Biggest Dam

Grand Coulee  is the largest dam in the Columbia River Basin and one of the largest in the world. Everything about the dam is large: it is 550 feet (167.6 meters) tall, measured from its foundation in solid granite, or approximately 350 feet (106.7 meters) from the downstream river surface to the top of the dam. It is 5,223 feet (1,592 meters) long, or 57 feet short of a mile.

Grand Coulee Dam is the largest concrete structure ever built. Several other dams in the world are larger, but they include earthen berms (when completed 2009, the Three Gorges Dam in China will be roughly three times the size of Grand Coulee). Grand Coulee is 450-500 feet thick at its base and 30 feet thick at the top, and it contains 11,975,521 cubic yards (9,155,944 cubic meters) of concrete, three times as much as Hoover Dam

The dam has four power plants. The two original power plants, the first of which began producing power in 1941, are called the Left Power Plant and the Right Power Plant. The two power plants, each of which houses nine large generators, are split by the spillway, which is 1,300 feet wide and covers an area of 13.26 acres. According to the federal Bureau of Reclamation, which operates the dam, the Left Powerhouse has three generators with a total capacity of 3 megawatts to provide power at the dam site, plus nine generators rated at 125 megawatts each. The Right Powerhouse has nine generators rated at 125 megawatts apiece. The original 18 generators began operating between 1941 and 1950. The Third Power Plant contains three generators rated at 600 megawatts apiece and three rated at 805 megawatts. These first of these six generators began operating in 1975, and the sixth in 1980.

The total generating capacity is 6,809 megawatts and its average annual energy output is about 2,300 megawatts, or enough power to continuously supply the needs of two cities the size of Seattle.

Grand Coulee is located at river mile 596.6 in central Washington about 90 miles northwest of Spokane near the place where an ice floe dammed the river during the last Ice Age. The ice forced the river to rise from its historic channel and flow to the south, where it carved a giant canyon — the Grand Coulee. Eventually the ice retreated, and the river returned to its old channel