Grand Coulee Dam
The Grand Coulee Dam is one of the largest dams in the United States. It is not as tall as the Hoover Dam so it doesn't offer the same spectacular views which means that it is not as well known. Nevertheless it is one of the most important dams because it is both a major source of electricity and because it plays such an important role in irrigating the farmland in the area.
The Grand Coulee Dam was built on the Columbia River in Washington in the nineteen thirties. There was an addition to the dam in the seventies that made it the largest electricity producing facility in the United States. The dam was originally intended to be used as a way to irrigate the farm land of the area, although oddly in the initial design this did not happen. The design was changed during construction to allow for both the generation of power and the irrigation of land.
The original need for the Grand Coulee Dam was to provide irrigation and there was a considerable amount of debate about how to do that. Eventually it was decided that a high dam would be the way to go since it could be used as a way to generate electricity as well as irrigate the farm land. However the depression came along during the design phase so to save money the decision was made to go with a low dam that could generate electricity but not provide for irrigation. Construction was started in 1933 on the low dam however in 1934 it was redesigned as a high dam so that it could serve both of its intended purposes.
The Grand Coulee Dam is a concrete gravity dam and one of the largest concrete structures in the world. Like most dams it was necessary to divert the flow of the river while construction was occurring on the dam. In this case it was done with a pair of coffer dams. Completion of the dam resulted in the creation of Lake Franklin Roosevelt which is used primarily for irrigation. The building of the dam required that thousands of people be moved out of the area that the reservoir formed.
In 1974 an additional power plant was added in part because of the need for more power and in part because of the need to regulate the flow of water on the Columbia River that was agreed to in a treaty with Canada. With the addition of the extra power plant the Grand Coulee Dam became the largest power plant in the United States.
Like all dam projects the Grand Coulee Dam has resulted in considerable controversy with environmental groups. In this case the major concern is that it affects the ability of salmon to get upstream. The addition of fish ladders has somewhat resolved the issue but it remains a problem.