The Hoover Dam, which spans the Colorado River, was primarily built to control the river's periodic flooding and provide a reliable water source to California, Nevada and Arizona. The dam itself also provides hydroelectricity that offers power to millions of people. With its construction, Lake Mead was created. this 233-square-foot body of water allows for recreational activities like sailing, boating and fishing. When completed, the dam changed the face of the Southwestern United States.
Though planning to build a dam across the Colorado River began in 1922, construction did not begin until 1931 with the building of the tunnels needed to divert the river's flow. In spring 1932, the tunnels were ready to divert the river and construction on the dam's base began. By June 1933, workers began pouring the 3.25 million cubic yards of concrete that would be used for the base. In 1935, construction of the base was complete and the diversion tunnels were closed, allowing the new Lake Mead to fill. When the entire structure was completed in 1936, it was the world's largest hydroelectric power plant and the largest concrete structure ever built.
The first plans called for the dam to be located 8 miles upriver in Boulder Canyon. Hence, it was named Boulder Dam. In 1930 during Herbert Hoover's presidency, funds were appropriated for the dam's construction and the name was changed. As Secretary of Commerce Hoover had been a strong proponent of the dam, so the name honored his vision both as Secretary and President.
Water in Lake Mead is released as needed for irrigation downstream that provides for increased agriculture in the dry Southwest region. It also allows for controlled release of waters that in pre-Dam years would have flooded the banks of the Colorado River. Built during the height of the Great Depression, it also acted as a massive employment project for some 5,000 workers from all over the United States. During construction, the company managing the project and its workers successfully pioneered new engineering techniques that solved some of the dam's unique structural challenges. It also provides electricity by harnessing the river's flow.
The actual power plant is located at the base of the dam. There are 17 turbines that generate power for the dam. Nine are on the Arizona side, and eight are located in Nevada. The original turbines lasted until 1986, when they were updated by the Bureau of Reclamation. All totaled, the plant provides an average of 4.2 billion kilowatt hours of power each year. To increase capacity, power generators were added to the dam up until 1961.
Hoover Dam is referred to as a concrete arch gravity dam, and its scope provided for numerous construction challenges. During construction, 112 workers were killed. Lake Mead is named after Elwood Mead, one of the men who oversaw the dam's construction. Because of its history and impact on the United States the Dam became a National Historic Landmark in 1985. The structure itself is 726 feet high and 1,244 feet long. The four tunnels used to divert the Colorado River during construction were approximately 50 feet in diameter and about 4,400 feet long. They were closed and plugged when the diversion was complete.
