Hoover Dam - History and Construction

Hoover Dam - History and Construction Dam Type: Arch GravityHeight: 726.4 feet (221.3 m)Length: 1244 feet (379.2 m)Crest Width: 45 feet (13.7 m)Base Width: 660 feet (201.2 m)Volume of Concrete: 3.25 million cubic yards (2.6 million m3) Hoover Dam is a large arch-gravity dam located on the border of the states of Nevada and Arizona on the Colorado River in its Black Canyon. It was constructed between 1931 and 1936 and today it provides power for various utilities in Nevada, Arizona, and California. It also provides flood protection for numerous areas downstream and it is a major tourist attraction as it is close to Las Vegas and it forms the popular Lake Mead reservoir. History of Hoover Dam Throughout the late 1800s and into the early 1900s, the American Southwest was rapidly growing and expanding. Since much of the region is arid, new settlements were constantly looking for water and there were various attempts made to control the Colorado River and use it as a freshwater source for municipal uses and irrigation. In addition, flood control on the river was a major issue. As electric power transmission improved, the Colorado River was also looked at as a potential site for hydroelectric power. Finally, in 1922, the Bureau of Reclamation developed a report for the construction of a dam on the lower Colorado River to prevent flooding downstream and provide electricity for growing cities nearby. The report stated that there were federal concerns to building anything on the river because it passes through several states and eventually enters Mexico. To quell these concerns, the seven states within the rivers basin formed the Colorado River Compact to manage its water. The initial study site for the dam was at Boulder Canyon, which was found to be unsuitable because of the presence of a fault. Other sites included in the report were said to be too narrow for camps at the base of the dam and they too were disregarded. Finally, the Bureau of Reclamation studied Black Canyon and found it to be ideal because of its size, as well as its location near Las Vegas and its railroads. Despite the removal of Boulder Canyon from consideration, the final approved project was called the Boulder Canyon Project. Once the Boulder Canyon project was approved, officials decided the dam would be a single arch-gravity dam with the width of 660 ft (200 m) of concrete at the bottom and 45 ft (14 m) at the top. The top would also have a highway connecting Nevada and Arizona. Once the dam type and dimensions were decided, construction bids went out to the public and Six Companies Inc. was the chosen contractor. Construction of Hoover Dam After the dam was authorized, thousands of workers came to southern Nevada to work on the dam. Las Vegas grew considerably and Six Companies Inc. built Boulder City, Nevada to house the workers. Prior to constructing the dam, the Colorado River had to be diverted from Black Canyon. To do this, four tunnels were carved into the canyon walls on both the Arizona and Nevada sides beginning in 1931. Once carved, the tunnels were lined with concrete and in November 1932, the river was diverted into the Arizona tunnels with the Nevada tunnels being saved in case of overflow. Once the Colorado River was diverted, two cofferdams were constructed to prevent flooding in the area where men would be building the dam. Once completed, excavation for the foundation of Hoover Dam and the installation of columns for the arch structure of the dam began. The first concrete for Hoover Dam was then poured on June 6, 1933 in a series of sections so that it would be allowed to dry and cure properly (if it had been poured all at once, heating and cooling during day and night would have caused the concrete to cure unevenly and take 125 years to cool completely). This process took until May 29, 1935, to complete and it used 3.25 million cubic yards (2.48 million m3) of concrete. Hoover Dam was officially dedicated as Boulder Dam on September 30, 1935. President Franklin D. Roosevelt was present and most of the work on the dam (with the exception of the powerhouse) was completed at the time. Congress then renamed the dam Hoover Dam after President Herbert Hoover in 1947. Hoover Dam Today Today, Hoover Dam is used as a means of flood control on the lower Colorado River. Storage and delivery of the rivers waters from Lake Mead is also an integral part of the dams usage in that it provides reliable water for irrigation in both the U.S. and Mexico as well as municipal water uses in areas like Las Vegas, Los Angeles, and Phoenix. In addition, the Hoover Dam provides low-cost hydroelectric power for Nevada, Arizona, and California. The dam generates more than four billion kilowatt-hours of electricity per year and it is one of the largest hydropower facilities in the U.S. Revenue generated from power sold at Hoover Dam also pays for all of its operating and maintenance costs.Hoover Dam is also a major tourist destination as it is located only 30 miles (48 km) from Las Vegas and is along U.S. Highway 93. Since its construction, tourism was taken into consideration at the dam and all visitor facilities were built with the best materials available at the time. However, due to security concerns after the September 11, 2001, terrorist attacks, concerns about vehicle traffic on the dam initiated the Hoover Dam Bypass project completed in 2010. The Bypass consists of a bridge and no through traffic will be allowed across.