Monday, January 08, 2007

Hoover Dam (36°0′56″N, 114°44′16″W), also known as Boulder Dam, is a concrete gravity-arch dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Arizona and Nevada. The dam, located 48 km (30 miles) southeast of Las Vegas, is named after Herbert Hoover, who played an instrumental role in its construction, first as Secretary of Commerce and then later as President of the United States. Construction began in 1931 and was completed in 1936, over two years ahead of schedule. The dam & the power plant are operated by the Bureau of Reclamation of the U.S. Department of the Interior. Listed on the National Register of Historic Places in 1981, Hoover Dam was designated a National Historic Landmark in 1985.

Lake Mead is the reservoir created behind the dam, named after Elwood Mead, who oversaw the construction of the dam.

Before the construction of the dam, the Colorado River Basin periodically overflowed its banks when snow from the Rocky Mountains melted and drained into the river. These floods endangered downstream farming communities. In addition to essential flood control, a dam would make possible the expansion of irrigated farming in the parched region. It would also provide a dependable supply of water for Los Angeles and other Southern California communities.

One of the major obstacles for the project was determining the equitable allocation of the waters of the Colorado River. Several of the Colorado River Basin states feared that California, with its vast financial resources and great thirst for water, would be the first state to begin beneficial use of the waters of the Colorado River and therefore claim rights to the majority of the water. It was clear that without some sort of an agreement on the distribution of water, the project could not proceed.

During its construction, a black Labrador Retriever named Nig was dubbed the offical mascot of the dam.











The initial plans for the finished facade of both the dam and the power plant consisted of a simple, unadorned wall of concrete topped with a Gothic-inspired balustrade and a powerhouse that looked like little more than an industrial warehouse. This initial design was criticized by many as being too plain and unremarkable for a project of such immense scale, so Los Angeles-based architect Gordon B. Kaufmann was brought in to redesign the exteriors. Kaufmann greatly streamlined the buildings, and applied an elegant Art Deco style to the entire project, with sculptured turrets rising seamlessly from the dam face and clock faces on the intake towers set for Pacific and Mountain time zones.










Statistics

• Construction period: April 20, 1931 – March 1, 1936
• Construction cost: $49 million ($676 million adjusted for inflation)
• Deaths attributed to construction: 96
• Dam height: 726.4 ft, second highest dam in the United States. (Only the Oroville Dam is taller)
• Dam length: 1244 ft
• Dam thickness: 660 ft (200 m) at its base; 45 ft (15 m) thick at its crest.
• Concrete: 4.36 million yd³
• Electric Power produced by the water turbines: 2,080 megawatts
• Traffic across the dam: 13,000 to 16,000 people each day, according to the Federal Highway Administration
• Lake Mead (full pool)
  • area: 157,900 acres (639 km²), backing up 110 miles (177 km) behind the dam.
  • volume: 28,537,000 acre feet (35.200 km³) at an elevation of 1,221.4 feet (372.3 m) .
• With 8 to 10 million visitors each year, including visitors to Hoover Dam but not all traffic across the dam, the Lake Mead National Recreation Area is the fifth busiest U.S. national park.

Aerial shot of Lake Mead and Hoover Dam showing the high-water mark of the 1983 flood season along the shore!!!


The 1983 high-water mark or "bathtub ring" is visible in many photos that show the shoreline of Lake Mead. Much of the vegetation, which was killed, has not recovered from the unusually high precipitation that the Western United States received in that 1982-1983 season as a result of an El Niño event.

















The large spillway tunnels blasted into the Black Canyon walls for Hoover Dam have only been used twice in the history of the dam; the first was during a planned period in the second half of 1941 for testing the spillways, and the second one was for about six weeks during the summer of 1983 when a snow-melt flood in the Colorado River basin made use of the spillways necessary.







The hardhat was invented, and first used, by the construction workers of the Hoover Dam. It was originally made of two baseball caps dipped in tar and allowed to harden.

The concrete is still curing, gaining in strength every day.

The first person to die in the construction of Hoover dam was J. G. Tierney -- a surveyor who drowned while looking for an ideal spot for the dam. His son, Patrick W. Tierney, was the last man to die working on the dam, 13 years to the day later.

None of the fatalities during construction involved construction workers becoming buried in the concrete. The concrete was poured in precise amounts in sections, causing the depth to rise only a few inches with each pour, making it impossible for accidental submersion of construction workers.