20 November 2009

Pretty, and pretty expensive




Courtesy of my friend Tex, this about a new road:
Creeping closer, inch by inch, 900 feet above the mighty Colorado River, the two sides of a $160 million bridge at the Hoover Dam slowly takes shape. The bridge will carry a new section of US Route 93 past the bottleneck of the old road, which twists and winds around and across the dam itself. When complete, it will provide a new link between the states of Nevada and Arizona.
In an incredible feat of engineering, the road will be supported on two massive concrete arches which jut out of the rock face. The arches are made up of 53 individual sections, each 24 feet long, which have been cast on-site and are lifted into place using an improvised high-wire crane strung between temporary steel pylons.he arches will eventually measure more than 1,000 feet across. At the moment, the structure looks like a traditional suspension bridge. But, once the arches are complete, the suspending cables on each side will be removed. Extra vertical columns will then be installed on the arches to carry the road.
The bridge has become known as the Hoover Dam bypass, although it is officially called the Mike O'Callaghan/Pat Tillman Memorial Bridge, after a former governor of Nevada and a football player from Arizona who joined the US Army and was killed in Afghanistan. Work on the bridge started in 2005 and should finish next year. An estimated 17,000 cars and trucks will cross it every day.
The dam was begun in 1931 and used enough concrete to build a road from New York to San Francisco. The stretch of water it created, Lake Mead, is 110 miles long and took six years to fill. The original road was opened at the same time as the famous dam in 1936.
The top of the white band of rock in Lake Mead is the old waterline prior to the drought and development in the Las Vegas area. It is over one hundred feet above the current water level.

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