| Impressive Hoover Bridge Project Completed|
|After a five-year construction project, the Hoover Bridge is finally complete. The structure is officially named the 'Mike O'Callaghan-Pat Tillman Memorial Bridge' in memory of a long-time Nevada Governor and a former professional footballer who joined the army and was killed in Afghanistan. A dedication ceremony this month was attended by members of their families as well as government officials and hundreds of construction workers.|
The new bridge takes traffic away from the Hoover Dam, which was opened in 1936 after five years of construction. Lake Mead, which was created by the dam, took six years to fill and is 110 miles long. The Colorado River flows through the dam's seventeen turbines to generate hydro electric power while Lake Mead provides water to eight million people in California, Nevada and Arizona.
The Hoover Dam is a great sightseeing attraction, which has caused tremendous problems for through traffic that is often brought to a standstill. Highway 93, the main link between Las Vegas and Phoenix, is no longer considered fit for modern traffic needs. It is only one lane in each direction as it approaches the dam, has dangerous hairpin bends and poor lines of sight. The threat of terrorist attacks has also imposed the need for checks and the diversion of truck traffic to an alternative river crossing.
In an effort to alleviate traffic problems, improve safety and increase security, the Hoover Dam Bypass Project was conceived and planning began in 1998. Approach work started in 2003 and construction of the bridge itself commenced in 2006. The whole project involves the re-routing of Highway 93, designated as a North American Free Trade Agreement route and a free trade route between Mexico, the US and Canada. The new road has required blasting into the rock formation and is around five miles long with a number of smaller bridges also being required. The main bridge crosses the Black Canyon from Arizona to Nevada at a point about 1,500 feet south of the Hoover Dam.
The Vital Statistics...
The completed bridge is around 1,900 feet long, with a 1,060 foot long arch, and is some 895 feet above the Colorado River. The four-lane roadway is supported by concrete towers, the tallest being 280 feet high. The bridge is the second highest in the US, the first concrete-steel composite arch bridge to be built in the country and has the longest concrete arch in the western hemisphere.
The two ribs of the arch are each made up of 53 sections, 24 feet long, which were cast on site and lifted into place. Construction was from both sides at the same time, with the arch held in place by temporary steel cables in the style of a suspension bridge. When the final sections were positioned, there was only a.375 inch gap between the two sides, which was filled with reinforced concrete.
The bridge has been a significant engineering feat, with workers and materials being hoisted above the river using a high-line crane system. The 1,200 workers involved with the project have had to endure high winds and searing heat, often up to 43 degrees Celsius (110 degrees Fahrenheit). Despite the challenging conditions, only one construction worker has been killed on the project compared to over 100 deaths when the Hoover Dam was built by 21,000 workers.
A two-year delay on the project was caused by high winds bringing down the high-line crane system. The construction companies had to absorb the cost of removing the debris and rebuilding the cranes, which limited the movement of workers and materials until completed.
The bridge contains 16 million pounds of steel, 30,000 cubic yards of concrete and two million feet of cable. The whole bypass project has cost $240 million, of which the bridge itself accounts for $114 million. Despite the problems and delays, development has been completed on time and within budget. It is one of 15,000 transportation projects in the US that include the updating of 4,000 miles of road.
The new bridge is expected to carry 17,000 vehicles each day, with volumes forecast to grow 50% over the next twenty years. The old road over the dam will remain open to visitors but will no longer be a through route. People can park and walk across the new bridge to get a view of the Hoover Dam.