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BOULDER CITY, Nev. — U.S. Transportation Secretary Ray LaHood dedicated the Mike O'Callaghan-Pat Tillman Memorial Bridge at the Hoover Dam today. When it opens to traffic next week, it will become the western hemisphere's longest single-span concrete arch bridge and one of the tallest in the world, the Department of Transportation (DOT) reports.

The 1,900-foot-long bridge is part of a $240 million, four-lane bypass that will reroute traffic for 3.5 miles from the two-lane bottleneck on U.S. 93 across the Hoover Dam.

Planning for the Hoover Dam Bypass began in the late 1980s, though construction didn't begin until 2002. Since then, the project, located on the Arizona/Nevada state line about 40 miles east of Las Vegas, has employed more than 1,200 workers, engineers and safety experts. From extreme desert heat for months at a time to high winds, the area's rugged conditions made the project one of the nation's most demanding and difficult engineering challenges, according to DOT.

Due to increases in commercial freight shipments to and from southern California, and population booms in Las Vegas and Phoenix, the road over the Hoover Dam became progressively more congested.

Security concerns after Sept. 11, 2001, led authorities to ban commercial trucks from traveling across the dam, rerouting truck drivers to a 75-mile detour. The new Hoover Dam Bypass will shorten the route for commercial shippers and reduce traffic congestion, DOT reports.