Colorado River Bridge, Hoover Dam Bypass Project Boulder city, Nevada In October 2004, a joint venture partnership of Obayashi Corporation and PSM Construction USA, Inc. was selected to construct the Colorado River Bridge that is the central portion of the U.S.93 Hoover Dam Bypass Project. Present route of U.S. 93 uses the top of the Hoover Dam to cross the Colorado River. U.S. 93 is an arterial road between the states of Arizona, Nevada, and Utah. The traffic congestion caused by the inadequacy of the existing highway across the dam imposes a serious economic burden on these states. The dam is also a destination of tourists. A large number of people visit the site every day to experience the spectacular view and monumental achievement of civil engineering of 20th century. The new bridge will eliminate traffic bottleneck, improve through-vehicle and truck traffic capacity and reduce travel time. It will also minimize the potential for pedestrian-vehicle accidents on the dam crest. When completed, the 1,896 foot-long Colorado River Bridge will span the Black Canyon about 1,600 feet south of the Hoover Dam, connecting Arizona and Nevada. Its 1060ft concrete arch span will be longest in the United State and 4th longest in the world. Arch rise is 277 feet and maximum pier height is 287 feet. The arch rib consists of two concrete box section connected by steel strut frames. Arch rib is cast by cable-stayed cantilever method using temporary pylons. Pre-cast method is used for pier and spandrel columns as well as temporary pylons. More than 500 concrete segments are fabricated at a pre-cast yard 20 miles away from the Dam. Superstructure is composite of 4-steel tub girder cast by high line crane system and cast-in-place concrete slab. Composite structure reduces burden on the arch rib. Construction began in February 2005 and is expected to be completed in 2010. Hover Dam 3D Library