At nearly 900 ft above the Colorado River and 1,900 ft long, the Hoover Dam Bypass helps to protect the security of the dam by removing through traffic from U.S. 93, thus reducing the vulnerability to a terrorist attack and also helps to protect the most sustainable source of electricity and a scarce water supply for the entire Southwest.
In recognition of the challenges to build such a structure in a difficult environment, the Hoover Dam Bypass Bridge has been honored with the American Society of Civil Engineer’s (ASCE) 2012 Outstanding Civil Engineering Achievement (OCEA) award. The announcement was made March 22 at the Renaissance Capital View Hotel in Arlington, Va., during the society’s annual OPAL Gala.
The structure, officially known as the Michael O’Callaghan/Pat Tillman Memorial Bridge, was constructed in a harsh environment where temperatures reached triple digits during the day. The structure is the highest and longest arch concrete bridge in the Western Hemisphere and features the world’s tallest concrete columns.
Because of the 800-ft gorge below with rock cliffs, steep canyon walls and winds of up to 70 miles per hour, the contractor used two 2,500-ft-long cableways connected to 330-ft-high towers on each side of the canyon to transport the construction crews and 50 tons of equipment and material into place during the construction. Due to the heat, concrete was poured from mid-air at night and was cooled with liquid nitrogen-filled tubes.
The bridge is part of the 5-mile-long bypass that consists of four lanes of roadway, eight bridges, interchanges in both Arizona and Nevada and more than 3.6 million cu yd of shot rock excavation.
The project was built for $240 million without a dispute or claim by contractors. Obayashi Corp. and PSM Construction USA were contractors for the bridge while HDR, T.Y. Lin International and Jacobs Engineering were the design and support team. The project is owned by the Arizona Department of Transportation, the Nevada Department of Transportation, the U.S. Bureau of Reclamation, the Western Area Power/Administration and the National Park Service. The Central Federal Lands Highway Division of the Federal Highway Administration was the project and program manager.
The other finalists were:
* Cherry Island Landfill Vertical Expansion Project, Wilmington, Del.;
* Nacimiento Water Project in San Luis Obispo County, Calif.;
* U.S. 191 Colorado River Bridge in Moab, Utah; and
* Willamette River Combined Sewer Overflow Tunnel, Portland, Ore.