The work requires a 900-ft-long precast concrete girder bridge, which crosses a 200-ft-deep ravine, plus a cast-in-place intersection bridge at the Hoover Dam Access and Kingman Wash roads. The two-year undertaking, slated to finish by October 2004, also includes 1.7-million cu yd worth of difficult excavation that must be drilled and blasted. The A+B contract has liquidateddamages of up to $10,000 a day, but also includes 5% bonuses for materials that exceed specifications.

"Essentially, it's a great way of ensuring that all parties deliver a quality project that will last over a long period of time," says Dave Zanetell, FHWA's project manager.

In October, the Western Power Administration awarded a $9.6-million utilityrelocation contract to Kansas City-based Par Electrical Contractors Inc. to move eight steel lattice transmission towers and accompanying 230-kV and 440-kV lines from the path of the bridge. The first phase will finish in June.

The project is expected to greatly relieve the congested two-lane U.S. 95 highway, identified as a NAFTA route, which currently runs over the crest of the dam. The 2,000-ft-long bypass bridge will be a single-arch, steel-and-concrete composite structure crossing the Colorado River 1,700-ft downstream from the dam. HDR Inc., Omaha, with Sverdrup Civil Inc., a unit of Pasadena-based Jacobs Engineering Group Inc., and T.Y. Lin International, San Francisco, are the project's engineering-design team (ENR 7/23/01 pg. 7)

Originally estimated at $198 million, FHWA adjusted its total costs to $234 million after the geotechnical survey, conducted by London-based AMEC PLC, found that Black Canyon's rigorous slopes would require pricey excavation. Contractors must create 90° and 73° sheer drops at theNevada and Arizona sides, respectively, to minimize the amount of excavation otherwise needed for more gradual transitions.Controlled explosives will be used to carve-out the canyon walls, which descend 850 ft to the Colorado River.

FHWA plans to advertise the second phase, the 2.5-mile, four-lane Nevada approach, in June followed by the bridge structure itself in October. The project is scheduled for completion in 2007.