Hoover Dam Bypass - Nevada Approach
River Roadway
by Tony Illia

Activity is humming along on Arizona's roadway approach to the Hoover Dam Bypass Bridge, an alternate crossing over the Colorado River that is expected to greatly relieve traffic over the dam''s existing two-lane highway, which sees more than 13,000 vehicles a day.

The U.S. Highway -93 route is a major commercial corridor identified in the North America Free Trade Agreement route between Mexico and Canada. But since the terrorist attacks of Sept. 11, truck traffic over the dam has been rerouted 23 mi. away, costing the industry an estimated $30 million annually.

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The Federal Highway Administration is awarding projects to fast-track bridge construction. In February 2003, >> a joint- venture of two Arizona firms, R.E. Monks Construction Inc., of Fountain Hills and Vastco Inc. of Chino Valley, landed the $21.4 million Arizona approach.

R.E. Monks serves as project manager, overseeing the excavation and paving, while Vastco is responsible for the structures. It's the first of four federal contracts needed to complete the 1,900-ft.-long, four-lane bypass bridge, which also includes 4.3 mi. of accompanying roadway.

The rugged topography, which consists of tuff and basalt rock, has required some tricky excavation. Subcontractor Western States Contracting Inc., of Las Vegas performed 1.7- million- cu. yds. worth of excavation. And due to the geology, the rock removal entailed drilling and blasting in a piecemeal fashion, carefully carving out the mountainside to the needed depth and angle.

The material was then crushed and used as an earthen embankment for a 1.8-mi. long, four-lane asphalt highway. Combs Construction Co. Inc., of Peoria, Ariz., is the paving subcontractor.

"The steep terrain was an initial challenge," said Pete Young, R.E. Monks' project engineer. "As far as the overall scope, it's a pretty simple project. At least, there aren't a lot of utilities in the way."

The project calls for a 1-mi. long, two-lane frontage road to divert traffic while the bridge is under construction. A total of 6,000 tons of asphalt will be used to complete the roadways. Additionally, the job calls for two major bridge structures: a full diamond interchange, plus another 902-ft.-long, 90-ft.-wide crossing.

The 16.7-ft.-tall interchange has 1,300-ft.-long ramps cut into the mountainside. It will enable two lanes of traffic to flow in each direction at Old Kingman Wash Road, which serves as a gateway into the Lake Mead National Recreation area.

The more challenging four-lane bridge crosses over a 160-ft.-deep ravine. The seven-span structure is supported by six tapered piers. There are 77 pre-stressed, 128-ft.-long concrete girders that sit atop pier abutments.

"Each of the girders weighs 132,000 lbs.," said Tim Kempkes, Vastco's project engineer.

With roughly 11 girders per span, Vastco used seven different cranes to maneuver the pieces into place, ranging from a Link Belt 250-ton crawler crane with 200- ft. of boom to 22-ton Grove hydraulic crane. Jake's Crane & Rigging International of Las Vegas was the crane provider.

"We had to come up with a complex scheme to place them in each instance," Kempkes said. "Due to the wind and conditions, we would pick-up some girders and change their location in mid-air in order to properly place them."

About 11,000- cu. yds. of concrete will be used to complete the bridges. Casino Ready Mix Inc., of Las Vegas, is supplying the concrete. The median concrete mix is 7,500 psi, or nearly double the strength of most structures.

Other contract work calls for 2,000 lin. ft. of cast-in-place box culvert, plus 4,400 lin. ft. of corrugated metal pipe. There is also 17,000 lin. ft. of game fencing to protect natural wildlife in the area, including big horn sheep and desert tortoise.

"We are really pleased by the work of the Monks-Vasco team," said Dave Zanetell, the highway administration's project manager. "They have played an important part in getting the overall bypass started."

The Monks-Vasco team expects to finish its project well in advance of its Oct. 15 deadline. But funding delays from the slow reauthorization of Transportation Equity Act for the 21st Century, the federal road and highways bill that expired last year, have pushed back the bridge's final completion date.

Initially, the $235 million project was to open by 2007, but that has been adjusted for a 2008 completion.

"We are hopeful that the remaining funds will come this summer, and if that is the case, the bridge portion will advertise in June," Zanetell said.

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