It’s hard to fathom a structure that can live up to the awe-inspiring architectural and engineering masterpiece that is the Hoover Dam, but a joint venture between Obayashi and PSM Construction USA comes close. Working in the presence of the Hoover Dam, the partnership is constructing a bypass bridge that will better and more safely serve the public, surrounding economies and the operations of the tourist attraction, all in an environmentally responsible manner.

“We are building a [bypass] in the shadow of what is one of the greatest engineering feats in the country, and that’s quite a reminder of the standards that we need to uphold,” says Dave Zanetell, Federal Highway Administration project manager. “We are working in a place that has achieved greatness and it is our job to live up to that standard.”

The Hoover Dam Bypass is a $234 million project to build 3.5 miles of four-lane highway and a 1,960-foot-long, 88-foot-wide arched bridge over the Colorado River. It was awarded to the joint venture in 2004.

Guided by the Central Federal Lands Division of the Federal Highway Administration (FHWA), the need for the project is driven by the heavy volume of commercial and tourist traffic on U.S. Route 93, the two-lane highway across the dam. Route 93 serves as the main link between Arizona, Nevada and Utah for commercial truckers, and is a connector route between Mexico and Canada.

The overall design and construction of the project is overseen by a project management team led by FHWA, and its stakeholders include the Arizona and Nevada departments of transportation, the U.S. Bureau of Reclamation, the National Parks Service and the Western Area Power Administration. The bypass is funded by federal, Arizona and Nevada state money.

Delivering on Its Promise
In January 2005, Obayashi-PSM started construction on the composite steel and concrete deck arch bridge. This type of bridge was chosen by the multi-agency project team because of its relatively low cost, technical excellence, aesthetic appeal and fit with an accelerated schedule.

Working 890 feet above the Colorado River, the joint venture has used proprietary construction methods and technologies. To prepare the site, the two firms and a team of subcontractors excavated roughly 40,000 cubic yards of rock at the abutments, approach piers and arch footings. The structure contains 10 pier footings and a total of 440 column segments.

To transport materials and set columns in the rough terrain, the crews used two tower cranes located on opposite sides of the canyon, connected via dual high lines. In addition, the crew set up a concrete batch plant for continuous quality control and quick delivery.

“We needed to select equipment suited to project needs that could consistently provide us with the range of mixes with a high degree of quality control, but without having a huge labor force to run it,” Project Manager Michiya Sadamatsu says. “Further, we needed to secure transport for the mix from the plant to the site – essentially taking on the role and responsibility of being our own concrete supplier.”

According to Fredrick Lazar, contract administration manager, all four cableway towers are up and ready to go. “On Oct. 30, a Silver State helicopter brought in the half-inch messenger cable from Arizona to Nevada as the first step in stringing cable, installing the travelers and hooks and bringing the cableways into operational status,” he says. “We are shooting to accomplish [operational status] before the end of the year. This is the primary focus right now, since the remainder of the project hangs on the cableways becoming operational.”

At the same time, pre-cast operations for the panels enclosing the arch struts are moving ahead efficiently, as are preparations for placing the steel girders on the Nevada approach, and then decking for both approaches, as soon as the cableway becomes operational.

Construction of the cast-in-place arch segments across the Colorado River continues, as does electrical and utility work. 

Overcoming A Setback
On Sept. 15, 2006, the project hit a major snag when the two 333-foot-tall highline cableway cranes used to transport materials collapsed in a windstorm. The event moved the project completion date from 2008 to 2010. At the time, the project was nearly 40 percent complete. Without the highline system, transporting materials to construct the columns and arch segments was impossible.

Despite the setback, the team procured two state-of-the-art temporary cranes to keep construction moving while the design, procurement and fabrication of a new highline system were underway.

If construction continues to progress on schedule, the FHWA projects the project will be completed in the second half of 2010.