Lifeline. Louisana bridge will increases mobility and server as possible evacuation route. (Photo courtesy of Lousiana Timed Managers)

The construction of what will be North America’s longest cable-stayed bridge could begin next month. Audubon Bridge Constructors, a joint venture of Longmont, Colo.-based Flatiron Construction Corp., Watsonville, Calif.-based Granite Construction Co. and Washington, D.C.-based Parsons Transportation Group Inc. (PTG), has won a $347.9-million design-build contract to build the John J. Audubon Bridge.

The new bridge will cross the Mississippi River between St. Francisville and New Roads, northwest of Baton Rouge, with a 1,583-ft-long cable-stayed main span. It will surpass South Carolina’s Cooper River bridge’s 1,546-ft-long span. The 2.5-mile-long bridge with 12 miles of accompanying new road will connect State Route 10 and U.S. 61, replacing a ferry that now is the only direct route between Natchez, Miss., and Baton Rouge (ENR 12/12/05 p. 18).

PTG is joined by Vancouver, British Columbia-based Buckland & Taylor Ltd. as designer. The joint venture edged out two other teams for the state’s first major design-build job: American Bridge Co. and Bilfinger Berger with URS Corp.; and MRB Constructors, with Traylor Bros. Inc., Massman Construction Co., Gilbert Southern Corp. and HNTB Corp.

Escalating construction costs due in part to last year’s hurricanes pushed the original $269-million engineers’ estimate up to $346 million, say Louisiana Dept. of Transportation and Development officials. The winning team’s base bid was $334 million, but LADOTD chose its option of adding extra lanes to two miles of new road, says Bryan Jones, spokesman for Louisiana TIMED Managers, the Parsons Brinckerhoff-led joint venture that manages a $4-billion statewide program for LADOTD.

As part of the Transportation Infrastructure Model for Economic Development (TIMED), the Audubon Bridge is meant to encourage development and mobility. But “after the hurricanes last year, the bridge took on a new focus,” as an evacuation route, Jones adds.

A notice to proceed is expected May 10. The team will have a 49-month calendar schedule, with $9,200 a day in late penalties, says Jones. Supported on drilled shafts, the bridge will rise 65 ft above high water. Wind loads and the flood level of the Mississippi River will be factors in design, says Greg Shafer, PTG design manager for the team.

“The loads imparted by the river’s flow against the structure as well as debris loads will be considered,” he says. “The river level is also important in determining the required resistance to vessel impact from barge traffic.”