...design is a departure from typical cofferdams and is necessary because of the strong current and the high-volume shipping traffic in the channel, Wagner says.

The cofferdam consists of 54-in-dia, 150-ft-long hollow-steel piles driven to -139 ft. Piles are joined with a connection to enable a pair of sheet piles to be driven in between. The main piles are braced by 54-in-dia batter piles on the inside. A steel frame ties it all together and is topped with 8 ft of concrete.

Awarded as an early-contractor-involvement contract, the West Closure Complex has experienced numerous design changes after feedback from GIC on constructability and a Corps-sponsored October design summit aimed at cost-cutting. The number of pumps dropped to 11 from 13, and a second sector gate was eliminated.

Working Wet

GIC is fighting above-average rainfall and soil-moisture issues as it places geotextile fabric and the first lifts of clay for the earthen levee. Corps specifications require clay with 10% moisture content, Wagner says, but with the rain, the moisture content at nearby sources, which previously were approved for the requisite 1 million cu yd of material, has risen to as high as 70%, which takes a lot of processing. To compensate, GIC is hauling material from a borrow pit more than an hour away, Wagner says. It is experimenting with a soil-directed jet-dry blower to reduce moisture on-site.

The St. Louis District is designing the 300-ft closure to tie the sector gate into the 4,000-ft-long T-wall that will enclose an environmentally protected area, the Bayou Aux Carpes. “We were originally looking at 54-inch king-and-batter piles with an A-frame bracket, but local sponsors have some concern about corrosion,” Wagner says. “They are looking at it from an operation-and-maintenance perspective.” Alternatives include a concrete T-wall atop steel piles or deep-soil mixing topped with a rock berm.

Bayou Wisdom

Key subcontractors are bringing local knowledge to the job. Boh Bros Construction, New Orleans, is driving pilings for the T-wall along the Bayou Aux Carpes. Bertucci Contracting Co. LLC, Jefferson, La., is dredging. MR Pittman Group LLC, New Orleans, is performing mechanical, electrical and instrumentation for the pump station. Phylway Construction LLC, Thibodaux, La., is doing dirt work on levee construction. “We thought it was important to include local and small businesses,” Proskovec says.

Both Kiewit and Traylor have had a large presence in rebuilding the New Orleans area after 2005’s Hurricane Katrina. “We partnered on the high-level portion of the new I-10 twin spans with Traylor,” Proskovec says. Also, alone, Kiewit delivered the interim closure structure at one of the city’s three outfall canals.

Kiewit also is partnered with Traylor on a portion of the Huey P. Long Bridge widening project, and both are partnered with Massman Construction Co., Kansas City, Mo., for T-wall levee construction in Chalmette, La. Kiewit spokesman Ken Grisham says the company intends to continue pursuing other projects in the area.

“We’ve been very active in the southern United States and Gulf Coast region, but not in New Orleans,” Grisham says, but that now has changed. “The post-Katrina work required the kind of capability of a company like Kiewit—bonding capacity, mobilization of force and overall resources,” he says.