Piers are taking shape on new I-35W bridge, with precast segments on the way.
The joint-venture team for the new Interstate 35W bridge expects to begin placing precast segments for the 504-ft-long main span this month and complete the superstructure in June at least two months earlier than anticipated and far ahead of the stipulated Dec. 24 deadline.
The 1,216-ft-long, 10-lane bridge will replace the steel truss that collapsed on Aug. 1, 2007, into the Mississippi River. By working two 10-hour shifts throughout the winter, the joint venture led by Longmont, Colo.-based Flatiron Constructors Inc. and Seattle-based Manson Construction Co. has completed all foundation work. The two quartets of 70-ft-tall piers will sit on foundations built with drilled shafts up to 8 ft in diameter, with rock sockets down to 100 ft. The north abutment and 70-ft approach span have 4-ft-dia. drilled shafts and the south abutment has 102 driven piles.
The team expects to finish placing the main span’s 120 precast segments, each 16.6 ft long and up to 25 ft deep, in June, says Peter Sanderson, project manager. “We intend to erect four segments a day,” with one crane operating on a barge in the river, he says. As of April 1, almost 40 precast segments were completed in the on-site yard. The key to speed is multiple operations with no reusing of forms, says Minnesota Dept. of Transportation project manager Jon Chiglo. “Normally, you don’t see six sets of formwork for the pier columns,” he says. “You usually use one set multiple times.”
Officials say they have cut no corners and taken no chances on quality inspection. “A regular job inspection normally would have one or two people inspecting for one or two hours,” says Sanderson. “Here, we’ve had eight people inspect [a job component] for 16 hours at a time.”
Almost 500 personnel are expected to work on site at peak, with several visits a week from Occupational Safety and Health Administration officials. The team stands to earn a $7-million completion bonus on its $243-million contract, plus $200,000 a day for each day before Dec. 24, up to 100 days. It would face an equivalent $27 million in late fees, plus unlimited liquidated damages.