The I-43 bridge in Green Bay, Wis., has a 2-ft-plus sag because pier pilings buckled from corrosion, state investigators say. Meanwhile, findings from monitoring equipment installed on the Leo Frigo Bridge show that Pier 22, which settled 2 ft on Sept. 25, settled another half-inch on Oct. 3. Supported by 100-ft-deep H-pilings, the pier is not the only one showing corrosion, says Tom Buchholz, the investigation team's leader.
"We also went to the adjacent piers—Pier 21, Pier 23, Pier 25—and did see corrosion on test pits," he told a news conference. "It's not to the severity, obviously, that caused the failure, but you could see corrosion. This isn't a one-pier … issue. It's a multiple-pier issue."
The DOT says crews are adding support towers adjacent to Pier 22 to increase stability. Though the investigation is not complete, work is under way on a repair plan, DOT spokesman Kim Rudat adds. The Leo Frigo Bridge repair will cost an estimated $50 million, though officials say that number could change. They expect to conclude their probe by Oct. 11.
The investigation team—state and federal structural and geotechnical experts aided by Michael Baker Jr. Inc. and Wiss, Janney, Elstner Associates Inc.—has excavated around Pier 22 and taken soil samples from the area surrounding it, Buchholz said. "We actually went 15 ft below ground, which was about 8 ft below the bottom of the footing," he said. "What we found there was the piling did buckle on Pier 22."
The corrosion is thought to have been caused by a combination of soil composition in the area and varying levels of the water table, the DOT said.
The Federal Highway Administration (FHWA) said on Oct. 4 it would fund 100% of the emergency repair costs within 180 days of the Sept. 25 bridge closure. "It does not appear to FHWA that there is anything that the state could have reasonably done to have anticipated or avoided this failure," George Poirier, FHWA division administrator, said in a letter to Mark Gottlieb, Wisconsin DOT secretary.