Corrosion caused a concrete pier on a Green Bay bridge to sink two feet, leaving a 400-foot section of the structure sagging across all lanes, Wisconsin officials have determined.
The steel pilings for the Leo Frigo Memorial Bridge's Pier 22, located eight feet below the concrete footing, buckled, "apparently due to corrosion," the Wisconsin Department of Transportation announced Thursday (Oct. 3).
On Friday (Oct. 4), the Federal Highway Administration mobilized emergency funds to repair the bridge—a project ballparked at $50 million—after determining that the state could not have anticipated the failure.
Police closed the four-lane bridge about 5:30 a.m. CT Sept. 25 after drivers started calling 911 to report that a stretch of the structure was sagging across all four lanes.
Photos: WisDOT / Facebook
Corrosion on steel pilings eight feet underground caused a concrete pier on the Leo Frigo Memorial Bridge to sink Sept. 25, a WisDOT investigation revealed.
The corrosion is believed to have been caused by a combination of soil composition at the location and the rise and fall of the water table, WisDOT said.
One side of Pier 22 sank 22 inches; the other side sank 27 inches.
The Leo Frigo Memorial Bridge in Green Bay carries Interstate 43 over the Fox River south of its mouth into Lake Michigan. An average of 40,000 vehicles use the bridge each day.
Slight Corrosion on Other Piers
On Thursday afternoon, WisDOT said Thursday afternoon that the bridge had not moved since it settled on Sept. 25, and officials believed there was no danger of collapse. Later that day, however, bridge engineers detected an additional half-inch settlement on Pier 22.
The department said that both the bridge deck and Pier 22 appeared to be in good shape, but reiterated that the investigation is ongoing.
The investigation also found that the "vast majority" of the other piers that have been checked are in "the same condition as they were when they were installed 33 years ago."
Adjacent Piers 21, 23 and 25 showed some corrosion on test pits, but not to the severity of failure, according to Tom Buchholz, WisDOT project manager.
"As the investigation concludes, work will get underway to consider possible repairs. Our goal is to do whatever is needed to quickly and safely reopen the bridge," said Will Dorsey, WisDOT's Northeast Region Director.
The department's next move is to erect support towers adjacent to the pier sometime "within the next few days" to stabilize the bridge and protect workers.
A few days after the bridge sagged, WisDOT placed equipment on top of three piers to monitor any bridge movement. According to the department, the equipment will send signals to a computer to record data and will trigger a horn to alarm workers below if any movement is detected.
WisDOT also assembled a bridge team that includes structural and geotechnical experts from both WisDOT and the FHWA to lead the investigation
Federal officials approved emergency funding for repairs to the bridge. The bridge carries Interstate 43 over the Fox River and sees approximately 40,000 vehicles per day.
"In addition to our on-site investigation, [w]e are also reviewing historical engineering and site data to help understand all aspects of this event," Dorsey said.
Once all existing data are gathered, the team will analyze the information and determine a course of action. WisDOT has not yet determined a time table for when the bridge might reopen.
"It could be months. It could be a year," WisDOT spokesman Kim Rudat said.
FHWA Approves Funding
On Friday, Gov. Scott Walker announced that the FHWA approved funding for the bridge repairs under the Emergency Relief Program. Walker signed a Declaration of Emergency for the bridge one week earlier, making it eligible for federal emergency relief funds to make necessary repairs.
"We appreciate the FHWA's prompt response to help us complete needed repairs to the Leo Frigo Bridge while meeting the Governor's commitment to get this work done safely and as quickly as possible," WisDOT Secretary Mark Gottlieb said on Friday.
The federal funds will cover 100 percent of emergency repairs within 180 days. After 180 days, federal funds will cover 90 percent of the cost of emergency and permanent repairs.
WisDOT has estimated the cost of repairs at $50 million but says that number could change as plans develop.
Design, Inspections in Order
The federal government has found no irregularities in the bridge's design, construction or maintenance.
"FHWA has determined that the bridge design and construction met applicable standards at the time it was constructed, and that the bridge appears to have been properly maintained and inspected," George Poirier, FHWA Division Administrator, said in a letter to Gottlieb.
"It does not appear to FHWA that there is anything that the State could have reasonably done to have anticipated or avoided this failure," Poirier said.
About the Bridge
The Leo Frigo Bridge was constructed in 1980, with repairs on the superstructure completed in 1988. The bridge was last inspected in October 2012 and is not on the list of 60 deficient bridges in the state, according to WisDOT.
In 2012 and 2013, the bridge underwent asphalt, joint and pin replacement.
Formerly called the Tower Drive Bridge, the structure was renamed in 2002 in recognition of a Green Bay civic and philanthropic leader whose legacy includes one of the largest food pantry programs in the nation.