Experts question soil under Green Bay bridge

CREATED Oct. 13, 2013

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  • Image by Wisconsin DOT

  • Barriers block access to the Leo Frigo Bridge in Green Bay after a large dip was discovered in the roadway. Image by Brian Miller

  • Side view of the Leo Frigo Bridge, closed after inspectors discovered a large dip across the roadway. Image by Brian Milller

  • Leo Frigo Bridge is closed after police discovered a large dip across all lanes of the roadway. Image by WI Department of Transportation

  • Traffic is halted on the Leo Frigo Bridge in Green Bay. Drivers are being detoured to HWY 172 and HWY 41 as inspectors determine what caused a large dip across the roadway. Image by WI Department of Transportation

  • Traffic is shut down on the Leo Frigo Bridge (Tower Drive) in Green Bay. The WIsconsin DOT is inspecting the surface after discovering a dip in the roadway. 9/25/13. Image by Wisconsin Department of Transportation

GREEN BAY (AP) -- Crews that built the now-closed Leo Frigo Memorial Bridge in Green Bay weren't able to rest its steel structure atop sturdy limestone bedrock, which some geologists and engineers say may have contributed to its sinking pavement.

Wisconsin highway officials discount that theory. They say steel corrosion at ground level is the likely culprit that forced the indefinite closure of the bridge, which carried about 40,000 cars daily over the Fox River.

The Green Bay Press Gazette reports Sunday that some experts say underground soil that was sturdy enough to support the bridge when it opened three decades ago might have deteriorated in subsequent years. Bill Kallman, a Michigan engineering consultant who has worked on bridges in New York, says he thinks that's a more plausible explanation than corrosion.