Shifting sand responsible for Mississippi River bridge failure, Iowa official says

The structural failure of a 93-year-old bridge connecting Iowa and Wisconsin over the Mississippi River was due to sand that had moved, according to a project manager with the Iowa Department of Transportation.

The bridge connecting Iowa Highway 9 and Wisconsin Highway 82 has been closed since Feb. 25, following a call made to the Allamakee County Sheriff’s Office expressing concern about the bridge deck.

After DOT confirmed there was a kink in the bridge deck, a structural inspection was conducted and data from two monitors on the existing bridge was analyzed, according to Project Manager Clayton Burke.

“It was found that a mass of sand had moved and two piers and an abutment showed movement in our sensor data,” Burke said. “We are currently investigating factors that may have contributed to the movement of the sand and bridge.”

Shortly after the incident occurred, Iowa DOT said it and other agencies were working to determine what had caused the piers to move, including whether construction of the new bridge had played a part in the movement.

Prior to the structural failure, the bridge had remained open to traffic during a project to build a new one right next to it.

Work is underway to stabilize the piers and reopen the roadway to traffic, but it could remain closed through April, and motorists have been told to take alternate routes, the Iowa DOT said.

In response to the incident, Iowa Gov. Kim Reynolds issued a disaster proclamation for Allamakee and Clayton counties.

The governor’s disaster proclamation is effective through March 30, 2024. It activates the Federal Highway Administration (FHWA) Emergency Repair Program, which authorizes emergency relief funding to cover the costs of repair or reconstruction of federal-aid routes that have suffered severe damage due to sudden structural failure.

The approximately 1,700-foot Mississippi River Bridge has connected the two states since 1931. It was previously closed from 1945 to 1957 when it was damaged by ice dams, according to the Iowa DOT.

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