'Risk Of Collapse' Evaluation Ordered For MI Bridge

MICHIGAN — As the investigation into the deadly collapse of the Francis Scott Key Bridge in Maryland continues, safety officials have identified numerous other bridges that are also at risk of collapse should a vessel collide with them.

The National Transportation Safety Board is recommending that 68 bridges — including one in Michigan — undergo a vulnerability assessment to determine the risk of collapse.

The NTSB this week released a report on the March 2024 Maryland incident that documented dozens of other bridges across the nation they say have "unknown levels of risk of collapse" from vessel collisions.

In Michigan, safety officials recommend the Mackinac Bridge, which connects Michigan’s two peninsulas, undergo a risk assessment. The bridge was built in 1957 and officials deem it as "critical/essential."

The NTSB is recommending the bridge owners, the Mackinac Bridge Authority, to calculate the annual frequency of collapse for the structures using the Method II calculation from the American Association of State Highway and Transportation Officials.

Ships have hit the Mackinac Bridge before, including on May 7, 2023 when a barge carrying a 160-foot crane smashed into the Bridge. Officials said both the captain and managers of the towing vessel, Nickelena, failed to see the crane was too high to pass safely under the iconic bridge.

The contact with the bridge bent the crane boom backward, causing the boom to eventually collapse onto the barge. There were no injuries in that incident, but damage to the Mackinac Bridge was estimated at $145,000, according to NTSB officials.

If a bridge exceeds that risk threshold, it is considered high risk, according to NTSB. The owners must inform the NTSB whether the probability of collapse is above the threshold.

"Today’s report does not suggest that the 68 bridges are certain to collapse. The NTSB is recommending that these 30 bridge owners evaluate whether the bridges are above the AASHTO acceptable level of risk. The NTSB recommended that bridge owners develop and implement a comprehensive risk reduction plan, if the calculations indicate a bridge has a risk level above the AASHTO threshold," the NTSB said.

A date by which the assessments must be complete was not immediately clear.