'Risk Of Collapse' Evaluation Ordered For 3 MA Bridges

MASSACHUSETTS - As the National Transportation Safety Board continues its investigation into the deadly collapse of the Francis Scott Key Bridge in Maryland, the safety administration has identified numerous bridges that are also at risk of collapse should a vessel collide with them.

As a result of the investigation, the NTSB is recommending that 68 bridges — including three in the state of Massachusetts — 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 the Commonwealth, the following bridges are recommended to undergo a risk assessment: both the southbound and northbound upper levels of the Tobin Bridge in Boston, the Bourne Bridge in Bourne and the Sagamore Bridge in Sagamore.

The Bourne Bridge is deemed "critical/essential," while the Tobin and Sagamore Bridges are "typical"

Both the Bourne and Sagamore Bridges have seen their wear and tear - they were constructed in 1935. The Tobin Bridge was built in 1950.

The NTSB is recommending the bridge owners — which is the Massachusetts Department of Transportation for the Tobin Bridge and the U.S. Army Corps of Engineers for the Bourne and Sagamore Bridges — calculate the annual frequency of collapse for the structures using the Method II calculation from the American Association of State Highway and Transportation 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 completed was not immediately clear.