The NTSB found that the “probable cause” of the disaster was loss of electrical power due to a loose signal wire connection, resulting in the vessel’s loss of propulsion and steering as it approached the bridge.
Maryland authorities had failed to conduct a vulnerability assessment of the bridge, which would have set the stage for repairs, the report said.
“Also contributing to the loss of life was the lack of effective and immediate communications to notify the highway workers to evacuate the bridge,” it said.
The NTSB has compiled a list of about a dozen American bridges that are at risk of collapse in the event of a collision with an ocean-going vessel.
They include both spans of a bridge across the Chesapeake Bay east of Washington, two bridges in the Philadelphia area and four over the Mississippi River in the southern state of Louisiana.
Vulnerability assessments are still under way for about 30 other bridges out of 68 that the NTSB earlier identified as potentially at risk of collapse in a similar scenario.
Yesterday, Maryland authorities said that the cost of repair of the Francis Scott Key Bridge had more than doubled to between US$4.3 and 5.2 billion, with completion now envisioned in 2030 instead of 2028.
-Agence France-Presse