Incorrect estimate of crane height causes $2 million in damage to bridge

A $2 million error was the result of misjudging a crane’s boom height, resulting in a collision with the Houma Twin Span Bridge, according to the National Transportation Safety Board (NTSB).

On March 6, 2022 the tugboat Robert Cenac pushed the sick boat mr dag and another deck barge along the Gulf Intracoastal Waterway. When the convoy attempted to pass under the Houma Twin Span Bridge, the crane was on board mr dag hit the bridge. The incident reduced eastbound vehicle traffic from two lanes to one for ten days, affecting nearly 30,000 vehicles a day.

Thankfully, no injuries or contamination were reported.

Crane Mr. Dawg in operation. (Source: Houma Times)

Sealevel Construction had chartered them Robert Cenac to tow them mr dag and a deck barge from Houma to Clovelly, Louisiana. Despite repeated inquiries about the height of the crane, Sealevel Al Cenac Towing has not provided verified information.

Due to the lack of verified information, the captain of the Robert Cenac estimated the height of the crane boom in the dark, resulting in an incorrect draft calculation. The NTSB determined that the probable cause of the incident was the captain’s incorrect estimate and decision to depart without receiving confirmed altitude readings. The failure of the crane’s owner to provide accurate airflow information also contributed to the accident.

“Tow operators need to know the draft of their ship and tows and should not make assumptions,” the NTSB report said. “As the NTSB has previously recommended, tow operators should have a detailed voyage plan with specific information on/about all known hazards, including calculated clearance limitations for tow aircraft. In this case, the captain would have had to wait to leave the port until the exact air passage of the tow was determined.”

The NTSB has previously recommended that the Occupational Safety and Health Administration (OSHA) revise regulations on the placement and securing of crane booms during transportation. However, OSHA declined to change the regulations.

The report concluded that operators need to have accurate and objective data before going ahead, especially in high-risk conditions. It required owners and operators to develop voyage plans that assess operational risks, including air trains related to bridge clearances along their intended route.

Navy Investigation Report 23-06? is available on the NTSB website.

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