Incorrect Crane Height Estimate Causes $2 Million in Damages to Bridge
A $2 million blunder was the result of an incorrect estimate of a crane’s boom height, leading to a collision with the Houma Twin Span Bridge, according to the National...
Last year, a drillship collided with a cargo vessel in Pascagoula, Mississippi, causing nearly $5 million in damages. The cause of the collision was found to be a deteriorated bollard that had broken away from its base during strong winds, the National Transportation Safety Board (NTSB) has now determined.
The incident occurred on March 12, 2022, at the ST Engineering Halter Marine and Offshore Shipyard (STEHMO) where the VALARIS DS-16 drillship was moored. During the passage of a cold front, the mobile offshore drilling unit broke away from the dock and drifted into the Bayou Casotte channel, colliding with the Akti cargo vessel. Fortunately, no injuries or pollution were reported.
Investigations revealed that the mooring lines of the VALARIS DS-16 were secured by six bollards on the pier at the STEHMO Shipyard. During strong winds of 30-40 knots, one of the bollards broke free at its base, snapping the bollard that secured the drilling unit’s four bow lines and a semisubmersible rig’s two stern lines.
Ultrasonic thickness tests conducted after the incident showed that there was deteriorated steel at the lower portion of several bollards, with some also showing signs of external corrosion and wastage. It was also discovered that all of the bollards used by the VALARIS DS-16 had been modified from their original 1997 design, with vertical components added to each to accommodate more lines.
The NTSB concluded that the probable cause of the breakaway and collision was the failure of one of the shipyard’s mooring bollards, which had been modified to increase its height for more lines, during a cold front with strong winds.
Since the incident, the STEHMO Shipyard has replaced 10 of the 14 bollards on the pier, with plans to replace another by the end of March 2023. Shipyard managers have also begun evaluating the safe working load of the new bollards and are scheduling a pull test using a tugboat.
This incident serves as a reminder of the importance of regularly maintaining and inspecting equipment to ensure their safe operation and prevent costly accidents.
“As a result of continuing increases in vessel size and sail area, bollards that were previously sufficient may not have adequate capacity to moor larger vessels,” the report said. “There are currently no U.S. Coast Guard or Occupational Safety and Health Administration regulatory requirements for facilities to inspect and verify loading capacities of bollards at shoreside facilities. Bollards and associated pierside mooring equipment are vital equipment that must be capable of withstanding the tremendous forces that large vessels exert on them. Due to their exposure to seawater, bollards and associated pierside mooring equipment are at high risk for corrosion, which can significantly affect service life. The Coast Guard has recommended that facility owners and operators develop a routine inspection program for bollards and other mooring equipment.”
Marine Investigation Report 23-05 is available on the NTSB’s website.
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