The Transportation Safety Board of Canada says a number of factors led to a fatal accident on a tug off Newfoundland's south coast last year.
The Western Tugger was towing the barge Arctic Lift I on May 10, 2013, when it ran into trouble in foggy weather about 33 nautical miles southwest of Burgeo.
The Arctic Lift I started to list heavily, perhaps because water had flooded in through hatches that had not been adequately sealed.
The barge's cargo of steel rebar was unsecured, and had shifted.
The fog, however, prevented the tugboat's crew from noticing how seriously the barge had begun listing. When the fog cleared a little, a significant starboard list was obvious.
A deckhand scrambled to the winch room to loosen the nut on a secondary brake.
"The bow of the barge rose out of the water and, as the barge capsized to starboard, the entire length of submerged tow wire was lifted out of the water," the TSB wrote in a report on the incident.
"When the strain came on the winch, it shattered the secondary brake drum. Shards of the brake drum were projected into the forward area of the winch room and struck the deckhand."
The noise from the incident drew the immediate attention of the crew, who administered first aid.
The man was airlifted to Stephenville, but was dead before he arrived at hospital.
In addition to focusing on the factors that caused the barge to list and capsize, the TSB determined that the emergency tow release "was prevented from operating by a nut-and-bolt assembly."
As well, the TSB determined that the company had not identified the situation as a potential risk, and that the nut-and-bolt assembly would need to be released manually if an emergency arose.