TSB: Cable ferry went adrift after ice caused attachment failureJun 15, 2012 04:37 PM
A buildup of ice that broke mechanical components caused an Ottawa River cable ferry to go adrift, the Transportation Safety Board (TSB) of Canada said.
Ice accumulated against the side of the battery-powered electric ferry Ecolos on Dec. 9, 2010, during a crossing between Thurso, Québec, and Rockland, Ontario. The ice put unusual strain on a cable and the guide components, causing them to fail, the TSB said in an investigative report.
The cable broke, and the 58.5-foot ferry drifted down-river, tethered to the one remaining cable.
At about 2045, Ecolos loaded three vehicles and five passengers and departed from Thurso. The operator was the only crewmember on board, and he noticed a significant increase in the number of ice pans flowing down the river. The pans of ice were accumulating against the side of the vessel as it crossed. When the ferry was approximately halfway across, there was a loud bang and the vessel stopped abruptly, the TSB said in a March 2012 report.
“Ice flowing down the Ottawa River got stuck to the upstream side of the hull of the Ecolos cable ferry. When the ferry was about halfway across, there was so much ice accumulation that some of the mechanical parts failed and the cable ferry went adrift,” said Wendy Jolliffe, TSB’s investigator-in-charge. “One of the axles, a cable and a shore attachment failed, but luckily the other cable got caught in the machinery and kept the ferry tethered to the shore at Rockland.”
Ecolos, which is 36 feet wide, is a flat-bottomed barge of welded steel construction. It is propelled by two electric drive motors powered by three battery banks.
The ice pans accumulating against the side of Ecolos created a greater lateral force on the ferry than that normally encountered, and the vessel was pushed downriver.
The TSB found that, in the event of both cables parting and without means for preventing the cable ferry from going fully adrift, the cable ferry, passengers and crew may be placed at risk. When vessel operators do not collect information about how many passengers are on board and do not transmit this information ashore, passengers are at risk of not being accounted for in the event of an emergency.
In addition, the TSB said that failure to declare distress to the appropriate authorities delays the search and rescue response, thereby placing vessels, passengers and crew at risk. A lack of a continuous lifetime maintenance record on a vessel may preclude proper maintenance and trend analysis, thus increasing the risk of machinery failure.
The TSB report states that, since the accident, the owner of Ecolos has modified the design of the drive system such that the idler wheel axles are of a continuous diameter, that is, 10.6 cm (4 inches), from bearing to bearing. Floating bearings have been installed on either side of the axles. The bottom rollers on Ecolos are now constructed of 100 percent polyurethane. There is now a failsafe device known as a “weak link” installed at the cable shore attachments. Swaged 6 x 26 independent wire rope core cables have also been installed.
Ecolos is owned and operated by Rockland-based Traversier Rockland-Thurso Ferry Inc. Gilles Laframboise, manager of Ecolos, told Professional Mariner that the improvements to the vessel will make it safer to operate.
“It is a new and improved version,” he said, noting that the addition of the “weak link” is a major modification towards a safer operation in the event of a similar ice load occurring. “The cable won’t break. The pulley won’t break. Once the ‘weak link’ goes, the cable won’t go through it and will prevent the boat from going down river.”
Laframboise explained that in the event of a similar high stress situation from ice on the river, rather than the cable breaking, the “weak link” ashore would break instead.
“The cable attachment between the cable and the link will stay on the cable,” he said. “That attachment is a wedge and if the end is torn off it will stay on the cable. That piece does not go through the opening for the cable on the ferry. The opening for the cable is only an inch and a quarter and the block (wedge) is six inches big.”
The ferry could still drift downstream, but it would remain anchored by the cable firmly attached to the other side of the river.