A tugboat sank in the St. Lawrence River when the excavation barge it was tending failed to raise one of four support pylons, pivoted in the current and swamped the tug.
On April 1, the 25-foot tug Ocean Uannaq was working with a larger tug and another smaller tug on excavation work that is part of the massive new Champlain Bridge under construction to connect the island of Montreal to the south shore of the St. Lawrence.
The bridge is being built by the private consortium Signature on the Saint Lawrence (SSL) and is one of North America’s biggest work sites. Thirty-eight concrete footings will be produced for the construction of the new Champlain Bridge.
The excavation work is performed by a rectangular barge, stabilized by four anchor posts, in addition to three ship’s tugs — a larger one in the center and two smaller vessels controlling the ends.
In the late afternoon on April 1, a maneuver to bring the excavation barge to the west pier did not go as planned, according to Annie-Claire Fournier, spokeswoman for SSL. The operation was taking place about 330 yards from the Île-des-Soeurs west jetty.
Due to the strong current, one of the anchor poles got stuck and did not raise, causing an unexpected rotation of the barge and exposing the side of Ocean Uannaq to the current.
The tug, powered by two Caterpillar C12 385-hp engines, was overcome by the current and sank to the river bottom in 16.5 feet of water. The two people on board the vessel evacuated safely without touching the water.
“After an internal investigation, reviewed by a maritime security expert, SSL conducted a comprehensive review of its maritime excavation methods from barges,” Fournier wrote in an email. “This helped in particular to improve some aspects related to maritime operations taking place in a context of strong current.”
A three-day salvage plan involved assembled barges from which a crane raised the tugboat. The removal operation was completed May 28. During the project, about 2.5 gallons of oil spilled from the vessel. All environmental contingency measures set out in the salvage plan were immediately carried out, including the use of booms to contain and absorb the oil.
Once out of the water, the boat was brought to the west jetty and handed over to the Transportation Safety Board of Canada (TSB) for analysis. Later the same day, the TSB returned the tugboat to Signature on the Saint Lawrence.
The TSB is continuing its investigation under Senior Marine Investigator Capt. Wendy Jolliffe.