Nova Scotia

Irving dry dock sinks

Scuba divers were in Halifax Harbour Sunday afternoon trying to salvage a floating dry dock, owned by J.D. Irving Ltd., that sank Saturday morning.

Scuba divers were in Halifax Harbour Sunday afternoon trying to salvage a floating dry dock that sank Saturday morning.

The massive platform was being submerged to allow a tugboat to enter the drydock for maintenance, but instead of lifting the tug out of the water, the dock kept sinking.

The drydock, owned by J.D. Irving Ltd., is now lying on the bottom of the harbour in about 15 metres of water.

An oil boom has been deployed around the sunken dock, but harbour officials said there was no visible slick on the water.

The tug was safely removed and no one was injured. The only equipment lost was a generator and some winches.

Luke Gaulton, spokesman for the Department of Fisheries and Ocean, said there was no need for the Coast Guard to respond.

Mac Mackay, a regular contributor to CBC Radio on matters relating to Halifax Harbour, was at the scene Sunday and predicted that the floating dock could take several days to retrieve.

Flotation chambers must be pumped out

"That thing, full of water, weighs thousands and thousands of tonnes, so you either have to displace that water or have something capable of lifting thousands and thousands of tonnes," Mackay said.

"Well, there isn't anything around capable of lifting something that heavy, so what they would need to do is find a way of forcing the water out that's in there now, to lighten it and then it will come up to the surface by itself, assuming it doesn't have too many holes in it."

Mackay said the drydock's hull is divided into multiple chambers, which have to be emptied at the same pace to raise it evenly.

"You put too much pressure on one tank, you can blow the wall out of the tank and then the thing will sink again," he said.

Mackay said Irving would want to get the dock fixed as soon as possible because it's an import tool for the company's ship-repair business.

A spokesperson for Irving Shipbuilding said the company is preparing plans to raise the dock. Naval architects were due to arrive in Halifax Sunday to figure out how best to proceed.

Investigators are hoping to learn more about why it sank once the dock is recovered.