Massive ice shelf break led to Dawson City Snowcat sinking, says construction company

Two workers on the machine escaped unharmed before it sank to the river bottom while working on an ice bridge in Dawson City, Yukon.

2 Dawson City ice bridge workers escaped the vehicle unharmed

This snowcat was working in the Northwest Territories last winter when it went through some ice. (Submitted by Clint Ambrose)

The construction company building the ice bridge in Dawson City, Yukon says the incident that saw a snowcat sink to the bottom of the Yukon River is highly unusual.

Cobalt Construction said the snowcat went under about 60 metres from open water, in an area that should have been safe. An ice shelf roughly the size of four NHL hockey rinks broke off.

"The whole thing broke off. It's 60 metres by 120 meters long," said president Jon Rudolph. "It wasn't just a hole in the ice. The whole shelf broke away and went under the ice."

The incident happened late Tuesday afternoon and work on the Dawson City ice bridge has since been put on hold.

Two operators working for a contractor were on the snowcat when it went through the ice, said Paul Murchison, the director of the territory's transportation engineering branch.

He said both were able to escape without going in the water.

"Thankfully with the contractor's health and safety plan, the measures were in place," he said.

The snowcat went through the river ice near the ferry landing at Dawson City. (Claudiane Samson/Radio-Canada)

The incident occurred in relatively shallow water near the ferry landing, but the snowcat is completely submerged.

The snowcat was used to move equipment around and clear snow from the ice.

Cobalt Construction hired NOR-EX Engineering to assist with the ice bridge. NOR-EX's website says it has expertise in ice engineering, construction and safety.

Rudolph said workers tested the ice thickness that day and it was about 60 centimetres, well above what is required.

The snowcat operator was training another worker when the ice gave way.

"[The operator] got him off to shore, told him to get to good ice, and then he tried to actually run the machine to shore," said Rudolph. "It wasn't going to make it so he bailed and ran off on the ice and got to shore."

Murchison said the contractors will devise a plan to recover the snowcat from the river. They'll also look into why the ice failed.

Director of transportation engineering in Yukon, Paul Murchison, says the government wants to know why supposedly safe river ice gave way underneath a snowcat on Tuesday. (Dave Croft/CBC)

The Yukon Workers' Compensation Health and Safety Board has stopped work on the ice-bridge project for now, he said.

"They will be doing an investigation as well too, and work with the contractor to look at the practice that the contractor was undertaking," Murchison said.

The ice bridge builders were able to install a second boom across the open water before the incident, he said.