Repair and temporary dam at Mount Polley Mine near Williams Lake.

Mount Polley design, steep additions led to failure

Glacial layer in dam base not understood, plans to buttress slope put off until weight of water and tailings caused breach

The Mount Polley mine dam failed because of an overlooked glacial material layer in the foundation and a series of steep additions that eventually overcame it, an independent engineering review has concluded.

“Basically the weight of the dam was too much for the weak materials in the foundation to bear,” said U.S. consulting engineer Steven Vick, one of three experts called in to examine the failure that caused the dam to breach and fail in August 2014.

The report concludes that the concrete-like glacial till material in the base of the dam wasn’t understood in enough detail when the dam was designed and built in 1997. Later raising of the dam to hold more water and tailings weakened the base layer and led to the failure.

Vick said the additions to the dam were built at a steeper slope than the original dam, and plans to buttress the area were delayed until it was too late.

Energy and Mines Minister Bill Bennett said the report shows there were no warning signs, and no surface inspections could have detected the problem that was overlooked in the design and original construction.

Two more investigations of the mine failure are pending. Bennett said the Chief Inspector of Mines is likely to release his report by June, and the Conservation Officers’ Service will also report when its investigation is complete.

Bennett said the government is willing to see the Mount Polley mine reopen, but the other investigations must be complete first. The parent company Imperial Metals has applied to use an existing pit to store tailings and resume operations without using the original tailings pond again.

 

Just Posted

Snow prayers answered as Manning Park ski hill opens Friday

Ski hill will be open seven days a week starting Dec. 14, and cross-country trails as well

Fleeing driver picks fight with Chilliwack police dog, loses

Good dog ‘Griff’ also locates large quantity of what police believe to be crystal meth in Abbotsford

UPDATE: Heavy rainfall, strong winds in forecast for Lower Mainland

Heavy rains, snow expected till Friday morning

DFO confirms that investigation of fish habitat destruction in the Fraser River is underway

Conservation and Protection reps ordered Herrling and Carey Island owners to take corrective action

Hope rescue crew remove man pinned in semi-truck on Highway 3

Tuesday night rescue was swift, with the man removed safely from the truck within an hour and a half

Fashion Fridays: How to change your beauty routine

Kim XO, lets you in on her style secrets each Fashion Friday on the Black Press Media Network

Vancouver police make arrest in hit and run that killed skateboarder

Charges stem from a two-year investigation into the April 17 death of 30-year-old Ryan Barron

5 to start your day

Powerful winds anticipated in Lower Mainland, Chilliwack company facing charges in chicken abuse case and more

Increase in downed power lines in B.C., how to stay safe

BC Hydro study finds a third of British Columbians may be putting themselves at risk

Woman dies after being struck by bus in Burnaby

RCMP officers from the traffic and collision teams are investigating

Judge sets bail at $2.5 million in 1987 slaying of B.C. couple

William Talbott II, 55, is charged with two counts of aggravated first-degree murder

EU leaders vow to press on with ‘no-deal’ Brexit plans

European Union leaders have offered Theresa May sympathy but no promises, as the British prime minister seeks a lifeline.

Powerful winds set to hit Metro Vancouver, Fraser Valley, Vancouver Island

The agency says winds in coastal areas will strengthen up to 70 kilometres an hour before the front moves inland and gusts reach 90 kilometres an hour.

Mandatory victim surcharge cruel and unusual punishment, top court rules

Stephen Harper’s Conservative government made the charges mandatory in 2013.

Most Read