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

Gitxsan forming cross-sector salmon management team

Nation again declares closure of fishery in territory for 2019

It’s the last day to vote in B.C.’s referendum on electoral reform

Ballots must now be dropped off in person to meet the deadline of 4:30 p.m.

Motorhome explosion in Houston

A motorhome by the Houston Motor Inn had an explosion Sunday, Dec.… Continue reading

Christmas is a comin’

Some of Houston residents are getting the ball rolling for the upcoming… Continue reading

Silverthorne Elementary to remain open, for now

School District 54 pursuing funding for possible school reconfiguration

VIDEO: This B.C. school leads country in vaccine donations to UNICEF

Federally funded Kids Boost Immunity uses quizzes to earn vaccinations

Boeser scores 3, Pettersson has 5 points as Canucks hammer Blues

Vancouver picks up impressive 6-1 win in St. Louis

B.C. police stop drunk driver who offered up burger instead of ID

Roadblock checks over the weekend found at least two other impaired drivers

In Canada, the term ‘nationalism’ doesn’t seem to have a bad rap. Here’s why

Data suggest that Canadians don’t see the concept of nationalism the way people do in the United States

Small quake recorded west of Vancouver Island

No injuries or tsunami warning after 5.4 rumble felt some 400 kilometres from Victoria

B.C. suspends Chinese portion of Asian forestry trade mission due to Huawei arrest

Huawei’s chief financial officer Meng Wanzhou was detained at the request of U.S. in Vancouver

Canadians spent $1.7 billion dollars online in December 2017

Online retail sales accounted for 3.4 per cent of total retail sales

2-year investigations nets $900,000 in refunds for payday loan customers

Consumer Protection BC says selling practices were ‘aggressive and deceptive’

China: Canada’s detention of Huawei exec ‘vile in nature’

Huawei is the biggest global supplier of network gear for phone and internet company

Most Read