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.

 

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

COLUMN: Diminished Parliament means diminished accountability for Canadians

Bloc Quebecois and NDP use resumption of parliament as bargaining chip

Penticton Farmers Market prepares for return

The weekly market was put on-hold for months due to COVID-19

No injuries in Penticton Indian Band structure fire

The structure, which sustained significant damage, was boarded up and seemingly vacant

B.C. legislature coming back June 22 as COVID-19 emergency hits record

Pandemic restrictions now longer than 2017 wildfire emergency

Central Okanagan schools ready to welcome students back

Students are set to go back to school next Monday, June 1

Houseboat company partly owned by Shuswap MLA withdraws controversial ad

The ad welcomed houseboaters from other provinces, contradicting anti COVID-19 measures.

Squabble between campers in North Shuswap leads to bear spraying

An argument over late night partying escalated into a fight which led to one person being sprayed

B.C.’s essential grocery, hardware store employees should get pandemic pay: retail group

Only B.C.’s social, health and corrections workers are eligible for top-ups

Edmonton, Vancouver and Toronto vying to be NHL hubs, but there’s a catch

The NHL unveiled a return-to-play plan that would feature 24 teams

B.C. sees 9 new COVID-19 cases, one death as officials watch for new cases amid Phase Two

Number of confirmed active cases is at 244, with 37 people in hospital

Penticton may soon allow drinking alcohol in some public places

Trying to inconspicuously drink on the beach could become a thing of the past

VIDEO: Flowers stolen from Vernon distillery

Okanagan Spirits Craft Distillery captured surveillance footage of the thief in a black car

Most Read