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

Most Victoria transit takers thank their driver: poll

Bus riders thank drivers on Transit Driver Appreciation Day

Victoria doctor forced into early retirement as specialist moves into rental space

General practitioner says he can’t afford rising rents, even amidst doctor shortage

Volunteer needed to empty dog poop can in Saanich Park

Local volunteers do the work of irresponsible dog owners at Mount Doug

Saanich mayor to ask CRD to study on uniting region’s fire dispatch

Haynes floats centralizing CRD fire dispatch at South Island E-Comm

Sexual assault charge dropped against former CFB Esquimalt member

Navy Lt. Ronald Clancy was charged with two counts of sexual assault in August 2018

VIDEO: RCMP ask kids to help name soon-to-be police dogs

13 German shepherd puppies will be born this year

BC Ferries has no plans to implement debit for vehicle ticket payments

Debit accepted for foot passengers, on-board purchases for all vessels

‘The whole city has changed:’ B.C. woman in New Zealand reacts to mosque attacks

An expatriate and Muslim students at UBC Okanagan deeply affected by white supremacist shooting

Trudeau condemns hateful, ‘toxic segments’ of society after New Zealand shooting

Prime Minister expressed sorrow at the many attacks in recent years

Air Canada grounds its Boeing Max 8s until at least July 1 to provide certainty

Airlines around the world have been working to redeploy their fleets since their Max 8s were grounded last week

Budget to tout Liberal economic record, provide distraction from SNC furor

This is the Liberal government’s fourth and final budget before the election

Horvat scores 16 seconds into OT as Canucks beat Blackhawks 3-2

Pettersson sets rookie scoring record for Vancouver

No injuries, pollution in Vancouver Harbour ship collision: Transport Canada

Transportation Safety Board says it has deployed a team of investigators look into the incident

Budget 2019: Five things to watch for in the Liberals’ final fiscal blueprint

Finance Minister Bill Morneau will release the Trudeau government’s final budget on Tuesday

Most Read