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Aerial view of Mount Polley tailings facility. The mine has received clearance to resume full operations, almost two years after one of the worst environmental accidents in Canada's history of mining.

Almost two years after one of Canada's worst environmental mining accidents, the Mount Polley mine is resuming full operations with a repaired and reinforced tailings pond dam.

B.C. Mines Minister Bill Bennett said Thursday he is confident that the conditions that led to the failure of the dam have been addressed, even though the long-term water-management plan at the copper and gold mine near Williams Lake has not yet been finalized.

"I know it is going to be welcome news for all the families that depend on those jobs," he said.

On Aug. 4, 2014, the tailings pond at Mount Polley breached, spilling approximately 25 million cubic metres of waste water and tailings into nearby water systems and lakes in central British Columbia. The facility is located near Quesnel Lake, nearly 400 kilometres northeast of Vancouver.

An expert panel concluded the catastrophic failure of the dam was a preventable accident. The design of the dam failed to address the unstable foundation of glacial silt below, a flaw that was compounded over the many years that the dam was repeatedly raised to accommodate a growing lake of toxic waste.

The initial dam was completed in 1997, and almost every year, the operators added to its height. As the load increased, that unstable foundation became weaker. Compounding the problem, in 2006, the operator ran out of rock fill, the material it used in construction.

To compensate, it changed the slope of the dam to a steeper angle – an interim measure that was never corrected.

Mr. Bennett told reporters a thorough geotechnical review has shown the repairs now meet appropriate engineering standards.

"Because no one knew this unstable layer of materials was under the perimeter embankment, everyone involved in this – the company, the regulator, the engineers – all thought what was designed and built there was appropriate," he said. "Obviously, the margin of safety was too narrow. Our approach now has to be to widen that margin of safety."

The mine resumed partial operations last summer using a different storage facility for the tailings. The Mines Minister said the decision was made to award the permit to resume full operations now, without waiting for the long-term water management plan, to keep workers on the job.

"They are out of ore and they would have to send people home over the next week," he said. A draft water plan must be submitted by the end of June, and a final decision by the ministry is expected at the end of the year.

Steve Robertson, spokesman for Imperial Metals, said the operation was due to shut down June 26 if the conditions of their permit were not altered. It will take less than two days to switch to full production and that means no layoffs for the 346 employees at the mine.

Imperial Metals has spent more than $70-million on remediation and restoration efforts. That includes the cost of planting more than 30,000 trees and shrubs over 16 hectares in the Hazeltine Creek area, the ministry says. The company is expected to continue remediation work on Polley Lake, Hazeltine Creek, Edney Creek and Quesnel Lake at least until the end of the year.

In the immediate aftermath of the spill, residents in the region faced a drinking-water ban. That ban was lifted after nine days, although concerns remain in the region about the long-term impact on fish and wildlife.

The damage to the mining sector and to the provincial government has been substantial. The mining sector now faces tougher safety rules, more oversight and stiffer penalties for pollution.

Still, the government's regulatory regime for the mining sector has been called into question. In a blistering report in May, Auditor-General Carol Bellringer concluded the province's management of the mining industry is failing to protect the environment against significant risk, due to too few resources, infrequent inspections and a lack of enforcement.

Ms. Bellringer found the ministry's economic interest in boosting the sector created a conflict because the ministry's role in promoting mining development is "diametrically opposed to compliance and enforcement."

Mr. Bennett said he expects some people will have lost trust in the ministry's ability to protect the environment. "There will be some who will question whether government has done a good enough job," he said. "We have done all the things the experts thought should be done."

The one major outstanding issue now is whether any charges will be laid as a result of the disaster. An investigation led by the B.C. Conservation Officer Service is ongoing.