On Aug. 4, 2014, a tailings dam breach at the Mount Polley mine in B.C.’s Interior flooded the local watershed with contaminated water and debris. 

The faulty dam released 25 billion litres of water mixed with mining waste — enough to fill about 10,000 Olympic swimming pools — into Polley Lake, Hazeltine Creek and Quesnel Lake. Contaminants included 134.1 tonnes of lead, 2.8 tonnes of cadmium and 2.1 tonnes of arsenic, according to a national inventory of harmful substances released into the environment. 

It was, and still is, the worst mine waste disaster in Canadian history.

Ten years later, here are five things you should know about the Mount Polley mine and Imperial Metals, the company that owns it.

Metals from the 2014 tailings dam breach are still detectable in Quesnel Lake

About 19 billion litres of toxic sludge poured into Quesnel Lake, the deepest lake in the province. The heavier elements eventually settled over six kilometres of lake bed in a waste plume up to two kilometres wide and up to 10 metres deep.

A decade later, tailings debris still coats the bottom of Quesnel Lake. Seasonal currents stir the material back up into the lakewater that flows out into the Quesnel River, a major tributary of the Fraser River.

“The fact that 10 years on we still see sediment enriched in copper coming out of the lake is quite amazing,” researcher Phil Owens told The Narwhal.

Owens and his colleague Ellen Petticrew are both research chairs at the Quesnel River Research Centre and professors at the University of Northern British Columbia. They have detected higher-than-usual concentrations of metal in zooplankton, a food source for local fish including lake trout and sockeye salmon. 

And the pair didn’t just find those metals in Quesnel Lake. 

Water samples collected from lower Hazeltine Creek also contained high levels of metals, including copper, which can disrupt the migration of fish like salmon and make them more susceptible to disease.

“We don’t know where that’s coming from,” Owens, who teaches environmental science, said. 

“There’s a problem somewhere and they don’t seem to be willing to deal with it,” Petticrew, a geography professor, added. “While they [Imperial Metals] say that they’re finished remediation, it’s not fixed.”

Imperial Metals never faced fines or legal repercussions for the disaster

An expert report commissioned by the B.C. government found the Mount Polley dam breach was the result of poor design that failed to account for a weak glacial silt layer underneath the tailings facility.

Eventually, the unstable ground underneath the tailings dam caused it to shift and shear, resulting in the breach, the 2015 report concluded.

Imperial Metals reports paying $70 million to clean up the spill and remediate Hazeltine Creek. 

But the company has never been fined or faced legal repercussions for the tailings dam failure — and B.C. taxpayers covered $40 million in cleanup costs.

Mount Polley is still operating and dumping wastewater into Quesnel Lake

Imperial Metals didn’t wait very long after the breach to restart mine operations. In 2017, the B.C. Ministry of Environment and Climate Change Strategy granted the company a permit to discharge wastewater into the fish-bearing Quesnel Lake. 

“Their water treatment only removes solids. It does not remove any of the dissolved chemicals, like nutrients and metals,” Doug Watt, who lives on the shores of Quesnel Lake and used to work at the mine, told The Narwhal. “They’re still dumping that into the lake.”

In December 2020, the provincial Environment Ministry issued a $9,000 administrative penalty to Imperial Metals for failing to investigate and test long-term water treatment systems at the mine in accordance with its permit. The company tried to have the fine reduced, an attempt rejected by B.C.’s Environmental Appeal Board in September 2021.

One year later, in 2022, Imperial Metals re-launched gold and copper mining operations at Mount Polley, which employs about 350 people. 

Imperial Metals now wants to extend the height of the same tailings dam

Imperial Metals is now seeking to expand the Mount Polley mine pit. The company wants to extend the same tailings pond dam by another four metres and continue discharging wastewater into Quesnel Lake. 

Notice of the public consultation period for the company’s application for the proposed tailings dam expansion is expected to go out by mid-August, according to an email from the B.C. Mines Ministry.

Imperial Metals under-reported emissions, inspections uncovered compliance issues

The B.C. Environment Ministry says it conducted 14 inspections of the mine since 2017 and issued five notices of compliance, five advisories and three warnings, as well as the 2020 monetary penalty. The ministry’s most recent Mount Polley inspection took place in 2021; a ministry spokesperson said the mine is scheduled for reinspection this year. 

According to a database of compliance and enforcement actions against natural resource companies, the ministry’s December 2021 review of the mine’s annual environmental and reclamation report found key information was missing. 

A January 2024 inspection to determine if Imperial Metals was obeying provincial greenhouse gas reporting rules found the company had under-reported its emissions by more than 6,600 tonnes and failed to have its figures verified by a third party, as required. The company subsequently corrected its reporting, the Environment Ministry said.

In its email responding to questions from The Narwhal, the Mines Ministry said officials have conducted five inspections at the Mount Polley mine since April 1. Those inspections resulted in a warning for improperly storing aerosol cans, an advisory about the potential need for a permit amendment and requests for more information about the tailings storage and dam, according to the ministry.

The Mines Ministry said it plans to conduct “a minimum of 12 inspections” at Mount Polley in the 2024-2025 fiscal year.

Updated on Aug. 1 at 3:15 p.m. PT: This story has been updated to add that B.C. taxpayers paid $40 million in clean-up costs following the Mount Polley dam breach.

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