British Columbia

Ecological impact of Mount Polley mine disaster confirmed by new study

Newly published research shows a higher concentration of copper and other heavy metals in freshwater scuds and mayfly larvae taken from Polley and Quesnel lakes.

Research shows higher levels of metals in invertebrates taken from Polley and Quesnel lakes

A restricted access warning sign at the Mount Polley spill remediation work site near Quesnel Lake in August 2021. (Betsy Trumpener/CBC)

A newly published scientific study confirms the deep ecological impact of the Mount Polley mine disaster in B.C.'s Cariboo region nearly eight years ago. 

The study, published last week in the academic journal Environmental Science and Pollution Research, shows small invertebrates taken from lake water affected by the tailings spill disaster had a higher concentration of copper and other metals than those taken from unaffected lake water. 

In the summer of 2018, University of Lethbridge biology professor Greg Pyle and his colleagues sampled freshwater scuds, which are shrimp-like crustaceans, and mayfly larvae, which are aquatic anthropod insects, taken from Polley and Quesnel lakes, both located near the Mount Polley mine. They also sampled the animals from nearby Little Lake, which was not directly affected by the toxic waste. 

Both freshwater scuds and mayfly larvae live on sediments and are considered important food sources for fish. 

Pyle, who has been studying the environmental impact of the Mount Polley mine disaster with the B.C. government and the University of Northern B.C. (UNBC) for years, says he's concerned about how the pollution may impact commercial fisheries operating on Quesnel Lake.

"When you exceed the nutrient requirement for copper, copper becomes very toxic to aquatic organisms, so it affects the animal's growth and survival in the system," he said.

Greg Pyle's research team sampled freshwater scuds and mayfly larvae from Polly and Quesnel lakes as the experimental group, and those from Little Lake as the control group. (Environmental Science and Pollution Research)

Pyle says the heavy metals will stay in the lake water forever unless they are flushed out or transported elsewhere, but doing so may worsen the water contamination.

"You have to understand the Mount Polley mine disaster was a massive disaster … and it would be an impossible task to try to dredge up that material," he said.

In August 2014, more than 17 million cubic metres of water and eight million cubic metres of tailings effluent, containing toxic gold mining waste, flowed into Polley and Quesnel lakes as well as Hazeltine Creek, which served as a drinking water source and sockeye salmon spawning ground.

After seven years of investigation, the professional regulatory and licensing body Engineers and Geoscientists B.C. concluded disciplinary actions on three engineers who were responsible for the failure of the tailings dam that was built on a sloped glacial lake.

study done by UNBC two years ago said the mine tailings spill will continue to affect nearby waterways in years to come.

On Aug. 4, 2014, a four-square-kilometre tailings pond breached, leaking millions of cubic metres of water and effluent into Polley and Quesnel lakes and Hazeltine Creek.

Pyle says his next step is to study how contaminants are transferred from invertebrates to fish, and he hopes research projects like his could help raise awareness about mining pollution.

"Rather than turning our backs on mine disasters, we should be doing everything we can to learn from them, so that we make sure that when these events happen again, we're prepared for it and we know how to remediate it effectively," he said. 

CBC requested comment from Imperial Metals, the company that owns the Mount Polley mine, but did not receive a response by the time of publication. 

With files from Jenifer Norwell, Betsy Trumpener and Yvette Brend