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Quesnel Lake scrutiny continues years after B.C.’s Mount Polley mine breach

Nearly a decade later, scientists monitor effects of 18 million cubic metres of copper mine sediment

Since before the Mount Polley Mine tailings breach in 2014, Quesnel River Research Centre (QRRC) has been studying the Quesnel River watershed and its aquatic environment.

QRRC presented some of their work at a recent open house for the community in Likely, on Sept. 30. In addition, researchers Dr. Phil Owens and Dr. Ellen Petticrew both spoke at a presentation for the Department of Geography, Earth & Environmental Sciences at UNBC on Oct. 13.

Their Oct. 13 presentation included images showing the stark differences between Hazeltine Creek before the breach of the tailings facility at Mount Polley and after. This area was the direct pathway for the tailings which flowed from a breach in the mine’s tailings facility.

The 2014 event saw about 25 million cubic metres of tailings released from the facility. These tailings, along with the forest in its path, travelled down along Hazeltine Creek, towards Quesnel Lake.

Of that 25 million, over 18 million cubic metres of tailings made it to Quesnel Lake.

This massive influx of tailings created a measurable impact on the water level of the entire lake, one of the deepest fjord lakes in the world, and the deposited tailings sediment in the west basin of Quesnel Lake has been measured to be between five and 10 metres deep on the lake bottom.

Interestingly, for several weeks after the spill, sediment was actually flowing up lake, before then flowing down the lake towards the Quesnel River.

The work of the QRRC continues to monitor for changes in the aquatic environment as a result of the tailings facility breach.

One of the things QRRC is looking for are changes in some chemistry related to the tailings and seeing if the harmful elements in the tailings are being flushed down the Quesnel River system, are remaining inert on the bottom of the lake itself, or bioavailable — that is they can be taken up into the food web.

QRRC research has shown levels of copper have been going down. Copper is toxic at high levels in the aquatic environment and can potentially impact behaviour in organisms and may inhibit salmon’s ability to find their way back to home streams to spawn. Concentrations of phosphorus have also been going down since the spill.

However, some of what has been observed so far includes a resuspension of the tailings sediment, leading to higher levels of these elements, during times of lake turnover. Turnover occurs when the stratified levels of the lake caused by temperature differences between the surface and the deeper levels breaks down as the surface and deep water reach similar temperatures.

During the summer and winter months, distinct layers caused by very different temperatures prevent the upper waters of the lake from mixing with the lower levels. As the “thermocline” temperature gradients breaks down, these layers are able to mix and deep water can come to the surface and vice versa.

In the first year they were able to very clearly observe an increase in sediment coming to the surface due to an obvious change in colour of the lake in the west basin.

Though this raises concerns about the potential for longer-term impacts of the tailings sediment, the good news of their research so far is the spill effect doesn’t appear to be getting into the lower reaches of the Quesnel River, which then flows into the Fraser River. Through the resuspension in the fall, there is, however, an annual pulse of copper into the river.

Higher levels of phosphorus have also been found after the spill, which has implications for the aquatic ecosystem, as phosphorus is associated with higher algae growth and can impact the quality of habitat for some species of fish, including salmonid species.

Their research has also shown elevated levels of sediment copper coming in from Hazeltine Creek in 2022, despite the concerted efforts made to rehabilitate this creek and remove the tailings sediment. With a pre-spill background level of around 100 mg of copper per kilogram of suspended sediment, researchers have measured amounts five to nine times this at different times in Hazeltine Creek.

No clear reason for the influx has yet been provided, said the researchers.

Their research has also indicated a bioaccumulation of copper in the spring, which the researchers said could be due to the sediment upwelling during seasonal lake turnover.

Don Parsons, chief compliance officer with Imperial Metals, said the mine does regular, widespread, and frequent monitoring, which it shares in regular reports. He said biological monitoring has shown successful plant and animal life in the remediated Hazeltine Creek.

The remediation work on Hazeltine Creek and Edney Creek was recognized by the BC Technical and Research Committee on Reclamation. Mount Polley Mine and the Habitat Remediation Working Group were awarded the Jake McDonald Annual Mine Reclamation Award in 2023.

The QRRC researchers are utilizing a number of different study methods, and have had a number of projects ongoing and have drawn on previous research done in the area to compile their current findings.

While the QRRC will continue to monitor for changes, their facility will also be collaborating on research on salmon eggs and survival in a project funded by Natural Resources Canada.

The project will be in partnership with Queen’s University, Environment and Climate Change Canada, and the University of Ottawa. Their facility will be able to host separate closed experiments to look at survival of salmon eggs after bitumen spills.

Another project with UBC, UNBC and Fisheries and Oceans Canada will be looking at climate change impacts on salmon looking at climate-induced stressors in the Quesnel River watershed, which includes the Horsefly River.

Dr. Owens said the QRRC does not sample salmon but their research can look instead at the health of the aquatic environment.

Logging, wildfires in the area, mine-related impacts and other stressors are considered concerning in terms of their cumulative effects.

READ MORE: Quesnel River Research Centre hosts open house for Cariboo area

READ MORE:Mount Polley Mine effluent permit extended for discharge into Quesnel Lake

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Ruth Lloyd

About the Author: Ruth Lloyd

I moved back to my hometown of Williams Lake after living away and joined the amazing team at the Williams Lake Tribune in 2021.
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