Environmental Science undergraduate student Jingyu Chen uses a multiprobe instrument to collect information on water column properties of Quesnel Lake (photo courtesy UNBC Geography student Tyler Halverson).

By Veronica Beltran

Quesnel Lake sediment

Resuspended contaminants from Mount Polley spill continue to impact Quesnel Lake

Aug 13, 2020 | 10:48 AM

PRINCE GEORGE—A UNBC geography professor is at the head of a multi-year research project into the natural mixing of lake waters and how they may be resuspending possibly harmful contaminants deposited in Quesnel Lake by the Mount Polley mine spill.

The paper, published recently in, Water Resources Research, found that turbidity—cloudiness— in parts of B.C.’s Quesnel Lake increase each spring and fall, when the lake mixes from top to bottom in a natural process called turnover.

“During the first turnover after the spill, mixing brought suspended sediment to the surface, turning the previous clear-blue lake to bright green. Twelve months after the spill, the suspended sediment loads had substantially reduced, and the lake waters had appeared to return to their pre-spill state—but it turns out this was only temporary.”—Andrew Hamilton, researcher, UBC and University of Alberta

According to the paper, the source of the turbidity comes from the resuspension of spill-related material from the bottom of the lake, which raises concerns about contaminants being reintroduced to the water column.

“We have seen a seasonal increase in some metal concentrations in the Quesnel River that corresponds to the timing of the turbidity increase observed in the lake,” says Dr. Ellen Petticrew, a UNBC geography professor, who is leading the research.

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“This paper explains some of these other processes we are observing, and helps build a more complete understanding of the long-term impact of the spill on the lake.”—Dr. Ellen Petticrew, UNBC geography professor

The study presents results from 2014 through 2017 in which Hamilton says that they saw sediment mixed from a depth below 100 metres over the whole water column.

The Mount Polley mine spill was the largest mine-related spill ever documented at the time, dumping 18 million cubic metres of waste water and sediment into Quesnel Lake. Hamilton also adds that the tailings contain elevated concentrations of some metals such as, copper, and if the metals are being resuspended, seasonally, they could potentially make their way into our food chain.

“Understanding all factors affecting the long-term water quality of Quesnel Lake is critical as its watershed supports substantial recreation, trout fisheries and Fraser River Pacific salmon stocks that are vital to Indigenous, recreational and commercial fisheries.”—Andrew Hamilton, researcher, UBC and University of Alberta

“Inevitably these spills end up flowing downstream into lakes or the ocean where they can disappear from view, yet that doesn’t mean the impact is over,” says Hamilton.