Contamination from Mount Polley spill continues to affect waterways, study finds

The Mount Polley mine tailings spill that sent more than 24 million cubic metres of mine waste into nearby waterways in 2014 continues to impact lakes, rivers and aquatic ecosystems, according to a new study.

Researchers have been monitoring Quesnel Lake since the spill, which is considered one of the largest environmental mining disasters in Canadian history.

Though samples taken one year after the spill showed the lake waters had potentially returned to their pre-spill state, new information from a three-year study reveals that is not the case; elevated levels of copper and fine sediment have been found in the lake in both the spring and fall. 

Turbidity in parts of the lake increases each spring and fall as it mixes up, bringing sediment up from the lake bottom turning the clear-blue lake green in a natural process called turnover, according to lead researcher Ellen Petticrew.

She said this raises concerns about contaminants being reintroduced into the water column.

It is unknown what effects those toxic sediments will have on the ecology of the lake; if these metals are being seasonally re-mobilized from the lake bed they could make their way into the food web, said researcher Andrew Hamilton. 

The research team said chronic exposure to elevated copper concentrations can reduce the growth, reproduction and survival of fish populations. Small changes to the colour and clarity of a lake can alter algal communities.

"Copper for aquatic organisms can be, not just toxic, but also has been found to modify some of the ability for organisms to move," said Petticrew.

Quesnel Lake flows into the Fraser River and ultimately into the Pacific Ocean. The state of the water in the lake could impact trout fisheries and Fraser River Pacific salmon stocks.

"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," said Hamilton.

Although the research team has run out of funding, Petticrew said it will continue to monitor the site. 

Phil Owens, another researcher on the project and a professor of environmental science at UNBC, said this project will help inform what happens with future environmental incidents.

"I think we need to understand what the environmental implications are when a catastrophic incident like this occurs, so that when other ones occur in the future … we have a much better understanding of what the implications are likely to be to aquatic systems."