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Mt. Polley dam spill indicates environmental effects

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Mt. Polley dam spill indicates environmental effects

Highlights

 

Six years after the Mount Polley gold and copper mine dam collapse sent millions of cubic metres of tailings into Quesnel Lake, academic research shows there are effects on the lake environment.

Studies by researchers at the University of B.C., the University of Northern B.C., the University of Alberta and the University of Lethbridge found changes in the bacteria in the lake bottom where the mine waste was deposited, increased seasonal cloudiness in the lake and copper that is getting into organisms that live at the bottom of the lake.

First Nations, lake residents and environmentalists have been concerned about the long-term effects of the catastrophic dam collapse, one of the worst mine spills in Canada in 50 years.

But to determine whether the spill will cause long-term harm to the lake, to the bacteria that live in the lake bottom, to the shrimp-like freshwater scud that live just above the surface of the mine tailings material deposited on the lake bottom and to trout or salmon, will need more research, say scientists.

Ellen Petticrew, a UNBC ecologist, said that while there is evidence copper and other metals are getting into the lower levels of the food web, “we don’t really know what that means for the longer term impacts for the resident trout and the migratory salmon.”

Imperial Metals, the Vancouver-based company that owns the now-closed open-pit gold and copper mine, has a different position on the effects of the spill on the environment.

The company says studies undertaken on the effects of the spill by its engineering consultants, which includes work by Golder Associates, concluded the effects of the failure were primarily physical and not chemical.

“Mount Polley tailings have been determined to have very low risk for chronic toxicity and are not acutely toxic. No chemical toxicity risks to aquatic or terrestrial wildlife or to humans have been identified from the tailings,”

Imperial Metals, CEO Brian Kynoch said in an email.

Imperial Metals has spent $71 million on remediation.

When the dam collapsed on Aug. 4, tailings — the ground-up rock remaining after the milling process and containing potentially toxic metals — was dumped into the environment along with water.

The spill scoured nine kilometres of Hazeltine Creek.

An estimated 12.8 million cubic metres of tailings (enough to fill 5,100 Olympic-sized pools) was deposited in Quesnel Lake along with natural soil stripped by the torrent. The covered area measured about 5.5 kilometres wide and up to 1.2 kilometres across the West Basin of Quesnel Lake, according to company and academic reports.

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The deposited material runs from one metre to more than 10 metres deep.

The most recent academic study, published in June in the journal Water Resources Research by scientists from UBC, UNBC and the University of Alberta, found each year since the spill, the turbidity, or cloudiness, of the lake has increased in the spring and autumn during lake turnover, apparently caused by spilled material being lifted off the lake bottom by wave movements.

The findings, and the continued discharge of mine waste water directly into the lake, raises concerns over the seasonal movement of mine contaminants and their effect on aquatic ecosystems, concluded the study.

Petticrew and a UNBC colleague, ecologist Phil Owens, both of whom helped write the study, say more research will be needed to determine the effects of this seasonal turbidity.

They said they’ve been told by Imperial Metals the company plans to write a rebuttal to their findings.

University of Lethbridge researchers expect to soon publish a study on the tiny aquatic creatures, such as the shrimp-like freshwater scud and Mayfly larvae, which live just above the sediment layer at the bottom of the lake.

Imperial Metals has long said the tailings is relatively benign and would not produce acid that would release heavy metals into the environment, including in the lake water.

While the rock that has been milled in the Mount Polley mine does contain acid-generating pyrite, the acid-generating potential is neutralized by the significant amount of carbonate in the rock, company officials said following the spill in 2014.

Company officials likened it to having a whole box of the antacid Tums to neutralize stomach acid.

Greg Pyle, a University of Lethbridge biologist, doesn’t disagree with that assertion, but says his team’s research shows there may be another mechanism in which aquatic creatures living at the surface of the tailings deposited at the lake bottom take up copper.

He says copper is likely getting into the organisms from the sediments — allowing digestive acids to liberate the copper — and not through the water in the lake.

Copper is a nutrient but it is also toxic at high levels, said Pyle, who specializes in the effect of environmental contaminants on aquatic animals.

More research will be needed to determine the broader implications, which Pyle said he hopes will start in the fall.

“It’s a beautiful lake to look at from the shore. But what is happening on the shore is not necessarily what is happening in the water column,” he observed.

Pyle and others, including Petticrew and Owens at UNBC, are collaborating on research and have received about $1 million from the federal government’s environmental damages fund. Other money has come from the universities themselves. The scientists will need more money to continue their research and have made another application to the federal environmental damages fund.

Federal Fisheries and Ocean scientists have also been involved in some research, but few details were available. For example, Fisheries scientists were involved in the turbidity research. Federal fisheries scientists and the department’s communications office did not respond to Postmedia’s request for information.

In response to Postmedia questions, the B.C. Ministry of Environment said it was involved in sampling of water and nutrients in Quesnel Lake, but did not respond to a question on whether it was involved in scientific research of the effects of the spill.

Christine McLean, who has a home on the lake and is an organizer with Concerned Citizens of Quesnel Lake, said the peer-reviewed research that is beginning to be published is an important development and welcome.

“This is bona fide research … We consider it an unbiased view of what is going on,” said McLean.

 

Originally published by Prince George Citizen.


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