Lake near Giant Mine will never recover from contamination, new research shows

Arsenic trioxide spewed from Giant Mine has done irreversible damage to the ecosystem of a nearby lake and continues to seep from the soil into water systems, according to a new study.

The research was published by scientists from the University of Ottawa and Queen's University.

They looked atareas within a 15 kilometre radius ofthe mine's roaster stack, and specifically atPocket Lake, which is one kilometre west of the stack.

"We consider this the ground zero of impact for the mine," says Jules Blais, who directed the research."We selected [the lake]because it would have received a maximum impact of emissions from the roaster stack."

The N.W.T.'s Giant Mine operated between1948 and 2004. When the gold mine closed, 237,000 tonnes of arsenic trioxide was left behind in underground chambers.

Blais and his team looked specifically at lake sediment deposits before the mine was built and while the mine was operating.

"We could see how the contamination changed over time," he says.

The team found that before the mine was built, the levels of arsenic trioxide were low, butincreased by 1,700 per cent when emissions were at their peakin the late 1950s and early 1960s.

Crustacea wiped out

Blais says the contamination in the lake was so high it wiped out the crustaceans that lived there. Crustacea,like small shrimps and crabs,are a valuable part of an aquatic ecosystem, providingfood for fish and other aquatic life.

Despite contamination levels dropping in recent years, the lake's ecosystem has not recoveredand the crustaceans have never returned.

"It's a striking result," says Blais."Becausewe have done similar studies in other mining areas, and we did not see such dramatic effects to the aquatic ecosystems."

Emissioncontrols at the mine only happened after 1958. Duringthe first 10years the mine operated, the arsenic from the roaster stack was airborne and settled to the ground 20,000tonnes of it.

"So here we are, about 50years after the major contamination happened and that arsenic is still in soils, and it's slowly leaching from soil to water," says Blais.

"This is part of the reason why some of the lakes in the area are still showing noticeably higher levels of arsenic."

Water systems safe

Blaisdoesn't believethe arsenic isa hazard to people, though. He thinksdrinking water from the tap is safe, and municipal water systems are safe.

He admitsthere are some lakes he'd avoid drinkingfrom, but he says they'resmall and isolated to the northwest of the roaster, where people don't typically go.

Blais says the research has revealedsome important takeaways.

"Ifwe start mucking up the environment,over long-term, we will be faced with longer term costs," he says.

Blais says the territory could continue to seehigher arsenic inlakes for many decades to come.