YELLOWKNIFE
A scientist two years into a three-year study of metals in Yellowknife Bay says the data studied so far indicates water from the bay is safe to drink.

A scientist in the second year of a three-year study looking at lake bed core samples and water column samples from Yellowknife Bay said dissolved arsenic levels in surface samples taken from the bay are below safe drinking water guidelines. - Walter Strong/NNSL photo

John Chetelat - a researcher for Environment and Climate Change Canada - said his team hasn't finished analyzing findings from the lake bed but he can report findings related to dissolved arsenic in the water from surface to sediment.

"At the north end of Yellowknife Bay toward Giant Mine, in general it's about 2 to 3 micrograms per litre," said Chetelat. "And that is below drinking water guidelines, which is 10 micrograms."

He said about 10 people from different organizations are collaborating on the project.

"We're partnering with several organizations including the Yellowknives Dene First Nation (YKDFN), the (territorial government) and several universities from the south," he said, adding in an e-mail that he also met with Chris Greencorn, the city's director of public works, to update him on his findings during the NWT Geoscience Forum in November.

In September, Greencorn told reporters he believes drawing water from Yellowknife Bay makes more sense than replacing the eight-kilometre water pipeline to the Yellowknife River in 2020 - at a cost of around $20 million. The water treatment plant has a room set aside for arsenic-filtration equipment, which is pegged at around $5 million to install.

When proposed in the past, drawing water from the bay was met with stiff opposition from city residents worried about arsenic.

Greencorn could not be reached for comment before press time.

Chetelat said arsenic particles in surface samples from the bay are dissolved.

"It's mainly inorganic arsenic. There are two forms of inorganic arsenic - arsenate and arsenite - and this is mainly the arsenate," he said.

"Arsenate is generally considered to be a more benign form; arsenite is considered to be more toxic. However, you also have to consider the levels - it's not just the type of arsenic. And the levels we're seeing in the surface waters are relatively low in Yellowknife Bay."

He said what he is finding is that the greatest inputs of metals in the bay occurred in the earliest years of mining operation, when there were few pollution controls in place.

"But we're seeing that many metals such as zinc, lead, antimony and copper, they are returning to near baseline conditions in the younger surface sediment due to burial over time," he said.

However, arsenic in the sediment is behaving differently, said Chetelat. He doesn't have the final numbers yet but the team is clearly seeing a higher concentration of dissolved arsenic closer to the surface of the lake sediment.

Some of the arsenic deposited in the sediment during the earliest years of mining operation seems to be dissolving and bubbling toward the surface. So peak concentrations of arsenic are in the younger surface layers even though much of that arsenic was deposited a long time ago, said Chetelat.

Chetelat said he told Greencorn - during their November meeting - he'll be providing the city, the Department of Environment and Natural Resources as well as YKDFN with complete findings of the report when it's finished next year.

It couldn't be determined by press time what the city intends to do with the findings.

Joanne Black, community liaison for the Yellowknives Dene First Nation, could not be reached for comment by press time.

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