Richard Gleeson
Northern News Services

Yellowknife (May 10/00) - Air quality in the city may be showing significant signs of improvement but it will take much longer for water in some city lakes to recover.

Last year, a study of water in city lakes by the Royal Military College showed arsenic levels were well above national drinking water standards. Signs were posted at Frame Lake, Rat Lake and Kam Lake cautioning people not to swim or drink the water from the lakes.

It will be awhile before the signs come down, said Brad Colpitts of Stanton environmental health services.

"Part of the thing that's driving it is the sediment. If you're going to improve arsenic levels in the water, you have to do something with the sediment. Which means you've got to do something serious with the lake."

It is believed the elevated arsenic levels in Rat Lake and Kam Lake are caused by mine tailings that may have been dumped into the lakes back in the 1930s and '40s.

"Otherwise, I guess you could speculate it's a combination of naturally-occurring arsenic in the environment, which is associated with the gold, and the aerial deposition from stacks," said Colpitts. "Years ago Con also had a similar kind of process that released arsenic through a stack."

The elevated levels are nothing to be alarmed about, Colpitts said.

"It's purely precautionary. People can still canoe and even fish. Fish are unaffected by the arsenic. Even if you fell in it wouldn't be something to be concerned about."

With Giant mine operating on its shores, Back Bay is also a big concern to many residents who use Great Slave Lake.

As part of its cleanup of Giant mine, the Department of Indian Affairs and Northern Development drilled through the ice over the winter. The drilling was done to determine if tailings had eroded from shore into the lake.

But the results of that testing is not yet available. And at a cost of $500 per sample for analysis, monitoring of water quality in Back Bay is not an ongoing process.

The last study of water quality in Back Bay was completed in 1996.

"A reminder to the public, if the water in Yellowknife-Back Bay area is going to be used for consumption, the water must be treated prior to use to kill or remove pathogenic organisms," the report concluded.

The study also indicated Back Bay and Yellowknife Bay are safe to swim in, if you can stand their cold temperatures.

Though perched on its shores, the city does not rely on Great Slave Lake for its drinking water. The water that comes out of your tap is piped to town from the Yellowknife River.