SOMBA K'E/YELLOWKNIFE - A naturally forming ice dam caused water in Baker Creek to overflow into a tailings pond near the Vee Lake turnoff last weekend, and now the water is draining back into the creek, which leads to Back Bay.

Dettah Chief Ed Sangris points toward Baker Creek, past Giant Mine, Wednesday. Water from the creek started overflowing into a tailings pond last weekend, which Sangris worries could be contaminated with deadly arsenic trioxide. That water is now draining back into the creek and into Great Slave Lake. - Ian Vaydik/NNSL photo

Dettah Chief Ed Sangris said a mishap like this is proof the city shouldn't move its water source downstream to Yellowknife Bay from the Yellowknife River, as it is proposing right now.

"You know how the city talk about switching the water intake from the river to the bay, well if the mayor's not careful, he's going to kill everybody in Yellowknife because stuff like this goes on," Sangris said, pointing towards the 237,000 tonnes of deadly arsenic trioxide - a byproduct from decades of roasting gold ore at Giant Mine through which the creek runs - stored underground.

"It's going to affect everybody's life, not only the First Nations."

As of noon Wednesday, the overflowing water had been diverted back into its channel and away from the tailings pond, located at the back of Baker Pond, said Henry Westermann, director of the Giant Mine project for Public Works and Government Services Canada.

Mayor Gord Van Tighem said the overflowing creek is no reason to write off Yellowknife Bay as a drinking water source.

"I think it's more an indication that there are people putting safeguards in place to ensure that doesn't become a problem and they responded immediately and that's why they're there."

Westermann said when the water diverted into the tailings pond, it picked up sediment that then flowed into Back Bay.

Public Works Canada couldn't say what was in the water or the tailings pond because it's currently being tested.

Water samples that were expected back from the lab Thursday afternoon have been taken throughout the creek, said Westermann.

"When we get the results we'll be working again with the regulatory departments to assess what actually entered into the stream and into Back Bay," he said Thursday morning.

Westermann said the breach is a concern, but he doesn't think it's a public health or safety risk.

Changing the city's water source to Yellowknife Bay, which encompasses Back Bay, would require the city to install an arsenic treatment system in the water treatment plant set to be built for about $18 million next year.

The city wants to change its drinking water source to Yellowknife Bay because the eight-km-long underwater pipeline running from the river to Pumphouse No. 1 on 48 Street near downtown is reaching the end of its life. The pipeline, which has been in place since 1968, needs to be replaced by 2020.

At a public meeting last week, a consultant hired by the city to design the water treatment plant said the cost of replacing the pipeline would be about $10 million, while installing an arsenic filter and drawing water from the bay would cost $3 million.

If approved by council, the city's drinking water source will change to Yellowknife Bay around 2020 to coincide with the end of the water pipeline's lifespan.

"The decision as to where the water source will eventually be is something to be looked at over the next eight years, not today or tomorrow. It's a longer-term discussion," said Van Tighem.

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