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SOMBA K'E/YELLOWKNIFE - The Giant Mine clean-up team has come up with two possible ways to ensure toxic tailings never mix with the water in Baker Creek again.

Baker Creek, near Vee Lake Road, as seen in mid-May 2011 after a naturally forming ice dam caused water to overflow into a historic Giant Mine tailings pond. The water subsequently drained back into the creek, along with toxic tailings. - photo courtesy of Aboriginal Affairs and Northern Development

The options - capping or dredging a historical tailings pond near Vee Lake Road - come in response to orders given last month by a water resource officer from Aboriginal Affairs and Northern Development, formally Indian and Northern Affairs Canada.

Capping the tailings pond would involve placing about 60 centimetres of granular material on top of the historical tailings pond, then another 30 cm of finer material, mixed with organics that would allow vegetation to grow, said Robert Girvan, Giant Mine project manager for Public Works Canada.

"The benefit of this particular option is it's the gentlest way to deal with the tailings," he said at a public forum Tuesday night.

The second option is to remove the tailings by dredging. Girvan said the drawback to dredging is it will introduce more sediment into Baker Creek.

Baker Creek became a concern May 14 when a naturally forming ice dam caused the creek to overflow into the tailings pond, which holds toxic by-products from decades of gold mining. The water then drained back into the creek, which flows into Back Bay.

The diversion of water - which was redirected with the use of a dam on May 18 - caused high levels of sediment, including arsenic and other metals, to enter the creek.

Hilary Machtans of Golder Associates conducted sampling of the water following the incident.

She said it took about two weeks for the sediment levels to reach background levels - which, because Giant Mine is a contaminated site, are already above Health Canada's Canadian Drinking Water Guidelines and the Canadian Water Quality Guidelines for the Protection of Aquatic Life.

"The drinking water guidelines were designed for water that's been treated, so it doesn't exactly compare to Baker Creek," explained Machtans, noting that people should never drink water off a contaminated site. As a result, human health wasn't as great a concern as aquatic life when Golder was sampling the water, she said.

On May 16, arsenic levels in Baker Creek were 700 times higher than the acceptable levels for drinking water and 1,500 times higher than the acceptable level for the protection of aquatic life.

Levels remained high for a few days, but were back to the creek's usual levels within a couple weeks - about five to 11 times over the acceptable level for drinking water and 12 to 24 times the acceptable level for the protection of aquatic life.

Although there was a large spike, results from a fish monitoring program show that the water was not toxic to aquatic life and that fish did use the creek to spawn and lay eggs. Machtans said the eggs hatched and the young fish survived.

Aboriginal Affairs and Northern Development has given the Giant Mine team until Aug. 1 to submit a plan outlining the measures it will take to ensure toxic tailings never come in contact with Baker Creek again. All subsequent work must be finished by April 30, 2012. The team must also submit monthly progress reports from September 2011 until April 2012.

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