Water Treatment at Giant Mine

Water management is an important aspect of the Giant Mine Remediation Project, both currently and in the future.

An aerial view of the water treatment plant, the settling pond and the polishing pond and the roads looping around them.

Current process

Currently all water that enters the mine drains to the bottom of the mine. Because this water may be contaminated, it is pumped to the surface where it is temporarily stored in tailings ponds. The tailings ponds are large enough to store all water collected in the winter months. During the summer, this water is pumped from the tailings ponds to an on-site water treatment plant that removes arsenic and other contaminants.

Treated water is transferred from the treatment plant to the settling pond. There, most of the remaining contaminants settle to the bottom of the pond and are not exposed to the environment. From that pond, the treated water passes into the polishing pond. Once remediation is complete, these two ponds will no longer be required. The contaminated sediments will be capped and covered with vegetation, preventing this material from getting into the environment.

When water quality in the polishing pond meets or exceeds the regulatory requirements set out in the mine's former water licence, it is discharged into Baker Creek.

Proposed future process

The Project Team is proposing to treat minewater to 10 micrograms of arsenic per liter, which meets the federal Guidelines for Canadian Drinking Water Quality.

This approach directly responds to the Yellowknives Dene First Nations' requests for effluent to meet drinking water standards. It also addresses concerns regarding the intake of drinking water for the City of Yellowknife. Lastly, this approach does not require the use of a diffuser and therefore addresses concerns around ice thickness in Back Bay. Further details on this treatment method can be found on the Mackenzie Valley Environmental Impact Review Board's public registry