The Giant Mine Remediation Project on Tuesday began a six-week winter drilling program on Yellowknife Bay, designed to examine the lake bed ahead of forthcoming clean-up work.
For the first three weeks, the project will flood the ice to strengthen it. Three weeks of drilling will begin in March, stretching for roughly a kilometre along the shoreline north of the Giant Mine boat launch.
Residents, particularly skiers or people using the nearby on-ice driving track, are asked to keep a safe distance from the work area. The safe distance will be clearly marked by the contractor.
Natalie Plato, the project’s deputy director, said ski trail groomers and Wayne Guy, who maintains the driving track, plan to adjust their tracks so they are not affected by the drilling.
As drilling moves along the shoreline, areas that were drilled and have since frozen again will be reopened for recreation.
“The drilling is expected to take place in different locations along the shoreline itself to approximately 300 metres from the shore at the foreshore tailings location,” said Plato in a prepared statement.
The foreshore tailings location is where approximately 300,000 tonnes of tailings were dumped along the beach and in the water on the north side of Yellowknife Bay.
“About 35 percent of the tailings are on the beach with the remaining in Back Bay. Submerged tailings have been dispersed along the western shore of north Yellowknife Bay by lake currents; however, the bulk of the tailings remain near the original disposal site,” explains a July 2007 Giant Mine remediation plan.
The drilling will give the project team information about the lake bed and how much weight it can bear for a proposed tailings cover.
Team members are figuring out what kind of rock cover – and how much of it – will be needed to cover the contaminated sediment and tailings, to keep people from interacting with it and to stop it shifting.
Blue dots on the above map identify foreshore tailings locations. Green dots signify sediment contaminated by the mine’s former activity. The project team plans to cap both areas.
The drilling will also provide information needed for work on the site’s new water treatment plant.
Part of the federal remediation plan for Giant Mine – a former gold mine that now sits on top of more than 200,000 tonnes of toxic arsenic trioxide – involves building a treatment plant to remove arsenic and other contaminants from water before discharging it near Baker Creek.
“The project team needs to know what kind of infrastructure the lakebed can support, such as the pipeline that will be discharging the treated water into Back Bay,” said Plato.