Two months after Snap Lake ceased operations and served 434 employees with layoff notices, De Beers is considering flooding the underground diamond mine.
“Flooding will allow for the care and maintenance period to be prolonged until the global markets improve and it can be re-opened by De Beers or another Qualified Operator,” according to a February “Environmental Update” slideshow from the Snap Lake Working Group.
Flooding has always been an issue at the mine, with many tunnels running under the lake the mine is named after. Ninety-five percent of the water in the mine comes from the lake and approximately 50,000 m3 of water are pumped from the mine every day, into tailings ponds to be treated. “Mining has ceased, but mine dewatering will continue in the near term,” the slideshow says.
Allowing the mine to flood would save considerable money on pumping operations. Furthermore, it would reduce negative environmental impacts, the slideshow claims, through “limited discharge of water to the receiving environment; reduced footprint and loading of mine effluent on the downstream water bodies; lower emissions as the mine would burn less diesel and reduced monitoring and supervision requirements.”
A known practice
“Flooding the mine is one of the options with reclamation; it’s a known practice, though I’m not sure if it’s been done before elsewhere in the North,” says Phillippe di Pizzo, executive director of the Snap Lake Environmental Monitoring Agency. “You have to do a number of steps first though, removing barrels, soil that’s contaminated by oil, just make sure everything is clean.”
“I haven’t looked at all the impacts yet, but there’s not too much worry about leakage. All the tunnels are underground,” says di Pizzo.
To get permission to flood the mine, De Beers will be making an application to the Mackenzie Land and Valley Water Board as part of an extended care and maintenance plan. In the shorter term, the company is expecting to transition to a “steady state” of care and maintenance by April.
The report says, “the care and maintenance may be 3 years or more, dependent on market conditions, but will be reviewed in late 2016.”
Di Pizzo expects it will probably be more: “That’s everyone’s guess, it could stay under care and maintenance for ten years.”
“If they want to close permanently they have to look at longer term closure issues, and they’d probably keep it flooded… If they do decide to reopen they’d have to pump and retreat the water. There are still millions of carats in proven reserves.”