N.W.T. minister sides with Diavik mine owner in water dispute

The N.W.T.'s minister of environment has sided with the owner of the Diavik diamond mine in a dispute with regulators about water quality inside Lac de Gras.

Rio Tinto is building a dike around its new A21 pit inside the lake, located about 300kilometres northeast of Yellowknife.

But the company has chafed against restrictions in its water licence specifically, a rule that forbids the water quality outside the dike to spike beyond 25 milligrams of total suspended solids (TSS) per litre on any day. TSS includes silt, clay andfine particles of organic and inorganic matter.

Rio Tinto appealed to the Wek'eezhiiLand and Water Board, the board for the N.W.T.'s Tlicho region, to change the daily limit to a more flexible monthly average.

Instead in a move the company deemed unfair the board recommended keeping the current daily limit and introducing a much more stringent monthly average of five milligrams per litre to Wally Schumann, the N.W.T.'s minister of environment.

• Diavik mine owner appeals to N.W.T. minister for help in regulatory dispute

But in a decision late last month, Schumann overturned the board's recommendation, sending the issue of the limit back to the drawing board.

Pitscheduled to open in 2018

Rio Tinto's schedule calls for the dike to be enclosed this year, and for mining of the A21 pit to begin in 2018.

Last year, when TSS levels in the lake near the dike went above the limit, a territorial inspector threatened the site with a potential shutdown.

Meanwhile, Rio Tinto has said this year's open-water dike construction season will be "more challenging" than last year's when it comes to managing TSS.

In a letter to the board Monday, Schumann said the clock is ticking.

"I urge the board to create an efficient process in order to minimize further delays," he wrote.