De Beers Canada says some recommendations for how to tackle a groundwater problem at its Snap Lake diamond mine could, if implemented, result in the mine closing down early — a move that would put 300 N.W.T. residents out of work.

De Beers has encountered higher than expected volumes of total dissolved solids (TDS) — including mineral salts — in water leaking through the inner walls of the underground mine, located 220 kilometres northeast of Yellowknife.

The company treats that water and releases it back into the lake. But to avoid going over the acceptable level of TDS for the lake, the company has also been storing TDS-high water underground since June 2014.

'It's a fine line between economics and environment.' - Ed Sangris, chief of Dettah

De Beers is asking the Mackenzie Valley Land and Water Board to nearly triple the highest allowed level of TDS in Snap Lake to 1,000 milligrams per litre.

"Snap Lake mine cannot continue to operate if a level of [total dissolved solids] is set that is not sustainable," said Glen Koropchuk, De Beers Canada's chief operating officer. 

Koropchuk said De Beers has already spent $20 million to capture and release TDS-high water at Snap Lake. It's one of several unanticipated issues Koropchuk says De Beers has faced at Snap Lake since the mine opened in 2008.

"In its seven years of operation, Snap Lake has not turned a profit," he said. "Members of our [impact benefit agreement] communities will know that because we have not been able to make profit-related payments to this date."

Differing opinions

The company says that, under a TDS level of 1,000 milligrams per litre, fish and water from the lake will still be safe to consume. 

But aboriginal groups and the territorial government say that level goes too far.

Glen Koropchuk

Glen Koropchuk, De Beers Canada's chief operating officer, speaks at a Mackenzie Valley Land and Water Board public hearing in Dettah on Wednesday. (CBC)

"We want to ensure that we can still continue to use Snap Lake once the mine is gone," said Ed Sangris, the chief of Dettah.

Koropchuk says the drinking quality of Snap Lake water will return to "acceptable levels" four to seven years after Snap Lake closes in 2028.

James Marlowe, a resident of Lutsel K'e and a member of the Snap Lake Environmental Monitoring Agency, is still skeptical, though.

"Knowing the reputation of De Beers, there's always doubt from people," said Marlowe. "Seven years to make the water back to its normal stage is a long time. Within that period, I don't know if people are going to be hunting, fishing and trapping there."

The N.W.T. Department of Environment and Natural Resources says De Beers needs to do more studies to prove that the company's preferred TDS limit won't leave Snap Lake's fish open to harm, and in the meantime it wants the TDS limit set at 690 milligrams per litre.

But De Beers says the additional water treatment option it's considering would be too costly at around that level.

"Such a condition would require closure of the mine,"​ said Erica Bonhomme, Snap Lake's environment manager.

'A fine line between economics and environment'

Koropchuk emphasized the financial repercussions of Snap Lake shutting down before its expiry date.

"It's important to make clear what's really at stake here," he said, adding that De Beers still has $1 billion left to spend on local salaries, taxes and business contracts.

Sangris says the Yellowknives Dene First Nation is not against development, but that it wants to see the environment protected nonetheless.

Ed Sangris

Ed Sangris, the chief of Dettah, says the Yellowknives Dene First Nation opposes De Beers' preferred TDS limit. (CBC)

"It's a fine line between economics and environment that we have to keep in mind as leaders," he said.

John Donihee, a lawyer for the Mackenzie Valley Land and Water Board, said the board's decision on a new TDS limit — which is expected in mid-May — could be a trade-off.

"The risk, I suppose, of some changes in the ecology of Snap Lake is going to have to be weighed against the social and economic considerations."