N.W.T. board OKs dissolved solid limit increase for Snap Lake

The Mackenzie Valley Land and Water Board is recommending that the limit be nearly doubled for total dissolved solids (TDS) — including mineral salts — in the Northwest Territories' Snap Lake.

The board's recommendation, if approved by N.W.T. Environment Minister Michael Miltenberger, would see the TDS limit increased to 684 milligrams per litre, from its current limit of 350 milligrams per litre. 

The recommendation comes in response to a request from De Beers Canada, which operates the Snap Lake diamond mine near the lake.

De Beers is encountering a higher than expected volume of TDS-rich water in the mine's underground workings. The company pumps that water to surface, treats it and releases it back into Snap Lake. De Beers says it needs the TDS limit increase to keep open the mine, which employs 800 people. 

In its decision, the board said it believes De Beers' monitoring of Snap Lake will be able to detect any potential effects on vulnerable fish "long before permanent ecosystem changes take place."

Even higher limit sought

But the new limit may only be temporary.

In May, the board is expected to decide on another De Beers' request, one asking for the TDS limit to be nearly tripled from its current level to 1,000 milligrams per litre. That limit would take effect in early 2016 and potentially be in place until 2028, when the mine is currently expected to close.

The company has said 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 have said that negative perceptions about the water could deter members from using the area for traditional practices, while the N.W.T. Department of Environment told a public hearing last month that De Beers needs to do more studies to prove that the company's preferred life-of-mine TDS limit won't leave Snap Lake's fish open to harm.