Minto must dump more wastewater: EMR

The Minto mine needs to dump more tainted water off its property and into the Yukon River Watershed. A lot more. The copper mine is in crisis because water being stored in the open excavation pit is damaging the pit's walls, according to a request for discharge dated August 5.

The Minto mine needs to dump more tainted water off its property and into the Yukon River Watershed.

A lot more.

The copper mine is in crisis because water being stored in the open excavation pit is damaging the pit’s walls, according to a request for discharge dated August 5.

The 900,000-cubic-metre discharge Minto is requesting is three times the amount the mine was permitted to dump last month, in what was also considered an emergency.

At the time, the Yukon Water Board scolded the mine, which is owned by Vancouver-based Capstone Mining, for abusing the emergency discharge provisions in its water licence.

Now, the mine wants to discharge 20 times more wastewater a day than it was permitted the last time around.

If it doesn’t dump the water, its water storage pond might break.

“The water storage pond could then overtop and that would be an uncontrolled discharge of water which has the potential to cause an adverse effect on the environment,” reads Capstone’s request.

The water storage pond hasn’t been able to contain all the wastewater on site this summer, and Minto has since been using its open pit to store water.

“Minto estimates that, at the rate of discharge, it will take two years to empty the current volume in the pit, without accounting for the additional water that is certain to arrive with the fall rains and spring freshet events during the two-year period of discharge,” says the request.

Robert Holmes, director of the Energy, Mines and Resources’ mines branch, inspected the site earlier this month and found the water-filled pit to be a danger to both people and the environment.

Holmes’ inspection concluded that the pit should be emptied immediately, “such that access to the ore body can occur along with necessary maintenance of pit walls and normal pit operations,” says his report.

The wastewater discharge must happen before expected freeze-up conditions begin on October 15, Holmes wrote.

The water-filled pit has also hurt profits for the mine, which has had to process piles of already-excavated copper while the more lucrative ore sits underwater.

Capstone’s production during the first half of the year was lower than expected because of the water in the pit, said a July 15 Capstone press release.

In the second quarter of this year, the Minto mine produced 12.75 million pounds of copper.

That’s a 15 per cent drop from its expected 15 million pounds of copper per quarter.

And the wastewater, if it’s allowed to freeze, could even lead to a mine shutdown, said Holmes’ inspection.

“(The situation) might lead to temporary closure of the project or permanent shutdown,” he wrote.

Slumping on the south wall of the pit might lead to a collapse that will make the water even dirtier, said Capstone president Stephen Quinn.

“The south side of the pit has some semi-frozen overburn,” he said.

“We’ve already had one small slump off the end of it, but there is potential for significantly more to fall into the pit and that would make the water dirtier because all the solids would get mixed up into it.

“Then you couldn’t clean it up and discharge it.”

The unexpected water is due to heavy snowfall – the same reason given for last month’s discharge request, said Quinn.

This year’s first discharge is nearly completed, says Capstone’s request, but it doesn’t look like all the water dumped since early July has been compliant with Minto’s water licence.

The mine is trying to recommission its water treatment plant and the water being treated is conforming with standards “sporadically” because of the amount of water being discharge a day, says Capstone’s latest request.

The nine-person Yukon Water Board is meeting Friday morning to discuss the discharge. The board provided less than 24 hours for interventions to be submitted.

The Yukon Conservation Society, Environment Canada, Environment Yukon, Selkirk First Nation, Selkirk Renewable Resource Council and the federal Department of Oceans and Fisheries all submitted interventions, said board manager Carola Scheu.

A decision is expected either today or Monday, she said.

Contact James Munson at

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