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Company drafts plans to prevent tailings dam failure at Yukon mine site

This photo, included in a Yukon government inspection report from last month on the Mount Nansen mine site in central Yukon, shows the tailings dam near the emergency spillway at the site. (Yukon government - image credit)
This photo, included in a Yukon government inspection report from last month on the Mount Nansen mine site in central Yukon, shows the tailings dam near the emergency spillway at the site. (Yukon government - image credit)

The company that manages the abandoned Mount Nansen mine in central Yukon has drafted plans, in tandem with a Yukon First Nation, to head off the possibility of catastrophic failure at the tailings dam.

Mount Nansen Remediation Limited Partnership has filed an emergency application to the Yukon Water Board. Company director Jim Harrington told CBC News the company is seeking permission from the regulator to draw down more water —  the amount of which could be doubled because of this year's spring freshet — for about two years.

The company wants to bring up a mobile water treatment plant, which would be capable of pumping out more than double what crews are allowed to now. Other plans include directly treating water in the tailings pond and adding on-site water storage.

The Little Salmon Carmacks First Nation recently warned that spring melt could cause the tailings pond to overflow or, worse, breach the dam — a problem Chief Nicole Tom said would kill land of high importance to citizens.

Asked why the water could be so high, Harrington said that may have something to do with thawing permafrost.

"Maybe climatic changes that are shifting how water is accumulating at site," he said.

"We're really hoping for a lot of understanding from the governments that we're doing the best we can with imperfect information."

Harrington hopes the new mobile treatment plant is installed at the site by mid-April.

This photo, included in a February 2024 Yukon government inspection report on the Mount Nansen mine site, shows a seepage pond viewed from the tailings dam.
This photo, included in a February 2024 Yukon government inspection report on the Mount Nansen mine site, shows a seepage pond viewed from the tailings dam.

A photo from the Yukon government's February inspection report shows a seepage pond viewed from the tailings dam at the Mount Nansen site. (Yukon government)

The Yukon Water Board now has to determine whether the circumstances described in the company's application "meet the threshold of an emergency," according to a document on the board's website.

A spokesperson with the water board, which has yet to sign off on the application, declined comment, saying the regulator is working to make a decision "very soon."

Crown-Indigenous Relations and Northern Affairs, the federal department ultimately responsible for the Mount Nansen site, said in an email it "will provide funding to implement solutions agreed upon by the parties."

Yukoners are listening, chief says

Chief Tom said since the First Nation started pressing for changes at the site, about 45 kilometres west of Carmacks, Yukon, it seems like Yukoners have started listening.

"Everybody in the Yukon knows now and everybody in the Yukon needs to be aware that these things are happening," she said. "The accountability and the transparency is there.

"Yukoners don't wanna see these kinds of things happen. They don't want to see massive mining destruction and water pollution and the salmon disappearing."

She said the looming emergency at Mount Nansen is part of the much broader push to get the site cleaned up, for good.

The First Nation has argued remediation isn't happening soon enough and that the site is leaching heavy metals like arsenic and zinc into the environment because, in part, there's not the proper infrastructure in place to prevent that from happening. The First Nation has said that the effects of that are infringing citizens' rights.

Among other things, the First Nation has requested that the water board soon facilitate a public hearing into impacts.

"The Yukon Water Board really needs to consider and look at having that public hearing and allow Yukoners to express how they're feeling about what's happening up at Mount Nansen," Tom said.