Board approves emergency plan to prevent tailings spill at Yukon’s Mount Nansen mine site

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. (Yukon government)

The Yukon Water Board has approved a plan that’s meant to reduce the risk of a catastrophic tailings spill this spring at an abandoned mine site in the central territory.

In a written decision dated March 27, the board agreed that the environmental threat from untreated water at the Mount Nansen mine site constitutes an emergency, and requires immediate action.

The mine site, abandoned decades ago when Toronto-based BYG Resources went bankrupt, is now the responsibility of the federal government and is being managed by a company called Mount Nansen Remediation Limited Partnership.

Mount Nansen Remediation applied to the Yukon Water Board last month for permission to take a number of actions aimed at drawing down the amount of untreated water held in a tailings storage facility on site. The company expected the water level to increase significantly with the spring melt, threatening the integrity of a tailings dam.

In its decision, the water board agreed there is “significant potential of a release of untreated water to the environment,” and that the situation requires “immediate preventative action.”

“Based on the findings of the issues presented in the evidence, the Board determines an emergency exists,” the decision reads.

Mount Nansen Remediation’s emergency amendment to its licence is now in effect until August 2026, when the licence is set to expire. The amendment allows the company to:

• Install and use a mobile water treatment plant.
• Increase the effluent discharge rate from the site’s water treatment plants, from 600 cubic metres to 1,500 cubic metres per day, when the tailings pond elevation reaches a certain level.
• Pre-treat water in the tailings storage facility pond under certain conditions.
• Use above-ground storage tanks for temporary storage of water.

The board denied the company’s request to allow water storage in another open pit on site, however, saying that plan was too risky for groundwater, and that it was likely unnecessary given the other measures that have been approved.

Jim Harrington, director of Mount Nansen Remediation, said the company was “not really excited” about that part of the application anyway. He’s pleased the rest of it was approved.

“I would say everything that we think we need we have now, in terms of authorizations,” he said.

He said the additional storage tanks will be installed at the site within the next month, and the mobile treatment plant should also be working by the end of April.

With files from Julien Gignac

This article is republished from RCI.