Water levels at the defunct Mount Nansen mine site are perilously close to overflowing contaminated tailings ponds, according to a recent filing with the Yukon Water Board.

An emergency water licence amendment request was filed on Sept. 7 to allow workers at the site to treat and pump out more water to bring the level down between now and when next spring’s snow melt again brings high water levels to the ponds.

As of Sept. 21, the water was 47 centimetres from overflowing the tailing pond’s dam spillway, according to an email to the Star from Daphné Pelletier Vernier, a spokesperson for Crown-Indigenous Relations and Northern Affairs Canada.

Fortunately, due to the time of year and cooler temperatures on the way, the pond is not expected to overflow in the short term. High water occurs in May.

Calling it a “developing emergency situation,” Pelletier Vernier said in her email “there is no immediate threat of water discharge to the environment.”

The water board request seeks to be able to almost double the allowed discharge of treated water at the site from 360 cubic metres per day to 600.

Mount Nansen is a former gold and silver mine near Carmacks first developed in the 1960s. It operated intermittently until it was abandoned by its operator in 1999.

Reclamation work is now being done by the Mount Nansen Limited Partnership, a joint venture between Ensero Solutions and JDS Energy and Mining, who bought the site in 2021.

They are tasked with carrying out the closure commitments of the federal government.

It was through due diligence on the partnership’s part that the issue was caught, Pelletier Vernier said.

“The concern of high water levels in the tailings storage facility pond was identified through regular monitoring, which is part of diligent care and maintenance of the site,” she said.

According to the water board request, if there is a similar spring melt as the last two years, the pond would overflow.

This would spill water laced with contaminants including zinc, magnesium, iron and arsenic into Dome Creek and the surrounding watershed.

“The impacts on fisheries can be very negative,” Lewis Rifkind, the the Yukon Conservation Society’s (YCS’s) mining analyst, told the Star.

“You can’t just discharge this stuff untreated into the receiving environment.”

In a scenario with a spring equal to last – which was not a typical spring – it is estimated that up to 27,000 cubic metres of this untreated water could flow into Dome Creek next summer.

Under the worst-case scenario, about 40,000 cubic metres of untreated water could enter Dome Creek next summer.

The tailings pond itself had about 53,000 cubic metres of water in as of Sept. 21. That is about the amount of water in 21 Olympic-sized swimming pools.

The emergency water board application also warns of potential erosion or undercutting of the dam slope in the case of high-velocity flows leaving the ponds.

“If they don’t do this, they could end up in a situation where the water could top over some of the storage barriers, and that’s very problematic because then you get erosion happening,” Rifkind said.

This situation is not a complete surprise, as inspections of the facility had shown progressive increases in the water level over the past couple years, particularly during the spring.

The water board application quotes a July 5 inspection by Tetra Tech in which they detailed high water levels in both of the last two years.

Tetra Tech did recommend amending the water licence after the July inspection to allow for more water to be treated and discharged.

While they seek an emergency change to the water licence, Rifkind said there is currently an ongoing permitting process where they will likely change it again.

This will involve creating a whole new remediation plan, and will likely involve a new water licence as well.

It is currently in the presubmission stages of the Yukon Environmental Socio-economic Assessment Board process.

Rifkind said this may force the site operators to up the cleanliness standards for water they are discharging into creeks.

But, he said, they still need to act in this situation, regardless of where they are at in the conversation about whether the water is being treated well enough.

“There’s not much else they could do – they have to increase the treatment of water, discharge it to make room for future water,” Rifkind said.

Looking ahead, the water board application notes the forecast for the remaining days of September and October looks wetter than usual.

They predict a water level rise of 25 cm more, which means overall capacity left in the tailing ponds would be about 10,000 cubic metres.

At that point, even a windstorm would be able to cause water to spill out.

“In this elevated water level condition in the TSF (tailings storage facility), wind and wave action could lead to impacts to the dam and the potential for waves to spill water into the spillway,” says an entry in the application.

On Wednesday, the conservation society submitted its comments on the application requesting that it be approved, but only for a discharge rate of 480 cubic metres per day.

The society also wants it to be assured they cannot decrease the water quality of any of the treated water beyond current limits.

And the YCS expressed concern that these issues were not antici-pated beforehand.

“Given that unexpected water amounts contributed to the current situation at the Minto Mine (bankruptcy, abandonment, and receivership), YCS is of the opinion that it would be prudent for all Yukon mine operators to reconsider their water balance models,” reads a letter to the water board signed by Rifkind.