Op-Ed: Poor water management, not Mother Nature, to blame for Minto mine’s water woes


Written by Randi Newton | May 31, 2023
Photo from Google Earth, Minto Mine and Yukon River.

Sources for this letter are either hyperlinked or available on the Yukon Water Board’s website Waterline. Click on the links or hover over any other green text for the title of the source and other information. You can find steps to access these sources from Waterline at the bottom of the page.

Read the full editorial as published in the Yukon News on May 31st, 2023.

Poor water management, not Mother Nature, to blame for Minto mine’s water woes

The departure of Minto Metals has saddled the Yukon with another abandoned mine. Employees were abruptly let go, royalties and many businesses left unpaid, and the Yukon government has been burdened with huge pits of contaminated water.

The government is now rightly focused on managing the site to ensure snowmelt doesn’t overwhelm the tailings pits. Otherwise, contaminated water could flow into Minto Creek, and ultimately the Yukon River. Later it will be time to unravel what went wrong, identify weaknesses in the territory’s regulatory regime, and hopefully put meaningful changes in place.

To figure out the right solutions, we need an accurate picture of the factors that led to the surplus of contaminated water and the mine’s eventual downfall. However, some of the current narratives about the mine’s water woes place too much accountability on Mother Nature, instead of poor water management. A good example is Minto Metals’ press release from April 20th. It paints a picture of the company being overwhelmed by a monstrous snowmelt, despite undertaking Herculean water treatment efforts. The release notes that Minto had faced a snowpack of 417% above normal, but still managed to discharge over 1.4 million cubic metres of water in 2022, “more than double what was cumulatively discharged over the prior 7 years.”

However, this leaves out key pieces of the story. For much of those prior seven years, Minto mine did not have a functioning water treatment plant and, year after year, was treating and discharging very little water.

Minto’s annual records show that the water treatment plant started to struggle in 2017 , when the mine was still owned by Capstone Mining. Challenged by low copper prices, Capstone put the mine into care and maintenance in 2018 and did not operate the plant that year. Pembridge Resources purchased the mine in June of 2019. The company restarted milling ore by October, but didn’t treat or move any water offsite that year.

While milling allowed Pembridge Resources to start making revenue, milling also contaminates a lot of water which then needs treatment before it can be safely discharged. If not treated, this water has to be stored, but tailings pits can only hold so much water.

Minto mine has faced water challenges in the past. Capstone relied on emergency discharges in 2009, so it’s puzzling why the new operators waited so long to try restarting the plant. It wasn’t until the spring of 2022, nearly three years after purchasing the mine, that the water treatment plant was finally brought back online by Minto Metals (who had by then taken over from parent company Pembridge Resources). But these efforts came too late.

Minto Metals had already notified the Yukon government in December 2021 that the mine’s water storage capacity had dropped below 1,000,000 cubic metres. That’s a safeguard required by the mine’s water licence, meant to reduce the risk of spring snowmelt overwhelming the mine’s tailings ponds.

In a follow-up memo, Minto Metals further explained that water had been allowed to accumulate at the mine since 2017 and that the setup of the existing water treatment plant “was insufficient to consistently remove water from site.” The company noted that their efforts to treat water in spring and summer of 2021 were not successful, leading them to hire a firm in the fall to improve the water treatment plant.

The Yukon government recognized the mine’s climbing liabilities, and in early 2022 increased Minto Metal’s financial security by $21 million. When the company missed the payment deadline, the government put the mine on restricted operating conditions. This allowed the mine to operate but not reduce its water storage capacity (meaning that if tailings were placed in the pits, at least as much water needed to be treated and discharged).

Minto Metals did not meet the conditions, failing to treat enough water to offset the tailings it continued to place in the pits. This April, a government mining inspector noted that the mine had lost over 200,000 cubic metres of storage. This was the result of continuing to deposit tailings and contaminated water, in a year the mine was meant to be gaining water storage capacity.

By the time Minto Metals abandoned the mine this May, storage capacity had plummeted to 318,000 cubic metres, less than a third of their water licence requirement. The Yukon government now sits ready to pump spring flood water into a previously mined pit. While this effort will likely keep contaminated water from spilling into the Yukon River, it also means that the site’s water liabilities will continue to climb for some time. Fortunately it appears that the Yukon government kept a much more watchful eye on Minto than the Wolverine mine, and was able to quickly jump into action.

This water management saga at Minto is akin to filling a bathtub with water, only to pull the plug and realize the drain was clogged. To make matters worse, the nature of mining meant that the tap kept flowing. While spring snowmelt added to the tub each year, so did water from the mill and from dewatering the underground mine. Save for a break of a few weeks, Minto continued to process ore, which added large amounts of contaminated water to the tailings pits year after year.

So while it is true that Minto Metals eventually managed to start treating and discharging water, and did face challenging years of snow, the full picture is that the efforts to treat water came too late, and the high snow years simply exposed the mine’s failure to manage risk.

While running the water treatment at the outset and shutting down the mill for a longer stretch would have obviously bought more time to focus on water treatment, it also would have gouged Minto Metals’ revenue. Companies are built to generate profits but managing environmental risks, like contaminated water, can be expensive. I say this not to excuse what happened, but to point out how important it is for the regulatory system to drive companies to act responsibly and avoid reaching a point where few good options exist.

Minto mine is certainly not the first mine in the Yukon to manage water poorly, and this letter isn’t intended to point fingers at specific individuals. The mine has had a number of changes in senior leadership since it was purchased in 2019, making it difficult to trace accountability. But Mother Nature and years of high snowpack aren’t the culprit – instead, they’re conditions the mine should have been managing for.

Fortunately, development of the new minerals legislation provides the Yukon with a chance to act on lessons learned and work towards transformational change. I hope we can now all agree that mining companies can’t be counted on to always make responsible decisions, and it would be a shame not to develop a regulatory regime that can better shield the territory from negligence.

Some of the sources in this letter are only available on the Yukon Water Board’s website Waterline and don’t have direct hyperlinks. You can hover over any green text for the title of the source and other information. Follow these steps if you’d like to access them:

  • Use this link and then hit the “Guest” button.
  • Copy and paste QZ14-031-2 into the search bar, then click on the link below to access Minto Metal’s documents.
  • Most documents cited are available under the “Reports” tab on the left. One document noted as an “Exhibit” is available under the “Exhibit List” tab.