Officials in Yukon say they believe about 19 million litres of cyanide-contaminated water leaked from a containment pond at the site of a mining disaster last year before the problem was spotted and the water diluted.
Erin Dowd, director of technical services for the Mines Ministry, told a technical briefing Tuesday that there is no timeline for when the pond at the Eagle Gold mine site north of Whitehorse could be repaired.
She said crews on the ground have to wait for the pond to be drained and ice removed before any repairs can happen, and in the meantime the receiver in charge of managing the site has begun constructing an interception system in the area to collect groundwater, should that be necessary.
"There's a strong incentive to fix that pond. It provides additional 90,000 cubic meters of storage on site, so it will be a priority action," she said.
The territorial government said cyanide-contaminated water was first added to the pond in December but it was stopped when a leak was suspected.
A statement says treated water, that does not contain cyanide, was transferred to the pond in early January to dilute the mix and that those water transfers are no longer occurring to the pond.
Tyler Williams, a water resources scientist, told the briefing that recent test results show contaminated water is now flowing into nearby Haggart Creek with levels of cyanide, cobalt, chloride and nickel that have been above guidelines since mid-January.
The mining operation was shut last year and the operator, Victoria Gold Corp., was put into receivership after millions of tonnes of cyanide-contaminated rocks spilled from a containment facility at the mine, located about 480 kilometres north of Whitehorse.
The mine used chemicals to extract gold from piles of ore in what is known as heap leaching.
"The data is showing us a cumulative effect from the containment pond leak and the ongoing contamination that continues to enter Haggart Creek from the heap leach failure," Williams said.
In cases where contaminants exceeded their aquatic life guidelines, there could be negative effects to the health of fish and other organisms. This is why the ongoing monitoring of water quality, aquatic life, and fish health downstream of the mine site remains important”
Crews continue to release the equivalent of about one Olympic swimming pool a day of copper-contaminated water ahead of the upcoming spring snow melt, which the government has said the receiver believes is "critical" to prevent cyanide-tainted water from leaking out in an uncontrolled way.
"A large volume of water will require management during the spring melt, along with the water currently stored in the heap leach facility and storage ponds," Dowd said.
"A significant amount of this water will require treatment prior to being discharged to the environment. There's a limit to how much water can be treated on a daily basis," she said.
The government has previously said that water's copper levels are "not fully compliant" with either federal regulations or the site's water licence, though it is meeting the requirements for cyanide.
Dowd said copper is added to the water as part of the cyanide removal process.
She said one of the final stages of the process, which involves building a separate pool to remove the copper itself, is expected to be complete by the end of the month.
This report by The Canadian Press was first published Feb. 18, 2025.
Ashley Joannou, The Canadian Press
