The Yukon government has been working urgently to protect the landscape surrounding a heap leach failure and landslide at the Victoria Gold Corporation’s Eagle Mine on June 24, but new information suggests that the mine’s on-site water treatment is not equipped to manage the level of contamination, which contains cyanide.
Heap leaching involves spraying a diluted cyanide solution on an open pit of crushed ore, collecting the metal-laden solution on a plastic or impervious surface. The Eagle Mine failure involved a slide of the ore stacked in the heap leach facility, which spilled over an embankment and also damaged some mine infrastructure just north of Mayo, Yukon.
Samples collected in July from monitoring stations show concentrations of weak acid dissociable (WAD) cyanide that significantly exceeds the aquatic life guideline of 0.005 mg/L, according to the Yukon Department of Environment. None of the samples collected from any of the monitoring sites, however, have exceeded drinking water guidelines for cyanide as of August 6.
“Our role as a regulator and enforcement body is to closely monitor the situation, and, when appropriate, direct the company and hold them accountable,” announced Yukon Minister of Energy, Mines and Resources, John Streicker, in a statement. “Our two key priorities are on-site safety and environmental protection.”
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Yukon officials said that workers at the gold mine — now in temporary closure — moved quickly following the landslide to create dams that could hold back contaminated water and allow it to be pumped into storage ponds. However, as of July 18, Yukon government mineral resources director Kelly Constable told a local press briefing that the mine did not have sufficient on-site capabilities to treat the level of stored contaminated water.
Two days later, Yukon-based CoreGeo began leading on-site water sample collection efforts and executing the water monitoring plan designed by the government and the First Nation of Nacho Nyak Dun.
Yukon officials announced that the Victoria Gold Corporation had not effectively completed specific environmental protection actions assigned by the site’s inspector.
“Due to the company’s failure to construct a safety berm, the Government of Yukon has engaged contractors to design and build this berm,” officials announced in a response bulletin on July 26. “The berm is critical to ensure that groundwater monitoring and interception wells can be installed safely.”
The work is expected to take around two weeks to complete and groundwater wells can be installed in certain locations as construction progresses.
Groundwater flowing towards Haggart Creek remains one of the most significant environmental risks at the site of the landslide. Yukon officials noted that off-site fish monitoring is taking place in at least 50 locations. While no dead fish have yet to be observed downstream, some fish were found dead on the mine property. The Department of Environment has collected approximately 65 arctic grayling and 50 slimy sculpin samples for laboratory analyses in B.C. that could help to determine heavy metal contamination.
“As a regulator, we are also trying to be flexible to adapt to a quickly changing situation,” Yukon officials announced. “We will continue to conduct water quality testing at the site and downstream. This will provide us with the data needed to understand the extent of the impact and to inform next steps.”
