Sixty-eight fish downstream of the Victoria Gold Corporation's mine site in the Yukon are dead and government scientists and officials believe a “pulse” of contaminated water is to blame. The fish deaths came shortly after water was discharged from the mine’s water treatment system that was upgraded to cope with conditions following the June 24 failure of the mine’s heap leach facility.
“Last week, discharge from the mine’s water treatment plant occurred on July 31 at 12:15 p.m. and ended on Aug. 2 at 12:30 a.m. Water Resources Branch was informed that the majority of the total volume discharged was released Aug. 1 while Victoria Gold Corp. was discharging from its water treatment plant to Haggart Creek,” said Brendan Mulligan, a territorial government water scientist speaking to a briefing about water monitoring and testing efforts in the vicinity of the mine.
Those at the briefing were told that the dead fish were a mix of slimy sculpin and Arctic grayling. The dead fish were stored by mine personnel for testing. After the construction of fish fences to keep fish out of the area where the deaths occurred, a salvage operation was undertaken to relocate fish still in the fenced zone. These measures were ordered by the federal Department of Fisheries and Oceans.
Mulligan said monitoring shows clear evidence that groundwater on the mine site is being contaminated. He stated that testing of groundwater reaching the surface within the mine site has turned up weak acid dissociable (WAD) cyanide concentration 10,000 times higher than the standard set to protect the long-term health of aquatic life. He emphasized that while the standard is a point of comparison, it is not actually enforced because the groundwater is collected and contained on the mine site. He said there is currently no evidence that groundwater from the mine site is directly discharging to Haggart Creek.
“To summarize, this portion of the water-quality story, contaminants are transported from the heap leach failure via groundwater to Dublin Gulch and then via surface water from Dublin Gulch to Haggart Creek," he said.
In the creek where the fish died, the briefing heard that WAD cyanide concentrations were detected in excess of the short and long-term guidelines for the protection of aquatic life. Even after the discharge from the mine’s water treatment plant had ceased, samples of the short and long-term guidelines were exceeded at one monitoring station and the long-term guideline was exceeded at another. Mulligan said Aug. 1 and 2 samples turned up WAD cyanide concentrations “several times higher” than samples taken the previous week.
Cameron Sinclair, a Yukon government fish biologist working on monitoring in the area of the mine, said that while more information including a tissue analysis of the dead fish is still being awaited, it is believed that they died due to a discharge of water from the mine’s treatment plant and not directly due to contaminants that have been seen in the receiving environment since the heap leach failure.
Mary Vanderkop, the Yukon’s chief veterinary officer, said the evidence points to acute cyanide poisoning as the cause of death for the fish. She said this is supported because a swift death of a group of more than one species of fish was observed.
Speaking with the News on Aug. 12, Victoria Gold CEO John McConnell said that the water from the treatment plant was tested prior to discharge and met requirements. He added that the plant was working fine during the discharge. The mine hasn’t discharged water since the fish deaths as they’ve gone back to the drawing board to analyze what went wrong. He posed the possibility that it was an issue with water hardness or temperature that killed the fish rather than cyanide but said he is also awaiting the results of the fish tissue analysis.
Vanderkop noted that cyanide doesn’t bioaccumulate and that animals harvested in the area are believed to be safe to eat. Because of the parallel concern that the mine facility failure will lead to heavy metal accumulation over a period of years, the government will solicit tissue samples from animals harvested in the area north of Mayo this hunting season to establish a baseline for future monitoring.
Yukon chief medical officer Dr. Sudit Ranade explained that despite the talk of groundwater contamination, regulated drinking water systems in the area remain safe.
The First Nation of Na-Cho Nyäk Dun has scheduled a press conference for the morning of Aug. 14 in which it plans to lay out its own findings about the environmental impact and Victoria Gold's efforts at the site.
Contact Jim Elliot at jim.elliot@yukon-news.com