Crown-Indigenous Relations and Northern Affairs Canada says the Giant Mine reclamation site within the city limits of Yellowknife is considered “low-risk” as wildfires force an evacuation of the Northwest Territories capital.
Giant Mine is Canada’s most expensive reclamation project, with a cost estimated at $4.38 billion to contain 237,000 tonnes of toxic arsenic trioxide.
“The arsenic trioxide at Giant Mine, of which the majority is stored underground, is considered low-risk,” Crown-Indigenous Relations spokesperson Jennifer Cooper said.
“Much of the remaining material on the surface is stored in drums and is located away from vegetation and is also considered low-risk.”
The former gold mine operated from 1948 to 2004. The arsenic trioxide is a byproduct of the gold roasting technique used at the mine. The toxic compound used to be released directly into the environment, and as a result some areas of Yellowknife contain high levels of arsenic.
Prior to the Yellowknife evacuation, the site crew prepared the mine for a total shutdown. This included collecting brush, clearing away construction materials and moving them to the tailings pond away from structures.
Materials from the deconstruction of the roaster, which are heavily contaminated with arsenic, are kept in locked shipping containers that are also near the tailings pond, away from vegetation.
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Arsenic trioxide is highly toxic and releases toxic fumes if burned, according to the U.S. Centers for Disease Control and Prevention.
The manager of the mine confirmed their comfort with the site before the crews left as part of the Yellowknife evacuation order on Aug. 16, according to Cooper.
The cost of the reclamation was initially pegged at $1 billion, but that estimate was updated last year to include all work since 2005 and the full scope of work associated with the reclamation.
The federal and territorial governments have determined that freezing the arsenic trioxide in place is the best solution to contain the toxic compound for now. The reclamation team notes this is a long-term solution, but not a permanent one. The reclamation team is working with researchers to determine a permanent containment method.
The total site is over 900 hectares, or 300 football fields. In addition to the mine, there is an old townsite that has 85 buildings, many of which contain asbestos.
With files from The Canadian Press.