Giant Mine
The territory around the Giant Mine was first staked for gold in 1935, but the Second World War delayed production until 1948. Stimulating the founding of the community of Yellowknife, and remaining in production almost continuously until 2004, the Giant Mine produced more than seven million ounces of gold. The deposits, contained in arsenopyrite mineral formations, necessitated the separation of gold from arsenic. Over four decades of production, 237,000 tonnes of arsenic trioxide dust were collected and stored in underground chambers. In 1999 the federal Department of Indian Affairs and Northern Development assumed control over the site after Royal Oak Mines went into receivership. DIAND continued to assume responsibility for the arsenic issue (even after the mine was sold to Miramar Giant Mine Ltd.), and instituted a program of monitoring, capturing, and treating groundwater at the site to prevent contamination in the surrounding area. More recently, DIAND has proposed to resolve the problem of arsenic contamination at Giant Mine by freezing the material permanently underground using thermosyphons, which are pipes containing pressurized CO2 that will draw heat from surrounding rocks in perpetuity.