Welcome to the Giant Mine, an abandoned gold mine in Yellowknife, capital of the Northwest Territories of Canada. The Canadian government first took charge of it in 1999 after the owner declared bankruptcy and walked away. It is one of an estimated 10,000 orphaned or abandoned mines in Canada’s north that are now the government’s responsibility. And it is full of arsenic trioxide, a compound that is produced by heating arsenopyrite ore, a mineral that has traces of gold. Arsenic trioxide is odourless, tasteless, highly soluble—and lethal. An amount smaller than a pea is enough to kill. The Giant Mine has 237,000 tonnes of the stuff.
The Giant Mine opened in 1948. For the first few years arsenic trioxide went up the smokestack as vapour and came down in the surrounding area as dust. Dust-collecting “scrubbers” were added to capture some of the poisons after newspapers began warning people not to drink water made from melted snow. Once captured, the arsenic, which has the consistency of talcum powder, was blown into underground chambers. As long as the poisonous dust was in the permafrost layer, the thinking went, it would freeze solid and no longer pose a problem.
That might have worked had mine managers not later decided to dig a series of open pits to extract more gold. Now much closer to the surface, the permafrost has melted. With water leaching into and out of the mine it was only a matter of time before the arsenic threatened the waters of Great Slave Lake.
The federal government’s proposed answer, which was approved last month and whose cost has been estimated at C$1 billion ($900m), is a variation on the original plan. The largest open pit will be filled and the 15 sealed vaults containing the arsenic will be refrozen. “
The Dene, the largest group of indigenous people in the territory, in whose homelands the Giant Mine sits, want the dust taken out and reprocessed into a more stable form. Under pressure from the Dene, environmentalists and the city of Yellowknife, the government is to set up an independent body to monitor its work and check every 20 years whether plans should change. It has stopped claiming its solution will last forever, shortening the period a tad, from eternity to 100 years.
If there is a golden lining in this cloud of arsenic dust it is that the studies, remediation work and monitoring create jobs in Yellowknife, now largely a government town. “That mine is still making money,” says Walt Humphries, who is leading a campaign to turn the Giant Mine’s former recreation centre into a museum. “And it will make money for years to come.”
Canada’s Giant Mine: Giant headache, Economist, Sept. 27, 2014, at 38