Giant Mine: Historical Summary

This report examines the history of arsenic pollution from Giant Yellowknife Gold Mine, and its
\nenvironmental and public health impacts. It is based on extensive archival research in national and
\nterritorial archives, as well as oral histories (published and unpublished) and a review of public reports
\non the issue.
\nOperating from 1948 to 2004, Giant Mine produced over 7 million ounces of gold mined from
\narsenopyrite ore formations located on the north shore of Yellowknife Bay. Gold processing entailed
\nroasting the ore, producing as a byproduct arsenic trioxide dust, a highly toxic form of arsenic. In the
\nearly 1950s, arsenic emissions from Giant and Con mines totalled an estimated 22,000 lbs. per day.
\nThough Con mine installed a scrubber in 1949, Giant mine (the source of most of the arsenic) did not
\ninstall pollution control equipment until the end of 1951, after a Dene child died of acute arsenic
\npoisoning at Latham Island. Local livestock also died as from arsenic poisoning. Government and mine
\nofficials met at the time to discuss how to address the problem of arsenic pollution, but never
\ncontemplated even a temporary shutdown of the mine.
\nThe capture of arsenic using a Cottrell Electrostatic Precipitator reduced but did not eliminate arsenic.
\nCollection rates were further improved by the installation of a baghouse in 1958. Studies undertaken
\nthrough the 1950s and 1960s revealed persistent high levels of arsenic on local produce and berries.
\nConcerns remained about water pollution from both atmospheric deposition and arsenic- and cyanidelaced
\ntailings effluent. The collection of arsenic, , also resulted in the fateful decision to store arsenic
\ntrioxide dust in underground chambers and mined-out stopes. Today, the 237,000 tonnes of arsenic
\ntrioxide underground at Giant remains the central environmental challenge for the reclamation and
\nremediation of the site.
\nPublic health studies undertaken in the 1960s suggested a possible link between arsenic exposure and
\nelevated cancer rates in Yellowknife, but these studies were not made public until the 1970s. A series
\nof independent and government studies followed these revelations as public concern mounted over
\nthe health effects of long-term arsenic exposure. Further reductions in arsenic emissions from Giant
\nwere achieved, and the mine constructed a tailings effluent treatment system in 1981. While local
\nactivists raised concerns about sulphur dioxide and arsenic emissions in the early 1990s, territorial
\ngovernment studies concluded these emissions did not pose a public health risk.
\nFor the Yellowknives Dene First Nation in particular, memories of mine development and subsequent
\narsenic pollution of their traditional lands are painful. Some Dene worked at the mine, but the
\ncommunities of Ndilo and Dettah saw few benefits from the mines overall. Yet these communities, due
\nto their location in relation to Giant, were on the front line of arsenic exposure over the half-century
\nofits operation. The Yellowknives Dene not only suffered disproportional health impacts from arsenic
\npollution, but also the loss of harvesting areas due to the appropriation of land for the mining
\noperations and urban growth in the city of Yellowknife.

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