Miner standing in a mine shaft

History of Giant Mine

Gold was first discovered by prospectors in the Yellowknife area in 1896, who were headed north for Klondike riches. Nothing came of the Yellowknife discovery at the time. The area was considered inaccessible.

However, it was 1935 and the arrival of commercial aircraft (bush planes) before the area became more accessible, and the gold boom began. At this time, eager prospectors returned, hunting the precious metal all along the northern shores of Great Slave Lake.

In the summer of 1935, C.J. "Johnny" Baker and H. Muir staked the original 21 "Giant" claims for Bear Exploration Company. The claims were on Great Slave Lake's Back Bay and along what is now the historic Ingraham Trail.

By 1937, Yellowknife Gold Mines Ltd. acquired Burwash's assets. From these, the subsidiary Giant Yellowknife Gold Mines Ltd was created. The company fell on hard times and by 1940, operations eventually came to a standstill. Frobisher Explorations took over the site in 1943. However, the advent of World War II halted the operation once again. Gold was not a priority in times of war, and there was a shortage of men to work the site.

Soon after the war ended, Giant Mine officially opened, and production moved into full swing. The first gold brick was poured on June 3, 1948.

From May to December 1948, the mine produced 8,152 ounces of gold from 49,985 tonnes of ore. With the nearby Con Mine also operating, Yellowknife was experiencing the rapid growth associated with a booming mining industry.

Those original claims would lead to the production of seven million ounces of gold and one of the longest continuous gold mining operations in Canadian mining history; however, they also led to a legacy of contamination.

Gold at Giant Mine was found in specific minerals called arsenopyrite ore. To release the gold, the ore had to be roasted at extremely high temperatures. Unfortunately, this roasting process also released arsenic rich gas, a highly toxic by-product.

In the early days, much of that arsenic was released directly into the environment. This was partially addressed in 1951, with the installation of a Cold Cottrell Electrostatic Precipitator, which acted as a "scrubber". It removed a lot of the toxic arsenic trioxide waste, so it did not get released into the environment.

Arsenic releases were further reduced, from 7,400 (in 1951) to 2,900 kilograms per day in 1956 This was the result of adding a second "scrubber" – a Hot Cottrell Electrostatic Precipitator – to the roasting process in 1955.

A further waste reducing innovation was added to the site in 1958. A Dracco baghouse was added to collect the waste. This reduced airborne arsenic emissions to 52 kilograms per day by 1959. Over the years, that number would fluctuate up to 300 kilograms per day. Since the waste was collected instead of released, it needed to be safely stored. In the 1950s, scientists and government agencies agreed storing it in underground stopes and chambers was an appropriate, long-term solution. They believed that, when Giant Mine closed permanently, the natural permafrost in the area would re-establish around the storage vaults and seal in the arsenic trioxide.

In the 1980s, Koppers Corp. of Pittsburgh, Pa. purchased 6,700 tonnes of the arsenic trioxide waste to treat wood. However, most of the arsenic trioxide created during production is still underground at the site.

Giant Mine was owned by different companies over the years. The Giant Yellowknife Mines, Ltd., a subsidiary of Falconbridge, owned the mine from 1948 to 1986. It was next owned by Pamour from 1986 to 1990.

In 1990, Royal Oak Resources Ltd. purchased Giant Mine, and formed Royal Oak Mines Inc. In May 1992, the local branch of the Canadian Association of Smelter and Allied Workers at Giant Mine went on strike. In September, during ongoing labour unrest, a deliberately ignited underground explosion killed nine. The striking miners eventually returned to work in December 1993.

In 1997, a technical workshop was held to discuss managing the arsenic trioxide waste stored underground at the mine. This included officials from:

  • Indigenous and Northern Affairs Canada
  • Royal Oak Mines Inc.
  • Environment Canada
  • the Government of the Northwest Territories
  • the City of Yellowknife

By 1999, however, Royal Oak Mines Inc. went into receivership. The courts transferred Giant Mine to the Government of Canada, represented by Indigenous and Northern Affairs.

Ore was no longer processed at Giant Mine after 1999. However, in that year, Canada sold the mine's assets to Miramar Giant Mine Ltd., a division of Miramar Mining Corporation. This ensured a maximum number of jobs continued at the mine and that a knowledgeable, experienced operator would stay on site to oversee the care and maintenance of the site.

As a condition of the sale, Canada acknowledged Miramar would not be responsible or liable for the existing state of the mine. This meant Indigenous and Northern Affairs Canada became a caretaker for the site, including the arsenic trioxide stored underground.

Miramar Giant Mine Ltd. ended its obligations under the Reclamation Security Agreement in 2005. At that time, Giant Mine officially became an abandoned mine site.

When CIRNAC became responsible for the Giant Mine site, they continued to care and maintain the existing infrastructure on the site. CIRNAC also inherited the environmental liability related to the arsenic trioxide dust stored underground, and the surface components of the site. And the plan to address the risks and liabilities at the site would be carried out via the Giant Mine Remediation Project.

For further information please visit: https://www.rcaanc-cirnac.gc.ca/eng/1100100027364/1617815941649