Yellowknife's Accidental Arsenic Mine: The Giant Mine

Heather Comeault
Aug 18
3 min read

Yellowknife is the capital of the Northwest Territories and the only city within the entire Territory. Situated along the Northern shores of the Great Slave Lake, Yellowknife is a beautiful city with some incredible scenery and amenities. The history however, is a little more complicated. While recognizing that Yellowknife is situated on Chief Drygeese territory, this story covers something that not only affected the indigenous communities, but everything around it, and it still continues to be a problem. This problem is none other than Yellowknife's accidental arsenic mine.

Yellowknife Giant Mine — The Giant Mine main office sign

From 1948 until 2004, the Giant Mine operated just outside of Yellowknife in the Northwest Territories. The mine was used to extract gold deposits within the area. On June 3rd, 1948 the first gold brick was poured and the mine was off to the races! While ever so lucrative, gold mines don't just produce the gold you see today, they also produce a byproduct which contains arsenic.

Between 1949 and 1950, the Giant Mine was emitting approximately 7,500kg of arsenic per day. In 1950, the first study of the arsenic emissions was completed and some minor changes were made. In 1951, the mine was emitting approximately 5,500kg of arsenic per day, which is reduced in turn by the emissions being pumped underground into large storage chambers below the surface. By 1959, with the help of some new construction to help collect arsenic trioxide dust, the mine was emitting as little as 200-300kg of arsenic per day.

Although the mine was reducing its emissions of arsenic, much of the damage had already been done and with the continued operations of the mine, more damage will follow. The soil, water and air had been contaminated, making it an unfit area for any wildlife or people, including the indigenous communities in the area. Traditional harvesting and fishing was impacting their way of life and their grounds were overrun with contamination. A young child even died after ingesting contaminated snow from the area, prompting serious concerns about the mine.

Contamination sign Giant Mine — Signs beyond the visitor centre are marked to keep people out.

Throughout the years, the Giant Mine ticked along, collecting tonnes of gold ore and continuing to store the arsenic emissions and trioxide dust undergrounds and within the hills. Regular inspections were done on the chambers and everything seemed to be as okay as they could be, aside from the fact that the mine had already poisoned the environment around it.

In 1990, Royal Oak Resources LTD. took over the mine and formed Royal Oak Mines Inc. In 1992, an explosion was set off by a disgruntled employee after union disputes brought in outside workers. A total of nine miners died as a result.

In 1997, discussions began between Royal Oak Mines Inc. and several groups including Environment Canada, the Government of the Northwest Territories and the City of Yellowknife on how to tackle the problem of the arsenic trioxide dust. Talks continued about remediation and in 2004, the Giant Mine officially ceased operations.

Remediation still continues today and with many complications and roadblocks ahead, remediation is expected to continue for many more years to come.

The Giant Mine is closed to the public with the exception of the Yellowknife Historical Museum which is located at the entrance to the site. The museum is located within the original miners recreation hall and features a plethora of exhibits and information from the early mining days to the current remediation project. The mine also features an outdoor exhibit with large equipment used in the past.