Arsenic spill dusts worker at Giant site

An accidental discharge of deadly arsenic trioxide at the old Giant gold mine in Yellowknife, Northwest Territories this fall has brought into focus the potential impact of an ongoing project to reclaim the mine site.

The project includes the future disposition of the 237,000 metric tons of arsenic trioxide currently stored underground at the site within the Yellowknife city limits. The hazardous substance was abandoned when mine owner Royal Oak Mines went bankrupt in 1999.

In order to prepare a remediation plan for the Giant Mine, Indian and Northern Affairs Canada and the Government of Northwest Territories spent eight years doing research and engineering work to develop a viable approach.

After conducting extensive public hearings and consultations, INAC has undertaken a study of freeze optimization technology for use at the mine site. The agency hopes to freeze solid the arsenic trioxide dust in its 15 sealed underground chambers to create a "frozen block" barrier to prevent any seepage of toxic material from the chambers.

Arsenic spill

In late October, INAC received a report that a small amount of arsenic dust was spilled and came in contact with a worker at the site.

INAC said the arsenic dust did not migrate out of the immediate vicinity of where the incident occurred, and the arsenic was cleaned up, containerized and properly stored.

The freeze optimization study was suspended pending investigation. Soil and water samples were taken and submitted to laboratory to ensure there was no further exposure in the surrounding area.

INAC also said the worker who came into contact with the dust was wearing personal protective equipment, including a waterproof suit and a specialty-fit respirator at the time of the incident. Following established safety procedures, he was immediately washed down and tested for exposure.

After it was notified of the incident, INAC said its inspector for the project contacted the mine manager to discuss the incident, and confirmed mitigation measures undertaken to that point. The inspector also visited the site October 26.

The worker, an employee of the project's care and maintenance contractor, Deton'Cho/Nuna Joint Venture, is still being monitored for possible effects of the exposure to arsenic. INAC has been advised that the worker had elevated, but not serious levels of arsenic in his urine, INAC spokeswoman Jennifer Moores told Mining News Dec. 15. Deton'Cho/Nuna Joint Venture has been keeping INAC informed of the employee's status, she added.

Independent oversight

Various individuals and groups, including the City of Yellowknife, continue to call for independent oversight of the project. They also have raised questions about the credibility of the agencies and contractors currently working on the reclamation effort.

The Mackenzie Environmental Impact Review Board is awaiting the developer's assessment of the project, which is expected in February.

Once a solution is found to control the contamination and the remediation plan is complete, the Giant mine site will still require monitoring indefinitely to ensure the health and safety of the community. Long-term water treatment also will require the construction of a new water treatment plant.