Glossary

A variety of substances and hazards are found at contaminated sites in the NWT. Some substances are naturally occurring but have become a problem due to development, while others were brought into the area for a specific purpose. Below is information about some significant contaminants and hazards found at contaminated sites in the NWT.

Acid-generating waste rock and tailings: Also commonly referred to as acid rock drainage. During mining, rock is disturbed and minerals that were contained in the rock are exposed to oxygen and the environment. If the rocks are naturally acidic, this can lead to the creation of an acidic environment which can be transported by water.

Ammonia: Commonly found at mine sites where cyanide is used. Ammonia occurs when cyanide breaks down (degrading), and is found in tailings and tailings water. Ammonia is also used in explosives.

Arsenic trioxide: Rock mined in Yellowknife and some other gold deposits in the NWT that is rich in arsenopyrite, a mineral that has a high arsenic content. The ore in this area was roasted to release the gold. When it was roasted, arsenic was also released as a gas. The gas cooled and became arsenic trioxide dust.

Contaminant: Any physical, chemical, biological or radiological substance in the air, soil or water that has an adverse effect. Any chemical substance with a concentration that exceeds background levels, or which is not naturally occurring in the environment, is a contaminant.

Contaminated Site: Site at which substances occur in amounts above what would be natural and pose, or likely will pose, a hazard to human health or the environment, or exceed levels specified in policies and regulations.

Cyanide: Chemical added during the floatation process to separate gold from ore. Cyanide is brought to the site as a powder. After it is used in the floatation process, it ends up in tailings and tailings water.

DDT: Commonly used pesticide at sites in the past to help workers deal with mosquitoes. It was brought to the site in barrels, and was used liberally.

Hazardous waste: Other potentially harmful substances brought to the sites, used in ongoing operations. For example, several sites had on-site assay laboratories, which involved lab chemicals. Antifreeze and asbestos were also common on sites.

Hydrocarbons: All petroleum-based products, such as fuels, oil and grease. It is used at sites for heating, power generation and vehicles. If these products are not handled or stored properly, there can be leaks and spills, which contaminate soil and water.

Lead: Substance found in paint, batteries and hydrocarbons, such as leaded fuels.

Mercury: Substance added during the floatation process to separate gold from ore. Mercury is brought in as a liquid. Once used, it remains a liquid and can be found in tailings and tailings water.

PCBs: Oily substance brought to sites as a coolant, for use in electrical equipment. PCBs were also mixed with paint to be used as a moisture barrier. If these products are not disposed of properly, they can cause contamination of soils, air and water, and bioaccumulation in mammals.

Physical hazards: Physical facilities required for ongoing operation of sites, such as buildings, air strips and mine workings, which have decayed over time and become safety risks.

Reclamation: Process of reconverting disturbed land to its former state or other productive uses.

Remediation: Removal, reduction, or neutralization of substances, wastes or hazardous material from a site. The goal of remediation is to prevent or minimize any adverse effects on the environment or public safety.

Uranium-related waste: Waste rock and other material left over from the mining process. Uranium naturally gives off radiation as part of the ongoing decaying process. When uranium is mined, it is exposed to oxygen and that decaying process is accelerated. Uranium-related waste is put in tailings containment areas, resulting in a higher concentration and higher than natural radiation levels.