Abstract
Ammonia is regulated under the federal MDMER regulations in Canada and is a known potential toxicant and a constituent of potential concern in mine influenced waters. Decisions about ammonia management and treatment often need to be made in very early project stages and certainly prior to permitting as they can materially impact project costs and risks. At these early stages, no operational data are available, which means that decisions are made based on predictions. Unfortunately, the methodology used for ammonia concentration predictions is rather crude and often rely on data collected at so called “reference sites” that are often of questionable applicability to the new projects. This paper analyzes the methodology of ammonia concentration predictions and compares actual ammonia loads released into mine influenced water to loads that would be predicted in the absence of mine operations data at a nickel underground mine in Quebec, Canada. The effects of site-specific factors are discussed and analyzed. The objective is to provide the mining industry with a new reference and propose modifications to the ammonia load predictions that could be used to support water management and treatment decisions made in early project stages to reduce project costs and risks.