British Columbia Mine Reclamation Symposium

Eskay Creek Mine environmental effects monitoring program and its implications for closure planning McGurk, Michael; Landry, Francois; MacGillivray, Randy


Effluent from the Eskay Creek Mine constitutes 6 to 12% of the flow of Ketchum Creek – the immediate receiving environment. Hence, the Metal Mines Effluent Regulations required an Environmental Effects Monitoring Program to determine the effects of effluent of aquatic organisms. Sampling of benthic invertebrates in Ketchum Creek in September 2005 showed significantly higher family richness at an exposed station compared to a reference station, but no significant variation in average benthos density or species diversity. Benthos characteristics may be driven more by variation in physical habitat than by exposure to mine effluent. The naturally high metal concentrations of Ketchum Creek caused bioaccumulation of metals in Western Pearlshell mussels (Margaritifera falcata) in two stream-side mesocosms (reference and exposed) run from early August to late September 2005. Metal concentrations were higher in the exposed mussels than in reference mussels. However, survival was slightly higher at the exposed mesocosm and growth was zero for both mesocosms. The conclusion was that the ecological effects of mine effluent are low in magnitude and difficult to distinguish from natural effects. Therefore, current closure planning, which will maintain or lower the existing discharge rates, should be protective of the receiving environment in perpetuity.

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