Development of a site-specific water quality objective for copper for a post-closure mine site discharge Martin, Alan J.; Goldblatt, Robert; Hiller, Dave
Detour Lake Mine, located 200 km northeast of Timmins, Ontario, operated from 1983 to 1999 using a combination of open pit and underground mining methods. As part of the historic tailings circuit, East Lake served as a tertiary polishing pond for gold mill effluents prior to final discharge to the receiving environment. The discharge from East Lake serves as the final point of discharge for the mine site, with copper concentrations ranging from 40 to 150 µg/L. As part of the overall closure management, Placer Dome Inc. has initiated a program to develop a site-specific water quality objective (WQO) for dissolved copper at East Lake discharge. WQO generation entailed the assessment of three components: 1) the assimilative capacity of the receiving environment downstream of East Lake, with consideration to dilution, Cu speciation and complexation capacity; 2) toxicity data, including chronic and acute toxicity testwork conducted on water collected at the East Lake discharge and in the downstream environment; and 3) use of the water-effect ration (WER) procedure as outlined by the government of Canada and the USEPA. Based on the testwork, a preliminary site-specific water quality objective for dissolved copper ranging from 34 to 75 µg/L has been proposed. The range in WQO values can be explained by temporal variability in Cu complexation capacity, which in turn can be related to variations in both the quantity and quality of dissolved organic carbon.
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