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Abstract

Canamax Resources Inc. operate the Ketza River Mine, a small gold mine in the Yukon Territory some 180 km north-east of Whitehorse. The mine has until now processed oxide ore only, depositing tailings in an impoundment created by the construction of two dams, and the diversion of existing watercourses around the facility. Gold recovery is by cyanidation. The resulting tailings pond water has significant concentrations of cyanide, copper and arsenic. Pond water cyanide concentrations are controlled by seasonal natural degradation and tailings treatment to destroy cyanide using the Inco SO2 - air process prior to discharge to the impoundment. Pond water is also treated to destroy cyanide using the Inco process, followed by discharge to the environment during a 6 month period per annum covering the duration of higher surface water run-offs. Seepage from the impoundment is collected and returned by strategically located sump and pump-back systems. Steffen, Robertson and Kirsten (B.C.) Inc. (SRK) was engaged by Canamax to investigate seepage from the tailings impoundment, and was subsequently retained to assist with operating and decommissioning issues related to the tailings impoundment and a proposal to mine and mill sulphide ores, pending regulatory approval. The proposed milling of sulphide ores raised a number of environmental issues regarding the tailings impoundment. Operating conditions could potentially yield higher contaminant concentrations in the tailings pond, which could have a concomitant effect on concentrations in seepage and water treatment plant effluent discharge. Further, decommissioning plans were needed to address the disposal and long-term storage of potentially acid generating tailings. This paper summarizes the investigations undertaken and predictions made in terms of the proposed milling of sulphide ores, the tailings impoundment and the receiving aquatic environment at the Ketza River Mine. The "sulphide" project at Ketza is considered an example of the sustainable development of a relatively small operation despite potentially adverse environmental circumstances, with development assisted by the assessment of specific environmental issues and the adoption of appropriate mitigative solutions.