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Abstract

The Copper Mountain Mine is situated in the Similkameen River valley in southern British Columbia, Canada. Sulphate and other parameter concentrations, resulting from tailings and waste rock sources, have been increasing over time in a drainage to the east of the mine named Wolfe Creek. The creek is predominantly groundwater fed, with the main source of recharge to the aquifer that feeds the creek being reclaim water that drains through the Tailings Management Facility (TMF). Concentrations of sulphate in the creek are nearing compliance station limits and mitigation through groundwater interception is required to reduce loading and ultimately concentrations in Wolfe Creek. A phased mitigation strategy has been developed, with the first phase comprising significant characterization and the installation of trial pumping wells in 2023. The second phase consisted of the testing of various short-term mitigation techniques, including the pumping wells and various configurations of interception ditches and trenches. The testing activities were implemented in 2024. The first two phases have significantly advanced the working hydrogeological conceptual model which is being used to develop medium to long-term interception options that are being tested using a numerical model. The removal of sulphate load through groundwater interception will result in reduced flows to the creek, which in turn will likely affect downstream flows, reducing them to pre-startup conditions during operations rather than in post-closure. A wetland is present downgradient of the TMF which may also become affected through load removal. Therefore, sulphate management needs to be carefully balanced with flow and load interception in the valley to manage the flow needs of the downstream environment. As this project is ongoing, this paper focuses on the mitigation strategy, characterization efforts and results, conceptual model, and considerations for sulphate management.