Integrated characterization of waste rock at the Detour Lake Mine

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Open pit mining at the Detour Lake gold mine is generating large volumes of waste rock that need to be managed to minimize the release of acid rock drainage. Previous mining operations at the Detour Lake site, from 1983 to 1999, resulted in the construction of four waste-rock stockpiles. Two of these stockpiles were excavated during the development of the current Detour Lake mine. Two stockpiles remain in place. These stockpiles have 16 years of operating history and 15 years of post-closure history under site conditions, and represent a valuable opportunity to examine the reactivity of rock types from the Detour Lake site, which can be used to improve water quality predictions. The stockpiles also provide an opportunity to understand the performance of waste-rock closure strategies used following the previous operation and provide a basis for improved closure designs. The proposed research at the Detour Lake site will include investigations on existing covered waste rock stockpiles 3 and 4 to develop a detailed analysis of the water balance for these stockpiles, to assess the impact of leachate from the stockpiles on underlying aquifers, and to assess the performance of the thin soil covers as a waste-rock management system. Additional investigations will focus on the new mineralized-waste stockpile (MWS) to assess potential interactions between the MWS leachate and the underlying foundation materials. The proposed research program will contribute a critical linkage between direct observations of historic rock stockpiles that have been weathering under natural field conditions for 31 years and freshly deposited stockpiles. It is expected that this study will lead to improved techniques for predicting and managing the long-term quality of effluent from waste-rock stockpiles.