Survey of closed and abandoned mines in British Columbia for acid rock drainage I : regional perspective

Abstract

In 1991, Environment Canada and the British Columbia (B.C.) Acid Mine Drainage Task Force initiated a project with the goal of compiling information for closed and abandoned mine sites throughout British Columbia. The ultimate objective of the study is to assess the current and potential impacts caused by acid rock drainage (ARD) on surface water quality throughout the province. In addition, in the Fraser River basin, non-mining sources of ARD (such as natural weathering, railway and road cuts and municipal developments) are also being considered. This paper presents the results of the evaluation with respect to the regional distribution of closed and abandoned mines throughout B.C. and the regional ARD potential based on a derived ranking scheme. Three regions of the province were identified as having a high potential for ARD. There are several acid-producing mines in the Smithers and Stewart regions and Vancouver Island, and other mines are in geological settings which could allow ARD to be produced. The Kootenay region has seen extensive historical mining activity, but there is a lack of environmental data for individual mines. The presence of limestone and calcite in the mine sequences limits ARD potential in the Kootenays, although this mineral is not always closely associated with ore minerals. In general, the Fraser River basin has less historical mining activity than the rest of B.C, partly as a result of glacial drift cover. The potential for ARD in the basin also appears lower than elsewhere due to the common occurrence of calcite-bearing volcanic rocks.