Influence of climate change on the ability of a cover with capillary barrier effects to control acid generation

Annual precipitation, temperature, and the frequency and duration of drought events are expected to increase in Québec (Canada) south of the 50th parallel as a result of climate change. Oxygen barriers such as covers with capillary barrier effects (CCBE), which are used to control acid mine drainage (AMD), are sensitive to climate change. Increases in precipitation may have positive effects on maintaining the saturation of a moisture-retaining layer (MRL), which is necessary for reducing oxygen fluxes to reactive tailings; however, drought events could cause temporary desaturation of a MRL and, consequently, increase the potential for acid generation. The Lorraine mine site, in western Québec, was reclaimed with a CCBE in 1999 and was used as a case study to assess the effects of climate change on reclamation performance. A two-dimensional numerical model was developed and validated using 3 years of meteorological and hydrogeological data. Numerical simulations were performed to assess the CCBE’s performance, considering the influence of: (1) climatic conditions (i.e., precipitation, temperature, relative humidity, wind speed, albedo and solar radiation) by 2100 for three different climate-change scenarios, and (2) extreme drought events. Performance targets were reached for all tested climate-change scenarios, thus indicating that the Lorraine CCBE design is robust with respect to climate change and extreme droughts. More broadly, this study illustrates how numerical simulations can be used to quantify the influence of climate change on the long-term ability of CCBEs to control the generation of AMD.