Dave Donohue from HydroSolutions and Tom Henderson from DEQ were invited to present at the May 2018 Mine Design, Operations, and Closure Conference held in
Fairmont Hot Springs, Montana. Their talk focused on a brief history of coal mines in the Sand Coulee area, Cascade County, Montana and the application of source control techniques for acid mine drainage. An evaluation of the feasibility of both horizontal and vertical gravity drainage wells to reduce drainage from the Kootenai aquifer overlying the abandoned underground coal mines in order to mitigate AMD was completed. The concept underlying this project is to intercept uncontaminated groundwater and reduce the natural leakage of clean water into the historic mine workings. This hydrogeologic investigation, which included adit discharge monitoring, monitoring well installations, aquifer testing, and water quality evaluation, has confirmed that gravity drainage wells are a feasible method of AMD source control in the Sand Coulee area. Based on the results of the work to date, proposed locations for both horizontal and vertical drainage wells were identified. Installation of pilot test wells to evaluate the selected drainage well locations is planned for 2018.
