Geophysical Investigation of the Clay Cap at a Closed Landfill in Southwestern Ontario, Canada

At a closed mixed waste landfill in southwestern Ontario, concerns have been expressed about rainfall infiltration, possibly resulting from a non-contiguous landfill cap, and the potential for leachate leakage at the southern edge of the landfill. This study examines the application of geophysical methods to investigate the contiguity of the landfill cap and to assess for leachate leakage outside the landfill. DC resistivity profiles were measured using an ABEM Terrameter. Analysis indicated that the cap thickness ranged from 0-3 meters and was not consistent, likely allowing the infiltration of precipitation into the refuse mound. The DualEM 2S/4S was used to map apparent conductivity in and near the problematic area, with values ranging between 2-570 mS/m. Higher conductivity values occurred in the northwestern and central area, while linear areas of midrange values extended from within the landfill to outside the landfill, suggesting leachate leakage