ELECTRICAL RESISTIVITY INVESTIGATIONS ON AND AROUND LANDFILLS

Electromagnetic induction (EM) and direct current resistivity (DC) surveys are proving useful in mapping subsurface conditions near, within and under closed landfills in northern Ohio. Geometrics OhmMapper EM profiles provided evidence that an old, poorly documented solid waste landfill does not extend under property being considered for industrial redevelopment. OhmMapper measures variations in apparent resistivity to depths of around 6 meters where buried waste or leachate are not present, but high conductivities decrease the skin depth, limited penetration through low resistivity leachate. DC measurements with Advanced Geosciences’ Supersting R1IP and 28 electrodes (10 m spacing) reveals resistivity variations up to 50 m under the surface near the center of each dipole-dipole array of long, multi-array profiles, providing information on conditions within and under a landfill. We are extending these methods beyond traditional surveys in search of leachate outside the perimeter of landfills to mapping the base of buried waste within landfills, searching for ponded leachate within and vertically migrating leachate under landfills. Resistivity measurements contribute to conceptual models of what lies within and under poorly documented landfills, an important step in developing effective remedial actions.