Several geophysical methods have been used at landfill sites in attempts to determine cover thickness, overall thickness, fill material, and amount of fracturing in the cover. Carpenter et al. [1991] used resistivity soundings, azimuthal resistivity measurements, and seismic refraction profiling to investigate cover thickness and fracturing at a landfill site in Illinois. Although neither seismic refraction nor resistivity methods provided accurate measures of the cover thickness, seismic velocity was found to decrease within fractured areas of the landfill cover and apparent resistivity was found to increase at azimuths parallel to fractures. Thus both methods proved useful in identifying areas of fractured landfill cover that could serve as pathways to infiltrating surface water and escaping landfill gas. Jansen et al. [1993] used EM methods to characterize fill materials and overall thickness at several landfill sites in the midwest and southern U.S. In one area, they used a magnetic survey to locate suspected buried steel drums. Horton and Busby [1993] and Horton et al. [1993] demonstrated a novel method of using differential EM conductivity measurements to separate instrumental drift effects from lateral conductivity variations to delineate an abandoned landfill site.