GEOPHYSICAL MAPPING THE TOP OF BEDROCK AT THE KING ROAD LANDFILL, LUCAS COUNTY, OHIO

The abandoned King Road landfill west of Toledo, Ohio was constructed on permeable sands of the Oak Openings belt. In order to model long-term patterns of contaminant transport under and near this site, and then to design a cost-effective site management strategy, we need to understand the geology under the mounded waste. Seismic refraction used to map variations in the depth to carbonate bedrock immediately north and south of the landfill reveals an irregular bedrock surface that generally deepens from 2 meters below the surface west of the site to 25 meters deep near the southeast corner of the site. Electromagnetic conductivity and DC resistivity measurements infer leachate in thick sand under the southwest corner of the landfill, where residential and commercial structures prevent tracking off-site contaminant migration. Although most borings near the landfill encountered silt or clay between surficial sand and bedrock, geophysical surveys thus far have failed to detect and map this structure. Because the presence or absence of a continuous confining layer is a critical boundary condition when developing flow models, ground-penetrating radar and high-resolution shallow seismic reflection surveys are planned to obtain this stratigraphic information.