3D Electrical Resistivity Tomography to Locate DNAPL Contamination in an Urban Environment

This study presents results from electrical resistivity campaigns performed around a housing estate located downstream to an old coke tar site in France. This coke tar has been previously studied with geochemical analyses and geophysical prospections. The previous results have shown a possible migration of the contaminant plume toward the housing estate. As geophysical measurements are difficult to perform in such an urban environment, the electrical array has been deployed all around the housing estate with an innovative arrangement of surface electrodes in C-shape and acquisition geometries in order to achieve a real 3D imaging of the subsoil and locate the contaminant plume above the housing estate. The electrical resistivity data were inverted with the ERTLabTM 3D inversion software developed by Multi-Phase Technologies and Geostudi Astier. Results show, at the depth of the aquifer, a very conductive plume emanating from old tar ponds and a slag heap and spreading through the housing estate.