Geophysical Method of Investigating Groundwater and Sub-Soil Contamination – A Case Study

Geophysical methods can be helpful in mapping areas of contaminated soil and groundwater. Electrical resistivity surveys were carried out at a site of shallow hydrocarbon contamination in Ahoada, South-South Nigeria. This was aimed at evaluating the subsoil conditions and groundwater quality of the area three years after the post-spill clean-up exercise. The geophysical investigation involved the Vertical Electrical Sounding (VES) technique using the Schlumberger configuration and the horizontal profiling method. The data from the two different approaches correlate well, and the generated profiles of the acquired data helped to map the contaminant plume, which was delineated as an area of high interpreted resistivities. The VES result shows that the subsurface layers up to a depth of 49 m is of moderate to high resistivity values (>200 Ώm) that may affect crops and groundwater development in the study area. However good aquifer can still be obtained from the depth of 30 m and above.