Electrical resistivity prospecting for geo-environmental investigation

Abstract

Among geophysical exploration techniques, the electrical resistivity prospecting method has been increasingly applied to geo-environmental investigations such as the detection of soil and groundwater contamination. The method is used to identify permeable soil layers that are possible channels of contaminant transport. Geo-environmental investigations deal with important cultural issues and are a growing field of innovation. This paper describes briefly the present state of soil and groundwater contamination guidelines in Japan, and the application of the electrical resistivity prospecting method to the identification of permeability structures that are possible channels of pollutants. Results from two field studies are presented. At the first site, the extent of seawater infiltration into a coastal aquifer was determined, allowing bores to be sited where fresh water could be extracted. At the second site, resistivity time lapse monitoring was successful in tracing the movement of saline water injected into a permeable layer. This allowed the arrival time of the salt water at a monitoring well to be predicted, and increased confidence in the estimates of flow rate.