Geophysical modelling and mapping of contaminated groundwater around three waste disposal sites in southern Ontario

Abstract

We present an approach to the use of electomagnetic geophysical methods for delineating groundwater contamination, and test the concepts at three waste disposal sites. The approach includes a technique for modelling a site's response to a variety of instruments, and a device-independent method of contouring the data. The modelling attempts to account for the noise inherent in the measurement process, particularly the effects of lateral variations in stratigraphy. These concepts are evaluated by comparing the geophysical response to groundwater conductivities measured in sampling wells. We conclude that geophysics offers a cost-effective supplement to drilling, and that it is best used in a reconnaissance mode to map the general distribution of contamination prior to a detailed sampling program. The correlation between the observed and predicted geophysical response as a function of groundwater conductivity is as good as can be expected given the uncertainties in the process. The methodology proposed is simple to use and practical. Key words: groundwater, contamination, geophysics, electromagnetic, mapping, modelling.