Geophysical Characterization of Smelting Wastes: A Case History

Abstract

AbstractThe thicknesses of slag piles at a smelling site in Midvale. Utah, were determined using geophysical methods; this information was needed to estimate the cost of removing or isolating slag that has the potential to contaminate ground water. From a small‐scale preliminary investigation that, included terrain‐conductivity profiling, low‐frequency resistivity measurements, and induction logging, the electrical resistivities of the slag and the underlying sediment were determined to be approximately 100 Ω‐m and 15 Ω‐m, respectively. Because electromagnetic measurements are affected by such significant contrasts, terrain‐conductivity profiling and time‐domain electromagnetic soundings were used to determine the thicknesses of the slag piles. Generally, the estimated thicknesses from both methods were consistent and geologically plausible. In some instances, reliable estimates of the thicknesses could not be obtained because, for example, the measurements were affected by buried metal objects.In this case study, we emphasize three principles that might help investigators at other smelter sites. First, a small‐scale preliminary investigation saves time and money because those geophysical methods that have the greatest likelihood of success can be determined. Second, when the results from several geophysical methods are consistent, the confidence in the interpretation increases. Third, geophysical characterization is not always successful. Nonetheless, because of its outstanding advantages, it should be used before other more expensive characterization methods arc tried.