Using geophysics to understand two hydrocarbon contaminated sites and protect culturally-important exposure routes
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This presentation includes results from several field seasons at two tribal leaking underground storage tank (LUST) sites. Havasu Landing Resort is on Chemehuevi land and includes two LUSTs; one at the hardware store and one at the marina. Surface and borehole geophysical surveys mapped utilities and a clay layer/lens. Both findings aid in conceptual site model (CSM) development and indicate the fate and transport of the hydrocarbon plumes are impacted by the clay lens and the preferential flow from utility trenches. The second site is the Davis Chevrolet LUST site in Tuba City, AZ. The plume migration as understood from monitoring wells is very perplexing suggesting secondary porosity/fractured flow. Surface and borehole geophysical surveys indicate complex geology, fractures, and geologic contacts likely explaining the monitoring well data as well as guiding the placement of additional wells. Both sites demonstrate the usefulness of geophysical surveys to enhance CSM understanding and guide future decisions at these sites.