An accidental hydrocarbon release into a residential water well provides a case study for an assessment of the transport mechanism of a hydrocarbon in an alluvial depositional geologic setting. Due to the failure of initial results to recover the injected hydrocarbon in nearby wells, we collected ground-penetrating radar (GPR) data, soil samples, and soil conductivity logs throughout the site with the following objectives: (1) to understand the geologic setting, and (2) to identify the migratory path of the contaminant in the subsurface. Integrated interpretation of the GPR data, soil samples, and the soil conductivity logs provided evidence that the spilled hydrocarbon migrated against the direction of the dominant groundwater gradient but instead moved upward along dipping layers characteristic of the meandering river system. These results demonstrated that at a contaminated site having complex stratigraphy, traditional methods of characterization (such as monitoring wells) may fail, and the judicious use of geophysical and geotechnical tools may be able to provide insight into the mechanisms for the fate and transport of the contamination.

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