Development Of A Continuously Monitoring Resistivity Probe For Free-Phase Petroleum Hydrocarbons

An in-situ electrical resistivity probe was evaluated for use in monitoring the vertical distribution of petroleum<br>hydrocarbon in contaminated soil. By installing the probe to intersect the water table, it continuously monitors the<br>presence of free-phase hydrocarbons by detecting electrical resistivity changes corresponding to the degree of oil<br>saturation in the sediment pores. At a field site where diesel contamination occurs within a fine-grained sand, the<br>results from the probe were compared to chemical analysis of total petroleum hydrocarbons (TPH) of soil borings<br>and measured free product (light non-aqueous phase liquid-LNAPL) thickness and groundwater level in wells. The<br>resistivity probe was also used to study LNAPL behavior under fluctuating water table conditions in a controlled<br>laboratory environment. Results from the resistivity probe reflect the distribution of the contaminant within the<br>sediment on a continuous basis and more accurately than contaminant thickness measurements in wells.