Low temperature thermal desorption of petroleum hydrocarbons from heavy clays

A 10,000 gallon underground gasoline tank was removed after a system tightness test indicated a possible leak. Subsequent soil and groundwater sampling indicated a release of hydrocarbons into the surrounding heavy clay soil. Free-phase hydrocarbons were also identified floating on the ground water. Corrective action was initiated by excavating soil in the immediate vicinity of the tank. A pump-and-treat system was installed to remediate groundwater. Two years of subsequent groundwater treatment provided no decrease in groundwater contamination levels. Unsatisfied with remediation progress, an additional subsurface investigation was performed that indicated significant levels of contamination were still present in site soil. After reviewing various remedial alternatives, a low temperature thermal desorption process was selected to remediate approximately 7,600 tons of contaminated soil. This paper will discuss permitting, planning, operational, and regulatory interface issues associated with thermal desorption at this site. The subsequent monitoring of site groundwater monitoring wells will also be discussed as well as the efficacy of the pump-and-treat system