Ground water remediation by controlled soil freezing

Spilled petroleum hydrocarbons will migrate into granular soil deposits, in the process contaminating local ground water supplies. These materials (oils), at temperatures of 0 °C to 20 °C, have viscosities which allow movement into and through porous media in the form of a continuous fluid or as globules of oil. Pumping can be used to remove larger masses of continuous contaminant with small globules remaining trapped in the soil. In water saturated granular soils, preliminary studies show that an advancing freezing front will exclude the small oil globules, forcing them to be concentrated at the frozen/unfrozen interface. With increase in contaminant concentration at the interface, less water is available for ice formation. With insufficient water the 0°C isotherm will pass through the oil (contaminant) and again form continuous pore ice in the adjacent unfrozen soil. A band of trapped oil becomes visible in 2-dimensional test cells. Contaminant removal and transport to the surface is accomplished by water injection and upward flow along the interface at a rate sufficient to displace oil globules. Bench tests on a 2-dimensional frozen wall indicate that water temperature and flow rates can be adjusted so as to minimize heat introduction and allow removal of trapped oil globules from granualar soils.