Soil Clean Up by in-situ Aeration. II. Effects of Impermeable Caps, Soil Permeability, and Evaporative Cooling

Abstract

The clean up of soils contaminated by volatile compounds by in-situ vapor stripping was recently modeled by Wilson, Clarke, and Clarke. Their approach is modified to include the effects of a gas-impervious cap on the velocity field of the moving soil gas. Calculations indicate that such caps reduce the excessive flow of gas in the vicinity of the axis of the cylindrical volume of influence of a vent pipe, and they increase gas velocities near the periphery of the volume of influence. One thus expects use of impervious caps to improve the efficiency of in-situ soil vapor stripping: modeling of contaminant removal with such modified gas flow fields shows that this is indeed the case. Modeling of gas flow around buried obstacles indicates that these are not likely to interfere seriously with soil vapor stripping; some strategies are suggested to reduce their effects. The soil vapor stripping model is used to show that low soil permeabilities can be compensated for by increasing the radius of the stripping well packing. Evaporative cooling during vapor stripping is found to be insignificant under most circumstances.