SECONDARY EFFECTS OF SOIL VENTING AND POTENTIAL LOW-COST ENHANCEMENTS

Soil venting, in addition to removing volatile organic compounds, has secondary effects on soil temperature and moisture content. A simple e nthalpy balance model is used to illustrate the magnitude and directio n of temperature and moisture content changes in the soil during ordin ary venting and with several potential modifications to venting. Becau se of the importance of latent heat of vaporization, injection of warm , dry air into the subsurface is generally ineffective in heating the soil. In contrast, injection of humidified, slightly heated air is fou nd to result in significant soil warming even at low flow rates. Soil warming is thought to be an important mechanism for enhancing remediat ion, particularly in the final or tail stage of cleanup where concentr ations slowly decline with time. A variety of soil venting alternative s are simulated at hypothetical sites in Chicago, Illinois, and Tucson . Arizona, including simple humidification, humidification with solar heating, and venting under positive pressure. All three methods result in higher final soil temperatures than the control case of normal soi l venting. Humidification of the input air at the rates applied does n ot result in significant change in average soil moisture content or sa turation of the soil with water.