Analysis of Selected Enhancements for Soil Vapor Extraction

Book excerpt: This report provides an engineering analysis of, and status report on, selected enhancements for soil vapor extraction (SVE) treatment technologies. The report is intended to assist project managers considering an SVE treatment system by providing them with an up-to-date status of enhancement technologies; an evaluation of each technology's applicability to various site conditions; a presentation of cost and performance information; a list of vendors specializing in the technologies; a discussion of relative strengths and limitations of the technologies; recommendations to keep in mind when considering the enhancements; and a compilation of references. The performance of an SVE system depends on properties of both the contaminants and the soil. SVE is generally applicable to compounds with a vapor pressure of greater than 1 millimeter of mercury at 20EC and a Henry s Law constant of greater than 100 atmospheres per mole fraction. SVE is most effective at sites with relatively permeable contaminated soil and with saturated hydraulic conductivities of greater than 1 x 10 or 1 x 10 centimeter per second (cm/s). SVE by itself does not effectively remove contaminants -3 -2 in saturated soil. However, SVE can be used as an integral part of some treatment schemes that treat both groundwater and the overlying vadose zone. Enhancement technologies should be considered when contaminant or soil characteristics limit the effectiveness of SVE or when contaminants are present in saturated soil. The five enhancement technologies covered in this report are as follows and are described in the following subsections: * Air Sparging * Dual-phase Extraction * Directional Drilling * Pneumatic and Hydraulic Fracturing * Thermal Enhancement.