Soil vapor extraction performance

A pilot soil vapor extraction test was performed to determine whether this method would be effective to mitigate the concern. Such a test provided information used to design a full-scale recovery and vapor treatment system. With air permeabilities on the order of 1 to 3 D and TPH vapor concentration on the order of 330 ppm (weight), the pilot test supported SVE as a viable remediation approach. 

VESTRIP is a system designed for the in situ treatment of soils contaminated with volatile organic compounds (VOCs) benzene, toluene, ethylbenzene, and xylenes (BTEX) and other contaminants that are amenable to soil vapor extraction (SVE). The vendor, Ejector Systems, Inc. (ESI) has combined the key components of SVE systems with an air stripper to form a product that performs the functions of both. The name, VESTRIP, is a contraction of VES (vapor extraction system) and air stripping. 

Soil vapor extraction is a commercially proven technology, and according to the vendor, the Vaportech enhanced volatilization method has been used in many full-scale remediations. The developer has performed held studies using hot air injection to further enhance the performance of this technology. The Vaportech technology is commercially available from Envirogen, Inc., formally MWR, Inc. 

Based on a cost analysis performed at the U.S. Department of Energy s Hanford site, in Richland, Washington, PSVE was found to be a cost-effective method for remediation of soils containing lower concentrations of volatile contaminants. PSVE used on wells that average 10 standard cubic feet per minute (scfm) airflow rates was found to be more cost-effective than active soil vapor extraction for concentrations below 500 parts per million (ppm) by volume of carbon tetrachloride. For wells that average 5 scfm, PSVE is more cost effective below 100 ppm (D14489S, p. iii). For further details of this analysis, refer to Table 1. 

The vacuum extraction method has been effectively applied to removing VOCs with low organic carbon content from well-drained soil, although it may also be effective for finer and wetter soils, but with comparatively slower removal rates. There are generally significant differences in the air permeability of various strata, which can influence process performance. Contaminants with low vapor pressure or high water solubilities are difficult to remove. 

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