Soil Vapor Extraction: A Proven Method of Reducing VOCs in Environmental Media
Soil vapor extraction (SVE) is a proven in-situ technology used to remediate various volatile organic compounds (VOCs) from soil and soil vapor within the vadose zone. Vapor extraction involves applying a vacuum throughout the area of soil that has been impacted by VOCs. Through the pressure differential created between the extraction wells and the surrounding soil, VOCs are stripped from the soil by moving air through the vadose soil zone. The applied vacuum, contaminant characteristics, soil type, and the volume of air passing through the soil dictate the time required to remediate a site using SVE.
SVE is most effective for sites with (1) permeable soils where the wells are screened within distinct units and the site is capped or paved, and (2) on VOCs, such as many chlorinated solvents and hydrocarbons, that have high vapor pressures. Therefore, EEC strongly recommends that a pilot test is performed to evaluate and confirm the applicability of this or any remediation method. SVE also has the added advantage of mitigating the potential for soil vapor intrusion by removing vapor-phase VOCs trapped in the subsurface beneath buildings. SVE will remove the potential pathway for vapor migration to indoor air by creating and sustaining an applied vacuum to the subsurface, thereby creating a negative pressure gradient beneath the structure.
A generic SVE system is composed primarily of subsurface wells, remediation piping, a blower that exerts the vacuum, and the remediation equipment. The equipment needed will be determined based on the contaminant of concern. The two most commonly employed remediation equipment are thermal oxidizers and vessels filled with carbon-absorbent material. In an SVE system targeting chlorinated solvents, generally, two or three vessels are fitted together in series and filled with granular activated carbon. As the constituents of concern flow through the vessels they are absorbed into the carbon, thereby decreasing in concentration. In an SVE system targeting hydrocarbon contaminants of concern, a thermal oxidizer is used to fuel an incinerator that decomposes the hazardous gases then releases them into the atmosphere.
EEC Environmental currently operates and maintains six SVE systems within Southern California and is scheduled to start up a seventh SVE system in Northern California in early 2014. For more information about this or other effective remediation methods, please e-mail firstname.lastname@example.org to contact a remediation expert.