A model for economically based conceptual design of soil vapor extraction systems

Soil vapor extraction, also known as in situ soil venting, is rapidly becoming a widespread technique for the remediation of sites containing soils contaminated with volatile compounds. In this process, the soil is decontaminated in place by inducing air flow through the contaminated soil zones. Air, removed from the soil through extraction vents using a vacuum blower, may be resupplied by infiltration from the surface or through forced or passive inlet vents. This air flow sweeps out the soil gas, disrupting the equilibrium existing between contaminants which are (1) sorbed onto the soil particles, (2) dissolved in soil pore water, (3) held in a separate contaminant phase, and (4) existing in the vapor phase. This causes vaporization of the contaminants and removal in the extracted gas stream. Emissions control devices are often necessary for treatment of the gas stream prior to discharge. By preventing the hazards caused by subsurface vapor movement and by removing the contaminants before they reach groundwater, soil vapor extraction is extremely useful in decontaminating unsaturated zone soils. The technology may also be used in conjunction with pump-and-treat groundwater remediation techniques for complete cleanup of soil and groundwater in cases where the contaminants have reached the water table. 22 refs., 9 figs.