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i <br /> r� I <br /> 3�t <br /> q ti <br /> m' <br /> In Situ Soil Venting <br /> A. 14a <br /> KGF', 'Td%�;, - �# ��J�"-. s-': � � ..SSS, 7•~'` - �� <br /> C- - - <br /> -w< ... - �s� - .,�e"`S'� •y.. .,s ::ma=r <br /> l S <br /> IN`ya�z,�s�yir;�l+ <br /> g : <br /> i <br /> r <br /> I <br /> ® In soil venting, a vacuum well ideally suited for remediation of the fuels--or low permeability <br /> induces vapor flow through the unsaturated zone. The formations such as soils with high <br /> unsaturated soil zone to enhance contaminant must be relatively clay content. Venting wells are <br /> II, the natural rate of volatilization. volatile and exert a vapor pressure usually two to four-inch diameter <br /> More volatile compounds are FVC>.001 atm at the ambient PVC pipe, screened through the <br /> removed first, and with time, temperature. Examples are contaminated region. They must <br /> residual contamination gradually gasoline and solvents such as be sealed properly to minimize <br /> becomes richer in the less volatile trichloroethylene. It is also possible °short-circuiting" airflow through <br /> + compounds. Due to composition to remove less volatile compounds the well casing. The vacuum pump <br /> i changes with time, effluent vapor by adding heat to the should be capable of 100 scfm at <br /> concentrations and mass removal contaminated zone. The soil 40-200 inches H2O vacuum. <br /> rates decrease with time. By should also be relatively Usually vapor flow rates are >20 <br /> adding air injection wells, permeable to airflow- A cfm from each well. A surface <br /> selectively screening venting permeability of more than one covering (tarp, pavement or clay) <br /> wells, or by adding heat to the darty (silty sands) is a good can minimize vertical air flow from <br /> I contaminated zone--by hot air, guideline. Typically, venting does the atmosphere. Information from <br /> steam or in situ radio-frequency not efficiently remediate soils Shell Remediation Workshop <br /> ' heating—the soil venting process contaminated with heavy Handbook.) <br /> can be optimized. Soil venting is compounds such as crude oil or jet Write in 636 for more information. <br /> 58 December 1992 Soils <br /> - _ ------ . __--- _ ..--------... .._�Y <br />