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C L E A kWA'T-ER ' G R O U P Envirnnmenfu! Services relatively ineffectual because the majority of sorbed-phase contamination is submerged beneath ' the water table The effectiveness of soil vapor extraction on sorbed-phase contamination beneath the water table is limited unless used in conjunction with groundwater extraction (GWE) to depress the water table or air sparging (AS) to strip volatiles from the dissolved-phase and induce continued partitioning of contaminants from the sorbed- to dissolved-phase for clean-up ' Field data collected during the March, 2002 SVE pilot testing at the subject site suggests that, in combination with AS and GWE, SVE could be a feasible, though not ideal technology at the site ' Based on data collected during the March, 2002 pilot test it is estimated that, if chosen, this option would likely require the installation of up to 12 additional combination GWE/SVE wells ' and 4 AS wells (Figure 7) This estimate assumes radius of influence will increase with depression of the water table through GWE It is likely that existing monitoring wells MW-1, ' MW-3, and MW-4 may also be used for the purposes of soil vapor extraction during remediation Use of SVE would also require treatment of the vapors before emission to ambient air The local Air Pollution Control District requires destruction efficiencies typically achieved by the following treatment technologies internal combustion engine, thermal oxidation, catalytic oxidation, and carbon adsorption Based on the limited areal extent and relatively moderate residual sorbed-phase concentrations, either catalytic oxidation or carbon adsorption would likely ' be sufficient treatment technologies for the anticipated air flowrates and contaminant concentrations on the influent air stream Most likely a beginning phase with a catalytic ' oxidation system followed by carbon adsorption phase of operation once influent concentrations had dropped off iHowever, carbon adsorption would likely be the appropriate treatment technology if SVE were used to recover air sparge vapors and remediate what little sorbed-phase contamination would be left following excavation of contaminated soil ' 6.3 Remedial Alternatives for Groundwater ' 6 3 1 Air S ar in In-situ Volatilization This technique uses air injection (air sparging) to introduce relatively large volumes of air into the groundwater in order to volatilize the dissolved phase hydrocarbons In-situ volatilization is ZB178C CAP 14 November 20,2002