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' INTERIM REMEDIAL ACTION PLAN <br /> 4491 West Durham Ferry Road <br /> Tracy, California <br /> Delta Prosect No 40-91-732 <br /> Page 9 <br />' of detection The ground water samples collected from monitoring wells MW-1 and MW-2 contained <br /> concentrations of petroleum constituents <br /> 5.0 SITE REMEDIATION <br /> 5.1 Soil Remediation <br /> 1 1 Excavation <br /> Based on the findings of the initial investigative work performed at the site, Delta had initially <br /> recommended to over excavate the old tank areas since the extent of petroleum constituents appeared to <br /> be localized However, the client and the County discussed this alternative and concluded that is not a <br /> feasible alternative because the existing building is not on a foundation Also, after further review of the <br /> surrounding structures at the site, another potentially expensive operation would have to be performed <br /> which would include the disassembly and reassembly of most of the canopy (Figure 2) that covers all of <br /> tank area No 1 and part of tank area No 2 For these reasons, the excavation alternative was abandoned <br /> and in its place an insitu remedial alternative was considered <br /> 5 1 2 Insitu Soil Vapor Extraction (SM <br /> As an effective alternative to excavating the soil, Delta recommends that the soil in the previously existing <br /> tank locations (1 and 2, Figure 2) be vented by installing an insitu SVE system The conceptual design <br /> of the SVE system would consist of two 15 feet deep 4-inch diameter SVE wells screened from 5 to <br /> 15 feet below the surface These wells would be installed in the immediate area of the old tank locations <br /> To induce soil vapor flow from the SVE wells, a vacuum blower would be installed The extracted <br /> vapors from the soil would then be treated by an abatement device before they would be discharger) to <br /> the atmosphere Figure 4 shows the conceptual design of the SVE system Figure 5 shows the SVE well <br /> and equipment locations Figure 6 shows a typical SVE well <br /> 5 1 2 1 Soil Vapor Treatment <br /> From the initial site investigation data, Delta has reviewed and selected one of four soil vapor air <br /> treatment alternatives - thermal incineration, catalytic incineration, activated carbon adsorption, and air <br /> biofiltration Delta recommends that air biofiltration be used as the alternative to abate the soil vapor <br /> since initial site data indicate that hydrocarbon concentrations in the soil vapor will be relatively low <br /> RPT045 TA <br />