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i 4.0 EM Dl 'r . ` RS recommends remediation of the TPHg contaminated vadose soil in the former tank emplacement by in-situ vapor extraction technology. In-situ treatment of the soil offers the advantage of removal of VOC where contaminated soil is located close to or under a building at depths not readily excavated,as has occurred in this case. Specifications for the Soil Vapor Extraction System are presented in Appendix B of this Work Plan. The Health &Safety Plan to be implemented during the remedial activities is included in Section 10.0 of the Specifications, 5.0 GROUN12WMR MON l VIT1E RS recommends monitoring of the groundwater to determine the extent of contamination beneath the site. However, due to the drought, the water table has dropped below the screened sections of the existing monitoring wells (70 feet deep) and groundwater samples cannot be obtained at this time. As an alternative,sampling of DWR Registered Wells 2, 5, & 7 (Table 4, WGR's November, 1989 report), located within an approximately one- quarter mile radius of the site,was considered. After reviewing pertinent information,this alternative is not recommended due to the technical difficulty of sampling for VOC in deep wells and information indicating the existence o&underground fuel tanks located on other properties in the immediate vicinity of the wells and the site. w If,during the 1991-1992 winter season,the groundwater elevation rises sufficiently to permit sampling of the onsite monitor wells,quarterly groundwater monitoring would be initiated - by RS. If groundwater has not risen sufficiently by the end of the 1991-1992 rainy season, then three additional monitoring wells would be installed so that site groundwater monitoring can be re-established. During vapor extraction operation, it is anticipated that some reduction of VOC in the groundwater beneath the treatment cell may be achieved. By reducing TPHg concentrations in the contaminated soil to low or non-detectable levels, further contamination of groundwater beneaih this site would be minimized. - 1 6.0 PRQJECrJCHRDULE Figure 4 presents the project schedule for this Soil Vapor Extraction project. REMEDfAT10N SERVICES. INC.