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V. <br /> contamination is cintained in the saturated sand unit which occurs at a` <br /> depth interval of 17 to 34 feet in the area east of the excavated tank <br /> site (monitor wells m,-I, -2, and -3), and at a depth interval of 17 to y <br /> 24.5 feet in the area southwest of the tank site (monitor wells MW-9 and <br /> l10), as shown in Figures 4 and 10. � <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> The site assessment investigations have determined that the lateral extent <br /> of soil contamination at this site terminates between 15 and 35 feet from <br /> the inner excavation boundary in all quadrants. Sail contamination begins <br /> _ at a depth of 7 to 12 feel below ground surface and extends down to <br /> groundwater, at approximately 17 to 18 feet below ground surface. <br /> Chemical contamination in groundwater extends laterally from the <br /> excavation area to the southwest a maximum of 100 feet. The vertical <br /> extent of groundwater contamination is confined to the shallow groundwater <br /> unit encountered at the site. A thick silty clay unit underlies the <br /> shallow groundwater throughout the area of investigation and this unit was <br /> encountered in all borings drilled during the assessment investigation. <br /> This silty clay unit is at least 5 flet thick. It's physical properties, <br /> including firmAtess, slight plasticity, and a moisture content from <br /> slightly moist to dry indicate an unsaturated condition. Fuel <br /> hydrocarbons would not, therefore, be expected to extend vertically beyond. <br /> the shallow groundwater unit at the site. In addition, analysis of <br /> fwater <br /> er <br /> samples from the'Xprimary supply well do not indicate g <br /> rouncontamination below the shallow unit, which is currently monitsupplyed t this <br /> Weil <br /> site. Construction information available for the primary <br /> suggests that the upper 40 feet of the supply well is cased and <br /> perforations start below that depth. <br /> Results of the site investigations at the Sebastiani Vineyards/Woodbridge <br /> Cellars facility indicate that site remediation would be required to <br /> cleanup soil and groundwater containing chemicals in concentrations which <br /> exceed regulatory standards. The specific recommendations for site <br /> remediation will be presented in a Final Remedial Plan. This plan will <br /> include an assessment of viable remediation alternatives for both soil and <br /> groundwater. Soil venting would be a key element of sail remediation at <br /> this site and in situ bioremediation may be considered. Groundwater <br /> extraction and on-site treatment would be utilized for groundwater <br /> remediation. <br /> [Oct s !i bf S,-- <br /> 25 <br />