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L-- . <br /> contamination is contained in the saturated sand unit which <br /> depth interval of 17 to 34 feet in the area east of the excavated tank <br /> site (monitor wells MW-1, -2, and -3), and at a depth interval of 17 to <br /> 24.5 feet in the area southwest of the tank site (monitor wells HW-9 and - <br /> n 10), as shown in Figures 9 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. Soil contamination begins <br /> at a depth of 7 to 12 feet below ground surface and extends down to <br /> groundwater, at approximately 17 to 19 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 <br /> including firmness, is at least 5 feet thick. It's physical properties, <br /> 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. <br /> samples From the primary In addition, analysis of water <br /> supply well do not indicate groundwater <br /> site. <br /> contamination below the shallow unit, which is currently monitored at this <br /> Construction information available for the primary su 1 well <br /> suggests that the upper 40 feet of the supply w pp y <br /> Mum perforations start below that depth, e11 is cased and <br /> Maw 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 far site <br /> remediation will be presented in a Final Remedial Plan. This plan will <br /> include an assessment of viable remediation alternatives for both sail and <br /> groundwater. Soil venting would be a kcy.element of soil 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 /> MAN <br /> 25 <br />