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„ani.. a.�z F _ x,a��r� � z1Z� ^�—z: -r� _-mc _ _ _ •.gym <br /> °1 <br /> f <br /> July 8, 1988 AGS Job No. 38032-1 <br /> '`. UNOCAL Service Station No. 6981, Stockton, California <br /> r� <br /> three locations at the site. Hydrocarbon odor was obvious from <br /> approximately 3 to approximately 18 feet below grade in the areas <br /> of sample locations Line2 and Line9 (Plate P-3) , adjacent to <br /> product lines. Soil samples tested for total petroleum <br /> hydrocarbons in other product-line locations either were not <br /> ” detected or were mitigated by excavation to 11 feet below grade. <br /> The results of analysis of soil samples collected at the limits <br /> of the excavation of the tank cavity indicate that soil <br /> contamination still exists in the center and in the northeastern <br /> corner of the cavity at 18 and 22 Feet below grade, respectively. <br /> Soil samples collected from other locations in the tank cavity <br /> " ranged from below the laboratory detection limits to 2.4 ppm. <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the results of this investigation, Applied GeoSystems <br /> recommends further wort[ at the site to delineate the vertical and <br /> horizontal extent of hydrocarbon contamination. A conductor <br /> casing was set through the approximate center of the tank cavity, <br /> between the two new gasoline storage tanks, to allow drilling of <br /> a soil boring and installation of a monitoring well with minimum <br /> risk of damage.to the tanks. This location will also be usefv <br /> in defining the vertical extent of contamination below the tanks <br /> and may be useful in designing a remediation system for the <br /> 13 <br /> k5`+ <br /> ARA"49d awsystems. <br />