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July 8, 19' it;;5 !u. J1W,j.! L <br /> • UNOCAL Se 'e .Station No. E981, Stockton, fornia <br /> a <br /> three locations at the site. Hydrocarbon odor was obvious from <br /> approximately 3 to approximately 18 feet below grade in the areas <br /> "s <br /> of sample locations Line2 and Line° (Plate P-3) , adjacsnt to E, <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 t',a limits :. <br /> of the excavation of the tank cavity indicate that so'! <br /> contamination still exists in the center and in the northeastern <br /> corner of the cavity at IS and 22 feet below grade, r�ispcctively. <br /> Soil samples collected from other locations in the tank cavity <br /> ranged from below the laboratory detection limits to 2.4 ppm. <br /> s` <br /> CONCLUSIONS AAD RECOMMENDATIONS <br /> Based on the results of this investigation, Applied Ge:^Systems <br /> recommends further work at the site to delineate the vsrtical 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 useful <br /> in defining the vertical extent of contamination below the tanks <br /> '= and may be useful in designing a remediation system fez the <br /> 13 <br /> A,cp/ied GeoSyetems <br /> oo <br /> 9 tpy <br /> i ,Yr <br /> P <br /> >L° <br /> 1 <br /> 1 1 <br /> '1y <br />