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r <br /> ff���� <br /> April 15, 1993 Working To Restore Nature <br /> ARCO Facility No 6020, Manteca, California <br /> SUMMARY <br /> i <br /> The following summarizes the findings gathered during this investigation and previous work <br /> that RESNA has performed at the site <br /> o Residual hydrocarbons were analytically identified in soil at low <br /> concentrations during the initial subsurface investigation (borings B-3 through <br /> B-6), but were not detected during the additional investigation in soil samples <br /> collected from borings B-8 through B-13 Therefore, residual hydrocarbons <br /> have been adequately delineated Because residual hydrocarbons were not <br /> detected in boring B-13, residual hydrocarbons initially detected from boring <br /> B-6 appears to be sporadic <br /> o The groundwater surface beneath the site in December 1992 was <br /> approximatel 28)Feet below grade The ground water flow direction was to <br /> the northwe with a hydraulic gradient of 0 014 <br /> o Dissolved gasoline hydrocarbons were not analytically identified in ground- <br /> water samples collected from each of the four monitoring wells <br /> o Nitrates were detected in monitoring wells MW-1, MW-3, and MW-4 <br /> LIMITATIONS <br /> This report was prepared in accordance with generally accepted standards of environmental <br /> geological practice in California at the time this investigation was performed This <br /> investigation was conducted solely to evaluate environmental conditions of the soil and <br /> ground water with respect to hydrocarbons identified in soil during previous work No soil <br /> engineering or geotechnical recommendations are implied or should be inferred Evaluation <br /> of the geologic conditions at the site for the purpose of this investigation is made from a <br /> limited number of observation points Subsurface conditions may vary away from the data <br /> 30055-5 <br /> 9 <br />