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4,. <br /> Onsite and Offsite Assessment Report 6 <br /> The Southland Corporation,2725 Country Club Boulevard,Stockton,California November 30,1998 <br /> Soil analytical data from north and northeast of the underground tank areas indicates no detectable <br /> hydrocarbon concentrations in borings GP-9 and GP-10. Low concentrations of up to 0.005 mglkg <br /> benzene were found in borings GP-11,GP-12,and GP-13,while TPH-g was non-detectable. <br /> Concentrations of benzene declined with depth in borings GP-11 through GP-13,to non-detectable at <br /> 25 feet below grade in boring GP-12. Soil MTBE levels were non-detectable in the samples from these <br /> three locations. <br /> Groundwater concentrations were similary highest in the tank pit area, ranging up to 1,930,000 ug/L <br /> TPH-g and 9,740 ug/L benzene (boring GP-17). Dissolved MTBE was not detected in any of the water <br /> ar samples collected from the Southland tank pit areas,including samples from borings GP-14, GP-15, <br /> and GP-17 (EPA Method 8260). <br /> �,. East and north of the tank pit areas,water from boring GP-12 contained 6.3 ug/L MTBE,the sample <br /> from boring GP-11 contained 24.2 ug/L MTBE, and water from boring GP-10 contained 8.9 ug/L MTBE. <br /> The water sample from boring GP-13 contained no detectable MTBE levels_ Dissolved hydrocarbons <br /> +r in these areas ranged up to 28.9 ug/L benzene and 167 ug/L TPH-g (boring GP-12). Dissolved <br /> hydrocarbons were not detected in water samples from borings GP-9 or GP-8. <br /> West and southwest of the tank pit areas,no detectable dissolved hydrocarbons were identified in water <br /> from boring GP-7,while dissolved benzene and TPH-g were found at levels of 2.7 ug/L and 350 ug/L <br /> (respectively)in water from boring GP-16. Dissolved MTBE was not found in water from boring GP-16. <br /> Chlorinated hydrocarbons (EPA Method 8010)were not detected in water from boring GP-16,while <br /> trace concentrations of chlorobenzene and dichlorobenzene were detected in boring GP-10 (up to 80 <br /> ug/L chlorobenzene). None of the other halocarbon species were detected. <br /> 4.0 CONCLUSION <br /> �.. The summary of soil analytical data indicates that the vertical extent of the soil hydrocarbon plume has <br /> been adequately delineated to depths of less than 30 feet below grade in the primary hydrocarbon <br /> source area, and the lateral extent of the soil hydrocarbon plume has been adequately characterized. <br /> 14 117sar.rpt <br /> V _ <br /> FLUOR DANIEL GTI <br /> � CJ <br />