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Additional Site Assessment Report <br /> 324 East 11 th Street <br /> Tracy,CA <br /> October 8,2014 <br /> LTCP Evaluation <br /> Based on recent site investigations,the site appears to meet the Low Threat Closure Policy (LTCP) media- <br /> specific criteria for soil and groundwater.As shown on Table 1,benzene concentrations in soil are below the <br /> direct contact and outdoor air exposure criteria of the LTCP adopted by the State Water Resources Control <br /> Board in May 2012. Ethylbenzene (11 mg/kg) concentrations detected in boring B-7 at approximately 1 ft <br /> depth are also below LTCP criteria.The groundwater plume that exceeds water quality objectives(commercial <br /> environmental screening levels where groundwater is a current or potential source of drinking water)appears to <br /> be less than 250 ft in length.No free product has been observed at the site. Based on our review of satellite <br /> images,there are no surface water bodies within 1,000 ft of the site. Pangea is not aware of any water supply <br /> wells within 1,000 ft of the site. Finally, the dissolved concentrations of benzene and MTBE are less than <br /> 1,000 gg/L. <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> To comply with permit requirements,this report will be submitted to the San Joaquin County Environmental <br /> Health Department(SJCEHD). Pangea understands that the SJCEHD and Regional Water Quality Control <br /> Board will review this information to determine if additional action is required. <br /> Based on the above site assessment information, Pangea offers the following conclusions and <br /> recommendations: <br /> • Field observations and analytical results suggest that petroleum hydrocarbon impact is primarily <br /> located in shallow soil near borings B-1 and B-7.The hydrocarbon impact to groundwater is primarily <br /> located at boring location B-1,with some additional impact in nearby boring B-7,and lower impact in <br /> crossgradient borings B-4 and B-6. <br /> • Petroleum hydrocarbons in select soil and groundwater samples exceed conservative environmental <br /> screening levels (ESLs). However, the extent of hydrocarbon impact appears to be adequately <br /> delineated by this investigation and downgradient data from the adjacent and closed case at Tracy <br /> High School. <br /> • Pangea recommends performing a well survey within 1,000 ft of the site to determine if the site meets <br /> LTCP criteria for groundwater.If no water supply wells are found,Pangea recommends case closure. <br /> 5 <br />