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SAFEWAY MEAT PACKING FACILITY, STOCKTON, CALIFORNIA <br /> TIER II RISK BASED CORRECTIVE ACTION <br /> FEBRUARY 26, 1996 <br /> PAGE 4 - 7 <br /> concentration of 29 Ag/L ) While the ground concentration used to set the soil SSTL is above <br /> both the California (1 Ag/L) and U S (5 µg/L) Maximum Contaminant Levels for benzene in <br /> drinking water, the risk assessment result, is not considered significant for future groundwater <br /> impact for four reasons <br /> 1 The RME SSTL for leaching to groundwater is based on conservative estimates <br /> soil characteristics and infiltration rates which are not likely to occur at the site, <br /> but were included to ensure risks would not be underestimated <br /> 2 The maximum soil concentration of benzene is 0 042 mg/kg (2 ppb) and is an <br /> order of magnitude below the FJV E SSTL Consequently the maximum soil <br /> concentration is unlikely to result in a groundwater concentration greater than 3 <br /> Ag/L In addition, the average or representative soil concentration is well below <br /> the maximum soil level, so the impacts on groundwater are conservatively <br /> characterized in this comparison <br /> 3 The groundwater beneath the site is not used to supply drinking water nor is it <br /> likely to be used in the foreseeable future <br /> 4 As indicated in the LLNL Report (LLNL 1995), the RBCA standard (ASTM <br /> 1995), and scientific literature (such as Bedient, et al 1994), benzene and other <br /> petroleum hydrocarbons are biodegradable under environmental conditions <br /> Consequently, the levels of fuel hydrocarbon will be naturally attenuated over <br /> time This risk assessment has been based on both the soil and groundwater <br /> concentration over 25-years Thus any measured soil or water concentration that <br /> is above the SSTL today is unlikely to be at this same concentration over the 25- <br /> year exposure period <br /> 0131CDJ1 <br /> r _ <br />