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None of the compounds exceeded the SSTLs levels for off-site groundwater ingestion (Appendix G, <br /> Update Status Report#53, Worksheet 9 3 ) <br /> DISCUSSION <br /> By definition, the SSTLs determine the concentrations at which the site will not pose a significant <br /> risk to the public or the workers at a site The SSTL only exceeded for on-site ingestion of <br /> groundwater, which is not a probable or likely occurrence <br /> RECOMMENDATION <br /> Evaluate this site as a low risk groundwater site, for closure based on the following <br /> 1 Source removal has been accomplished and documented in the soils beneath this site with <br /> documentation borings SB4, S135, S136 and S137 <br /> 2 The lateral and vertical extent of the groundwater plume has been delineated and is shown to be <br /> reducing and stable with evidence that bio-attenuation is occurring <br /> 3 This site has been shown to contain only occasional trace amounts of MTBE in wells The <br /> source of the MTBE may be from an off-site source <br /> 4 The Lawrence Livermore Study has shown that gasoline range hydrocarbon plumes do not <br /> migrate very far laterally and reach stabilization and degrade with time <br /> 5 With the exception of MWI, MW2, MW8 and MW12 the BTEX's have met the primary MCL's <br /> for drinking water standards <br /> 6 The residual gasoline contaminants associated with R603 due not pose a health threat, RBCA <br /> Tier 2 results <br /> 7 The shallow groundwater (Zone A) that contains the dissolved phase gasoline range hydrocarbon <br /> plume associated with R603 is non-useable in large part due to the Lincoln Village solvent <br /> plume found in the same aquifer zone <br /> LIMITATIONS <br /> The information presented in this report is based on the following <br /> I The observations and data collected by field personnel <br /> 2 The result of laboratory analyzes performed by a state certified analytical laboratory <br /> 3 Our understanding of the regulations of San Joaquin County, the City of Stockton and the <br /> State of California <br /> 4 References reviewed for this report <br /> Changes in groundwater conditions can occur due to variations in rainfall, temperature, local and <br /> regional water use and local construction practices In addition, variations in the soil and <br /> groundwater conditions could exist beyond the points explored in this investigation <br /> 13 8603 Update#54/CLOSURE 3 12198 <br />