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RECOMMENDATIONS <br /> 1 Continue to air sparge MW2 and MW13 When groundwater elevations are high (between 35 <br /> and 40 feet below top of casing) sparge both MW2 and MW13, when groundwater elevations are <br /> low(lower than 40 feet below top of casing), switch MWi3 to vapor extraction <br /> 2 Using LTT vacuum pump system, sample all wells for TPHg, BTEX using 8020 method during <br /> the May 1998 quarterly sampling and again during the August 1998 quarterly sampling to <br /> provide two quarterly sample events to confirm plume stability <br /> 3 This site has been shown to contain only occasional trace amounts of MTBE in offsite wells <br /> Discontinue analysis for the Oxygenants <br /> 4 Source removal has been accomplished and documented in the soils beneath this site with <br /> documentation borings SB4, SB5, SB6 and S137 The soil contamination for this site should <br /> be considered rcmediatcd, with no further action needed <br /> 5 The groundwater plume is shown to be stable with evidence that bio-attenuation is occurring <br /> 6 Evaluate this site as a low risk groundwater site, for closure <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 /> State Certified Laboratory analytical results are included in this report This laboratory follows EPA <br /> and State of California approved procedures, however, WEGE is not responsible for errors in these <br /> laboratory results <br /> The services performed by Western Geo-Engineers, a corporation under California Registered <br /> Geologist 0037 and/or Contractors License #513857, have been conducted in a manner consistent <br /> with the level of care and skill ordinarily exercised by members of our profession currently <br /> practicing under similar conditions in the State of California, the City of Stockton and San Joaquin <br /> County <br /> 7 R603 Update#51 5/98 <br />