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The samples were delivered with accompanying chain of custody documentation to Kiff <br /> Analytical Laboratories (DHS Certification 92236) The certified laboratory analyzed the <br /> groundwater samples for concentrations of TPH-G and BTEX and MTBE using EPA <br /> method 8260B <br /> RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES MW4 <br /> The groundwater sarnple from MW4 showed a TPH-G concentration of 510 ug/l and a <br /> Benzene concentration of 37 ug/l MTBE was not detected above the laboratory <br /> detection limits of 0 5 ug/1 <br /> The TPH-G and BTEX concentrations at 70-80 feet bgs in MW4 are well below the <br /> values observed in monitor wells MW 1 MW2, and MW3 that are slotted between 30 and <br /> 50 feet bus They are also significantly lower than the hydropunch groundwater samples <br /> collected previously from nearby soil boring SB 1 at the 70-72 and 80-82 foot depth <br /> intervals (see Table 2) Additional quarterly sampling at MW4 should indicate whether <br /> TPH-G and BTEX concentrations observed during the cui rent sampling round were <br /> residual contaminants that were drug down to the 80 foot depth during the drilling of <br /> MW4 or if the historical groundwater contamination truly extends to the 80 foot depth <br /> RECOMMENDATIONS <br /> Continue quarterly groundwater monitoring at existing wells MW1-MW4 <br /> Proceed with the installation of additional offsite monitor wells using information <br /> obtained from MW4 <br /> LIMITATIONS <br /> The discussion presented in this report is based on the following <br /> 1 The observations and data collected by field personnel <br /> 2 The results of laboratory analyses performed by a state certified analytical laboratory <br /> 3 Our understanding of the regulations of San Joaquin County and the State of <br /> California <br /> Changes in groundwater conditions can occur due to variations in rainfall, temperature, <br /> local and regional water use, and local construction practices In addition, variations in <br /> the soil and groundwater conditions could exist beyond the points explored in this <br /> investigation <br /> State Cei tified Laboratory analytical results are included in this report This laboratory <br /> follows EPA and State of California approved procedures however, WEGE is not <br /> responsible for errors in these laboratory results <br /> 6 Are Pump QM 4-6, 2001 <br />