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RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES The results of the certified analyses of groundwater samples collected from the three monitor wells on September 9 1999 are shown in Table l Copies of the laboratory reports are included as Appendix C of this report TPH-G concentrations ranged from a maximum of 20000 ug/1 at monitor «ell MW1 to 4800 ug/1 at monitor well MW2 Benzene concentrations ranged from a maximum of 6200 ug/l at MW l to 510 ug/1 at MW2 MTBE concentrations ranged from a maximum of 51 ug/1 at MW') to 15 ug/i at MW2 Figure 5 shows the distribution of TPH-G BTEX, and MTBE in groundwater and the estimated lateral limits of the TPH-G in groundwater as determined from groundwater samples collected on September 9, 1999 The decrease in overall groundwater elevation has been accompanied by an increase in concentrations of TPH-G and BTEX at all three monitor wells RECOMMENDATIONS 1) Continue quarterly groundwater monitoring 2) Implement September 28 1999 workplan to install addLtional _ro,ndwater monitoring wells following approval by SJCEHD LIMITATIONS The discussion presented in this report is based on the following 1 The observations and data collected by field personnel 2 The results of laboratory analyses performed by a state certified analytical laboratory 3 Our understanding of the regulations of San Joaquin County and the State of California Changes in groundwater conditions can occur due to variations in rainfall, temperature, local and regional water use, and local construction practices In addition, variations in the soil and groundwater conditions could exist beyond the points explored in this investigation State Certified Laboratory analytical results are included in this report This laboratory follows EPA and State of California approved procedures, however, WEGE is not responsible for errors in these laboratory results 3 Arc Pump QM 7-9 1999