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RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES <br /> The results of the certified analyses of groundwater samples collected from the three <br /> monitor wells on September 30, 1998 are shown in Table 1 Copies of the laboratory <br /> reports are included as Appendix C of this report <br /> TPH-G concentrations ranged from a maximum of 24,000 ug/l at monitor well MW1 to <br /> 2, 100 ug/l at monitor well MW3 <br /> Benzene concentrations ranged from a maximum of 8700 ug/1 at MW1 to less than the <br /> laboratory detection limits of 0 5 ug/l at MW2 <br /> MTBE concentrations ranged from a maximum of 100 ug/1 in MW1 to less than the <br /> laboratory detection limits of 0 5 ug/1 in MW2 <br /> Figure 5 shows the distribution of TPH-G, BTEX, and MTBE in groundwater and the <br /> estimated lateral limits of the TPH-G in groundwater as determined from groundwater <br /> samples collected on September 30, 1998 The increase in groundwater elevation and <br /> change in flow direction from east to north-northeast since the previous quarterly <br /> monitoring round has been accompanied by a significant increase in TPH-G <br /> concentrations at MW 1 and MW3 but a reduction of benzene concentrations at MW2 and <br /> MW3 The field collection techniques have not varied over the last year of quarterly <br /> groundwater monitoring <br /> RECOMMENDATIONS <br /> 1) Continue quarterly groundwater monitoring <br /> 2) Complete well records review that is in progress to determine historical groundwater <br /> elevations <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 /> 3 Arc Pump QM 7-9 1998 <br />