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(YVATC <br /> • ASSOC IATES INC <br /> Benzene concentrations in the samples collected from wells MW2 and MW3 exceeded the <br /> California Maximum Contaminant Level (MCL) of 10 ppb for benzene in drinlung water <br /> Analytical results of groundwater samples are summarized in Table 2 <br /> GROUNDWATER FLOW DIRECTION <br /> Water level measurements were collected from wells MW 1 through MW3 on September 12, <br /> 2000 Water levels ranged from 25 18 to 25 82 feet below the tops of the well casing elevations, <br /> representing an average decrease in the water table elevation of approximately 2 23 feet since <br /> June 2000 The water level data were used to develop the groundwater elevation contour map <br /> (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost <br /> aquifer beneath the site flowed towards the northeast The average hydraulic gradient on <br /> September 12, 2000 was calculated to be 0 002 ft/ft or approximately 9 ft/mile A summary of <br /> groundwater monitoring data is presented in Table 1 <br /> CONCLUSIONS <br /> Concentrations of TPHg increased in wells N1W1, MW2, and MW3 since the previous sampling <br /> event Benzene concentrations decreased in well MW1 and increased slightly in wells MW2 and <br /> • MW3 Toluene, ethyl benzene, and xylenes concentrations generally remained consistent with <br /> previous sampling events The direction of groundwater flow is consistent with the previous <br /> sampling event and groundwater elevations have decreased since June 2000 <br /> RECOMMENDATIONS <br /> Based on the results of the third quarter 2000 monitoring episode, we recommend the following <br /> • Perform Fourth Quarter 2000 groundwater monitoring event in December 2000 <br /> Groundwater samples should be analyzed for TPHg and BTEX <br /> w 1149811guafdy\3gr-2000 dw 3 <br />