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(VATC <br /> A S S O C I A T E S I N C <br /> Benzene concentrations in the samples collected from wells MW1 and MW2 exceeded the <br /> California Maximum Contaminant Level (MCL) of 10 ppb for benzene in drinking water <br /> Analytical results of groundwater samples dre 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 02 to 25 58 feet below the tops of the well casing elevations, <br /> representing an average increase in the water table elevation of approximately 0 20 feet since <br /> September 2000 The water level data were used to develop the groundwater elevation contour <br /> map (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the <br /> uppermost aquifer beneath the site flowed towards the north The average hydraulic gradient on <br /> December 13, 2000 was calculated to be 0 001 ft/ft or approximately 5 ft/mile A summary of <br /> groundwater monitoring data is presented in Table 1 <br /> CONCLUSIONS <br /> Concentrations of TPHg and BTEX generally remained consistent with previous sampling events <br /> The direction of groundwater flow has shifted slightly since the previous sampling event, from a <br /> . northeasterly direction to a northerly direction, and groundwater elevations have increased since <br /> September 2000 <br /> RECOMMENDATIONS <br /> Based on the results of the fourth quarter 2000 monitoring episode, we recommend the <br /> following <br /> • Perform First Quarter 2001 groundwater monitoring event in February 2001 <br /> Groundwater samples should be analyzed for TPHg and BTEX <br /> • Resurvey the wells to confirm wellhead elevations <br /> Prepare a workplan to further define the vertical and lateral extent of impacted soil and <br /> groundwater <br /> • <br /> w Q49811quart1y14gr-2000 doc 3 <br />