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GEOMATRIX <br /> 3.1 GROUNDWATER ELEVATION;FLOW DIRECTION,AND GRADIENTS <br /> fi Groundwater elevation data from September 23, 2004 (Table 1), were used to construct <br /> potentiometric contours on Figure 3. No se crate base petroleum <br /> hydrocarbons were reported <br /> in the site wells: Groundwater levels_ have.declined about 1A to 1.6 feet in the site monitoring <br /> wells since second quarter 2004. <br /> Groundwater elevation data for September 23, 2004, indicate a groundwater flow direction <br /> primarily to the south at a gradient of about 0.011 to 0:007 (Table 2 and Figure 3). Groundwater <br /> r <br /> flow direction and gradient for third quarter 2004 are consistent with those during previous <br /> quarters. <br /> ' 3.2 LABORATORY RESULTS <br /> The following sections provide ani evaluation of the quality assurance/quality control results for. <br /> the laboratory analyses and present analytical results. Copies of analytical reports for the <br /> groundwater samples collected for the third quarter.2004 groundwater monitoring event are <br /> included in Appendix B. <br /> 3.2.1 Quality Assurance/Quality Control Evaluation <br /> Groundwater samples collected b WGR for wells MW3-1 MW3-2 MW3-4 M 3-5 <br /> p Y W , and <br /> MW3-6 were received by MAI on September 24, 2004. Holding times for the requested <br /> analyses were met. Recoveries of surrogate spikes, matrix spikes, and laboratory control <br /> samples were within laboratory quality control limits. <br /> 3.2.2 Analytical Results <br /> Analytical results for.quarterly groundwater monitoring parameters are presented in Table 3. <br /> Historical analytical results for grab groundwater samples collected from soil borings are <br /> included in Table 4. During.third quarter 2004, groundwater samples from three of the five <br /> sampled groundwater monitoring wells had detectable.concentrations of TPHg or.BTEX. <br /> Historical andthird quarter 2004 TPHg concentrations in groundwater samples collected from <br /> the site soil borings and monitoring wells are plotted and contoured on Figure 4. <br /> Groundwater wells MW34 and MW3-5 are background.wells;wells MW3-1, MW3-2, and. <br /> MW3-3 are completed near the former UST; and well MW3-6 is a downgradient well. Low <br /> concentrations of TPHg and BTEX,compoun.ds have been detected occasionally in groundwater <br /> samples from-background wells MW34 and MW3-5 (Table 3). However, during the third <br /> quarter 2004 monitoring event, TPHg and.BTEX were not detected in groundwater samples from <br /> I:IPROJECT16000s56437.00016437-2ldoc 3 °' <br />