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RESULTS OF QUARTERLY GROUNDWATER MONITORING <br /> GROUNDWATER GRADIENT AND FLOW DIRECTION <br /> Figure 4 shows the groundwater elevation gradient and flow direction determined from <br /> depth to water measurements at the five on-site monitor wells on December 6, 2000 The <br /> groundwater elevation has increased by an average of 0 2 feet at the five monitor wells <br /> since the previous quarterly monitoring round on September 27, 2000 The groundwater <br /> elevation gradients form a trough through the site with flows towards the west The <br /> groundwater elevation gradient at the site for December 6, 2000 averaged 0 003 <br /> feet/linear foot over the site <br /> RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES <br /> The i esults of the certified analyses of groundwater samples collected from the five <br /> monitor wells on December 6, 2000 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 8700 ug/1 at MW l to less than the <br /> . laboratory detection limits of 50 uZD at MW2 01 <br /> Benzene concentrations ranged from a maximum of 1300 ug/I at MW 1 to less than the <br /> laboratory detection limits of 0 5 ug/1 at MW5 <br /> MTBE concentrations ranged from a maximum of 46 ug/I at MW 1 confirmed using EPA <br /> method 8260 to 0 7 ug/l (non confirmed) in MW4 <br /> Figure 5 shows the distribution of TPH-G BTEX, and MTBE in -groundwater as <br /> determined from groundwater samples collected on December 6, 2000 The decrease in <br /> groundwater elevation at the site since the previous quarterly monitoring round did not <br /> produce significant changes in the concentrations of TPH-G, BTEX, and MTBE observed <br /> in the five monitor wells at the site <br /> RECOMMENDATIONS <br /> Commence, after obtaining UST fund pre-approval, on the San Joaquin County Health <br /> approved workplan that provide specifications for the following items <br /> 1) Install offsite monitor wells west of MWl to define downgradient extent of <br /> groundwater contamination plume <br /> 2) Install onsite groundwater recovery well north of the former UST area <br /> 3 Sanchez QM 4-6, 2000 <br />