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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 February 23, 2000 The <br /> groundwater elevation has increased by an average of 4 98 feet at the five monitor wells <br /> since the previous quarterly monitoring round on December 2 1999 The groundwater <br /> elevation gradients form a northwest-southeast trending ridge through the site with flow <br /> towards the north, northwestern, and southwestern quadrants The groundwater elevation <br /> gradient at the site for February 23, 2000 averaged 0 012 feet/linear foot over the site <br /> RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES <br /> The results of the certified analyses of groundwater samples collected from the five <br /> monitor wells on February 23, 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 17000 ug/l at MW1 to less than the <br /> laboratory detection limits of 50 ug/l at monitor well MW2 <br /> Benzene concentrations ranged from a maximum of 2500 ug/1 at MW1 to less than the <br /> laboratory detection limits of 0 5 ug/l at MW2, MW3, MW4, and MW5 <br /> MTBE concentrations ranged from a maximum of 120 ug/l at MW1 to 1 ug/l in MW3 <br /> Figure 5 shows the distribution of TPH-G, BTEX, and MTBE in groundwater as <br /> determined from groundwater samples collected on February 23, 2000 The large <br /> increase in groundwater elevation at the site since the previous quarterly monitoring <br /> round was accompanied by slight reductions in the concentrations of TPH-G BTEX, and <br /> MTBE observed in the five monitor wells at the site <br /> RECOMMENDATIONS <br /> Constiuct a workplan to provide specifications for the following items that have been <br /> pre-approved by the UST Cleanup Fund Program <br /> 1) Install offsite monitor well west of M W I to define downgradient extent of <br /> groundwater contamination plume <br /> 2) Conduct pump test at existing on-site monitor well to determine feasibility of <br /> dewatering during overexcavation of former UST area and/or dewatering in conjunction <br /> with vapor extraction <br /> 3 Sanchez QM 1-3 2000 <br />