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QUARTERLY GROUNDWATER MONITORING, DECEMBER 5. 1997 Is Del-Tech Geotechnical Support Services collected quarterly groundwater samples from the five monitor wells at the site on December 5, 1997 See Appendix A for QA/QC, details, methods, procedures, abbreviations, and acronyms used in sampling and analysis DEPTH TO WATER MEASUREMENTS Depth to water was measured at all wells on December 5, 1997 The measurements were made from the surveyed elevation at the top of casing at each well using an electrical air/water interface probe (Table 1) No free product or product sheen was observed in any of the monitor wells COLLECTION AND CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES Following depth to water measurements, each well was purged of three to four well volumes of water using a centrifugal pump and dedicated polyethylene tubing The purged wastewater was contained on-site in labeled 55 gallon DOT approved drums After purging, the wells were allowed to recover to at least 80% of their original well volumes A groundwater sample was then collected from each well with a stainless steel bailer and decanted with no headspace into four 40 ml VOA vials containing 0 5 ml HCL acid as a preservative The samples were delivered with accompanying chain of custody documentation to Sherwood Labs (DHS Certification#1400) The certified laboratory analyzed the water samples from each monitor well for concentrations of TPH-G, BTEX, and the oxygenants TBA, DIPS, ETBE, TAME, and MTBE (see Appendix A for methods) GROUNDWATER GRADIENT AND FLOW DIRECTION Figure 4 shows the groundwater elevation gradient and flow direction determined from depth to water measurements at the five on-site monitor wells on December 5, 1997 The groundwater elevation has decreased by an average of 196 feet at the five monitor wells since the previous quarterly monitoring round on July 31, 1997 The flow direction is to the west-northwest The overall gradient is 0 001 feet/linear foot RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES The results of the certified analyses of groundwater samples collected from the five monitor wells on December 5, I997 are shown in Table 1 Copies of the laboratory reports are included as Appendix C of this report TPH-G concentrations ranged from a maximum of 28,600 ug/l at MW1 to less than the laboratory detection limits of 50 ug/1 at the remaining four monitor wells Benzene concentrations ranged from a maximum of 5450 ug/l at MW1 to less than the laboratory detection limits of 0 3 ug/1 at the remaining four monitor wells MTBE concentrations ranged from a maximum of 490 ug/1 in MW 1 to less than laboratory detection limits of 5 ug/1 in the remaining four monitor wells Tert-butanol was the only other oxygenant that showed concentrtations above the laboratory detection limits in any of the five samples from the monitor wells The concentration of tert-butanol in MW 1 was ug/1 2 Sanchez QM 12-97