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QUARTERLY GROUNDWATER MONITORING MAY 18 1998 WEGE and Lawrence Tank Testing (LTT) collected quarterly groundwater samples from the three monitor wells at the site on May 18, 1998 See Appendix A for QA/QC, details, methods, procedures, abbreviations, and acronyms used in sampling and analysis DEPTH TO WATER MEASUREMENTS WEGE measured depth to water in all wells on May 18, 1998 The measurements were made from the surveyed elevation datum 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, Lawrence Tank Testing (LTT) purged three well volumes of water from each well using a truck mounted vacuum lift pump and dedicated one inch diameter PVC tubing The purged wastewater was temporarily contained on-site in labeled 55 gallon DOT approved drums Evergreen Environmental Services transported this wastewater to their recycling center under a non-hazardous manifest on July 20, 1998 (see Appendix D) 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 disposable polyethylene bailer and decanted with no head space 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 American Environmental Network (DHS Certification #1172) The certified laboratory analyzed the water samples from each monitor well for concentrations of TPH-G, BTEX, 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 three on-site monitor wells on May 18, 1998 The groundwater elevation has increased by an average of 1 5 feet at the three monitor wells since the previous quarterly monitoring round on March 10, 1998 The flow direction is to the east The overall gradient is 0 0 1 feet/linear foot RESULTS OF CERTIFIED ANALYSIS OF GROUNDWATER SAMPLES The results of the certified analyses of groundwater samples collected from the three monitor wells on May 18, 1998 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 5,400 ug/l at the downgradient monitor well MW2 to 2,800 ug/l at the upgradient monitor well MW1 Benzene concentrations ranged from a maximum of 1,600 ug/1 at MW3 to 790 ug/1 at MW1 MTBE concentrations ranged from a maximum of 80 ug/1 in MW2 to 30 ug/l in MWI 2 ARC- QM 4-6, 98