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} Mr .teff Wong Page 3 of 4 • Of the wells sampled, only wells MW2 and MW4 contained detectable concentrations of TPHg Wells MW2 and MW4 contained 770 parts per billion(ppb) and 160 ppb TPHg, respectively Benzene was detected in wells MW2, MW3 and MW4 at concentrations of 17 ppb, 5 6 ppb, and 18 ppb, respectively No benzene was detected in wells MW5, MW6, MW7, MWS, or MW9B MTBE was detected in wells MW2, MW3, MW4, MW5, and MW6 at concentrations of 150 ppb, 7,900 ppb, 17,000 ppb, 26 ppb, and 14 ppb, respectively No MTBE was detected in wells MW7, MW8, or MW9B Toluene, ethylbenzene, and xylenes were detected only in well MW2 at low to moderate levels Table 3 presents a summary of groundwater analytical results Attachment D contains a copy of the laboratory report and chain-of-custody documentation Figures 3 and 4 present isoconcentration maps of MTBE and benzene, respectively, in shallow groundwater beneath the site Attachment E contains plots showing the concentrations of TPHg, benzene, and MTBE over time in all site wells i i 4.0 SUMMARY AND CONCLUSIONS Free product thickness in well MW1 ranged from non-measurable to 0 15 feet between December M 30, 2002 and April 1, 2003 A total of approximately 123 gallons of product/water mixture has been removed from this well since August 16, 2001 Figure 5 presents a chart showing the measured depths to water and product over time in well MW 1 Groundwater levels rose an average of 0 72 feet in the shallow aquifer between December 2002 and March 2003 Groundwater flow beneath the site was somewhat irregular in March 2003 The lateral extent of TPHg and BTEX has been defined in shallow groundwater beneath the site except to south and west of well MW2 The lateral extent of MTBE has not been completely defined in shallow groundwater beneath the site Based upon analytical results of groundwater samples collected from well MW9B, it does not appear that dissolved gasoline constituents in the shallow aquifer has migrated vertically to deeper water-bearing zones 5.0 RECOMMENDATIONS/ADDITIONAL WORK Ground Zero recommends continued groundwater monitoring at the site and implementing interim remediation Ground Zero is preparing a revised workplan for additional investigation and interim remediation pursuant to EHD correspondence dated February 13, 2003 A passive skimmer will be installed in well MW1 during the week of April 28, 2003 A M groundwater sample will be collected from well MWl once free product can no longer be measured in the well Future groundwater analyses will be modified to include a detection G 1GROUNDZE\TULEBURG\Reports%QMR\2003%IQM2003 doc