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' 09 May 2003 • AGE-NC Project No 96-0232 Page 14 of 16 • At well RDW-1, impacted ground water in the First and Second Zones migrated vertically ' to Rocky's Upper Zone, the Secondary Aquifer and Primary Aquifer via mixing along the RDW-1 casing and possibly along the filter pack (Figures 10, 11 and 12) ' • During non-pumping periods,MTBE-impacted ground water migrated from the well casing and/or filter pack laterally along the coarse-grained members of the lower hydrologic units • Continuous ground water extraction activities from Flag City Chevron site has pulled back some impacted ground water, lowering MTBE concentrations in `First Zone' and `Second Zone' ground water in the general extraction area and prevented additional lateral and vertical migration of the impacted ground water • AGE has modeled a separate, dissolved MTBE plume from the Three B's Truck Plaza in ' `First Zone', `Second Zone', `Rocky's Upper Zone' and `Secondary Aquifer Zone', this second plume is located on the Three B's Truck Plaza site The plumes from Flag City Chevron and Three B's Truck Plaza converge in the area of the former Rocky's Restaurant ' domestic drinking water well • AGE has modeled a possibly third plume of dissolved MTBE in `Second Zone' near 1 monitoring well MW-8, the source of this plume is uncertain at this time 6.0. CONCLUSIONS AGE interpreted the results of all work completed to indicate that a Flag City Chevron release of ' petroleum hydrocarbons and associated MTBE occurred in the areas of the fuel dispensers,UST pit and/or storm drain, which then migrated through and along the First Zone and upper Second Zone to the area of the former Rocky's Restaurant domestic water well, at which point it may have fmigrated vertically through the the Rocky's Upper, Secondary Aquifer and Primary Aquifer Zones ' Analytical results from the March 2003 quarterly monitoring event indicates that the highest concentrations of on-site MTBE occur in First Zone ground water samples EW-7,EW-8 and EW-4 at 38 µg/1, 96,ug/l and 45 pg/I, respectively(Figure 8), and in Second Zone samples MW-8A and ' MW-9A at 900,ug/l and 20,ug/l,respectively(Figure 9),the MTBE concentration reported in sample MW-8A is a significant increase from previous quarters The highest concentrations of off-site MTBE occur in First Zone, Second Zone and Rocky's Upper Zone in the vicinity of the former Rocky's Restaurant well RDW-1 at maximum concentrations of 91 ug/l (MW-16), 220 ,ug/1 (MW-17) and 200,ug/l (MW-18), respectively I Figures 8 and 9 depict depict Flag City Chevron wells EW-1,EW-4 through EW-10,MW-8,MW-9, MW-11 and Three B's Truck Plaza wells MW-1,MW-2,MW-4,MW-6 and MW-8 through MW-12 I Advanced GeoEnvnronmental,Inc