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1 ' 15 October 2002 AGE-NC Project No 96-0232 ' Page 16 of 19 • Once released to the subsurface,the contaminants rapidly migrated to and Impacted shallow ' ground water at 2 to 20 feet bsg, at which point the contaminants migrated laterally • Impacted ground water in the First Zone mixed with ground water in the Second Zone and ' Rocky's Upper Zone during migration toward the west-southwest There is no well-defined aquitard between the three zones ' The low-gradient ground water table was strongly influenced by pumping from the Rocky's Restaurant Domestic Well (RDW-1)which induced migration of MTBE-impacted ground water in the First and Second Zones from the UST/dispenser/storm drain area on the Flag City Chevron site westward toward RDW-1, RDW-1 was abandoned in March 2002 • Impacted ground water in the First and Second Zones migrated vertically to Rocky's Upper Zone, the Secondary Aquifer and Primary Aquifer via mixing in 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 ground water in the general extraction area, and has prevented additional lateral and vertical migration of the impacted ground water 7.0. CONCLUSIONS AGE interpreted the results of all work completed to indicate that a Flag City Chevron release of hydrocarbons and MTBE occurred in the areas of the fuel dispensers, UST pit and/or storm drain, which then migrated through the First Zone and upper Second Zone to the former Rocky's Restaurant domestic well, at which point it apparently migrated vertically to the Rocky's Upper, Secondary Aquifer and Primary Aquifer Zones During March 2002,June 2002 and September 2002 sampling events, significant concentrations of dissolved MTBE were detected from Second Zone well MW-8A (screened 40 to 50 feet bsg) at concentrations of 700 µg/l, 250 µg/1 and 8 6 gg/l,respectively However, intermediate well MW-4, located between MW-8 and the UST area,continued to have no detection of MTBE,albeit screened ' in the First Zone Since initiation of ground water extraction activities at the site,ground water flow direction in the First Zone in the area of MW-8 has generally been inferred to be towards the south- southwest, ground water flow direction in the Second Zone in the area of MW-8 has been inferred ' towards a slight depression in the water table located between wells MW-6B and MW-9A, it is not iclear at this time why substantial MTBE is present in MW-8A after nine consecutive quarters of ' being non-detect Advanced Geo Environmental,Inc 1