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11 August 2003 AGE-NC Project No 96-0232 Page 13 of 15 S 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 migrated vertically through the the Rocky's Upper, Secondary Aquifer and Primary Aquifer Zones First Zone ground water flow direction at the site appeared to be oriented radially inwards toward a ground water depression in the area of Flag City Chevron wells MW-1, MW-2 and MW-4 (Figure 4), Second Zone ground water flow direction appeared to be oriented radially inward toward a ground water depression in the area of Flag City Chevron wells MW-6B, MW-8A and MW-9A (Figure 5) First Zone, and possibly Second Zone ground water flow direction and gradient during the Flag City Chevron monitoring event appeared to be influenced by the Flag City Chevron pump- and-treat ground water extraction activities Ground water elevation data collected in the Secondary Aquifer Zone and Primary Aquifer Zone at the Flag City Chevron site Inferred a general ground water flow direction towards a southwest- oriented trough, the orientation of the trough appeared to ver west-northwest in the vicinity of the Rocky's Restaurant site The ground water trough appeared to terminate at a significant ground water depression in the area of Three B's Truck Plaza wells MW-9 and DW-1 (Figure 6),the ground water depression may have been due to ground water pumping at the domestic drinking water well DW-I Analytical results from the June 2003 quarterly monitoring event indicates that the highest concentrations of ori-site MTBE occur in First Zone ground water samples EW-4 and EW-5 at 26 �tg/l (Figure 8), and in the Second Zone sample collected from MW-8A at 290 µg/I (Figure 9), the MTBE concentration reported in sample MW-8A is a significant decrease from the March 2003 sample Albeit similar MTBE concentration increases were observed atMW-8A dunngMarch 2002 and March 2003, and concentration decreases during June 2002 and June 2003, an increasing or f decreasing trend of MTBE concentrations has not been established at MW-8A Furthermore,itis still not clear why MTBE was not detected at MW-8A for nine consecutive quarters, but has fluctuated between 4 7 µg/1 and 900 gg/1 over the past six 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 79 µg/1 (MW-16), 140 µg11 (MW-17) and 140 µg/1 (MW-18), respectively Between March and June 2003, substantial MTBE decreases were observed between First Zone well MW-16,Second Zone wells MW-11A,MW-14 and MW-17, and Rocky's Upper Zone wells MW-15 and MW-18 at the Rocky's Restaurant site i Advanced GeoEnviron mental,Inc