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r - 31 January 2003 'S AGE-NC Project No 96-0232 , Page 14 of 17 • The average increase in ground water elevation of approximately 4 41 feet between ISeptember 2002 and December 2002 may be due to seasonal fluctuation Hydrographs depicting recorded ground water elevations at wells MW-2, MW-6A and MW-6B vs time are provided in Appendix IIV The highest on-site concentrations of dissolved MTBE were detected in the sample collected from First Zone extraction well EW-8 at 53 µg11,lower concentrations of on-site MTBE were ` detected in water samples from First Zone extraction wells EW-1, EW-2, EW-4 through EW-10,and from Second Zone monitoring wells MW-8A and MW-9A(Table 6),generally, significant MTBE increases were reported in wells EW-4 and EW-8 IThe highest off-site concentrations of MTBE were detected from Rocky's Upper Zone wells MW-11B,MW-15 and MW-18 at concentrations as high as 220 lig/l(MW-18),in First Zone water from monitoring well MW-7 at 26 gg/l, and in Three B's Truck Plaza monitoring well MW-4 at 85' lig/l (Table 6, Appendix F), increasing MTBE concentrations were reported from all three off-site wells between the September 2002 and December 2002 sampling events • On isolated occurrences, low concentrations of TPH-d have been detected at various wells during previous quarterly monitoring events at Flag City Chevron Dunng December 2002, a low concentration of TPH-d was detected in the ground water sample from well MW-12A, screened within the First Zone aquifer AGE requested McCampbell Analytical to further review the TPH-d sample chromatograms from the December 2002 sampling event, the laboratory indicated to AGE that the low TPH-d detections from MW-12A did not have typical diesel characteristics, and that the detected chromatogram peaks were probably the ' result of biological interference I6.0. ' CONCLUSIONS r h , i AGE interpreted the results of all work completed to indicate that a Flag City Chevron release of ; hydrocarbons and MTBE.occur'red 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 both laterally and vertically through the Rocky's Upper Zone and into Secondary Aquifer and Primary Aquifer Zones ' During the March and June 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 �Lg/l and 250 µg/1, respectively,whereas intermediate well MW-4, located between MW-8 and the ' UST area, had no detection of MTBE, albeit screened in the First Zone Since initiation of ground water extraction activities at the site, First Zone ground water flow direction in the area of MW-8 . has generally been towards the south-southwest while Second Zone ground water flow direction has Advanced GeoEnvironmentak,Inc