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s 1} • 29 July 2005 AGE-NC Project No 96-0232 Page 7 of 9 (Figure 8, Table 3) • Low to moderate off-site MTBE concentrations(as high as 56 pg/1)were detected in Second Zone wells west-southwest of the site at Rocky's Restaurant wells MW-11A, MW-14, and MW-17,west-northwest of the site at Three B's Truck Plaza,from wells MW-8B,MW-9A, MW-IOB, MW-I IB and MW-13B, and from the northeastern-most well MW-19B (Figure 9) • Low to moderate offsite MTBE concentrations (as high as 170 pg/l) were detected in Rocky's Upper Zone wells west of the site at Rocky Restaurant from wells MW-11B, MW-15 and MW-18 (Figure 10, Table 4) • Low concentrations of TPH-d have been detected at various wells during previous quarterly monitoring events at Flag City Chevron During December 2004, a low concentration of TPH-d was detected in the water samples collected from well MW-12A AGE had previously asked McCampbell Analytical Laboratory to review the TPH-d sample chromatograms from MW-12A, the laboratory concluded 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 4.0. CONCLUSIONS Based on the initial site conceptual model, AGE previously interpreted the results of all work completed to indicate that historically,a Flag City Chevron unauthorized release of MTBE occurred in the areas of the fuel dispensers and UST pit,which then migrated westward through 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 Rocky's Upper, Secondary Aquifer and Primary Aquifer Zones The vertical extent of Flag City Chevron MTBE-impacted ground water was interpreted to be between 25 feet bsg and 45 feet bsg Relative to the inferred source area near the Flag City Chevron UST area(EW-1), the Flag City Chevron plume previously extended westward for approximately 200 feet, where vertical migration appeared to have reached depths as great as 75 feet bsg (MW-11 B), the maximum westward extent of the Flag City Chevron plume was most likely in the area of the former Rocky's Restaurant domestic drinking water well (RDW-1), where the plume appeared to converge with that of a Three B's Truck Plaza MTBE ground water plume Figures 8, 9 and 10 depict two,distinct MTBE-impacted ground water plumes that previously converged near the vicinity of the former Rocky's Restaurant domestic well RDW-1 Recently,a third,distinct MTBE ground water plume has been defined north-northeast of Flag City Advanced GeoEnvironmental,Inc