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' 15 October 2002 . AGE-NC Project No 96-0232 ' Page 11 of 19 ' 3 4 1 3 Secondga Aquifer Zone Ground water elevation data collected in the Secondary Aquifer Zone (85 to 105 feet bsg) was ' Inferred to be towards the west-northwest in the area of Flag City Chevron wells MW-8B, MW-9B and MW-10D and towards the west-southwest between Flag City Chevron wells MW-11C, MW-12C and MW-13C (Figure 6) Ground water gradients ranged from approximately 0 004 ft/ft ' near the Flag City Chevron site to 0 006 ft/ft near the Rocky's Restaurant and Three B's Truck Plaza sites ' 3 4 14 Primary Aquifer Zone ' Ground water elevation data collected in the Primary Aquifer Zone(130 to 150 feet bsg)was Inferred to be towards the west-northwest in the area of Flag City Chevron wells MW-8C, MW-9C, ' MW-10E, MW-11D, MW-12D and MW-13D (Figure 7) Ground water gradients ranged from approximately 0 002 ft/ft near the Flag City Chevron site to 0 001 ft/ft near the Rocky's Restaurant and Three B's Truck Plaza sites 3 4 2 Laboratory Results of Ground Water Samples During the September 2002 sampling event, TPH-g was not detected in any of the analyzed water samples, however, TPH-d was detected in samples collected from MW-9B and MW-11B at concentrations of 64µg11 and 62µg/1, respectively The laboratory reports noted that the TPH-d sample chromatograms had no recognizable patterns and/or a few Isolated peaks Based on further laboratory review of the TPH-d sample chromatograms,the laboratory further indicated to AGE that ' the TPH-d detections did not have typical diesel characteristics,and that the detected chromatogram peaks were possibly the result of biological interference (Appendix H) MTBE (utilizing EPA Method 8260M) was detected in water samples collected from monitoring wells MWA, MW-7, MW-8A, MW-11Band MW-11D at concentrations as high as 79 µg/1 (MW-11 B),Isoconcentration maps displaying the estimated extent of dissolved MTBE in First Zone and Second Zone aquifer are depicted in Figures 8 and 9 MTBE was detected in water samples collected from extraction wells EW-1, EW-2, and EW-4 through EW-10 at concentrations as high as 43 µg11 (EW-9), an Isoconcentration map displaying the estimated extent of dissolved MTBE in fthe area of the ground water extraction wells is depicted in Figure 10 ' No other constituents of concern were detected above laboratory reporting limits in the water samples collected during the third quarter sampling event Analytical results of ground water monitoring well samples are summarized in Tables 5 and 6 The laboratory reports (McCampbell Advanced GeoEnvironmental,Inc