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28 January 2005 AGE-NC Protect No 96-0232 Page 7 of 8 between 35 and 50 feet bsg(Second Zone) Geologic cross section E-E'depicts the Informal hydrogeologic units beneath the site (Figure 3) • No petroleum hydrocarbons were detected from the above soil samples by laboratory analysis • The detections of organic vapors by the PID meter are probably erroneous due to the water- saturated condition of the soil samples, the PID meter is sensitive to water vapor on the detector The findings of the ground water investigation results are as follows • During well development, first-encountered ground water was measured at approximately 13 5 feet bsg, first encountered ground water was within the screened interval of well MW-20A, which should yield samples fully representative of shallow (First Zone) ground water conditions Ground water in well MW-20B is from a deeper screen interval (45 to 50 feet bsg) and should be more representative of deeper (Second Zone) ground water conditions • TPH-g, TPH-d, TPH-mo and BTEX constituents were not detected from initial well development water samples • MTBE was detected from First Zone `grab' water samples collected from MW-20A (screened 10-25 feet) at a concentration of 230 µg11, MTBE was not detected from Second Zone water samples collected from MW-20B The dissolved MTBE-impacted plume beneath the site is depicted in cross-sectional view E-E'(Figure 4) Based on the data collected during the November and December 2004 investigation, there appears to be a third, distinct MTBE-impacted ground water plume north of the Flag City Chevron, concentrated in the area between wells MW-8,MW-19 and MW-20(Figure 4), offsite to the north, the plume is most prevalent in the First Zone,with decreasing concentrations observed in the Second Zone On the northern edge of the Flag City Chevron property(MW-8), the MTBE plume is most prevalent in the Second Zone,however,there is no repeatable First Zone monitoring point in the area of MW-8, so it is not known how extensive MTBE-impact is in First Zone near MW-8 AGE concludes that this third MTBE-plume may have migrated from the First Zone near Banner Avenue to First ZonelSecond Zone at the northern Flag City Chevron property boundary, and was previously drawn by the induced ground water depression created by ground water extraction at the Flag City Chevron site AGE's interpretation of a third MTBE-impacted ground water plume could explain the recent phenomena of MTBE being detected at Flag City Chevron well MW-8 following nine consecutive quarters of being non detect Advanced GeoEnvironmental,Inc