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4 <br /> 10 August 2004 <br /> AGE-NC Project No 96-0232 <br /> Page 9 of 10 <br /> The findings of the ground water investigation results are as follows <br /> y 0 First encountered ground water was within the screened interval of well MW-19A, which <br /> should yield samples fully representative of shallow (First Zone) ground water conditions, <br /> however, the screen interval at MW-19B was approximately 33 feet `drowned', and should <br /> be more representative of deeper ground water conditions (Second Zone) <br /> • TPH-d and TPH-mo were detected from P-43 `grab' water samples at depths between 13 to <br /> 18 feet (97 µg/1 and 350 µg11, respectively) and 47 to 51 feet (63 µg/1 and 380 µg11, <br /> respectively) <br /> • MTBE was detected from First Zane `grab' water samples collected from P-40A,P-41 and <br /> P-43 at concentrations as high as 540µg/1 from P-43,MTBE was detected from Second Zone <br /> `grab' water samples collected from P-39,P-40A, P-41,P-42 and P-43 at concentrations as <br /> high as 1,900 gg/l(P-41) The dissolved MTBE-impacted plume beneath the site is depicted <br /> in cross-sectional view E-E' (Figure 4) <br /> • MTBE was detected from ground water momtonng well MW-19A in First Zone at a <br /> concentration of 5,300 µg/1, MTBE was detected from MW-19B in Second Zone at a <br /> concentration of 58 µg/1 <br /> • A low concentrations of dissolved TBA was detected in the Second Zone from P-43 at a <br /> concentration of 13 pg/l <br /> Based on the data collected dunng the January and May 2004 Investigation, there appears to be a <br /> third, distinct MTBE-Impacted ground water plume north of the Flag City Chevron, concentrated <br /> in the area of well MW-19 and soil boring P-43 (Figure 4), offslte to the north, the plume is most <br /> prevalent in the First Zone,with decreasing concentrations observed in the Second Zone However, <br /> on the northern edge of the Flag City Chevron property, the MTBE plume is most prevalent in the <br /> Second Zone AGE concluded that this third MTBE-plume may have migrated from the First Zone <br /> near Banner Avenue to the Second Zone at the northern Flag City Chevron property boundary,drawn <br /> by the induced ground water depression created by ground water extraction at the site AGE's <br /> interpretation of a third MTBE-impacted ground water plume could explain the recent phenomena <br /> of MTBE being detected at Flag City Chevron well MW-8 following nine consecutive quarters of <br /> being non detect <br /> • <br /> Advanced GeoEnvironmental,Inc <br />