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i ' 21 June 2004 AGE-NC Project No 97-0249 Page 7 of 7 140 µg/1 (Figure 12), and from Hydrologic Unit 3 in the area of Flag City Chevron wells ' MW-1113 and MW-18 at concentrations as high as 190 µg/1 (Appendix A) • The highest off-site concentrations of dissolved MTBE were detected toward the east, in ' water samples collected from Flag City Chevron wells EW-7 (120 µg/1), screened within Hydrologic Unit 1, and MW-8A(400 µg/1), screened within Hydrologic Unit 2(Figure 12) • Low concentrations of TBA and 1,2-DCA have been detected from wells MW-1, MW-2, ' MW-3, MW-5, MW-6, MW-8A, MW-10A and MW-11A, suggesting that only a minor TBA-impact and 1,2-DCA-impact to ground water in Hydrologic Unit I is present at the site ' • The lateral and vertical extent of the dissolved petroleum hydrocarbon plume is not known toward the northeast of Three B's Truck Plaza well MW-3, toward the south of Three B's Truck Plaza well MW-6 and toward the south of Flag City Chevron wells MW-16/17/18 ' (Figures 9, 10, 11 and 12) ' 5.0. RECOMMENDATIONS Based upon the results of the first quarter 2004 investigation, AGE recommends C Continued quarterly ground water monitoring of wells MW-1 through MW-12, the next quarterly ground water monitoring event is tentatively scheduled for June 2004, e Continue to conduct future ground water monitoring events concurrently with the Flag City Chevron site (6421 Capitol Avenue), and • Additional ground water monitoring wells(screened in Hydrogeologic Unit 1)are warranted in the area northeast of Three B's Truck Plaza well MW-3, south-southeast of Three B's Truck Plaza well MW-6 and southwest of MW-16/17/18, installation of the additional ' ground water monitoring wells should aid in the preparation of a site conceptual model ' 6.0. LIMITATIONS Our professional services were performed using that degree of care and skill ordinarily exercised by environmental consultants practicing in this or similar localities The findings were based mainly upon analytical results provided by an independent laboratory Evaluations of the hydrogeologic ' conditions at the site for the purpose of this investigation are made from a limited number of available data points (ground water samples), and subsurface conditions may vary away from these data points No other warranty,expressed or implied,is made as to the professional interpretations, ' opinions and recommendations contained in this report i' IAdvanced GcoEnvironmental,Inc I