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t30 October 2003 i AGE-NC Project No 96-0232 ' Page 15 of 15 ' were recorded in nine previous quarters of monitoring Since initiation of ground water extraction activities at the site, First and Second Zone ground water flow direction in the area of MW-8 has generally been towards the south-southeast,and should draw on-site contaminants away from MW-8 ' (Figure 5) The most intense MTBE detections were reported during the March 2002 and the March 2003 sampling events, which could be related to re-mobilization of adsorbed MTBE in'soil as a result of the seasonal high ground water levels observed at the site each year near March(Table 4), ' however, intermediate well MW-4, located between MW-8 and the UST area,have no detection of MTBE, although screened in the First Zone, and three soil borings (P-36 through P-38) advanced in October 2002 to assess the area near MW-8 (Figure 2)did not detect MTBE in grab ground water ' samples collected from First Water and Second Water At this time,AGE has tentatively concluded that the MTBE detections in MW-8 is a separate dissolved MTBE plume(Figure 10) ' 6.0 RECOMMENDATIONS ' Based upon data collected from the site, AGE recommends • Continued quarterly ground water monitoring and sampling of monitoring wells MW-1 '• through MW-18 Continued coordinated quarterly ground water monitoring and sampling events with Three B's Truck PIaza G Continued ground water extraction from wells EW-4 and EW-5, extraction wells EW-7, EW-8, EW-9 and EW-10 should be alternated into the ground water extraction system A work plan addendum for additional site investigation(i e soil borings)in the vicinity of Flag City Chevron well MW-8 was included in Quarterly Report-Second Quarter 2003,dated 31 July 2003, data collected from the additional site investigation will be utilized to better assess the migration pathway o fMTBE-impacted groundwater detected at MW-8A Upon RWQCB review and approval of the work plan addendum, AGE will tentatively schedule field work 7.0. LIMITATIONS Our professional services were performed using that degree of care and skill ordinarily exercised by Ienvironmental 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 Iavailable 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 IAdvanced GeoEnvironmental,Inc