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1 ' 10 December 2001 • AGE-NC Project No 96-0249 ' Page 5 of 6 ' may be screened within or near a "core area" of a dissolved petroleum hydrocarbon plume However, the area of greatest dissolved petroleum hydrocarbon-impact was observed in the area near wells MW-3 and MW-6 (Figure 4) Lower petroleum hydrocarbon concentrations ' were detected from Intermediate well MW-1 which may indicate a separate plume of dissolved petroleum hydrocarbons in the area of MW-6 • The distribution of MTBE concentrations detected in Three B's Truck Plaza wells MW-1, ' MW-4, MW-6 and Flag City Chevron wells MW-7 and MW-13A suggest the possibility of two separate dissolved MTBE-plumes (Figure 6) ' • The distribution of TPH-d concentrations detected in Three B's Truck Plaza wells MW-1, MW-2, MW-3, MW-6 and Flag City Chevron wells MW-12A and MW-13A suggest the possibility of two separate dissolved TPH-d-plumes (Figure 5) ' • Laboratory results of grab water samples collected from DW-1 and RDW-1 indicate that there is no MTBE-Impact to the Three B's Truck Plaza or Rocky's Restaurant domestic ' drinking water wells at this time, however, MTBE was previously detected in the Rocky's Restaurant drinking water well from February 1999 to March 2001 (Table 4) 5.0. RECOMMENDATIONS Based upon data collected during September 2001, AGE recommends 1 Continued quarterly ground water monitoring at wells MW-1 through MW-6, the next quarterly ground water monitoring event is tentatively scheduled for December 2001 2 Continued coordination of quarterly ground water monitoring events with Flag City Chevron 3 Installation of additional shallow- and deep-screened ground water monitoring wells based on the findings of the existing shallow ground water monitoring wells and CPT soil borings, the screen Intervals for the deep-screened monitoring wells will be placed to define and monitor the horizontal extent of the impacted ground water plume In each informal hydrologic unit 4 Conduct a ground water pump test to obtain general aquifer characteristics such as hydraulic conductivity, transmissivity, storativity and drawdown at various pumping rates Results of the pump test would be utilized to estimate a radius of influence for the zone of capture of dissolved petroleum hydrocarbons 5 Install and continuously operate a ground water extraction system (interim remediation) in the area between MW-3 and P-12 to inhibit further vertical and off-site migration of the fuel- impacted ground water plume IAdvanced GeoEnvironmental,Inc