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i CONCLUSIONS ' There are petroleum hydrocarbons remaining in the soil and groundwater The direction of groundwater flow and the magnitude of hydraulic gradient are generally consistent with the previous event ' Groundwater elevations have decreased approximately 0 26 feet since October 2005 TPHg and/or BTEX constituents were detected at or above laboratory reported detection limits in groundwater samples collected from MW1, MW2, MW4, VW 1, and VW2 ' MTBE was detected in the groundwater samples collected from MW I, MW2, MW4, and MW9 TBA was detected In the groundwater sample collected from MW2 MTBE was detected above laboratory ' method detection limits for the first time in MW 1 The analyte 1,2-DCA was detected In the groundwater samples collected from MW1 and MW8 None of the groundwater samples collected contained detectable concentrations of ETBE, TAME, DIPS, or EDB Dissolved petroleum hydrocarbon concentrations in groundwater from MWI, MW2, MW4, MW8, MW9, MW 10, CW, VW1, and VW2 generally remain consistent with the results from previous sampling events RECOMMENDATIONS ' Based on the results of the Fourth Quarter 2005 monitoring event,we recommend the following • Conduct the First Quarter 2006 groundwater monitoring and sampling of MW 1 through MW 10, VWI, VW2, and CW and analyze samples for TPHg and BTEX by EPA methods 8015B and 8021 B, respectively, and MTBE,ETBE, TBA, TAME, and DIPE by EPA method 8260B • Perform a remediation system optimization analysis • Separate remediation system reporting from quarterly groundwater monitoring reporting Continue remediation monitoring on a monthly basis and groundwater monitoring on a quarterly basis Reduce the frequency of the system O&M report submittal to semi-annually Continue to ' submit the groundwater monitoring reports on a quarterly basis � r s lenviro1625961quart1yl4gr-2005 doc 9 ATC ASSOCIATES INC