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1 <br /> 11 January 2006 <br /> AGE-NC Project No 95-0130 <br />' Page 13 of 14 <br /> • Dissolved TPH-g was detected from grab samples collected at the Influent end of the <br />' treatment system at concentrations as high as 30,000 [g/l, benzene concentrations as high <br /> as 16,000 µg/1 and MTBE concentrations as high as 3,100 Pg/l Laboratory analysis of grab <br />' water samples collected from the P&T effluent did not detect any constituents of concern <br /> during the third quarter 2005 (Table ) <br /> • Between 03 June and 07 September 2005, an estimated 54 pounds of petroleum <br />' hydrocarbons were extracted from ground water (Table 9) <br /> • A noticeable decrease in P&T influent concentrations was evident between the second and <br />' third quarter 2005 monitoring events,a plot of the influent TPH-g concentrations versus time <br /> is included in Appendix L <br /> • Since initiation of the P&T system in November 2004, the total volume of petroleum <br /> rhydrocarbon-impacted water extracted is estimated to be approximately 520,300 gallons <br /> (Table 7), the mass of petroleum hydrocarbons removed from the above total volume of <br />' 520,300 gallons is estimated at approximately 171 pounds of extracted petroleum <br /> hydrocarbons <br />' 6.0. RECOMMENDATIONS <br />' Based upon the results of the third quarter 2005 investigation, AGE recommends <br /> • Continued quarterly groundwater monitoring of wells VW-1 C,VW-2A,VW-3A,MW-6(A- <br />' E)and MW-7(A-E) The Fourth Quarter 2005 groundwater monitoring event was conducted <br /> on 06 December 2005 <br />' • Conduct future ground water monitoring events concurrently with the Knowles/Roek <br /> Property site (102 South Wilson Way) and the Arco AM/PM site (130 South Wilson Way), <br />' • Continued quarterly depth-to-water measurements in all monitoring wells at the site, but <br /> reduced ground water sampling frequency from a quarterly to a semi-annual program, AGE <br /> believes that continued quarterly ground water sampling from wells MW-1 through MW-5 <br />' at this stage of the investigation is not cost effective and will not provide enough useful <br /> information to supplement the ongoing Investigation Semi-annual sampling events should <br /> be adequate to monitor ground water impact at these wells and should be re-evaluated on a <br />' semi-annual basis <br /> 1 <br /> i <br />' Advanced GeoEnvironmentsl,Inc <br />