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1 <br /> 26 April 2002 <br /> AGE-NC Project No 95-0173 <br />' Page 7of8 <br /> and AW-2A (Table3)which may be interpreted as a mass reduction of the dissolved plume <br />' due to air sparging at the site <br /> • Previous and current laboratory results of ground water samples suggest that there Is a minor <br />' MTBE- and 1,2-DCA-impact to ground water in the areas of wells MW-2, MW-3, MW-4 <br /> and MW-5 (Tables 2 and 3) <br /> • Laboratory results of ground water samples collected from MW-13 (screened 95 to 100 feet <br /> bsg)suggest that the dissolved petroleum hydrocarbon plume extends to at least 100 feet bsg, <br /> and is at least 65 feet thick, however, a trend of decreasing contaminant concentrations has <br />' been observed from well MW-13 for seven consecutive sampling events <br />' Based on SVE remediation data collected between 01 October 2001 and 31 December 2001,AGE <br /> concludes <br /> • The average SVE inlet vapor concentration was approximately 1,200 µg/l, the average SVE <br /> inlet flow rate was approximately 82 cubic feet per minute(Table 6) <br /> • The volume of hydrocarbons extracted by the SVE system was calculated to be <br />'. approximately 107 gallons ofpetroleum hydrocarbons(Appendix F)during the fourth quarter <br /> 2001 monitoring period (Table 7) <br />' • Since initiation of the SVE system,the total volume of petroleum hydrocarbons extracted is <br /> estimated to be approximately 1,155 gallons (Table 7) <br /> • No general concentration trends were evident in the PID field measurements, however, a <br /> general decline from extracted soil-gas samples was apparent in analytical results over the <br /> Fourth Quarter 2001 monitoring period <br /> 6.0. RECOMMENDATIONS <br />' Based upon fourth quarter 2001 data collected from the site, AGE recommends <br /> P <br /> • Cnnt,nuefiquarterly ground water monitoring and sampling ofwellsMW-l through MW-13, <br /> AW-lA, AW-1B, AW-2A and AW-2B, ground water sampling results will be used to <br /> monitor progress of the SVE and IAS remediation system <br /> • Continued operation of the on-site SVE and IAS remediation system, remediation progress <br /> will be reevaluated on a quarterly basis <br /> To address deeper petroleum hydrocarbon-impact, AGE proposes that ground water pump testing <br />' Advanced GeoE nvi ronmental,Inc <br /> 1 <br />