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10 <br /> 14 February 2006 <br /> AGE-NC Project No 98-0448 <br /> Page 8 of 9 <br />' <br /> (14%) of the total hydrocarbons removed <br /> • The average SVE inlet flow rate was estimated to be 50 cfm at an average differential <br /> pressure of 0 63 inches of water (Table 6) <br />' • Since Initiation of the SVE system(April 2001),the total volume of petroleum hydrocarbons <br /> extracted Is estimated to be approximately 320 gallons (Table 7) <br />' TPH-g was not detected in the influent air flow sample collected from the October 2005 <br /> sampling event However, TPH-g and BTEX were detected In the November 2005 influent <br />' sample at concentrations of 230 gg/l TPH-g, 6 5 gg/l benzene, 21 µg11 toluene, 4 0 µg11 <br /> ethylbenzene and 24 gg/l total xylenes <br /> • On 16 May 2005, vapor well VW-2 and air sparge wells AW-1, AW-2 and AW-3 were <br />' closed to focus vapor extraction on the remaining areas of petroleum hydrocarbon-Impacted <br /> soil and ground water <br />' The SVE system may have extracted the majority of the available adsorbed soil <br /> contamination, as based on the decline trend in vapor samples collected <br /> • On 23 November 2005, the SVE remediation system was turned off <br /> I � <br />' 6.0. RECOMMENDATIONS <br /> Based upon the results of this investigation, AGE recommends <br />' AGE has suspended SVE and IAS remediation operations at the site until May 2006 A <br /> rebound response test has been tentatively scheduled for February 2006 and May 2006 to <br /> Ievaluate remediation progress in both groundwater and subsurface vapor Rebound response <br /> testing will be performed at the site by collecting ground water samples from wells MW-1, <br /> MW-2,MW-4(A and B),MW-6 and VW-6,additionally,the SVE system will be turned on <br /> rand allowed to operate for one full day, and air samples collected from wells VW-1 through <br /> VW-6 and MW-4A If monitoring of ground water monitoring wells and SVE wells do-not <br /> show any significant hydrocarbon increases at the conclusion of the rebound response test, <br /> a site closure report may be warranted <br /> • Until site closure is warranted, continued quarterly ground water monitoring and sampling <br /> of wells MW-1, MW-2, MW-4A, MW-4B, MW-6, MW-8 and vapor well VW-6 , ground <br /> water sampling results will be used to monitor progress of the SVE and IAS remediation <br /> system <br /> Advanced GeoEnvironmentai,Inc <br />