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' 27 October 2003 AGE-NC Project No 98-0450 Page 15 of 17 ' direction within the area contained by the six monitoring wells, wells BMW-2 would be down- gradient from the former dispenser system and the former UST area ' 5 3 3 Analytical Results of Ground Water Samples ' TPH-g was detected in three of the two ground water samples collected at the site at concentrations of 77 micrograms per later(µg11) in sample MW-5 and 1,700 11g/1 in sample BMW-4 (former UST area) Benzene was not detected in the samples analyzed, the other BTEX compounds were detected ' at various concentrations with the highest concentrations occurnng in BMW-4(37 µg/1 of toluene) MTBE was detected in sample MW-5 by EPA method 8021 at a concentration of 13 µg/1 MTBE ' was detected in samples BMW-2 and MW-5 by EPA method 8260M at concentrations of 14 µg/1 and 19 µg/1, respectively TBA was also detected in samples BMW-4 and MW-5 by EPA method 8260M at concentrations of 5 8 µg/1 and 7 9 µg/1, respectively The laboratory report(MAI Laboratory Report No 0309034),Quality Assurance and Quality Control ' Data(QA/QC) and chain-of-custody forms are presented in Appendix C The results of the analysis are summarized in Tables 3 and 4 The lateral extent of dissolved MTBE is depicted in Figure 7 ' 6 0. SOIL VAPOR EXTRACTION REBOUND ANALYSIS ' The SVE/IAS system utilizing the vacuum blower operated at varying rates during the remediation period The influent soil-vapor samples hydrocarbon concentrations(TPH-g)detected had decreased to concentrations less than 100 µg/1, during the operational penod of January to July 2003 The ' concentrations typically were near 50 µg/l, with very low detections of BTEX compounds (Appendix B) ' Confirmation soil vapor extraction rebound response analysis was between 02, 03 and 18 September 2003 The soil vapor extraction pump was allowed to hiatus during the month of August 2003 The SVE system was reactivated, extracting vapors from all the wells on the site The SVE ' vacuum blower was reactivated and monitored on 02 September The SVE system operated for approximately 24-hours The system was then again monitored on 03 September and allowed to operate until an additional monitoring on 18 September During the monitoring events the flow rate of extracted soil-gas(influent)was measured using direct ' measure flow meter, and vacuum potential was measured at the two-inch influent line using a magnehelic vacuum gauge The organic-vapor concentration in the extracted soil-gas stream was imeasured prior to entenng the blower using an organic vapor meter(OVM)equipped with a photo- Advanced GeoEnvironmental,inc