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12 September 2002 <br /> AGE-NC Project No 95-0137 <br /> ' Page 5 of 8 <br /> ' 3 1 SOIL VAPOR EXTRACTION/IN-SITU AIR SPARGING <br /> The SVE unit was operated continuously during the period between 13 December 2001 and 11 June <br /> ' 2002,except during maintenance The unit operated at extraction flow rates varying between 25 and <br /> 85 cubic feet per minute (cfrn) An Induced vacuum (negative pressure) of approximately 21 to <br /> 28 Inches of water was measured in the piping between the blower and extraction wells Utilizing <br /> ' a photo ionization meter(PID),hydrocarbon concentrations were measured between 5 8 and 46 ppm <br /> at the SVE Intake during this period The field measurements are summarized in Table 3 <br /> ,t Air-sparging rates were measured at approximately scfm during each monitoring event A pressure <br /> of approximately 5 psi was maintained for the air sparging flow rate <br /> Elevated concentrations of dissolved oxygen were periodically detected in monitoring wells used as <br /> observation wells within and outside the IAS network on the site, the highest dissolved oxygen <br /> value,measured in well MW-1,was 22 51 % Generally,dissolved oxygen concentrations measured <br /> ' in the wells remained stable at /or sporadically increased above pre-remedial levels Dissolved <br /> oxygen measurements are presented in Table 4 <br /> 32 ANALYTICAL RESULTS OF SOIL-GAS VAPOR SAMPLES <br /> b� <br /> TPH-g was detected from all influSVE air flow samples at concentrations as high as 430 µg/1 <br /> TPH-g was detected only in the 1tanuary and 11 March 2002 effluent SVE air flow samples at <br /> concentrations of 130 µg/1 and 170 µg/1, respectively <br /> Various BTEX compounds were detected in all influent SVE air flow samples at maximum <br /> ' concentrations of 1 5 gg/l benzene,20 gg/l toluene,3 8 µg/1 ethylbenzene and 24 ggh xylenes, from <br /> the 11 March 2002 sample Various BTEX compounds were detected in the January,March and June <br /> 2002 effluent SVE air flow samples at maximum concentrations of 12 µg/1 benzene, 15 gg/l toluene, <br /> ' 2 9 gg/l ethylbenzene and 17 gg/1 xylenes, from the 11 March 2002 sample <br /> The analytical results of the soil vapor samples are summarized on Table 1 The laboratory reports <br /> ' (MAI Sample Numbers 88121, 88122, 91106, 91107, 0203204-01/02, 0204287-01/02, <br /> 0205177-01/02 and 0206187-01/02),Quality Assurance and Quality Control(QA/QC)reports and <br /> chain-of-custody forms are included in Appendix B <br /> 1 Y <br /> 33 MASS OF RECOVERED HYDROCARBONS <br /> ' . The hydrocarbon mass (TPH-g) removed during the operating period was calculated using the <br /> ' equation M = C•Q•t <br /> Advanced GeoEnvironmental, Inc <br /> 1 <br />