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25 January 2012 <br />AGE-NC Project No. 02-0926 <br />Page 3 of 7 <br />DO was measured at concentrations ranging from 0.87 mg/I (9.5%) to 9.40 mg/I <br />(104%) in well MW-5. <br />Plots of dissolved oxygen versus time in wells nearest to the sparging location (MW-1, <br />MW-2 and MW-5) were used to evaluate the lateral influence of the pilot sparging. Based <br />on these plots a significant increase in DO was observed at the location of well MW-5 <br />(approximately 7 feet from active sparging location; Appendix B). Baseline dissolved <br />oxygen was measured at 0.87 mg/I and reached a maximum measured concentration of <br />9.40 mg/I at the beginning of the final day of monitoring. <br />DO concentrations in the remaining observations wells (MW-1 through MW-4) generally <br />fluctuated and did not show discernable increases in DO. The general fluctuations likely <br />indicate that the sparging radius of influence is limited to areas directly near the sparging <br />point (MW-6) or the lateral migration of low concentrations of dissolved oxygen (mixing) <br />may have occurred over a short span of time. <br />4.0 SOIL VAPOR EXTRACTION FINDINGS <br />From field and laboratory data collected at the SVE remediation system during the 72-hour <br />IAS pilot test performed between 19 December and 22 December 2011, AGE determined <br />the average TPH concentration, the average flow rate and calculated the approximate <br />mass and volume of hydrocarbons removed. <br />4.1. SOIL VAPOR EXTRACTION PERFORMANCE <br />Between 19 December and 22 December 2011, the SVE remediation system was <br />operational for a total of 72 hours. During this operational period, SVE inlet flow rates (total <br />flow) were generally observed between 78 SCFM and 82 SCFM. Utilizing a photo ionization <br />meter (PID), hydrocarbon concentrations were measured from the SVE influent at <br />concentrations ranging 204 parts per million volume (ppmv) to 508 ppmv. Field <br />measurements are summarized in Table 2. <br />4.2. ANALYTICAL RESULTS OF VAPOR SAMPLES <br />A total of four influent and three effluent vapor samples were collected during the pilot test <br />to evaluate the effects of pilot sparging on the influent vapor stream of the on-site SVE <br />system. TPH-g were detected in all four samples at concentrations of 3.50Q micrograms <br />per liter (pg/I), 60Q pg/I. 39.0 pg/I and 45Q pg/I, respectively (Table 4). All four BTEX <br />Advanced GeoEnvironmental, Inc.