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15 November 2011 <br />AGE-NC Project No. 99-0670 <br />Page 3 of 4 <br />Between 09 August and 22 August 2011, the SVE unit operated a total of 313 hours; <br />between 19 October and 20 October 2011, the SVE unit operated a total of 24 hours <br />(Table 3). The analytical concentrations from the 09 August 2011 and 20 October 2011 <br />influent SVE samples, average influent flow rates and the operational period were used to <br />calculate the approximate mass of extracted total petroleum hydrocarbons during these <br />periods. <br />During the remainder of the third quarter 2011 operational period (09 August and 22 <br />August 2011), the mass of hydrocarbons extracted by the SVE system was calculated to <br />be 19 pounds, or equivalent to a volume of approximately 3 gallons of gasoline. <br />During the SVE rebound testing period (19 October to 20 October 2011), the mass of <br />hydrocarbons extracted by the SVE system was calculated to be 1.1 pound, or equivalent <br />to a volume of approximately 0.2 gallons of gasoline. Volume/mass calculations of <br />extracted hydrocarbons are included as Appendix B. <br />CONCLUSIONS <br />Results of the SVE rebound response test did not indicate any significant spike in vapor <br />concentrations had occurred, and generally appeared to be within the range of previously <br />encountered hydrocarbon concentrations. <br />RECOMMENDATIONS <br />Conclusion of SVE remediation at the site. Based on the data collected during the 2011 <br />operation year and the SVE rebound test, asymptotic levels appear to have been <br />approached, and further SVE remediation is of little benefit for this site, without active <br />ground water treatment. Currently, AGE is in the process of competing an in-situ air <br />sparging pilot test at the site. Results from the pilot will further conclude if the on-site SVE <br />remediation will be used for future sparged hydrocarbon recovery or if the system should <br />be decommissioned and removed from the site. <br />LIMITATIONS <br />Our professional services were performed using that degree of care and skill ordinarily <br />exercised by environmental consultants practicing in this or similar localities. Findings were <br />based mainly upon analytical results provided by an independent laboratory. Evaluations <br />of the hydrogeologic conditions at the site for the purpose of this investigation are made <br />from a limited number of available data points (soil vapor samples), and subsurface <br />Advanced GeoEnvironmental, Inc.