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26 October 2011 <br />AGE-NC Project No. 02-0926 <br />Page 4 of 4 <br />3.0. CONCLUSIONS <br />Based on SVE vapor remediation data collected during the operational period, AGE <br />concludes the SVE system has effectively removed a significant portion of the residual <br />adsorbed hydrocarbon impact at the site. However, the SVE system appears to have <br />reached a point diminishing returns, as influent vapor concentrations continue to decline <br />to near non-detect levels (trend for influent TPH-g concentrations over time is provided in <br />Appendix D). A cumulative total of 8,258.2 pounds or 1,321.4 gallons of hydrocarbons as <br />gasoline were extracted by the SVE system since start-up in September 2010. <br />4.0. RECOMMENDATIONS <br />As of 22 August 2011 the SVE system has been temporarily shut down for the <br />performance of a SVE rebound test. On 19 October 2011 the SVE system was restarted <br />for a period of 24-hours and soil vapor samples were collected on 20 October 2011 to <br />evaluate influent soil vapor concentrations. Upon receipt of SVE rebound analytical data, <br />AGE recommends preparation of a report of findings evaluating future vadose zone <br />remediation at the site. <br />5.0. 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 />conditions may vary away from these data points. No other warranty, expressed or implied, <br />is made as to the professional interpretations, opinions and recommendations contained <br />in this report. <br />Advanced GeoEnvironmental, Inc.