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10 September 2004 <br /> . AGE-NC Protect No 03-1100 <br /> Page 9of10 <br /> influence is approximately 40 feet for both screened intervals, at a vacuum pressure of 10 inches <br /> of water, the radius of influence is approximately 25 feet for both SVE1 and SVE2, at a vacuum <br /> pressure of 10 0 inches of water the radius of influence is less than 10 feet Based on the United <br /> States Environmental Protection Agency (EPA)-prepared document How to Evaluate Alternative <br /> Cleanup Technologies For UST sates, the radius of influence is considered to be the distance from <br /> the extraction well at which a vacuum of at least 0 1 inches of water is observed Based upon an <br /> effective vacuum pressure of 0 1 inches of water, the calculated effective radius of influence at the <br /> site will be approximately 40 feet for the screened vapor wells,the majority of the residual impacted <br /> soil would be collected within the 40-foot radius of influence The effective radius of influence is <br /> shown on Figure 3 <br /> 44 ANALYTICAL RESULTS OF SOIL VAPOR SAMPLES <br /> TPH-g was detected in the soil vapor samples (vapor samples) at concentrations ranging from <br /> 7,500 µg/l to 13,000 gg/l (Table 3) Toluene, ethylbenzene and total xylenes were detected in the <br /> vapor samples at concentrations as high as 550 gg/l toluene, 150 µg/l ethylbenzene and 1,100 µg/l <br /> total xylenes Benzene and MTBE were not detected at or above laboratory reporting limits in the <br /> analyzed samples No other analytes of concern were detected in any of the samples submitted for <br /> analysis Laboratory results from the soil vapor samples are included in Appendix B <br /> 5.0. SUMMARY AND CONCLUSIONS <br /> On the basis of the information collected and analyzed during this investigation, AGE concludes <br /> • Soil encountered in the soil borings consisted of sandy silt,clayey silt and silt with an orange <br /> brown to grey brown color, silty sand was encountered at 30 feet and 45 feet bsg, and <br /> medium-to fine-grained sand was identified below 54 feet bsg in boring OZ2 Constituents <br /> of concern were not detected in any of the analyzed soil samples <br /> • Based upon an effective vacuum potential of 0 1 inches of water, the calculated effective <br /> radius of influence at the site will be approximately 40 feet <br /> • Up to 13,000 [.g/l TPH-g, 550 ggll toluene, 150 µg/l ethylbenzene and 1,100 µg/l total <br /> xylenes were detected in soil vapor samples collected during SVE testing Based on overall <br /> high hydrocarbon concentrations in soil vapor samples and the calculated effective radius of <br /> influence, SVE should effectively reduce adsorbed hydrocarbon concentrations in vadose <br /> zone soils <br /> Advanced GeoEnvironmental,Inc <br />