Laserfiche WebLink
1 <br /> 01 June 1999 <br /> AGE-NC Project No 95-0137 <br /> Page 10 of 26 <br /> EPA methods 8015 Modified, 8020 and 8260 Modified,respectively TPH-g was detected in the soil <br /> gas/vapor samples (vapor samples) at concentrations ranging from 7,700,ug/l to 53,000,ug/l BTEX <br /> compounds were detected in the gas/vapor samples at concentrations as high as 290 ,ug/1 (benzene, <br /> VS I) Analytical results of the gas/vapor samples are included in Table 7 Laboratory data for the <br /> soil gas/vapor data is included in Appendix B <br /> Results The SVE unit was operated at approximately 2,000 RPMs for the first four hours of the test <br /> and at approximately 1,500 RPMs for the second four hours of the test Initial flow rates were <br />(' measured at 20 scfm (standard cubic feet per minute) and reached 35 scfm after 7 5 hours OV <br /> readings ranged from 384 to 748 ppmv Induced vacuum measured at the extraction well (VW-1 or <br /> VW-2)ranged from 48 to 80 inches of water <br /> ' As expected, the greatest vacuum was measured in observation points nearest the extraction well <br /> (VW-2 or MW-1) The lowest vacuum was measured in MW-4, approximately 45 to 65 feet <br /> northwest of the extraction points The maximum vacuum measured at the observation points during <br /> the pilot test was plotted versus the distance from the extraction well The effective radius of <br /> influence can be determined by drawing a best-fit line though these data points to correlate distance <br /> to vacuum data At a vacuum potential of 0 10 inches of water, the radius of influence is <br />' approximately 45 feet, at an induced vacuum potential of 10 inches of water,the radius of influence <br /> is approximately 30 feet, at 10 0 inches of water the radius of influence ranges from 11 to 17 feet <br /> ' Based upon an effective vacuum potential of 10 inches of water,the calculated effective radius of <br /> influence at the site will be approximately 30 feet However,the actual effective radius of influence <br /> achieved may be somewhat less Figure 5 depicts the theoretical and effective radius of influence <br /> ' Additional data obtained during the installation of soil borings and monitoring wells may be useful <br /> in determining a theoretical radius of influence Installation of additional extraction wells would be <br /> ' required at the site to implement an SVE system <br /> ' One drawback of SVE is that not all contaminated zones of soil are remediated effectively or at the <br /> same rate For instance, a sandy soil zone will cleanup more quickly than a silty one SVE is not <br /> usually effective in soil with high clay content Other drawbacks of SVE include ineffective <br /> ' treatment of soil lying below ground water or within the "smear" zone and moderately effective to <br /> ineffective treatment of longer-chain hydrocarbons(i e ,diesel,motor oil) Ground water remediation <br /> should be conducted concurrently with SVE to facilitate remediation of the smear zone <br /> 515 Duration <br /> ' Cleanup periods for soil vapor extraction typically range from several months to several years Based <br /> upon the plume size and the presence of fine-grained clay-rich soil, an SVE cleanup period of 12 to <br /> Advanced GeoEn ironmenial,Inc <br /> 1 <br />