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' 15 June 1999 • AGE-NC Project No 98-0450 ' Page 11 of 27 ' Analytical, Inc (MAI),a California Department of Health Services (DHS)-certified laboratory Each sample was analyzed within 72 hours for TPH-g, BTE&X and oxygenated fuel additives (methyl tertiary butyl ether [MTBE],tertiary butyl alcohol [TBA]), di-isopropyl ether [DIPE], ethyl tertiary ' butyl ether [ETBE] and tertiary amyl methyl ether [TAME] in accordance with EPA methods 8015 Modified, 8020 and 8260 Modified, respectively TPH-g was detected in the soil vapor samples(vapor samples) at concentrations ranging from 19,000 ,ag/1 to 23,000/,eg/l BTEX were detected in the gas/vapor samples at concentrations as high as 740 ug/i (xylene, VS-1) Analytical results of the soil vapor samples are included in Table 6 Laboratory ' data for the soil vapor data is included in Appendix C ' Results The SVE unit was operated at approximately 1,900 to 2,000 RPMs for the test Initial flow rates were measured at 75 scfm (standard cubic feet per minute) and averaged at 60 sefm after 5 hours OV readings ranged from 2,400 to 4639 ppm (Appendix D) ' Induced vacuum measured at the wells(BMW-3 and VW-1)ranged from 0 9 to 1 30 inches of water The highest measured vacuum at the extraction well (VW-2) was 19 inches As expected, the greatest vacuum was measured in observation points nearest the extraction well (VW-1) The lowest vacuum was measured in MW-5, approximately 35 to 40 feet south of the extraction point Ground water monitoring wells not screened above 45 feet bsg had little to no influence from the extraction ' The maximum vacuum measured at the observation points during the pilot test was plotted versus the distance from the extraction well The effective radius of influence can be determined by di awing ' a best-fit line though these data points to correlate distance to tiacuum data At a vacuum potential of 10 inches of water, the radius of influence ranged from approximately 20 feet to 34 feet, at 10 0 ' inches of water the radius of influence ranges from 4 to 8 feet Based upon an effective vacuum potential of 1 0 inches of water, the calculated effective radius of influence at the site will be approximately 25 feet However, the actual effective radius of influence achieved may be somewhat ' less Figure 5 depicts the theoretical and effective radius of influence Additional data obtained during the installation of soil borings and monitoring wells may be useful ' in determining a theoretical radius of influence Installation of additional extraction wells would be required at the site to implement an SVE system ' One drawback of SVE is that not all contaminated zones of soil are remediated effectively or at the same rate For instance, a sandy soil zone will cleanup more quickly than a silty one SVE is not usually effective in soil with high clay content Other drawbacks of SVE include ineffective ' treatment of soil lying below ground water or within the "smear" zone approximately 45 feet to 55 feet bsg, with out air-sparging and ineffective treatment of longer-chain hydrocarbons (i e , diesel) ' Ground water remediation should be conducted concurrently with SVE to facilitate remediation of A&airced GeoEn%rronmenlal,Inc