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The field engineer collected a soil vapor sample from well MW-13. The soil ' vapor sample was analyzed for total fuel as nonmethane hydrocarbons and benzene, toluene, ethylbenzene, xylenes, ethylene dichloride, and ethylene dibromide by Coast to Coast Analytical Services, Inc. of San Luis Obispo, ' California. Appendix F includes a description of the sample collection procedures. Additional data were collected at periodic intervals during the SVET and recorded on field data forms. The field data forms are included in Appendix H. ■ 5.2 SVET Results Radius of influence data are presented in Table 5. The data collected while extracting from G-2 indicate that a radius of influence of approximately 60 feet is possible at this site using readily available equipment operating ' at a well head vacuum of less than 25 in. we (about 0.90 pounds per square inch). ' The data collected while extracting from well MW-13 indicate that a radius of influence of approximately 12 feet is possible while extracting soil vapor at a well head vacuum of 30 in. we. Extraction vacuum at well MW-13 was limited due to the upwelling of the ground-water table as described in the previous section, and the short screened interval, approximately 5 feet, above the ground water. The radius of influence data are depicted graphically in Figure 2 as.a plot of vacuum versus distance. Data collected during extraction from well MW-13 are not included on this plot since effects of the vacuum were only ' detected at one monitoring point. Theoretically, vacuum in the subsurface should decrease rapidly with increasing distance from the extraction well. As shown in Figure 2, data collected while extracting from gallery riser G-2 ' deviate from this expected result. As listed in Table 4, the vacuums measured at wells MW-12 and MW-13 (6 and 19 feet from G-2) were lower ' than the vacuum measured at well MW-3 (30 feet from G-2). This result was likely caused by heterogeneous geologic conditions (varying air permeabilities) in the subsurface. Extraction well and gallery riser vacuum and flow rate data are graphically depicted on Figure 3. Due to the ground-water upwelling in well MW-13, the SVE vacuum at this well is likely limited to around 30 in. we with a corresponding flow rate of 20 cfm. The plot of the data collected at gallery pipe G-2 indicates that much higher flow rates are generated from G-2 than well MW-13 at comparable vacuums. I t pjO\Ot9010f900020.1 ag 5 - 2 Rev. 0 December 15, 1992 j I