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' 15 November 1995 AGE-NC Project No 95-0142 ' Page 6 of 19 ' extraction Initially, an induced vacuum potential was applied to the upper screen (depths of 10 to 25 feet) in VE-1 However, from 12 45 pm to 2 30 pm, the vacuum potential was applied to the lower screen(depths of 30 to 45 feet)in VE-1 At 2 30 pm, the induced vacuum potential was again ' - applied to the upper screen of VE-1 - The induced vacuum pressures were monitored at surroundmg observation points (VE-2, VE-3, VE- 4, MW-3 and MW-4) Air tight well caps pre-connected with Magnehehc vacuum gauges were attached to each of the observation points ' A sample port was tapped into the PVC near the wellhead and a portable photo-ionization detector (PID M&crotip model 1000 calibrated to isobutylene) was used to measure organic vapors (OV) ' concentrations OV concentrations, as well as induced vacuum at the observation points, flow rate and RPMs of the SVE unit,were measured at 0 5-hour intervals and logged on field sheets Pilot test data are summarized in Table 4 Field data sheets are presented as Appendix F 1 53 COLLECTION AND ANALYSIS OF VAPOR SAMPLES A total of 4 vapor samples were collected during the pilot test Vapor samples were collected at two- hour intervals from the inlet of the extraction well to measure hydrocarbon concentrations in the ' extracted vapor The samples were collected in Tedlar bags using an air pump Samples were transported under chain-of-custody to McCampbell Analytical Inc (MAI) in Pacheco, California Each sample was analyzed within 72 hours for TPH-g and BTE&X in accordance with EPA methods ' 8015m and 8020, respectively ' 5 4 RESULTS OF SOIL VAPOR EXTRACTION PILOT TEST The SVE unit was maintained at approximately 2,000 RPMs Initial flow rates were measured at 15 ' scfm(standard cubic feet per minute)and reached 30 scf n after 7 5 hours OV readings ranged from 1,400 to 4,800 ppm Induced vacuum measured at the extraction well(VE-1) ranged from 75 to 115 inches of water 1 As expected, the greatest vacuum was measured in observation points nearest the extraction well ' (VE-3) The lowest vacuum,was measured in MW-3, approximately 30 feet north of the extraction point No measurable vacuum was observed in MW-4 ' The maximum vacuum measured at the observation points dunng the pilot test was plotted versus the distance from the extraction well (Figure 4) The effective radius of influence can be determined by drawing a best-fit line though these data points However, no clear correlation is observed from ' the graph At a decline of vacuum potential to 0 1 inches of water, the radius of influence may range 1