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Treatability Study Report and Feasibility Evaluation for In Situ Petroleum Hydrocarbon Remediation Field Maintenance Shop #24, 8020 South Airport Way Stockton, California o TPH-g concentrations decreased from 24,000 pg/L to 8,200 pg/L (66% reduction), located at 34.5 feet from the test well. • AS technology effectively transferred VOCs from the saturated zone into the vadose zone where it can be captured by an SVE system: o TPH-g vapor -phase concentrations increased from 2,300 ppmv to 6,300 ppmv (174% increase) at FMS-DPE1, located 17 feet from the test well; o TPH-g vapor -phase concentrations increased from 3,300 ppmv to 5,300 ppmv (61% increase) at FMS-MW5, located 20 feet from the test well; and o TPH-g vapor -phase concentrations increased from 350 ppmv to 3,900 ppmv (1,014% increase) at FMS-DPE2, located 34.5 feet from the test well. • Based on visual observations (bubbling), increase in DO concentrations, reduction in groundwater concentrations, increase in vapor concentrations, increase in helium concentrations, groundwater mounding, and pressure increases at the monitoring wells, the AS ZOI was estimated to be a radial distance of 20 to 30 feet. • Based the evaluation of the above parameters, confinement of detected helium concentrations to a maximum distance of 34 feet from the test well, and the rapid dissipation of air pressure observed post AS testing: o Injected air was distributed efficiently within the subsurface; and o Injected air did not remain trapped within the subsurface. • Step testing conducted at the end of the FMS-AS1A and beginning of the FMS-AS1 B tests confirmed that air can be injected into the subsurface at reasonable flow rates and injection pressures. At the beginning of FMS-AS1 B testing, pressures between 34 and 47 psig produced air sparge flow rates between 7 and 22 scfm. After step testing, the sparging pressure stabilized at approximately 29 psig with a flow rate of approximately 20 scfm. • AS well spacing of 20 ft within the source area is recommended to provide adequate overlap of coverage. 6.1.3. High Vacuum Dual -Phase Extraction Analyses of field and analytical data from HVDPE testing on wells FMS-DPE1 and FMS-MW5 confirmed that both vapor and groundwater can be extracted with the HVDPE technology. The following conclusions are presented for the HVDPE test conducted at wells FMS-MW5 and FMS-DPE1: Vacuum versus flow rate step testing conducted at wells FMS-MW5 (screened between 27.5 and 57.5 feet bgs) and FMS-DPE1 (screened between 20 and 60 feet bgs proved that the placement of well screens within the subsurface has a significant effect on performance. During the FMS-MW5 test, a vacuum of approximately 204 in. w.c. was required to draw vapor at 40 scfm while the well was dewatered. However, a vacuum of only 35 in. w.c. was required to extract soil vapor from well FMS-DPE1 at 53 scfm. • The soil vapor radius of influence for HVDPE was estimated at 100 feet based on the results of FMS-DPE1. OTIE 37