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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 • The sand zones encountered throughout the site between approximately 20 and 28 feet bgs creates a wide, flat capture zone above the saturated zone and is amenable to soil vapor extraction. • Based on the average flow rates and sample analytical results, soil vapor extraction from well FMS-SVE1 removed petroleum hydrocarbons from the subsurface at a rate of approximately 18 lbs/day. However, this initial rate would be expected to decline during remediation as petroleum hydrocarbon mass removal rates become limited by the rate of soil diffusion and groundwater volatilization. • Given the large ROI and high mass recovery rate, soil vapor extraction is likely to be a cost effective means for removing petroleum hydrocarbon from the vadose zone relative to excavation or other in situ technologies. • SVE well spacing of 30 to 60 feet at 40 to 50 scfm per well is recommended and would ensure ROI overlap and effective capture. • 1,2 -DCA was detected in the soil vapor which may require considerations for air permit requirements for a full-scale SVE system. Air Sparge Results Analyses of field and analytical data collected during air sparge testing at FMS-AS1A and FMS-AS1 B confirmed that AS is effective at treating the saturated zone. The following conclusions are presented for the air sparge testing conducted at wells FMS-AS1 A and FMS- AS1 B: • Air sparge significantly reduced groundwater concentrations after two days of testing at FMS-AS1A and FMS -AS -B: o TPH-g concentrations decreased from 48,000 pg/L to 6,700 pg/L (86% reduction) at FMS-DPE1, located 17 feet from the test well; o TPH-g concentrations decreased from 18,000 fag/L to 15,000 pg/L (17% reduction) at FMS-MW5, located 20 feet from the test well; and 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 OTIE