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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 groundwater radius of influence was not calculated because drawdown was not observed in the monitoring wells. • Vapor concentrations during FMS-MW5 and FMS-DPE1 testing decreased from 5,900 ppmv to 2,400 ppmv and 4,700 ppmv to 1,100 ppmv, respectively, over the course of testing. Concentrations are expected to further decline during continued HVDPE operations. • Water production during HVDPE testing ranged from approximately 0.8 gpm at well FMS-MW5 to approximately 2 gpm at well FMS-DPE1 maintaining maximum drawdown of 23.6 feet to 27.6 feet. • Vacuum enhanced aquifer parameters were calculated as: o Transmissivity: 11.3 gpd/ft at FMS-MW5 and 1.2 gpd/ft at FMS-DPE1 o Hydraulic Conductivity: 0.41 gpd/ft2 at FMS-MW5 and 1.2 gpd/ft2 at FMS-DPE1 o Specific Capacity: 0.031 gpm per foot at FMS-MW5 and 0.076 gpm per foot at FMS- DPE1 • Based on the average groundwater, vapor flow rates, and groundwater and vapor -phase concentrations, TPH-g was removed from the subsurface at a rate of 63.1 lbs/day during testing at well FMS-DPE2 and 44.4 lbs/day during FMS-MW5 testing. However, it should be noted that this initial rate would be expected to decline during full-scale remediation. A goal of HVDPE remediation is to dewater the contaminated area, therefore allowing it to be treated by vapor extraction. During HVDPE testing at wells FMS-MW5 and FMS-DPE1, drawdown was not observed in nearby monitoring wells. The lack of drawdown in nearby wells indicates that pumping groundwater from the test wells created narrow cones of depression in the groundwater table that is less than 16 feet, based on the nearest observation well. Because HVDPE is primarily effective at treating the dewatered soil within the cone of depression, extraction well spacing would need to be less than 16 feet to effectively dewater the entire contaminated zone. 6.1.4. General Feasibility Conclusion Statement Based on pilot testing conducted between May 14 and May 18, 2012, it is apparent that soil vapor extraction and air sparging are highly feasible options for remediating the vadose and saturated zone impacted with petroleum hydrocarbon contamination at the site. Air sparging effectively reduced groundwater concentrations and transferred petroleum hydrocarbons from the saturated zone into the vadose zone. Soil vapor extraction demonstrated effectiveness at removing petroleum hydrocarbon vapors from the vadose zone. High vacuum dual phase extraction will be a more costly remedial technology due to the required tight extraction well spacing and high volume of groundwater (that will require treatment) in order dewater the source area at the Site. OTIE 38