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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 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. 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. REMEDIAL FEASIBILITY EVALUATION AND RECOMMENDATIONS A preliminary evaluation of remedial alternatives was performed by OTIE. The analysis considered the applicable cleanup criteria as they relate to the impacted soil and groundwater. OTIE weighed the various selection criteria to determine the most feasible technology(ies) for remediation of petroleum hydrocarbons at the site. A feasibility matrix was developed to present a relative numeric evaluation of the various remediation technologies (Table 5). For this qualitative evaluation, the relative value and importance of each specific category was provided with a numeric value, between "1" (least feasible) to "5" (most feasible). Then each of the technology categories was summed and the numeric rating or score was recorded. This Remedial Matrix preliminarily identified Air Sparging with SVE as the most feasible treatment method. As described above, these methods will provide source zone mass removal for expediting site cleanup. After the hydrocarbon source zone is removed to the extent feasible and adsorbed -phase hydrocarbons are no longer a primary concern, further "polishing" steps may be considered. Air Sparging with SVE could be converted to a low flow biosparge system as a "polishing" measure. This would only be needed if the AS/SVE system went asymptotic before reaching remedial action objectives and it was determined that natural attenuation of the remaining dissolved phase plume was not feasible. For unsaturated soils, the Remedial Matrix identified soil vapor extraction as the most feasible remedial alternative. OTIE iv