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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 • VOC concentrations measured in well FMS-DPE1 (16.95 feet from the injection well) increased from 4,900 ppmv (9% LEL, as methane) to >10,000 ppmv (30% LEL, as methane) by the end of FMS-AS1 B testing; • VOC concentrations measured in well FMS-DPE2 (34.25 feet from the injection well) increased from 4,580 ppmv (9% LEL, as methane) to 8,000 ppmv (15% LEL, as methane) by the end of FMS-AS1 B testing; and • VOC concentrations measured in well FMS-SVE1 (7.95 feet from the injection well) increased from 1,620 ppmv (3% LEL, as methane) to 6,340 ppmv (12% LEL, as methane) by the end of FMS-AS1 B testing. 4.3.8. Vapor Concentrations Vapor samples from monitoring wells FMS-DPE1, FMS-DPE2, and FMS-MW5 were collected prior to the first day of AS testing and within '/z -hour of completing the second day of AS testing. Each vapor sample was submitted to State -certified BC Labs in Bakersfield, California for analysis of TPH-g by EPA Method TO -3 and VOCs by EPA Method TO -14. The TPH-g vapor concentrations increased in observation wells FMS-DPE1 (approximately 17 feet from the injection wells) from 2,300 ppmv to 6,300 ppmv, in FMS-MW5 (approximately 20 feet from the injection wells) from 3,300 ppmv to 5,300 ppmv, and in FMS-DPE2 (approximately 34.5 feet from the injection wells) from 350 ppmv to 3,900 ppmv. Vapor -phase BTEX concentrations at the observation wells generally increased over the course of the air sparge test. Benzene vapor concentrations increased in observation wells FMS-DPE1 from 36 ppmv to 120 ppmv, in FMS-MW5 from 47 ppmv to 610 ppmv, and in FMS-DPE2 (approximately 34.5 feet from the injection well) from 4.3 ppmv to 98 ppmv. 1,2-dichloroethane (1,2 -DCA) was detected in the during vapor sampling at concentrations ranging from 1.6 to 7.9 ppmv at FMS-DPE1, FMS-DPE2, FMS-MW5, and FMS-SVE1. The vapor analytical results are summarized in Table 4. Laboratory reports and Chain -of -Custody are provided in Appendix C. 4.3.9. Zone of Influence The air sparging ZOI was determined by the following findings: • Decreased TPH-g and VOC concentrations in groundwater samples collected from wells FMS-MW5, FMS-DPE1, and FMS-DPE2; and • Increased TPH-g and related VOC concentrations in soil vapor samples collected from wells FMS-MW5, FMS-DPE1, and FMS-DPE2; • Visible bubbling in wells FMS-MW5, FMS-DPE1, and FMS-DPE2 after completion of air sparge testing; • Increased dissolved oxygen concentrations in monitoring wells FMS-DPE1 and FMS-DPE2; and • Significant increase in groundwater levels (mounding) in wells FMS-MW1, FMS-MW5, FMS-DPE1 and FMS-DPE2. OTIE 26