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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 4.2.6. Groundwater Sampling Groundwater samples were collected from wells FMS-MW5, FMS-DPE1, and FMS-DPE2 before (May 14, 2012) and after (May 17, 2012) air sparge testing, as described in Section 2.5 of this report. 4.2.7. Vapor Sampling Prior to air sparging, soil vapor samples were collected from wells FMS-MW5, FMS-DPE1, and FMS-DPE2. A Gast® oil -less vacuum pump was used to collect soil vapor from the sample port on top of each well into a new Tedlar° bag. Samples were delivered to the analytical laboratory (BC Labs) under proper chain -of -custody and analyzed for TPH-g, VOCs, and fuel oxygenates using U.S. EPA Methods TO -3 and TO -14. 4.3. RESULTS 4.3.1. Step Test Flow rate versus pressure step testing was performed immediately after breakthrough was established at both FMS-AS1A and FMS-AS1 B. During the FMS-AS1A step test, injection air pressure increased from 25.5 to 30.5 prig when flow was manually increased from approximately 9.7 to 16.2 scfm. During the FMS -ASI B step test, injection pressure increased from 34 to 47 psig when injection flow rate was increased from 7.1 to 21.9 scfm. The results of air sparge step testing are summarized in Pilot Test Data Summary sheets in Appendix F. 4.3.2. Pressure Response Pressure in the observation wells was measured before, during, and after the test. During the FMS-AS1A test, the following notable pressure responses were observed by the end of testing: • Pressure in well FMS-MW1 (98.50 feet from the injection well) increased from 0.0 to 0.11 in. w.c. • Pressure in well FMS-MW5 (20.16 feet from the injection well) increased from -0.02 to 0.68 in. w.c. • Pressure in well FMS-DPE1 (16.66 feet from the injection well) increased from 0.03 to 0.55 in. w.c. • Pressure in well FMS-DPE2 (34.59 feet from the injection well) increased from -0.05 to 0.45 in. w.c. • Pressure in well FMS-SVE1 (7.63 feet from the injection well) increased from -0.02 to 2.25 in. w.c. During the FMS-AS1 B air sparge test, the following notable pressure responses were observed by the end of testing: • Pressure in well FMS-MW1 (98.80 feet from the injection well) increased from -0.04 to 0.20 in. w.c. • Pressure in well FMS-MW4 (172.45 feet from the injection well) increased from -0.02 to 0.08 in. w.c. OTIE 22