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Treatability Study Report and Feasibility Evaluation for In Situ Petroleum Hydrocarbon Remediation Field Maintenance Shop #24, 8020 South Airport Way Stncktnn California • Complete baseline monitoring of water levels, wellhead pressures/vacuums, and VOC concentrations in test and monitoring wells; • Initiate groundwater extraction; • Collect initial groundwater sample from pump discharge line; • When groundwater has been sufficiently drawn down within the test well and reached steady-state extraction conditions, initiate vapor extraction; • Collect initial soil vapor sample from extracted vapor stream; • Conduct a vacuum versus flow rate step test (FMS-MW5 step test was performed just prior to completion of testing); • While continually extracting groundwater and soil vapor, periodically monitor water levels, applied and induced wellhead vacuums, and vapor concentrations in test and monitoring wells; • Just prior to shutting down testing, collect final soil vapor and groundwater samples from the extracted streams; Shut down extraction of soil vapor and groundwater; and • At the completion of HVDPE testing at each well, shut down groundwater and vapor extraction, and monitor the recovery of groundwater levels using the Troll° 9500 transducers. A HVDPE testing chronology is summarized in Appendix F. The following sub -sections describe the HVDPE testing procedures in greater detail. 5.2.1. Vacuum Versus Flow Step Testing During HVDPE testing at wells FMS-MW5 and FMS-DPE1, vacuum versus flow step tests were conducted. Near the completion of testing at well FMS-MW5, the applied vacuum was incrementally stepped down from 204 to 41 in. w.c., and the resulting vapor flow rates were recorded on field logs. The FMS-DPE1 vacuum versus flow step test was conducted near the beginning of testing by incrementally reducing the applied vacuum from 108 to 10 in. w.c., recording the resulting flow rates. 5.2.2. Depth to Water Monitoring The goal of HVDPE is to dewater contaminated areas below the saturated zone, allowing soil vapor to be extracted from previously saturated zones. To monitor for groundwater drawdown in the HVDPE test area, the Troll® 9500 multi -parameter groundwater quality monitors installed in wells FMS-MW1, FMS-MW5, FMS-DPE1, and FMS-DPE2 were programmed to record a water level reading every 30 seconds. Water level measurements in wells not equipped with a Troll® 9500 multi -parameter groundwater quality monitor were collected periodically using a 100 -foot water level meter. 5.2.3. Induced Vacuum Monitoring Prior to beginning groundwater or vapor extraction from the test wells, PVC slip caps with sample ports were installed on the casings of monitoring wells FMS-MW1, FMS-MW2, OTI E 29