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a Soil Remediation Feasibility Study Work Plan - Unocal Station No 0187 Apnl 30, 1996 Chemical.Distribution In Groundw ter Free-phase hydrocarbons have not been observed in any of the groundwater monitoring wells installed at the subject site Gasoline range petroleum hydrocarbons are currently detected in on-sate ground water monitor wells U-2 and U-3 (adjacent to and west of the former UST pit) and U-4 (downgradient, or north, of the former UST pat), and in off-site wells U-7 (upgradient, or south, of the sate) and U-8 (east of the site) On-site wells U-5 and U-6, situated northwest and west, respectively, of the former UST pit, do not contain detectable concentrations of petroleum hydrocarbons Historical chemical analytical results of groundwater samples are included in the MPDS quarterly sampling report dated February 27, 1996 SOIL REMEDIATION FEASIBILITY STUDY GSI proposes to conduct a long-term soil vapor extraction test (VET) to evaluate its feasibility as a remedial alternative Because of the areal extent and depth of hydrocarbons in soil, excavation does not appear to be a feasible remedial alternative The following sections detail the proposed long-term VET at this site GSI proposes to operate the VET for a period of six months to evaluate the effectiveness of the system to remediate hydrocarbons from the soil beneath the site Site Health„anal„Sgf ly Plan Prior to commencing the long-term VET, a Health and Safety Plan (HSP) will be prepared to reflect the activities to be conducted onsite The HSP will be prepared in accordance with Occupational Safety and Health Administration (OSHA) guidelines set forth in "Hazardous Waste Operations and Emergency Response" (29 CFR 1910 120) The HSP will be reviewed and signed by all GSI personnel and subcontractors performing work on-site Long-Term Vapor Extraction Test To conduct the long-term VET, GSI proposes to extract soil vapor from the on-site vapor extraction well UV-1 for a period of six months The well is screened from approximately 15 to 45 feet bgs The VET will consist of an internal combustion (IC) engine equipped with a blower, used to extract and abate hydrocarbon-bearing vapor from soil A Process Flow Diagram is included in Appendix B VET parameters will be monitored and evaluated after startup of the system During the VET period, GSI will also monitor vacuum levels in existing monitoring wells to evaluate the radius of influence UN0187 SRW 4827 05-1