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INTERNATIONAL TECHNOLOGY CORPORATION 2.0 Field Procedures TT Corporation was retained by BP Oil Company to conduct a soil vapor extraction (SVE) pilot test at their facility located at 1403 Country Club Boulevard in Stockton, California. The test was conducted on January 21, 1992 utilizing horizontal collection piping, vertical vadose wells and vertical monitoring wells installed during tank backfill and subsequent investigative activities. Data collected was evaluated to determine the viability of WE for remediation of onsite gasoline impacted soils. 2.1 Soil Vapor Collection System The original onsite tanks were excavated and removed by Paradiso Construction Company during renovation efforts conducted in January and February, 1991. Based on soil sample analytical results from the tank excavation and knowledge of subsurface geology, a decision was made to install slotted piping in the excavation for possible future remedial implementation. The piping was installed concurrent to excavation backfill activities by Paradiso representatives in February, 1991. The excavation reportedly measured 35' x 33' x 12'. According to Paradiso representatives, a thin layer of drain rock was installed in the base of the excavation. 'File 4" dia., large slot sch 40 PVC, '--Iorizanha! pipe was laid adjacent to the east wall for the entire length of the excavation. The slotted pipe was coupled to a section of 4" dia., sch 40 PVC solid riser, and stubbed out approximately six inches below grade. The excavation was backfilled to grade with suitable material. Access to the riser fstub out is through a 36" dia., steel manhole cover, installed during resurfacing operations (Appendix A). It should be noted that the bottom of the vault around the riser is not sealed, which could significantly reduce the effectiveness of soil venting. 2.2 Vapor Monitoring Points A series of wells existing on the site property (6 monitoring wells, 2 vadose wells) served as monitoring ports for vacuum and hydrocarbon concentrations during the SVE pilot test. Three of the wells, initially installed for groundwater observation have been dry since August 1991. The other three are screened above as well as below the water table. Although these wells can't serve their original purpose, they can provide useful information during soil venting activities. IT recommends these wells remain in place to monitor a future vapor extraction system. MW03-10-9Z UST/M 7M M 3