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Work Plan for Refined Plume Definition and Management of Floating Product-7500 W I1 th St., Tracy, CA. Page 60 9.4.2 Technology B —P]j=ing of LNAPL from Extraction Wells into Vacuum Trucks This proposed floating product remediation method is based vacuum extraction of floating product from three 6-in. diameter, 20-ft. deep wells that will be installed, as shown on Figure 13, along a line extending to the east and west of Monitoring Well MW-7. The line of wells will run parallel to West Eleventh Street in a zone where floating product, based on the known characteristics of the plume of affected groundwater that has been established from the site characterization and groundwater monitoring programs completed to date, is expected to be present on the groundwater, 9.4.2.1 Extraction Well Installation The extraction well borings will be drilled using hollow-stem auger technology and samples of soil will be recovered from them at 5-ft. vertical intervals in accordance with the procedures described in Section 7.2 for installation of groundwater-quality monitoring wells. Similarly, the wells will be developed and the development water and drill cuttings will be disposed as described in Sections 7.5 and 7.3 respectively. Soil samples recovered from the +— well borings will be analyzed for TPH(d), TPH(g) and the BTEX compounds in the manner described in Section 7.2. As is described in Section 7.6, the extraction wells' casing elevations and wellhead locations will be surveyed in compliance with California Water �- Code Sections 13195-13198. The well casings will be 6-in. diameter PVC with 0.02-in. machine cut screen slots. The �-- casing will be centered in the 12-in diameter well boring. The screen will extend from approximately 1 ft. above the high groundwater elevation to the bottom of the well. The annular space between the screened interval and the boring wall will be filled with No. 3 Monterey sand, which will serve as a filter. Above that, 2 ft. of bentonite will form the well seal. The casing will be closed at the top using a removable PVC casing cap and the well head will be enclosed in a flush-mounted well head housing rated for heavy vehicular traffic. " These and other details of the extraction well construction are shown on Figure 14. These wells will be numbered EW-1 through EW-3. The well borings will be drilled and the extraction well casings and appurtenances installed by a drilling contractor holding a C 57 specialty contractor's license issued by the California Contractor's State Licensing Board. 9.4.2.2 Measurement of Depth to Groundwater and Thickness of Floating Product When the extraction wells have been installed and have been permitted to come to equilibrium for at least one week, the depth to groundwater and the thickness of floating product on the groundwater in the wells will be measured using a groundwater/floating product-interface meter. sic