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Southwest Pond Assessment Work Plan Lathrop Facility,San Joaquin County,California Before beginning field activities, Wood will: • update the site-specific health and safety plan for worker protection during field activities, • subcontract with a California C-57 licensed drilling contractor for soil boring drilling and soil sampling, • subcontract with a California-certified analytical laboratory, • obtain soil boring permits through the San Joaquin County Environmental Health Department, • mark soil boring locations and clear underground utilities through Underground Service Alert and a private utility locator, and • obtain sample containers from the laboratory. 3.1 Soil Borings Eight soil boring will be drilled through the asphalt liner into the cemented soil beneath the liner(base borings; designated as B-1 through B-8), and three soil borings will be drilled through the top of the sidewalls (sidewall borings designated SW-1 through SW-3) (Figure 3). The soil borings will be drilled using the direct-push drilling method. Based on discussions with drilling contractors, a track-mounted, direct-push rig should be able to access the interior of the pond to drill the base borings and collect soil samples. In the event the strength of the cemented soil beneath the asphalt liner is too great for the rig to penetrate, the sample collection method will be reevaluated.The soil borings will be drilled by the drilling contractor in conformance with Wood's field protocols (Appendix A). Fieldwork will be conducted under the direct supervision of a Wood professional engineer. The soil borings will be continuously cored and soil cores will be logged for lithology using the ASTM International Standard D 2488-09a, Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), or similar. Drilling equipment will be decontaminated before drilling and between soil borings. Soil cuttings and decontamination water will be drummed and remain on site pending waste characterization analysis. Each soil boring will be backfilled by the drilling contractor using a tremie pipe set near the bottom of the borehole and then filling the borehole with neat cement grout or bentonite cement grout to the surface, or by the method described in the approved soil boring permits issued by San Joaquin County. 3.2 Subsurface Soil Sampling Soil samples will be collected in the base borings from immediately below the asphalt liner and then every 5 feet down to a depth of 10 feet or until groundwater is encountered, whichever is shallower. Soil samples will be collected in the sidewall borings from the surface and then every 5 feet down to a depth of 15 feet or until groundwater is encountered, whichever is shallower. One sample will be collected from the drummed soil cuttings generated by drilling activities for characterization and disposal purposes. The waste sample will be collected using pre-cleaned hand tools and deposited directly into sample containers provided by the analytical laboratory.The relatively small amount of wastewater generated from cleaning equipment between samples will be spread on the base of the pond following sampling. • wood.