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GENERAL DYNAMICS Additional Investigation — RoO 3; SWMU21 Workplan, Revised Novem*003 3.0 SCOPE OF WORK ' The following subsections of this workplan responds to the DTSC memo of June 27, 2003, and presents tasks to further assess the limited area of TPH in soil, and the TPHd 1 measured in monitoring well S-33 east of SWMU 21. ' 3.1 Safety Plan Preparation and Implementation The Site Specific Safety Plan (SP) employed will be the same as that used during site evaluation in March of 2003. The equipment used for the sampling and drilling operation will be the same as used previously. Modifications to the plan may be implemented upon the Direction of the Site Safety Officer or Project Manager if there are any changes in the site or work conditions. ' 3.2 Permitting Prior to the performance of soil sampling activities and the drilling of monitoring wells ' CE will secure permits from the San Joaquin County Public Health Service Environmental Health Division. Installation of soil borings and groundwater monitoring wells (MW), will be in accord with applicable local and State of California requirements. 1 3.3 Targeted Assessment of TPHd and O&G Soil Impact CE proposes to collect soil samples from a boring approximately 5 feet downslope of the storm drain outfall east of SWMU21. Soil samples from this boring S-35 will be ' collected at depths of 5' and 10' bgs, or until refusal, and analyzed for TPH-d and TPH O&G. CE also proposes to collect soil samples at 5' intervals beginning at 15' bgs until productive groundwater is reached in the monitoring well installation boring S-37 which ' is south of S-26. Based on field observation and field test kit results, soil samples from the monitoring well boring at S-37 will be analyzed for TPH-d and Semi-Volatile Organic Compounds (SVOCs). ' At each soil sample collection point, total petroleum hydrocarbon will be characterized using the Dexsil PetroFlag® field testing kit (or equivalent). These field tests along with visual observations and soil logs will be used as additional information in the subsurface characterization. ' Logs of soil penetrated by the boring will be compiled from samples collected from the borings using the Unified Soil Classification System. Soil cuttings and equipment decontamination liquids that are generated during the drilling of the boring will be ' properly containerized pending disposal of the material by the client. The locations of the proposed borings are presented on the site map. See Figure 3. CHOW ENGINEERING, INC. 3