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Mr. Gerald Djuth March 6, 2003 Page 2 south of AASC Building 2 could interfere with soil vapor sampling by blocking soil pores. Therefore, several days before implementing the soil vapor survey, water levels will be measured in several site wells including MW-5R. If the water level has risen more than 5 feet from the depths measured on 10 February 2003 (to a depth shallower than 41 ft bgs at MW-5R), a conference call will be held between the RWQCB, BP, and Parsons to determine whether to proceed with the investigation. The proposed sample borings would be advanced using a direct push drilling rig (Geoprobe® or similar equipment). Soil gas will be collected using the Geoprobe® PRT (post run tubing system). The PRT system consists of a stainless steel probe tip that is pushed to the desired sampling depth attached to 2-inch diameter drill rods; then the drill stem is retracted several inches exposing the soil formation. The soil vapor probe is connected to the surface by Teflon-lined tubing inside the drill rods. Clean new tubing will be used for each sample. After each sample is collected the drill rods will be withdrawn to the ground surface, the probe will be decontaminated, and the used tubing will be replaced. Vendor descriptions of the equipment and sampling process are included in Attachment A. Sample collection and analysis will be performed in the same manner as in previous mobilizations for SVE system closure sampling in January 2001 at the source area. The methods to be used are similar to those described in the Soil Closure Work Plan for Fortner Hazardous Materials/Waste Storage Area (Parsons, 2001 a) and the Soil Closure Report (Parsons, 2001b). Soil vapor sampling will consist of operating a 1-cfm vacuum pump for an appropriate length of time at each location, dependent upon depth, to purge soil gas in the sampling apparatus and collect a representative sample. The samples will be collected in 1 L Tedlar®bags. All analyses will be performed by Method TO-14 with requisite QC including method blanks and surrogate recovery analyses. Two field blind duplicate samples will be collected and analyzed to demonstrate repeatability. Analyses will performed by a fixed base laboratory within the method required holding time of 72 hours for Tedlar bag samples. The detection limit will be less than 0.02 mg/m3 (0.004 ppmv) for TCE. The analytical laboratory performing the work will be Environmental Analytical Service, Inc., San Luis Obispo, CA, a laboratory that specializes in air analyses and which performed the fixed base lab analyses for the source area soil closure investigation. Groundwater Sampling Groundwater samples will be collected from the boring 20 feet west of MW=5R and the three outermost borings in the array (Figure 1). Each sample will be a grab sample collected after driving the push-rod at least 5 feet into groundwater and then retracting the rods to expose approximately 1 foot of the water bearing formation. The grab sample will be collected through the hollow rods from the exposed soil chamber using a narrow- gage stainless steel bailer. If sufficient water is produced, the first bailer-full will be discarded. SVsurvey%vp_MW-SR.doc 3/6/03