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• Exploratory boring permits were issued November 14, 2005 from the San Joaquin County Department of Public Health. Soil Gas Sampling for VOCs and Naphthalene A total of four borings (SV-1 through SV-4) were advanced in the former drill room at 1856 Field Avenue by a direct-push technology (DPT) drill rig. As shown on Figure 1, one boring (SV-1) was placed adjacent to the location of former soil boring S617, while the remaining three borings were placed within a radius of 20 feet around the location of SB17. A summary of samples collected is presented in Table 1. Soil gas samples were collected using the "post-run tubing" (PRT) sampling method. This method consists of advancing a drive rod to the required depth and then withdrawing the tip of the probe several inches to expose the surrounding soils. A 3/8- inch PRT, located inside the drive rod, forms a vacuum- tight seal near the probe tip. The PRT was purged to remove ambient air. The sampling canister(s) were then attached to the PRT, and soil vapor samples were collected. Soil gas samples were collected in general accordance with the guidelines provided within the document Advisory-Active Soil Gas Investigations developed by DTSC and the Los Angeles RWQCB (DTSC/RWQCB, 2003). Soil gas samples were collected at a depth of approximately 5 feet below ground surface (bgs) in each boring. During installation of the probe, hydrated bentonite was used to seal around the drive rod at ground surface to prevent ambient air intrusion from occurring. To ensure a representative sample, a dedicated purging laboratory-supplied 6-liter pre-evacuated stainless steel Summa canister with flow controller was used to extract three purge volumes of vapor at a flow rate of approximately 167 millimeters per minute (mL/min) prior to soil gas sampling in order to rid the tubing of ambient air and allow subsurface soil gas to enter. A laboratory-supplied 6-liter pre-evacuated stainless steel Summa canister with a 30-minute flow controller was used to collect soil vapor samples at a flow rate of approximately 167 mUmin. A duplicate soil vapor sample was collected at SV-2 and identified as SV-5 for quality assurance and quality control (QA/QC). All soil gas samples were delivered to Air Toxics Ltd. In Folsom, California, a state-certified laboratory, for analysis by EPA Method TO-15 (open scan) for VOCs plus naphthalene. Grab Groundwater Sampling for Naphthalene and Bis(2-ethylhexyl)phthalate Upon the completion of soil vapor sampling, each boring was further advanced by the DPT drill rig to a depth of approximately 20 feet bgs. A slotted PVC casing with filter sock was inserted into each boring, and grab groundwater samples were collected from each location using a peristaltic sampling pump. A duplicate groundwater sample was collected at SV-1 and identified as SV-5. Triple volumes of the sample collected at SV-4 were supplied to the laboratory for matrix spike/matrix spike duplicate (MS/MSD) analysis. Additionally, an equipment blank was collected by drawing laboratory-supplied deionized water through new tubing using the peristaltic pump. The groundwater samples were delivered to Entech Analytical Labs, Inc. in Santa Clara, California, a state-certified laboratory, in an iced cooler for naphthalene and bis(2-ethylhexyl)phthalate analyses using EPA Method 8270C. Page 2 of 4 January 2006