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r ' f v ASSOCIATESkT I N C . A total of eight soil borings were advanced at the site using 1.5-inch diameter stainless steel probes to depths of ranging from approximately 10 to 16 feet below ground surface (bgs) for the purpose of soil gas collection. -Once the desired sampling depth was reached_an-inert '/4 inch diameter Teflon tube was inserted down the sampling probe, the probe was then retracted approximately one-foot, releasing a detachable tip and exposing the vapor sampling point. Using a vacuum pump, the sample train was then purged and a soil gas sample was subsequently collected in a 1-liter tedlar bag. Borings SG-1 through SG4 were located on the northeastern portion of the property (in the immediate vicinity of the existing bank building). ` The other four borings, SG-5 through SG-8, were located on the southeastern portion of the property. The soil gas collection locations are shown on Figure 2. The collected gas samples were analyzed immediately by an on-site State-certified mobile laboratory provided by Mobile Chem Labs Inc. of Lafayette, California. Laboratory Analysis and Results- Soil Gas Soil gas samples collected from the northeastern borings were analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTE3), and methyl tertiary-butyl ether (MTBE) by EPA Methods modified 8015 and 8020, respectively. Samples collected from the southeastern borings were analyzed for halogenated volatile and aromatic hydrocarbons (HVOCs/VOCs) by EPA Methods 801018020. No constituents of concern were detected above laboratory method detection limits. Soil vapor analytical results are summarized in Table 1. Laboratory data sheets and chain of custody documentation is included in Attachment 1. i Confirmation Groundwater Sample Collection Two additional soil borings (SBI and SB2) were advanced at the site to depths of approximately 32 feet below ground surface to collect groundwater confirmation samples. The placement of these borings was based on the results of the soil gas samples and/or site accessibility. Although the water table was anticipated to be at approximately 23 feet bgs based on UNOCAL data, groundwater was first encounter at approximately 31 feet bgs during field activities. The groundwater samples were collected by advancing extendable screen samplers into the saturated zone. When the desired sampling depth was reached, the sampler case was retracted a distance corresponding to the length of the screen. This disengaged an expendable point and allowed the slotted screen to extend into the open borehole. The water was then allowed to enter the sampler screen for collection. Groundwater samples were subsequently collected by oscillating Teflon® tubing with a check valve. i w:u 7292.05VuummaWLdoc 3