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SUR 0 • ' ground surface on approximately 20-foot centers. As observed during the site visit on ' July 24, 2006 with San Joaquin County personnel, limited residual petroleum hydrocarbon-impacted soil remains present beneath the concrete containment pad beneath the valve assembly. This soil was not excavated in order to avoid compromising the integrity of the pad. To assess concentrations of residual hydrocarbons present in soil immediately beneath the concrete pad, 4 soil samples were collected from beneath each of the excavation sidewalls of the concrete pad. Confirmation soil samples were collected in 2-inch-diameter brass liners using hand-sampling equipment. Upon collection, each sampling container was immediately capped, labeled, and placed ' into an ice-chilled cooler. Decontamination of reusable sampling equipment was conducted using the following procedures: ' • non-phosphate detergent and tap water wash, in a 5-gallon plastic bucket, using a brush ' • deionized/distilled water rinse, in a 5-gallon plastic bucket • decontamination water was transferred to the onsite oil-water separator Two groundwater samples, designated GW-1 and GW-2, were collected from the water table immediately beneath the floor of the excavation (Figure 2). At both locations, a boring was hand- advanced to approximately 24-inches below the floor of the excavation and a 0.01-inch screened PVC casing set. No product was observed in these temporary wells. Once static water levels were established at each location, a total of three casing volumes were purged by hand bailing using a ' new, unused disposable bailer. Groundwater samples were collected directly from the bailer into laboratory-supplied, 40-milliliter volatile organic analysis (VOA) vials. Water produced during groundwater sampling activities was transferred to the on-site oil-water separator for processing. ' Collected soil and groundwater samples were delivered to Alpha using strict chain-of-custody protocol and analyzed for TPH-DRO, TPH-GRO, and TPH - Jet Fuel Range Organics (TPH- ' JFRO) using EPA Method 8015M and BTEX compounds, MTBE, DIPE, ETBE, TAME, and TBA using EPA Method 8260B. ' Results of Remedial Response and Soil Sampling Activities ' Product Sample Results Analytical results for the product sample collected on July 24, 2006 indicated that the product ' present in the collected samples was comprised of approximately 50-percent TPH-DRO and 50- percent TPH-GRO. These data confirm that a transmix interface was released from the back- pressure valve on July 24, 2006. ' 5