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Probeholes PH-6 through PH-8, driven on March 15, 2002, were designated as "hydropunch" borings to collect groundwater samples for the evaluation of the lateral extent of groundwater impact Geoprobe rods were driven continuously to a depth of 44 feet at each location without collecting soil samples Probehole PH-6 was placed in a cross-gradient location (relative to the former UST) at the northwest end of the 1725 El Dorado Street traffic island Probehole PH-7 was placed downgradient of the former UST at the southwestern end of the traffic island Probehole PH-8 was placed downgradient of the former UST at the western edge of the traffic island Groundwater "grab" samples were obtained by inserting clean polyethylene tubing, equipped with a check valve, through the Geoprobe rods and manipulating the tubing until samples could be transferred into clean, laboratory-provided, glass containers These probeholes were not purged or developed prior to sampling The 40-milliliter glass sample containers were capped, labeled, and stored in an iced chest for cham-of-custody delivery to Acculabs analytical laboratory Samples were analyzed for BTEX, TPHg and oxygenate compounds Groundwater sample analytical results are described in Section 3 3 Following sample collection, Geoprobe rods were removed and probeholes were properly abandoned Probeholes were abandoned by placing cement grout within the borings to the ground surface Soil samples and cores not submitted to the laboratory were placed in 55-gallon drums, sealed, and temporarily stored onsite for later disposal 2.2 Air Sparging, Soil Vapor Extraction and Monitoring Wells Air sparging well SPA and soil vapor extraction well VW-1 were drilled and completed March 14, 2002 by Cascade Drilling Inc of Rancho Cordova, California These wells were placed in close proximity to the former UST to prepare for possible future remedial activities at the Site Air sparging well SP-1 was drilled to a depth of 50 feet with an 8 25-inch diameter hollow stem auger Forty-eight feet of blank, 3/4-inch diameter, PVC i' casing, attached to a 2-feet long Filtros ceramic air diffuser, was placed within the augers Approximately 5 feet of sand filter pack was placed within the bottom of the annular space, topped by about 7 feet of hydrated bentonite pellets and 38 feet of neat cement grout to the ground surface Well SP-1 was completed flush with the ground surface and was covered by a bolted steel cover A well construction diagram for SP-1 is contained in Appendix A Soil vapor extraction well VW-1 was drilled to a depth of 25 feet with a 10- inch diameter Hollow stem auger Twenty feet of 4-inch diameter, 0 02- 8 March 2002 Subsurface Site Investigation 1717 South Center Street-Stockton,California Prepared by Philip Services Corp H\ENV1624001321121362£GlNrojxtslS*ckCent\rnarch2002invmttgauon dm May 14,2002