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Report on Additional Site Assessment 5 7-Eleven Inc.,Store#19976 1399 N.Main St. Manteca,California March 5,2001 3.3 Soil Borings and Sample Collection Groundwater monitoring well MW-7 and vertical delineation boring SB-2 (Figure 2)were drilled on November 1,2000. Well MW-7 was drilled to a total depth of 30 feet below grade using a drill rig equipped with 8-inch diameter hollow-stem augers. Soil boring SB-2 was drilled with a hollow-stem auger using Simulprobe (two-barrel soil sampling)drilling techniques. All drilling equipment was steam cleaned prior to drilling each boring,and sampling equipment was washed in an Alconox® (detergent) solution and rinsed with water between sampling intervals. All soil and rinse water generated during the drilling was placed in labeled Department of Transportation (DOT)-approved 55-gallon drums and left on the site pending transportation and disposal. Most of the soil samples were collected at 5-foot intervals to 30 feet below grade using a split-spoon sampler lined with 2-inch-diameter by 6-inch-long brass sample tubes. Continuous core sampling of SB-2 was conducted from 30-37 and 41 -45 feet below grade (the depth interval from 37 to 41 feet below grade contains flowing sands). Sample tubes were sealed with Teflon pads, plastic caps and tape, labeled, placed on ice in an insulated container, and submitted for analyses under chain-of- custody manifest to a state-certified laboratory for analysis. Soil samples were field screened for hydrocarbon vapors using a flame-ionization detector(FID). Soil was logged using the Unified Soil Classification System by a IT Corporation field geologist working under the supervision of a California registered geologist(Appendix A). Soil samples were collected at depths of 5, 10, 15,20,25, and 30 feet below grade during installation of well MW-7. Soil samples were retained from depths of 5, 10, 15, 20,25, and about 35 feet below grade during installation of boring SB-2. Samples from 10, 15, and 20 feet below grade from well MW-7 and samples from 30, 33, and 34.5 feet below grade were analyzed from boring SB-2. All soil samples analyzed were tested for BTEX, MTBE, and TPH-G by EPA methods 8020/8015 modified, for oxygenates MTBE,TBA, DIPE, ETBE, and TAME using EPA method 8260, and for EDB and 1,2-DCA by EPA Method 8260 (Table 2). One grab groundwater sample was also collected from 40 feet below grade in soil boring SB-2;this sample was analyzed for BTEX, MTBE, and TPH-G by EPA methods 8020/8015 modified, for oxygenates MTBE,TBA, DIPE, ETBE, and TAME using EPA method 8260, and for EDB and 1,2-DCA by EPA Method 8260 (Table 2A). 19976.4SA