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2.0 Field Investigation 2.1 Drilling Locations and Soil Sampling Methods Subsurface conditions were investigated at the site on August 18, September 7, and September 8, 1993 Five HydroPunch Ih borings (HP-1, HP-2, HP-3, HP-4, and HP-5) were drilled on August 18, 1993, to depths of approximately 12 feet The ' borings were continuously cored for visual observation of the soils (Figure 4) Two HydroPunch Ho borings (HP-6 and HP-7) were drilled on September 7, 1993, (Figure 4) These borings were also continuously cored for visual observation HP-1, HP-2, and HP-3 were located in a triangular pattern around MW-1 in an attempt to ' confirm groundwater contamination in MW-1 reported in previous investigations HP-4, HP-5, HP-6, and HP-7 were located to assist in determining the lateral extent of groundwater contamination and to assist in the placement of additional monitoring wells Two borings were drilled and sampled to a depth of 25 feet bgs at the locations ' marked as MW-8 and MW-9 (Figure 4) Monitoring wells were installed in both borings MW-8 was located approximately 10 feet south of the former 1000-gallon UST removed in 1987 MW-9 was located southwest of MW-1 to determine the extent of the plume in the downgradient direction A truck-mounted, continuous- flight, hollow-stem auger drilling rig was used to drill the HydroPunch II® and ' monitoring well borings BVWST personnel supervised the placement, drilling, sampling, soil ' classification, and installation of the HydroPunch Ho samplers and monitoring wells Soil samples were collected from the monitoring well borings at the surface, 5 feet bgs, 10 feet bgs, and at the water table in 6-inch long brass liners placed inside a split-spoon sampler The split-spoon sampler was driven through the soil formation by a 140-pound hammer dropped from a height of 30 inches One of the sample ' liners for each sampling interval was packaged, Iabeled, and submitted to the District's laboratory for chemical analysis of the soil as specified in the Work Plan ' The boring and monitoring well installation logs are presented in Appendix B Steam-cleaned augers were used to drill each monitoring well boring The split- spoon sampler was cleaned with a detergent solution, rinsed with deionized water, and assembled with clean brass liners prior to each sampling event to reduce the potential of cross contamination 931122 East Bay Municipal Utility Distnct ' 40429500 asa 5 Stockton Svc Ctr -Site Assessmcnt/Remedia] Options