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�- AflMICX�lfANfA Mr. Charles Leubner 10 October 1991 Page 3 Investigation. Soil Sam lin Drilling and sampling were performed in accordance with ASTM Standard Method D1452- 84, "Soil investigation and Sampling by Auger Borings." Drilling operations were performed with a wheel-mounted, CME-75 drill rig equipped with 7.75-inch outside diameter hollow-stem augers Soil samples were collected from each of the boreholes at five-foot intervals for logging and analytical purposes. Samples were collected by advancing the auger to a point immediately above the desired sampling depth interval and then driving a California Modified Sampler, lined with four brass tubes, into the undisturbed soil. The sampler was driven using a CME 140-1b Automatic SPT Hammer, which is a hydraulically driven hammer with a per-blow force equivalent to a 140-pound hammer with a 30-inch free-fall drop, in accordance with ASTM Standard Method D1586-84, "Penetration Test Split Barrel Sampling of Soil." Blow counts were recorded in six-inch intervals after every sampling event. The ends of the bottom brass tube were wrapped in sheets of Teflon and capped with tight-fitting plastic caps. The sample was then labelled with a unique sample number, date and time sampled, individually bagged in zip-lock bags, and placed in an chilled cooler for preservation. The middle and top tubes were used to visually describe the lithology and for qualitative field screening. Each soil sample was classified using the Unified Soil Classification System in accordance with ASTM Standard Method D2488-84, "Description and Identification of Soils (Visual-Manual Procedures)", by an experienced environmental geologist. Logs of the soil borings are presented in Appendix A. Representative soil samples submitted for laboratory analyses were selected based on organic vapor analyzer (OVA) field screening values and stratigraphic location. Selected samples were delivered with a Chain of Custody form to Pacific Environmental Laboratory in San Francisco, a State-certified laboratory, for analysis. To minimize the potential for cross-contamination, all augers and associated equipment were steam cleaned with a high pressure washer prior to drilling each boring. The split spoon sampler, associated sampling equipment and the brass sample tubes were cleaned with a trisodium phosphate wash and rinsed with distilled water prior to collecting each soil sample. During drilling, the soil cuttings were placed in 55-gallon drums and stockpiled onsite. After each boring had been drilled to its total depth, it was backfilled with a cement grout consisting of approximately 4 per cent bentonite using a tremae pipe to place the grout.