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3.0 FIELD INVESTIGATION AND RATIONALE This section describes the field activities and methods employed to obtain data through the collection of soil and/or groundwater samples Well boring N1W-12 was installed at the location proposed in the approved workplan dated January 6, 1999 3.1 Soil Boring Methods and Installation of Groundwater Monitoring Wells ' One(1) soil boring, completed as groundwater monitoring well MW-12, was advanced to total depth of 73 feet bgs The location of the well bonng is shown on Figure 2 The Iocation of the boring was chosen based upon review of prior Site assessment data, discussions with PHS-EHD's personnel, and the accessibility to conduct field work The boring was advanced by Spectrum Drilling, Inc of Stockton, California, using a truck-mounted drill ng (CME-85), ' equipped with 8'/4-inch outside diameter (OD), hollow-stem, continuous-flight augers The augers were steam-cleaned pnor to drilling the boring The soil types encountered and other pertinent data were recorded on a field boring log, and described in accordance with the Unified Soil Classification ' System (USCS) Field boring logs are presented in Appendix A Soil cuttings generated during the drilling activities were placed in Department of Transportation- (DOT-) approved 55-gallon drums and stored on-site, pending disposal by Thrifty 3.2 Soil Sampling Soil samples were collected at 5-foot intervals through the hollow-stem auger using a California- modified spht-spoon sampler lined with 2-inch OD brass sleeves The samples were driven into the underlying soil by dropping a 140-pound hammer a distance of 30 inches (blow count) The brass sample tubes and split-spoon sampler were washed in an Alconox solution and double-nnsed with distilled water prior to each use The blow counts, recovery, and soil descriptions were recorded on the field logs One (1) brass sleeve filled with soil was capped, sealed, and labeled in accordance with EPA protocol, recorded on a chain-of-custody from, placed in a cooler at 4°C or less, and submitted to a California State-certified laboratory for the specified analyses ' 3.3 Field Screening of Soil Samples ' The material from the top brass sample sleeve was used for field screening The soil from this sleeve was placed in a sample container to approximately 50% capacity, shaken, and stored for a period of 15 minutes A standard head space reading was obtained for each soil sample using an HNu Systems Incorporated photoionization detector(PID) calibrated with isobutylene gas 1 A.11528J1 ASA 7