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Limited Environmental Investigation May 21, 1990 <br /> Proposed Unocal Station, Stockton, California AGS 30010-1 <br /> FIELD WORK AND METHODS <br /> An Applied GeoSystems geologist was at the site on April 12 and 14, 1990, to observe the <br /> drilling of four soil borings (B-1 through B-4). The boring locations are shown on Plate P- <br /> 2. Borings B-1 through B-3 were drilled to 50 feet below grade. Refusal was encountered <br /> in boring B-4 at approximately 37 feet; this interval caused difficult drilling in the other <br /> borings and prevented a fifth boring from being drilled. <br /> Applied GeoSystems conducted field work at this site in accordance with Applied <br /> GeoSystems' Site Safety Plan 30026-1S (March 29, 1990). Applied GeoSystems' standard <br /> methods for field work are described in Appendix A. <br /> Wayne Drilling of Lincoln, California, drilled the four borings using a CME 55 drill rig. <br /> The rig was equipped with clean, 8-inch-diameter, hollow-stem augers. Soil samples were <br /> collected at 5-foot intervals and were classified according to the Unified Soil Classification <br /> System (Plate P-4). Descriptions of the materials encountered are presented in the Logs <br /> of Boring (Plates P-5 through P-12). The materials encountered consisted predominately <br /> of silt and sand. The geologist evaluated the soil samples for hydrocarbon vapors with a <br />• field photoionization detector (PID). No positive PID readings were observed. <br />• <br /> 5 <br />• <br /> APPA49d GeoSystems <br />