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L � � 303 S. Cherokee Lane, Lodi, California TL A91701.01 February 7, 1995 Page S 4.0 PROPOSED FIELD ACTIVITIES ` Proposed field activities are summarized in the following subsections. Standard operating L procedures (SOPs), relevant to the field activities, are described in Appendix A. 4.1 Soil Boringk_ Twining proposes to drill one angle soil boring and two vertical soil borings around the L northern dispenser island using a CME-75 truck-mounted drill rig equipped with 6-5/8-inch diameter hollow-stem augers. Initially, the angle soil boring will be drilled from the south side of the dispenser island to assess the vertical extent of PPC-containing soils. The depth of this boring will be based on field screening of soils for petroleum hydrocarbons. It is anticipated that the boreholes will extend a minimum of 10 feet below field detectable petroleum hydrocarbons or a maximum vertical depth of 50 feet BSG. The depth of the L remaining two soil borings will be based on data generated from the angle boring. The remaining two vertical soil borings will be located to the north and east to assess the lateral boundaries of PPC-containing soils (Drawing 2). If PPCs are detected in soil samples through the field screening process, then additional soil borings would be necessary to fully assess the lateral extent of PPC migration. Additional soil borings would be proposed approximately 20 feet beyond the nearest soil boring containing PPCs detected through field screening. Actual soil boring locations will be determined based on field data. Soil samples will be collected at five-foot intervals beginning at five feet BSG. A Twining geologist will log the soils in accordance with the Unified Soil Classification System and will screen the samples for evidence of contaminants. The screening will consist of visual observation for staining or unusual fluids, unusual odors, and head space analysis with a Lphotoionization detector (PID) for the presence 'of organic vapors. PID operation and procedures for the performance of head space analysis are described in our SON presented Lin Appendix A. Six vertical soil borings will be drilled in the vicinity of the three former product USTs. One soil boring will be drilled to a depth of approximately 20 feet BSG on each end of each former UST. One soil sample will be collected from native soil at the bottom of each soil boring. Each soil boring will be backfilled with bentonite neat cement. S'Io - �„ Drill cuttings will be stored on and covered by plastic. Soil samples from each boring and the resulting soil stockpile will be preserved and retained for laboratory analysis. Soil disposal will be the responsibility of the client. Drilling activities will be supervised by a Twining geologist. The 'Dining geologist will be working under the direct supervision of a California registered geologist. L