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�..� Sow, City of Stockton, Fire Station No. 12 A68105.01 August 7, 1995 Page A-1 .r APPENDIX A STANDARD OPERATING PROCEDURES This appendix contains the standard operating procedures used by The Twining Laboratories, Inc. (Twining) in performing investigations. Standard operating procedures used in this investigation are described below. Twining observes these procedures in order to obtain consistent, reliable data. The procedures used for this investigation included the following. ,.r • Drilling and Soil Sampling • Equipment Decontamination • Sample Handling and Chain-of-Custody .. • Laboratory Quality Assurance/Quality Control (QA/QC) • Decontamination Rinsate and Soil Cuttings Disposal • Using Photoionization Detector (PID) �•+ • Performing Headspace Analysis A-1 Drilling and Soil Sampling: Subsurface assessment and/or well construction permits are filed with the appropriate government agency before conducting field operations. Underground Service Alert is notified at least 48 hours prior to initiation of field activities. -� The soil borings are drilled using a Central Mine Equipment Company 75 truck-mounted drill rig equipped with 6-5/8-inch outside diameter, continuous-flight, hollow-stem augers. Twining is a licensed drilling contractor under C-57 classification (Contractor's License No. 506159). The soil borings are drilled under the direction of a Twining geologist. Soils encountered during drilling are logged consistent with the Unified Soil Classification System. The soil boring logs note soil types encountered at depth including consistency, soil hum moisture, particle size, color, and other distinguishing features. Soil samples are retained using a 1-1/2-inch inside diameter split-spoon sampler. The sampler contains three six-inch long brass or stainless steel sleeves for containment of the soil samples. Samples are obtained by attaching the sampler to the drive rod, followed by driving the sampler into undisturbed soil below the lead auger with a 140-pound hammer that is continuously dropped 30 inches until the sampler penetrates 18-inches of soil. The number of drops are recorded for each six-inch increment the sampler is driven into the soil and recorded on the field log of soil borings. The values for the bottom two six-inch increments are added together to obtain a standard penetration resistance value for each sample. Once the soil sample is brought to the surface, the bottom sleeve is capped with Teflon® tape, fitted with plastic caps, placed in a zip-lock plastic bag, and placed in a cooled ice chest for subsequent transport to Twining's laboratory. This sleeve is either be retained for V