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i City of Stockton A68104 01A October 25, 1995 Page A-1 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 • Drilling and Soil Sampling • Installation of Groundwater Monitoring Well • Development of Groundwater Monitoring Well • Sampling of Groundwater Monitoring Well • 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 4$ hours prior to initiation of field activities Field activities are performed under the direction of a California registered geologist or certified professional engineer Soil borings are drilled using an appropriate method The method selected will depend upon project objectives and subsurface conditions Typically soil borings are drilled using a Central Mine Equipment Company model 75 (CME-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 Drilling and sampling equipment are thoroughly cleaned before, during and after each use Cleaning procedures are described in a subsequent paragraph Soil samples are collected using a continuous-coring device, by driving a split-spoon sampler, or by grabbing samples from the drilling cutting returns The sampler or coring device is lined with brass, stainless steel, or acrylic tubes, in which samples may be retained for subsequent chemical analyses To collect samples using the split-spoon sampler, the sampler is initially lowered to the bottom of the soil boring and driven 6 inches into undisturbed soil