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City of Stockton Redevelopment Agency B34604.01a February 16, 2001 Page.4 - I APPENDIX A THE TWINING LABORATORIES INC. STANDARD OPERATING PROCEDURES ' This appendix contains the standard operating procedures used by Twining in performing the investigation. Twining observes these procedures in order to obtain consistent, reliable data. ' Standard Operating Procedures for 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. Field activities are performed under the direction of a California registered geologist or certified professional engineer. ' Soil boring are drilled using an appropriate method. The method selected will depend upon project objectives and subsurface conditions. Typically soil boring 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 boring 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. It is then driven 12 inches deeper by repeatedly dropping a 140-pound weightom a height of 30 inches. The number of blows required to advance the sampler 12 inches is recorded on the boring logs as "blows per foot". This ' information is used in estimating soil density. Soil samples are examined for the purpose of preparing lithologic logs. Soils are logged consistent ' with the Unified Soil Classification System (USCS). The soil boring logs note soil types encountered at depth including consistency, soil moisture, particle size, color, and other distinguishing features. The soil samples are field screened for evidence of volatile organic chemicals(VOCs)and/or other contaminates. The field screening consis of;visual observation for straining or free fluids,unusual odor,and head space analysis using apho oionization detector(PID). The procedure for performing head space analysis are describe in a subsequent paragraph(if pertinent to this investigation). The soil borings will be abandoned by grouting with a sand-cement slurry. If the borings are deeper then 30 feet the grout will be emplaced by treming through a tremie pipe which extends to within 15 feet of the bottom of the boring.. The tremie pipe or augers are withdrawn from the boring in 5-