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N Frontier Transportation B23502.0IA ' January 2, 1996 Page A-2 Generally, soil samples selected for analyses typically represent those which the field screening indicated will be most likely to contain the contaminate of concern. In most instances the deepest two samples and/or and sample collected from just above groundwater are selected for analyses. Samples intended for chemical analyses are sealed with Teflon tape and plastic end caps, labeled, placed on ice, and delivered to a laboratory, along with chain-of-custody documentation. The soil borings may be completed as groundwater monitoring wells, or abandoned by grouting with a 6-sack cement slurry containing 3 to 5 percent bentonite or by backfilling with clean soil. Abandonment procedures depend upon the boring depth, depth to groundwater, project objectives, and regulatory requirements. For borings greater than 15 feet deep, grout is emplaced through the hollow augers which will extend to within 15 feet - of the bottom of the boring. If required by the local regulatory agency, grout is emplaced by pumping 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 The tremie pipe or augers are withdrawn from the boring in 10400t increments as the boring fills with grout. SOPS for groundwater monitoring well installation are described in a subsequent paragraph (if pertinent to this investigation). Soil cuttings generated during drilling are containerized in United States Department of Transportation (DOT)-approved drums, or placed on and covered with plastic sheeting, and stored on site in an area inaccessible to the general public. Typically, the stockpiled soil is characterized by collecting and analyzing composite samples from the stockpile. Twining can recommend an appropriate method for disposition of the cuttings based on the analytical results. Disposal will be the responsibility of the client. A-2 Standard Operating Procedures for Groundwater Monitoring Well Installation Standard operating procedures (SOPS) used by The Twining Laboratories, Inc. (Twining) when installing groundwater monitoring wells are presented below. Twining observes these procedures in order to obtain consistent, reliable data. Twining is a C-57 licensed water well drilling contractor (Contractor's License No. 506159). The groundwater monitoring wells will be installed under the direction of a California- registered geologist or -certified professional engineer. Soil borings for monitoring wells will be drilled and sampled according to Twining's "Standard Operating Procedures for Drilling and Soil Sampling". Equipment used for drilling, sampling, and constructing wells, and well construction materials will be thoroughly cleaned according to Twining's "Standard Operating Procedures for Equipment Decontamination Groundwater monitoring wells will be material constructed of Schedule 40 polyvinyl chloride (PVC), stainless steel, or other suitable casing material. Well screen may be machine-