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City of Stockton A68104 02A August 28, 1996 Page A•2 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pumping through a tremae pipe which extends to within 15 feet of the bottom of the boring The tremie pipe or augers are withdrawn from the boring in 10-foot increments as the boring fills with grout SOPS for groundwater monitoring well installation are described in a subsequent paragraph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 Equipment Decontamination. Proper decontamination procedures reduce the potential for. cross-contamination among sample locations, and introduction of contamination from outside sources Before, during, and following drilling operations, drilling equipment is thoroughly cleaned using a high pressure hot water (steam) washer Well casing, screen, end caps, and centralizers will also be cleaned using the steam washer Steam clearnng condensate will be containerized for later disposal. Generally, disposal will be the client's responsibility Sampling equipment and any tools, measuring devices, or other equipment which will contact soil, groundwater, or any media being assessed will be washed in a low-phosphate soap and water solution, and rinsed in clean water before each use The type of soap used will depend upon project requirements A-3 Standard,Operating Procedures for Using Photoionization Detector (PID) The PID is calibrated in accordance with the manufacture's recommendations prior to use in the field Upon arrival at the project site, the PID is used to monitor background concentrations of r