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APPENDIX A THE TWINING LABORATORIES, INC STANDARD OPERATING PROCEDURES This appendix contains the standard operating procedures used by The Twining Laboratories, Inc. (Twining) in performing investigations. Twining observes these procedures in order to obtain consistent, reliable data. The procedures used for this investigation included the following. Standard Operating Procedures for Hand Angering and Soil Sampling Subsurface assessment permits, if required, are filed with the appropriate regulatory agencies prior to conducting field operations. Field activities are performed under the supervision of a California registered environmental assessor II. Sampling equipment is thoroughly cleaned before, during, and after each use according to Twining's "Standard Operating Procedures for Equipment Decontamination". Hand auger soil borings are between 1.5 and 3.0 inches in diameter depending upon the size of the auger. These soil borings are advanced by turning the hand auger handle repeatedly which causes the auger bit to cut into the soil. After approximately 6 inches of advance, the bucket of the auger fills with soil cuttings and it is then removed from the borehole and the cuttings are emptied. The auger is then replaced in the borehole to advance another 6-inch interval. In this manner the borehole is extended to the designated sampling depth. Soil samples are collected from hand auger soil borings by lowering a soil sampler equipped with a stainless-steel retention sleeve into the undisturbed soil at the bottom of the borehole. The soil sampler is then driven approximately 6 inches using a slide hammer. The soil borings are abandoned by grouting with a 6-sack cement slurry containing 3 to 5 percent bentonite, or backfilling with clean soil. Abandonment procedures depend upon the boring depth, depth to groundwater, project objectives, and regulatory requirements. Soil cuttings generated during hand augering are either replaced in the borings, or stockpiled, depending upon project requirements. Stockpiled soil is containerized in United States Department of Transportation-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 stockpiled soil based on the analytical results. Disposal will be the responsibility of the client. 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.