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A Following proper development of each well, a nitrogen-driven bladder pump, stainless steel bailer , or teflon bailer will be used to evacuate an additional amount of water before samples are taken. The amount of water evacuated will be defined by the stabilization of pH and electrcial conductivity readings for three consecutive measurements taken 5 minutes apart. When pH and electrical conduc- tivity have been determined to have stabilized, water samples will be collected and submitted to the laboratory to be analyzed for BTX by EPA Method 602, for total petroleum fuel hydrocarbons by EPA Method 8015 modified , and for total lead . Sample bottles will be filled directly from the discharge line of the bladder pump or from the bailer , and will be filled to the brim. A teflon-lined cap (septa) will be placed on the bottles, and the volatile organic analysis (VOA) bottles will be checked to determine that no air bubbles remain within. All water samples will be labeled and stored as described in the soil samples section above, and transported to the BC laboratory in Emeryville within 48 hours . Decontamination Procedures To prevent cross-contamination, soil sampling equipment and all pumps, bailers, and their related tubing will be washed with laboratory-grade detergent, rinsed with tap water , and rinsed with deionized water before sampling and development. Downhole drilling equipment and the development pump will be steam-cleaned before and between use at each borehole. Quality Assurance Plan The procedures to be followed in sample collection, identifica- tion, and handling at the ARCO site are described below. The analytical quality assurance program is also discussed. Sample Collection and Handling. Proper collection and handling are essential to ensure the quality of the sample . All samples will be collected by experienced field personnel. The samples will be collected in suitable containers which have been precleaned at the laboratory. The containers will be clearly marked and dated for identification. All samples will be cooled and stored for analysis no longer than the maximum allowable holding time. Sample Identification and Chain-of-Custody Procedures. Sample identification and chain-of-custody procedures ensure sample integrity and document sample possession from the time of collection to its ultimate disposal. Each sample container submitted for analysis will have a label affixed to identify the job number , sampler , date and time of sample collection, and a sample number