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t <br /> 3 <br /> The wells will be packed with No. 20/40 sand from the bottom of the screen to <br /> approximately 2 feet above the top of the screen. A 2-foot seal of bentonite pellets will <br /> be placed on the top of the sand pack. The wells will be grouted with bentonite-cement <br /> slurry or neat cement from the top of the bentonite seal to the surface. Ilie wells will be <br /> completed below grade, fitted with top and bottom PVC caps, and have locking covers <br /> installed. Typical well construction is illustrated on Figure 2. <br /> The monitoring wells will be screened in a silt or sand horizon a_nd not be completed <br /> opposite significant clay zones. <br /> Well Developmr it and Crodudwater Samples. Each well installed will be developed by <br /> surging and bailing ur pumping until clean, sediment-free water is produced from the well. <br /> The length of development time will vary depending upon field conditions. Water produced <br /> during development and sampling will be contain-ed on sitr.. ARCO will be responsible for <br /> the disposal of water and product collected. Prior t, and following development, the <br /> thickness of free product,if any,will be gauged. <br /> ,y Following proper development of each well, a nitrogen driven bladder pump or stainlew <br /> steel bailer will be used to evacuate an additional amount of water before samples are <br /> s taken. The amount of water evacuated will be defined by the stabali.ation of pH and <br /> d electrical conductivity readings for three consecutive measurements taken 5 minutes apart. <br /> When pH and electrical conductivity have been determined to have stabilized, water samples <br /> will be collected and submitted to the laboratory to be analyzed for benzene, toluene, and <br /> xylene (EPA 602). Results will, be made available to ARCO within 48 hours. San <br /> nple bottles <br /> will be filled directly from the discharge line of the bladder pump or from the hailer, and <br /> will be filled to the brim. A teflon-lined cap (septa) will be placed on the bottles, and the <br /> volatile organic analysis (VOA) bottles will be checked to determine that no air bubbles <br /> k-; remain within. <br /> All water samples will be labeled and stored as described in the soil samples section <br /> t ` above, and transportedto the Eureka laboratories, Inc., (Eureka) in Sacramento within 48 <br /> hours. <br /> Decontamination Procedures <br /> To prevent cross-contamination, soil sampling equipment and all pumps. bailers, and <br /> �-' their related tubing will be washed with laboratory-grade detergent, rinsed with tap water, <br /> and rinsed with deionized water before sampling and development. Downhole drilling <br /> equipment and the development pump will be stearn-cleaned before and between use at earn <br /> F <br /> r borehole. <br /> i" (duality Assurance Plan <br /> The procedures to be followed in sample collection, identification, and handling at the <br /> ARCO site are described below. The analytical quality assurance program is also discussed. <br /> Sample Collection and Handling. - - ------- ------ ------- -------- ---------- <br /> Proper collection .and handling are essential to ensure the quality of.the sample. All <br /> samples win be collected by experienced field personnel. The samples will be collected in <br /> r <br /> r� <br />