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M 4 <br /> Ego <br /> 4� <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 he bentonite seal to the surface. The 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 and not be completed <br /> opposite significant clay zones. <br /> Well Development and Groundwater Samples. Each well installed wilt be developed by <br /> surging and bailing or pumping until clean, sediment-free water is produced from the well, <br /> The ltngth of development time. will vary depending upon field conditions. Water produced <br /> during development and sampling will be contained on site. ARCO will be responsible for <br /> the disposal of water and product collected. Prior to and following development, the <br /> thickness of free product,if any,will be gauged. <br /> Following proper development of each well, a nitrogen-driveti bladder pump or stai;-Jass <br /> steel bailer will be used to evacuate an additional amount of water before samples are <br /> taken. The amount of water evacuated will be defined by he stabilization of pH and <br /> 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 tv be analyzed for benzene, toluene, and <br /> xylene (EPA 602). Results will be made available to ARCO within 48 hours. Sample bottles <br /> jwill be filled directly from the discharge line of the bladder pump or from the bailer, 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 (VCA) bottles will be checked to determine that no air bubbles <br /> remain within. <br /> Y All water samples will be labeled and stored as described in the soil samples section <br /> above, and transported to 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 /> thein 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 steam-cleaned before and between use at each <br /> borehole. <br /> Quality 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 /> -_---- Sam le Collection and-Handling <br /> Proper collection and handling are essential to ensure th. quality of the sample. All <br /> samples will be collected by experienced field personnel. . The samples will be collected in <br /> . ., .�..— _,..y...RNfYpi'�XWy^Sa.ek� A41-':�1'.'s^f.�il�.-+.w.-•_—..+-.ar ... <br /> .. .'. .- .-., ..a..awl:w:. c..w• . -•..ir...ti�--v.—..kw.....rw.�.+wr�-n.w.N�YC <br />