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?evine•Frick • <br /> EN INEERS,HYDFiOGEOLpGI$T$e Recon <br /> QAPP. The boring would then be overreamed to the appropriate diameter for the selected well <br /> configuration. If only one well casing is to be installed in the boring, the work would be conducted <br /> according to procedures presented in Section 2.7.2 of the FSP and in the QAPP. If multiple casings <br /> are to be installed, the work would be conducted according to procedures presented below. In <br /> either case, constructed wells would be developed and sampled subsequent to their installation. <br /> Proposed Multi-Completion Well Construction <br /> Based on the sampling results, if more than two discrete coarse-grained B-zone sediment layers are <br /> selected for monitoring within the proposed borehole, a multi-completion method of well <br /> construction would be used. Each individual well would consist of a 2-inch-diameter schedule 40 <br /> PVC casing and 2-inch-diameter stainless steel well screen. Each well would be installed <br /> sequentially, from the base ofthe borehole upwards. Each individual well strin <br /> mg would be <br /> equipped with centralizers to aintain separation within the borehole and to offset each well string <br /> into a different quadrant of the borehole. If the bottom of the borehole is drilled to below the target <br /> depth of the lowest well screen, the borehole would first be backfilled with delayed hydration <br /> bentonite pellets tremied into the hole to a depth one foot below the target screen depth. The well <br /> casing would then be lowered into the borehole and the filter pack tremied around the casing to an <br /> elevation one foot above the top of the well screen. The well would then be gently developed with <br /> a surge block to settle the filter pack. Additional filter pack material would then be added, as <br /> necessary, to bring the filter pack height back up to a foot above the well screen. The borehole <br /> would then be backfilled with delayed hydration bentonite pellets through a tremie pipe up to a <br /> depth one foot below the target screen depth of the next higher interval. This well construction <br /> process would then be repeated for each of the targeted screen intervals. For illustration purposes, <br /> Figure 1 shows the hypothetical construction for a three-well scenario. <br /> During installation of the delayed hydration bentonite pellets, the time to hydrate the pellets would <br /> be monitored using a test bucket on the ground surface containing equivalent wellfluids and <br /> pellets. The subsequent well casing and filter pack would not be installed until the pellets are <br /> considered hydrated. Once all target screen intervals are constructed, the well would be completed <br /> in a normal fashion with Portland cement grout containing approximately five percent powdered <br /> bentonite, tremied in place. The multiple well casings would be terminated at the ground surface in <br /> a shared; traffic-rated well box. Each well casing would be permanently identified with the well <br /> name and screen interval. <br /> Proposed Boring and Well Location, Work Area, and Traffic Plan <br /> The proposed boring would be located approximately 10 feet upgradient of well MW-21 as <br /> presented in Figure 1. This offset distance is considered appropriate to reduce the potential for <br /> migration of the grout from the boring to existing well MW-21, should this well remain in place, <br /> or alternatively, from MW-21 to the replacement well, if MW-21 is abandoned. The proposed <br /> work area and traffic control plan are presented in Figure 2. Asindicated in Figure 2,'the mud <br /> rotary drill rig, pipe rack, mud shaker, and support trucks require a combined work area of <br /> approximately 40 by 80 feet. Because of the nature of this drilling method, it will be necessary to <br /> LCM W2 f.3.LTR:SRL 4 <br />