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3 3 LOCATION OF WELLS <br />' The locations of the UVB well and UVB monitoring wells UVB-MW 1 and UVB-MW2 are <br /> shown on Figure 2 All three wells are located in the northeast corner of the site, downgradient <br /> of the former underground storage tank (UST) field <br /> The UVB well replaced monitoring well RW3 The UVB well was installed at this location to <br />' remediate the onsite plume and to control downgradient migration The part of the downgradient <br /> plume beyond the boundaries of the UVB circulation cell will be addressed at a later time The <br /> installation of the UVB well at the location of former monitoring well RW3 was deemed the <br />' most effective location, because it is situated within the site and near the center of the plume <br /> UVB-MW 1 is located upgradient of the UVB well and will be used to monitor the influent of the <br />' UVB well UVB-MW2 is located downgradient of the UVB well and will be used to monitor the <br /> effluent of the UVB well In order to allow the collection of samples representative of the <br /> groundwater entering and leaving the lower and upper screens of the UVB well, the two UVB <br />' monitoring wells were installed 2 feet away from the edge of the UVB well borehole, as close to <br /> the UVB well as practicable, while avoiding any damage to the UVB well packing <br />' 3.4 DRILLING OF SOIL BORINGS <br /> 3.4.1 UVB Well <br /> Groundwater recover well RW3 was removed and overdrilled on 11 November 1996 b Viking <br /> Y Y g <br />' Drilling Corporation (C57 License#476668), using a spiral drill rig equipped with solid stem <br /> augers Soil cuttings and well debris generated during the destruction of RW3 were stockpiled <br /> onsite, awaiting appropriate disposal After the destruction of RW3, the borehole was widened <br /> to a diameter of 24 inches and the UVB well was installed in the borehole on 25 November 1996 <br /> by Viking <br />' 3.4 2 UVB Monitoring Wells <br /> The borings for UVB-MW 1 and UVB-MW2 were drilled on 11 February 1997 by Bayland <br />' Drilling Inc of Menlo Park, California (C57 License#374152), using a truck-mounted rotary <br /> drill rig equipped with 8-inch-diameter hollow-stem augers Prior to drilling, a 10-inch-diameter <br /> hole, designated as the delineation area, was cleared by hand-digging the first 1-2 feet of surface <br />' soil, probing, and then hand-augenng the remainder of the delineation area to a total depth of 5 <br /> feet bgs UVB-MW 1 was drilled to a total depth of 40 feet bgs, and UVB-MW2 was drilled to a <br /> total depth of 32 feet bgs The hollow-stem augers and downhole equipment were <br />' decontaminated by steam-cleaning prior to and following drilling Decontamination water <br /> generated during drilling activities was contained in a Baker tank stored on the site A <br /> description of drilling methods and procedures is provided in Appendix B <br />' wP6t 73942 R01397 3 7 <br />