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pUR <br />�n <br /> screened interval will be placed completely within the lowC- aquifer zone. Blank <br /> (D casing will extend from the top of the screened interval to the surface in each well, <br /> The annular Space between the screen casing and wall of the borehole wil! be <br /> backfilled with P3 Monterey sand. The sand pack will be placed to extend 2 feet <br /> above the screened interval. The annular spacc immediately above the sand pack will <br /> be scaled for a distance of 2 feet with hydrated bentonite pellets. The remaining <br /> annular space above the bentonitc seal will be backfilled. to surface with a <br /> cement/bentonite grout, <br /> 1Jpan completion of the well, the top of lite well will be enclosed with a below ground, <br /> locking Christy box to prevent tampering with the well or introduction of foreign <br /> material into it. <br /> Monitor well MW-4D will be constructed with a surface casing to help nrevrnt <br /> contaminants associated with the free-floating product in the upper aquifer from <br /> migrating dawn the bore hole and contaminating the lov4c aquifer during well <br /> construction. A 12-inch diameter bore hole will be advanced approximately I ft. into <br /> the first aquitard below the top aquifer. The bore hole will then be back filled to the <br /> level of the water table with cement/bentonite grout. A 12' diameter steel surface <br /> casing with a 12 inch PVC cap placed over the bottom end will be placed in the bore <br /> hole, water in the well bore will be pumped out prior to setting the surface casing. <br /> if the water from the well bore contains floating product it will be pumped into lined <br /> 55 gal. drums. As the surface casing is lowered into the bore hole the grout will be <br /> displaced upward and seal the annular space between the casing and the wall of the <br /> boreholes. Grout that is displaced to the level of the ground surface will be collected <br /> and placed in drums for disposal. <br /> After the grouted surface casing has been allowed to set overnight, :he well bore will <br /> be advanced through the PVC cap to a depth of approximately 50 ft. with a 10 in. OD <br /> hollow stem auger lowered through the center of the surface casing. The final <br /> completion depth will be dependent on the local stratigraphy, however the well bore <br /> will be advanced at least 10 ft. into the, second aquifer. Following surface casing <br /> installation, well construction procedures will be the same as those specified for the <br /> other monitor wells. A typical surface casing well completion is shown in Figure 3.2- <br /> esssa.atlastso/uxtaN.z 8 <br />