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4.0 WELL DESTRUCTI®N <br /> Destruction of wells will be completed in accordance with applicable state and local <br /> requirements. If required, permits for destruction will be obtained from the appropriate <br /> regulatory agency. As part of destruction design and implementation, care will be taken to <br /> seal groundwater pathways between multiple aquifers and to limit surface water infiltration <br /> through the destroyed borehole. <br /> If practical, the well casing will be removed from the borehole. If the well casing cannot be <br /> removed, the casing should be cut and/or pressure-grouted in accordance with regulating <br /> agency requirements. For shallow wells and if the well has been completed in the uppermost <br /> aquifer, the casing may be pulled from the borehole before auger entry. Alternatively, and if <br /> the well has been completed below the uppermost aquifer, the annular fill may be drilled out <br /> with hollow stem augers and the casing removed from the borehole through the augers. If the <br /> well casing is PVC or other similar material and cannot be removed as described above, it <br /> may be removed by drilling out the casing and annular fill using a tricone or drag bit and a <br /> rotary drilling method. The borehole will be redrilled to the same or a slightly larger diameter <br /> than the original borehole. The redrilled borehole will be plumb and adequately centered, and <br /> all of the well casing will be removed. <br /> The borehole will be filled with a neat cement, cement/sand, cement/bentonite grout, or a <br /> high-solids bentonite grout. Before its initial set, the grout will be placed in one continuous <br /> pour from the bottom of the boring to the ground surface. The grout will be emplaced by <br /> pumping through a tremie pipe or flexible hose which is initially lowered to the bottom of the <br /> borehole. The augers should be raised incrementally as emplacement proceeds, but not exceed <br /> increments of 20 feet or increments greater than allowed by borehole stability. Boreholes that <br /> are terminated above the water table and are not greater than 20 feet deep may be grouted by a <br /> continuous pour originating at the ground surface. If the aquifer is confined and the head <br /> pressure is great, the grout may need to be placed under pressure. <br /> INSTALLATION AND DESTRUCTION OF WELLS Page 7 of 8 <br /> MSC^,PROTO-IW.::YT REVISION DATE:MARCH 1996 IW-7 <br />