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4.07.1 GENERAL REQUIREMENTS <br />With the exception of drillholes completed as either water supply wells or <br />monitoring wells, all exploration drillholes, boreholes, and exposed underground <br />openings will be plugged and sealed in order to prevent acid or toxic drainage, <br />minimize disturbance to the prevailing hydrologic balance, and assure the safety <br />of animals, persons and equipment within the permit and adjacent areas. <br />4.07.2 TEMPORARY SEALING <br />Drillholes completed as water supply or monitoring wells will be cased to just <br />above the ground surface and capped. No other temporary sealing measures are <br />proposed since capping of wells will adequately address any potential concerns <br />and will facilitate access to the wells when needed. As part of the hydrologic <br />monitoring program, the condition of well installations including surface casing <br />and caps will be inspected on a regular basis. Any damage will be noted and <br />repairs will be completed on a timely basis, as appropriate. <br />4.07.3 PERMANENT SEALING <br />Any drillholes not completed as monitoring wells will be sealed and abandoned. <br />Abandonment will involve establishing a cement grout seal extending <br />approximately 20 feet above and below any water-producing zones(s), backfilling <br />the remainder of the drillhole with cuttings to within approximately 10 feet of the <br />collar, cementing an interval from the top of the backfill to approximately three <br />(3) feet below the surface, cutting-off any surface casing below grade, placing a <br />metal fence post as a permanent marker, backfilling the remainder of the hole <br />with soil material, and regrading and revegetating the associated surface <br />disturbance area. Where boreholes or welts extend into open mine workings, a <br />suitable expanding plug or packer will be used to contain and support the initial <br />cement grout seal until it sets-up, and expanding grout will be used to assure a <br />tight seal. <br />When mining was completed, the mine portals were sealed, to prevent access. <br />Sealing involved filling the entries with compacted, incombustable material for a <br />distance of at least 25 feet. The void between the portal seals and the portals <br />was backfilled with overburden and demolition debris in conjunction with <br />MR-50 4.07-1 Revised -June 2003 <br />