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2.0 IN CLIIJED MINE ENTRY SEAL AND BACKFILL <br />2.1 Description <br />This specification covers all material and work required to construct a steel <br />backstop and concrete olock wall or bulkhead seal within the open inclined <br />mine entry at the Sunlight mine, and to backfill the portion of the mine <br />opening remaining between the constructed seal and the surface. <br />2.2 Materials <br />The concrete masonry units to be furnished by the CONTRACTOR shall consist of <br />solid 8"x8"xl6" concrete blocks of the standard type used in active <br />underground coal mine operations for bulkhead seals. An example of the type <br />of concrete block to be used will be shown to prospective bidders at the <br />on-site pre-bid meeting. Mortar shall be ASTM C270, Type S consisting of one <br />(1) Dart Portland cement, 0.5. part lime putty, 3.5 to 4.5 parts sand, and <br />water sufficient to produce a stiff plastic mixture. Structural steel for the <br />backstop shall consist of straight steel I-Beam material at a minimum size of <br />W4x13 or straight sections of railroad track taken form the floor of the <br />inclined mine entry. Any steel material to be used other than the existing <br />rail track must be approved by the PROJECT MANAGER prior to use. Grout shall <br />conform to ASTM C416, and aggregate shall conform to ASTM C404. <br />2.3 Execution <br />1. Backstop - The CONTRACTOR shall construct a steel I-Beam or rail track <br />backstop for the concrete block wall in the configuration shown on <br />drawing sheet 6 of 9. Tne backstop shall consist of four (4) vertical <br />posts positioned as shown on the drawing. The based of each vertical <br />post shall oe Keyed a minimum of 12" into competent rock along the floor <br />of the incline. The posts shall extend up to the rock roof line <br />presently supported by timbers. It will oe necessary to remove a 1.5 ft. <br />to 2.0 ft. section of the existing roof and wall timbers to provide 100 <br />contact between the backstop posts, the concrete block wall, and the rock <br />floor, walls, and roof of the incline. Two (2) of the vertical posts <br />positioned adjacent to the existing rail line shall be supported by <br />welding a straight section of rail or I-Beam at an angle to each of the <br />two vertical posts and to each of the two existing rail tracks which must <br />remain in place behind the position of the block wall for a minimum <br />distance of 20 ft. as shown on the attached drawing sheet 6 of 9. The <br />base of each of the two angled posts shall extend a minimum of 6" into <br />competent floor rock. A steel stop block shall be welded to each of the <br />two vertical I-Beam posts and to the top of each of the two angled posts <br />as shown on drawing sheet 6 of 9. <br />-5- <br />