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3.0 MINE ENTRY SEALING AND BACKFILLING <br />3,1 Description <br />This specification covers all materials and work required to seal and backfill <br />the two open mine entries at the East mine area of the Hawk's Nest Mine. The <br />first opening is located on the north side of the highway inside the <br />ventilation fan facility. The second opening is located on the south side of <br />the highway behind the wash plant. These two openings are shown as items 23 <br />and 32 on Exhibit 3A respectively. <br />3.2 Materials <br />The concrete masonry units to be furnished by the CONTRACTOR shall consist of <br />solid 8"x8"x16" 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 C210, Type S consisting of one <br />(1) part 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 from the floor of the lower <br />mine entry, Any steel material to be used other than the existing rail track <br />must be approved by the PROJECT MANAGER prior to use. Grout shall conform to <br />ASTM C476, and aggregate shall conform to ASTM C404. <br />3.3 Execution <br />A. Ventilation Fan Mine Entry <br />1. Backstop - The CONTRACTOR shall construct a steel I-Beam or <br />rai rack backstop for the concrete block wall by installing <br />five vertical posts on 36" centers across the concrete lined <br />portion of the mine entry and between 2 to 5 feet of the end of <br />the lining, shown as the location of cross-section A-A' on <br />Exhibit 6F. Each post shall be fastened to both the roof and <br />floor of the mine entry by welding a flange on each end of each <br />post and lag bolting each flange piece to the concrete using a <br />minimum of two (2) 3/4" diameter by 6" long lag bolts. The <br />posts shall be installed along a plane such that each post <br />makes 100% contact with the back of the block wall for entire <br />length of each post. The CONTRACTOR shall install additional <br />backstopping around the entire perimeter of the rear of the <br />wall by lag bolting (3/4" diameter x 6" long bolts) minimum <br />3"x3" angle iron or channel iron pieces to the concrete lining <br />with lag bolts placed on 12" to 18" centers. The angle iron or <br />channel iron shall be placed such that a 3" high lip is formed <br />to make 100% contact with the rear of the block wall, <br />-16- <br />