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2. Concrete Block Wall - The CONTRACTOR shall construct a solid concrete <br />block wall in the configuration shown on attached drawing sheet 6 of 9. <br />This work will involve removing a 1.5 ft. to 2.0 ft. section of the <br />existing roof and wall timbers, and a corresponding section of the <br />existing rail line, rail ties, wood plank walkway, and any wiring and <br />piping running along the incline. A level trench or keyway for the first <br />course of concrete blocks shall be excavated a minimum of 12" into the <br />floor of the incline, or to competent rock if encountered less than 12" <br />below the ore sent floor elevation. The constructed wall shall extend to <br />contact each rock side wall and the rock roof line. All voids remaining <br />between the roof, walls, floor and the concrete blocks shall be filled <br />with grout. Masonry units shall be laid plumb, level and true to line in <br />full beds of mortar. <br />Joints shall be made in block work uniform and not more than 3/4 inch <br />wide. After becoming "thumb-print" hard, joints exposed shall be tooled <br />to a weather joint. Mortar placement shall be discontinued when the air <br />temperature reaches 40°F and is falling and shall not be resumed until <br />the air temperature reaches 35°F and is rising. No mortar shall be <br />placed on base course containing frost or other frozen material. Mortar <br />shall be machine mixed in an approved type of mixer in which the quantity <br />of water can be accurately and uniformly controlled. The mixing time <br />shall be not less than five (5) minutes, approximately two (2) minutes of <br />which shall be for mixing the dry materials and not less than three (3) <br />minutes for continuing the mixture after the water has been added. For <br />work requiring only small batches of mortar or grout, it may be mixed by <br />hand in a water tight mortar mixing box. The materials for each batch <br />shall be well raked and turned over together before the water is added, <br />until the material is an even color throughout the mass, after which the <br />water shall be gradually added until a throughly mixed mortar of the <br />required plasticity is obtained. All mixing boxes and equipment shall be <br />kept clean. Mortars shall be prepared in batches or volume that will be <br />used before initial set takes place and in no case longer than 45 minutes <br />before delivery to mason's mortar board at point of use. Retempering <br />will not be permitted. Mortar shail be allowed to cure fora minimum of <br />48 hours after block wall completion and prior to placement of backfill <br />material. <br />3. Backfill - The CONTRACTOR shall backfill the portion of the opening <br />remaining between the block wall and the existing ground surface, and <br />shall place additional fill material over the backfilled opening in the <br />configuration shown on attached drawing sheet 7 of 9. Fill material <br />shall oe placed such that the toe of the fill within the opening contacts <br />the base of the concrete wall. The slope of the fill shall extend from <br />the base of the block wall to a point along the roof approximately 2 ft. <br />inside the access gate of the incline as shown on attached drawing sheet <br />6 of 9. The remainder of the opening shall be completely filled to the <br />ground surface, with additional fill placed above grade to form a mound <br />in the configuration shown on attached drawing sheet 7 of 9. Fill <br />material shall be obtained from the crest of the mine bench fill slope <br />located immediately west of the loadout/tipple building and within the <br />borrow area limits delineated on drawing sheet 1 of 9. Excavation of <br />fiil material sha 11 be done in such a manner that leaves an even 2h:ly to <br />3h:ly slope between the crest and toe of the excavated area as depicted <br />on drawing sheet 8 of 9, and which is evenly tapered on either side to a <br />maximum slope of 2h:ly as measured across the borrow area. <br />-5- <br />