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3.3 Execution The CONTRACTOR shall construct a solid concrete block wall in the configuration shown on attached drawing sheet 9 of 9. A level trench or keyway for the first course of concrete blocks shall be excavated a minimum of 16" into the floor of the entry, or to competent rock if encountered less than 16" below the present floor elevation. ALL material excavated from the keyway trench shall be completely removed from the mine opening and away from the mine drainage channel. The back or rear portion of the wall shall be placed against the existing 6" x 6" vertical wall and horizontal roof timbers, and the wall shall be constructed to contact both wood plank side walls and the wood plank roof. All voids remaining between the roof, walls, floor and the concrete blocks shall be filled with grout. The CONTRACTOR shall install three drainage pipes within the wall between the second and fourth courses as shown on the attached drawing. The ends of each segment of pipe shall be cut to set flush with the front and rear wall faces, and all voids remaining between the pipe and concrete blocks shall be filled with grout sufficient to prevent any water from passing between the installed pipes and concrete blocks. Masonry units shall be laid plumb, level and true to line in full beds of mortar. Joints shall be made in block work uniform and not more than 3/4 inch wide. After becoming "thumb-print" hard, joints exposed shall be tooled to a weather joint. Mortar placement shall be discontinued when the air temperature reaches 40°F and is falling and shall not be resumed until the air temperature reaches 35°F and is rising. No mortar shall be placed on based course containing frost or other frozen material. A 6 ft. long wood plank with a minimum cross sectional size of 3"x6" shall be bolted vertically to each side wall of the mine opening immediately in front of the constructed block wall, with minimum 6" long wood bolts on 12" centers. ALL voids remaining between the wood planks and the block wall shall be filled with grout. Mortar shall be machine mixed in an approved type of mixer in which the quantity of water can be accurately and uniformly controlled. The mixing time shall be not less than five (5) minutes, approximately two (2) minutes of which shall be for mixing the dry materials and not less than three (3) minutes for continuing the mixture after the water has been added. For work requiring only small batches of mortar or grout, it may be mixed by hand in a water tight mortar mixing box. The materials for each batch shall be well raked and turned over together before the water is added, until the material is an even color throughout the mass, after which the water shall be gradually added until a throughly mixed mortar of the required plasticity is obtained. All mixing boxes and equipment shall be kept clean. Mortars shall be prepared in batches or volume that will be used before initial set takes place, and in no case longer than 45 minutes before delivery to mason's mortar board at point of use. Retempering will not be permitted. 3.5 Measurement and Payment No measurement for payment shall be made for ventilation entry mine seal construction. Payment shall be made for the lump sum bid price established on the Invitation and Bid Form. The price bid shall include all of the CONTRACTOR'S cost of whatever nature to furnish materials, prepare the mine opening, and construct the concrete block wall and drainage pipes. -8-