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3.2 SAFETY REQUIREMENTS <br />A. All work shall be done in conformance with Colorado state law, OSHA, and any other <br />rules and regulations pertaining to safety. <br />' 3.3 BACKFILL CLOSURE <br />A. Description <br />' 1. This work shall consist of backfilling mine openings with on-site or imported fill <br />materials and revegetation of disturbed areas as designated in these specifications <br />' or as directed by the RESIDENT PROJECT REPRESENTATIVE. <br />B. Backfilling <br />1. Prior to backfilling adits, the Subcontractor must remove all wood, garbage, <br />cribbing, or other materials as directed by the RESIDENT PROJECT <br />REPRESENTATIVE. All trash and debris must be hauled to an approved land <br />fill as directed by the RESIDENT PROJECT REPRESENTATIVE. <br />' 2. Adits shall be backfilled with a minimum depth of 15 feet from the inner top of <br />the fill to the outer top of the fill. There shall be no spaces between the top of <br />the fill and the roof of the adit that exceed 3 inches and there shall be no space <br />between the top of the fill and the roof of the adit at the entrance of the adit. The <br />backfill shall consist of large rocks (riprap) whose individual size is a minimum <br />1 foot in largest dimension mined with fill, with the outer 3 feet of backfill <br />consisting entirely of rock. In certain situations, a tamping device or fabricated <br />ram may be required to place the necessary rock. <br />~~Iternatively, where acceptable rock is not available, or where duetted by the <br />~IDENT PROJECT REPRESENTATIVE, asoil-cement mixture may be used. <br />The il cement will consist of on-site soil and portland cement in a ratio of 20:1 <br />(20 u 'ts of soil to 1 unit of cement). The on-site materials used as fill must be <br />well-g ded, and approved by the RESIDENT PROJECT REPRESENTATIVE. <br />' Th m y not be acidic or toxic in nature. Soil materials and Portland cement <br />sh~ b thoroughly blended by mechanical means prior to placement. This may <br />be do by machine or by hand. The entire length of the backfill except for the <br />' feet shall be composed of soil~ement materials. The last 3 feet shall be <br />composed of backfill materials suitable for plant growth. <br />' 4. The adit will be overfilled a minimum of 3 feet to allow for future backfill <br />subsidence. The maximum exposed backfill slope will be determined in the field <br />by the RESIDENT PROJECT REPRESENTATIVE but will in no event exceed <br />1.SH:1V. <br />' 6-8 <br />