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1 <br /> side of Dutch Creek immediately east of the designated rock- <br /> disposal area. These ponds are designed in accordance with <br /> Colorado Mined Land Reclamation Board regulations . They have <br /> been constructed in sparsely vegetated stream alluvium on a bench <br /> approximately 25 feet above the stream channel outside a buffer <br /> zone adjacent to Dutch Creek. The sediment ponds have been <br /> located above the 100-year floodplain. The ponds are designed <br /> for a 10-year 24-hour storm event . <br /> Mine waters and surface runoff waters from <br /> the disturbed area, including the rock-disposal area, will be <br /> channeled to the settling ponds via a 2, 800 foot-long perimeter <br /> ditch more or less parallel to Dutch Creek and to the rock- <br /> disposal area. The perimeter ditch is designed to carry and also <br /> bypass flows in excess of those calculated for a 10-year 24-hour <br /> storm event . <br /> For further details on the rock tunnel area <br /> drainage control plan, including maps and cross-sections, see <br /> Section B-8, Appendix II-B-5. <br /> (5) Rock spoil disposal area <br /> Spoil material from the construction of the <br /> rock tunnel will amount to approximately 1, 900, 000 cubic yards <br /> and will be placed in a designated 13 .4 acre disposal area . The <br /> tunnel spoil material will be trucked to the disposal area and <br /> spread and compacted to Colorado Mined Land Reclamation Board <br /> specifications. The perimeter slope of the disposal area will be <br /> maintained at the ratio of 2H: 1V or less . <br />