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The culvert is designed to convey the peak flow runoff from a <br /> 100-year, 24-hour storm event . <br /> Both of the preceding culverts have been <br /> designed and constructed in accordance with U . S . Forest Service <br /> specifications as well as the Colorado Mined Land Reclamation <br /> Board and the Office of Surface Mining specifications . <br /> Runoff waters accumulating on the No . 1 and <br /> No . 3 mine haul roads are prevented from entering the disturbed <br /> area with, respectively, a culvert and a "daylighted" bar ditch. <br /> Sediment ponds with a capacity totalling <br /> 10 . 54 acre feet have been designed and approved for construction <br /> on the south side of Dutch Creek immediately east of the desig- <br /> nated rock-disposal area . Ponds are designed in accordance with <br /> Colorado Mined Land Reclamation Board regulations . Sediment <br /> ponds will be constructed in sparsely vegetated stream alluvium <br /> on a bench approximately 25 feet above the stream channel . The <br /> sediment ponds will be located about the 100-year floodplain. <br /> The ponds are designed 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-S . <br /> 38 <br />