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in Technical Revision 5, which Salt Creek Mining Company submitted in <br />answer to the Division's Mid-Term Review in 1986. <br />Refuse Pile Sediment Pond <br />The proposed sediment pond for the underground development waste disposal <br />pile is designed for a total capacity of 0.185 acre-feet. This will <br />allow for the detention of the volume of runoff from the 10-year, 24-hour <br />event (0.12 acre-feet) in addition to a three-year accumulation of <br />sediment from the disposal pile (0.062 acre-feet). A sediment clean-out <br />marker must be installed which indicates the level at which sufficient <br />storage remains in the pond for both runoff and sediment generated by the <br />10-year, 24-hour storm event. <br />The collector ditch for the pond at the underground development waste <br />disposal site will be stable under flows form the 10-year, 24-hour event <br />and the emergency spillway will be stable during flows resulting from the <br />25-year, 24-hour event. As in the case for the pond at the mine bench, <br />the permit application has been amended in response to the original CMLRD <br />Stipulation No. 2 to include provisions for installation of a dewatering <br />device to dewater the pond down to the maximum sediment storage level. <br />Central Facilities Area Sediment Pond <br />The proposed pond at the central facilities area is designed to hold a <br />volume of runoff and sediment of 5.53 acre-feet. This capacity allows <br />for the storage of runoff from two 10-year, 24-hour storm events <br />(3.5 acre-feet) as well as storage of five years' volume of sediment <br />accumulation (0.145 acre-feet). The Division requires that a sediment <br />clean-out marker be installed in the pond to indicate the maximum levei <br />at which sufficient storage remains for both runoff and sediment <br />generated by the 10-year, 24-hour storm event. <br />Central Facilities Topsoil Stockpile Sediment Pond <br />The proposed pond at the central facilities topsoil stockpile is designed <br />to hold a volume of runoff and sediment of 0.3 acre-feet. This capacity <br />allows for the storage of runoff from one and one-half 10-year, 24-hour <br />storm events (0.20 acre-feet) as well as storage of three years' volume <br />of sediment accumulation (0.10 acre-feet). The Division requires that a <br />sediment clean-out marker be installed in the pond to indicate the <br />maximum level at which sufficient storage remains in the pond for both <br />runoff and sediment generated by the 10-year, 24-hour storm event. <br />The collector ditch into the pond will be stable under the flow from the <br />10-year, 24-hour storm event. The emergency spillway is designed to <br />convey flow from the 25-year, 24-hour event without eroding. Due to the <br />small size and incised nature of this pond, dewatering will be <br />accomplished through the use of a pump once the water quality meets or <br />exceeds effluent standards. <br />Coal Processing Waste Disposal Area Sediment Pond <br />The proposed pond at the coal processing waste disposal area is designed <br />to hold a volume of runoff and sediment of 3.95 acre-feet. This capacity <br />_23_ <br />