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iiiiiiiiiiiiiiiiiii <br />999 <br />f~~~ MINE AREA CULVERTS AND DRAINAGE CROSSINGS Doc Date:12/1112001 <br />• <br /> <br />Culverts and drainage crossings were designed according to the procedures <br />set forth by the U.S. Bureau of Public Roads. The peak discharge from the <br />10-year, 24-hour storm was used to design all culverts. Because it will <br />remain as a permanent structure, the south mine fan light use road <br />crossing has been designed using the 100-year, 24-hour storm event. Peak <br />flows were calculated using the "THYD1" computer model for all culverts <br />except the culvert located at the refuse storage area. Peak flows for <br />the culvert located at the refuse storage area and the south mine fan <br />light use road crossing were calculated using the "SEDCAD+" computer <br />model. Five (5) culverts and two drainage crossings exist within the <br />Southfield Mine permit area. Their locations are shown on the Drainage <br />and Sediment Control Map, (Map 20). Culvert designs are summarized in <br />Table 20, Mine Area - Culvert Design Summary. Figure 1, U.S. Bureau of <br />Public Roads Nomograph, illustrates the procedure utilized to size the <br />culverts. <br />HAUL ROAD CULVERT AT REFUSE PILE <br />The 21-inch culvert previously proposed for placement in the South Refuse <br />Collection Ditch was never installed. The decision not to install this <br />culvert was based on the fact that the road is moved as the refuse pile <br />advances and on the practical constraint of balancing culvert capacity <br />with cover limitations. The refuse haul road is routed around the <br />western-most end of the South Refuse Collection Ditch, eliminating the <br />need fora culvert. <br /> <br />pEVTR15.REV <br />17/15/93 11em <br />156R Revised - November 1993 <br />