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Doc Date:12/11/2001 <br />sss -- °' <br />Appendix 12-4 <br />5 ~a <br />Culvert and Ditch Design <br />A meeting was held in the field between the Colorado Division of Minerals and Geology ICDMGI and Hayden Gulch <br />Terminal, Inc. IHGTII personnel. It was agreed at this meeting that existing hydrologic structures required designs. <br />Those designs would be limited to structures within the immediate facilities area (i.e., crusher, conveyor, tipple, etc.- <br />and not extended Cie entire length of the railroad. Although numerous culverts extended beneath the railroad <br />embankmem, these were constructed for flood control and not to route runoff through the transportation network <br />or to sedimentation ponds. Two of the railroad ditches (Ditches 7 and el also fall under this category. <br />Most of the culverts and ditches listed have been in place for a number of years. This design effort is, therefore, <br />a verification that these structures will continue to function properly. Existing ditch shapes and sizes were derived <br />from aerial photography, surveying, and topographic maps. This information was used in the SEDCAD computer <br />• analysis. P.Ithough ditch shapes may rot be consistent throughout the entire length, the cross-sectional area is more <br />than adequate due to the largely insignificant drainage areas. <br />Design Considerations <br />The SEDCAD computer analyses were rudimentary. Most information can be found in the computer printouts. All <br />ditches and culverts were designed to safely pass the runoff from the 10-year, 24-hour precipitation event. Only <br />two differem curve numbers were used: 11 rangeland, 84 and 21 dirt roads, 89. A-eas, slopes, and land use <br />categories are as stated. <br />The following is a list of ditches and culverts that have been designed or a[ least have been assessed by HGTI. <br />Other ditches and culverts do not have specific designs for reasons noted above. All existing structures meet <br />current design criteria. If culverts are to be replaced in the future due to maintenance problems, Larger culverts will <br />generally be employed. <br />• <br />l~-~~ <br />SuBm~tYA~ ON7E S~a~Y6 <br />