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• one toot of head at the culvert. As previously stated, runoff from haulroads is, for the most part, routed <br />through sedimentation ponds. <br />Road Surface Dreinage: <br />Ditches are provided at all cut sections (refer to Figure 3.7-1). These ditches are censtruded and <br />maintained to carry the road water runoff from glen-year, 24hour event Standard ditch designs for <br />roads at Trapper Mine are contained In Appendix P. <br />The topography at the Trapper Mine is sloped and rolling such that sufficient natural ditch drainage is <br />provided. Cut-outs through road beans and surface dips allow road water runoff to drain from the <br />haulroad area. Cul-outs are riprepped or otherwise treated when necessary to minimae erosion. <br />Culverts and Bridges: <br />There are no bridges or culverts at the Trapper Mine with an end area of 35 square feet or greater. <br />Culverts are designed to safely pass the ten-year, 24hour precipitation event. Cuhrerts are designed <br />and installed to avoid plugging as much as is predicable. Trash racks are trrstalled where necessary to <br />aid in this endeavor (refer to Figure 3.7-3). Culverts are designed, canstroded and maintained to <br />withstand the loads and forces encountered. All culverts are covered by compacted fill to at least one <br />• foot in depth. <br />Culverts required to provide drainage continuity are provided where necessary. The cuhrerts are <br />designed to safely pass the area runoff from glen-year, 24hour evert. The location of these culverts <br />and the design calculations are shown on Map M51 and Section 4.8.1.2. <br />Culverts, surface dips and cut=outs provide drainage of the road water runoff. The bcations of these <br />three kinds of structures are coordinated to provide the most logical and environmentally sound method <br />of diverting road water nrnoft away from the road itself and into stable drainages. These structures <br />• 3-187 <br />--: -PR-~1 - .:_.. <br />- -. _ ~ :::MAY 1 '31998.: <br />