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Intr <br />NOy C-95-007 was issued for failure to minimize erosion and <br />siltation associated with road drainage structures applicable to <br />roads outside the disturbed area. Two areas in particular, at the <br />outlets of Culverts ME-5 and G-2, were receiving an extraordinary <br />amount of silt. To assist in minimizing the erosion and siltation <br />taking place along the Mine Entrance Road and Haul Road G an <br />additional alternate sediment control measure will be implemented. <br />General designs for porous rock check dams have been calculated for <br />each road. These designs were for check dams that would be placed <br />approximately 500 feet apart. Straw bale barriers in combination <br />with the rock check dams will be installed along both haul road <br />ditch systems. Utilizing this alternate sediment control measure <br />should minimize the amount of silt being carried through Culverts <br />ME-5 and G-2. <br />General Design Analysis <br />The hydrology of the watershed for each section of haul road that <br />the check dam would control was analyzed utilizing the SEDCAD+ <br />computer program. In performing this analysis, the characteristics <br />of the local site drainage and haul road ditch statistics were <br />considered and utilized. Table 13-6A-1 contains the design <br />hydrology summary. <br />TABLE 13-6A-1 <br />DESIGN HYDROLOGY SUMMARY <br />Description i0 Yr - 24 Hr Storm <br />MINE ENTRANCE ROAD HAUL ROAD G <br />Precipitation Depth 1.6 in. 1.6 in. <br />Runoff Volume 0.03 ac.-f t. 0.01 ac.-f t. <br />Peak Discharge Rate 0.35 cfs 0.10 cfs <br />• Input consists of precipitation amount (inches), watershed area <br />(acres), time of concentration (hours), runoff curve number (CN), <br />13-6A-1 Revised 06/08/95 <br />