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Standard corrugated metal culverts were installed at approxi- <br />mate intervals of 1000 feet on Pit 4 haul road. <br />Because the headwater will exceed 1.5 times the culvert diameter, <br />the inlet end of all culverts will be protected by riprap and the <br />discharge end viill be riprapped to prevent erosion. .4 typical haul <br />road drainage culvert is shown on Figure 3. The culvert locations <br />are shown on the Mining Plan Map. The drainage areas contributing to <br />each culvert are presented in Table 2, together with other design <br />information. <br />2.05.3(4) Ponds, Impoundments and Diversions <br />Each mining pit (including the strip auger areas) will have a <br />sediment pond associated with it. The Plining Plan Flap shows the <br />approximate location of each sediment pond. <br />Each pit v+ill have a system of diversion ditches and collection <br />ditches surrounding it. The diversion ditches v+ill capture natural <br />overland flow and conduct it around the mining operation. Water will <br />be discharged from the diversion ditches into natural channels. <br />Collection ditches will be located on the downslope side of all mining <br />pits. These ditches will capture runoff from the disturbed areas in <br />and around the mining pit, conducting the water to the sediment ponds. <br />. The sediment ponds will allow settlement of suspended solids prior to <br />release of runoff water to the natural drainageway. <br />All of the diversion ditches and collection ditches have been <br />sized to pass a 10-year, 24-hour precipitation event. The methods used <br />to estimate peak flows at various locations are the same as those <br />described in Section 2.05.3(3) for the haul road culverts. Ditches <br />have been divided into incremental sizes. A Type A ditch is the <br />largest; a Type C ditch is the smallest. All collection and diversion <br />ditches have been designated as Type A, B or C, depending on the <br />contributing drainage area and the ditch slope. The ditches are <br />listed in Table 3. Typical drainage ditch cross-sections are shown <br />on Figure 7. <br />The collection and diversion ditches shown on the Flining Plan flap <br />will be constructed prior to any topsoil or overburden removal. In <br />this manner, once the first box cut is begun, it will act as the sedi- <br />ment pond. It will take approximately 2 working days to create an <br />impoundment large enough to hold all anticipated runoff from a 10-year, <br />24-hour storm. This system v+orked very well for Pits 1, 2 and 3. <br /> <br />2-35 III-15 <br />