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• Other culverts were sized for the maximum discharges from 10-year 24-hour storms (20-year, <br />24-hour storms for culverts with areas exceeding 35 square feet). The technique used was that <br />presented in SCS-TP-149 (Rev. 1973) and was applicable to watersheds with areas less than 2000 <br />acres. See Section V-B-2 for a discussion of runoff calculations. <br />Drainage ditches along the haul road and plant access road were sized to handle runoff from a <br />10-year 24-hour storm. Where velocities were expected to exceed four feet per second due to <br />steepness of grades, ditches were lined and riprapped. All ditches were seeded along with cut and <br />fill slopes as previously discussed. Straw dikes, rock check dams, and other erosion control <br />methods were field specified to minimize erosion prior to vegetation establishment. <br />All culverts were designed assuming that inlet conditions control, the headwater to diameter ratio is <br />1:0, and that the culvert ends protrude from the fill. Culverts larger than 48 inches in diameter were <br />designed assuming that inlet conditions control, the diameter ratio was not greater than 1:5, and that <br />rock or concrete head walls were used. <br />There is a minimum of three feet of compacted material over all culverts. Generally culverts over 36 <br />inches in diameter were installed along with embankment construction. Culverts less than 36 <br />inches in diameter were installed after road embankment construction is completed and before the <br />final gravel or crushed rock and finish courses were placed. <br />• Sizes and locations of all culverts are shown on the plan and profile drawings. The drainage areas <br />for the major culverts and typical calculations for ditches and culverts along the haul road and plant <br />access road are included in Illustrations 1, 2 and 3. <br />Haul roads and other unpaved roads are maintained by periodic regrading of the gravel surface and <br />regraveling as required. Ditches antl culverts are also cleaned periodically to assure proper <br />drainage. The surface of the road is watered and treated with magnesium chloride or other <br />appropriate additive for dust control. Maintenance complies with Section 4.03.1(6) requirements. <br />The haul road will be completely reclaimed. The culverts will be removed and the gravel surtace will <br />be mixed with the fill during grading. The terrain will be regraded to approximate original contours, <br />covered with topsoil and reseeded. Typical cross sections showing how the haul road will be <br />reclaimed are shown on Map 69. <br />Refuse is transported from the preparation plant to the Refuse Disposal Area by 35 to 100-ton <br />off-road trucks. These trucks operate at a maximum speed of 40 mph. The speed is restricted to <br />20 mph on some curves and near the plant site. <br />• Permit Rev. 4 (11/2002) IV-15 <br />