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7) The slope stability analysis included in Appendix 2.05.3(4) -2A demonstrates that the long term slope <br />safety factors exceed 1.3, given the pond design parameters for all cases. <br />Ditch Design <br />The collection ditches will be constructed around or cross the drainage area to convey runoff from a disturbed site <br />to a sediment basin. The design methodology of ditches is based on the limited permissible velocity method in <br />SEDCAD version 4.0 and sediment laden algorithm was used. All of ditches are assumed to be constructed by D- <br />7 Dozer resulting in a bottom width of a minimum of 12 -ft and 2:1 side slopes. The typical cross section is shown <br />in the Figure 7. All ditch design details can be found in the appendix in SEDCAD output format. Table 4 displays <br />ditch design details. <br />All six ditch designs are simulated in SEDCAD under the assumption that the channel slope will be constant for <br />the length of the ditch. In reality, that will not be the case, as channel slope for each ditch will vary according to <br />prevailing ground. For ditch segments with channel slopes that will generate water velocities higher than the <br />maximum allowable velocity, rip rap must be placed in the ditch segment. For the ditch of NHN -002 south the rip <br />rap, D50= 6 inch rip rap recommended, is required for the channel with slopes greater than 2.00 %, or the other <br />option using drop structures periodically constructed along the ditch reach in order to maintain a maximum slope <br />of 2.00 %. <br />Dam Classification Criteria <br />The dam classification criteria follows the guidelines of the USDA soil Conservation Service TR60 regarding <br />potential for loss of life and damage as a result of dam failure. These classification criteria are shown below: <br />Class (A): Dams located in rural or agricultural areas where failure may damage farm buildings, agriculture land, <br />or township and country roads. <br />Class (B): Dams located in predominantly rural or agricultural areas where failure may damage isolated homes, <br />main highways or minor railroads or cause interruption of use or service of relatively important public utilities. <br />Class (C): Dams located where failure may cause loss of life, serious damage to homes, industrial and <br />commercial buildings, important public utilities, main highways, or railroads. <br />Special demonstrations are needed for ponds that have Class B or C. The following show that all of three ponds, <br />NHN -001, NHN -002 and NHN -003, are meets the Class A criteria. <br />The locations of all three ponds are selected near or at the natural drain lines for their drainage area and in the <br />rural or agriculture area. In case of dam failure, the water can drain along their natural drain lines. And there are <br />no structures below the Ponds except country roads (2600 and AA) next to them. So these volume and locations <br />for all three ponds would not result in any damage to property or life. For these reasons all three ponds are given <br />a Class A designation. <br />