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will not be routed through a sedimentation pond since they are derived from <br />undisturbed areas. The other ten ditches will collect run-off from topsoil <br />stockpiles, the raw coal silos, the substation, the process ponds and the <br />preparation plant. The prep plant ditch and the north and south yard ditches <br />will serve as perimeter collector ditches, and these three will carry the flow <br />to the D-Portal sedimentation pond. The ditches are V-shaped with side slopes <br />of 2h:ly with the exception of the lower preparation plant ditch. This segment <br />is trapezoidal with a 10-foot bottom width and 2h:ly side slopes. Flow <br />velocities do not exceed four feet per second in channels lined with grass. <br />Riprap is used in segments with greater velocities. In two instances a channel <br />segment is lined with an open metal flume where velocities exceed 19 feet per <br />second. The east topsoil ditch discharges into such a flume as does the north <br />topsoil ditch. The outlet of the flumes is riprapped to prevent erosion (see <br />Map 32 of the permit application). _The applicant must suooly the orooosed <br />ditch dimensions for both the upQer and lower segments of the north topsoil <br />d~Jl,.w+rich were omitted- from Illustration_7 of the permit application (see <br />"Stipulations" in this section of the TEA). <br />The proposed collector ditches at the railroad loop and clean coal storage area <br />will be grass-lined and V-shaped with side slopes of 2h:ly. Minimum depth is <br />set at one foot, which translates into an actual depth of 0.7 feet when <br />allowances are made for 0.3 feet of freeboard. Although proposed ditch depths <br />were not submitted for these collector ditches, a check of estimated 10 year-24 <br />hour flows and ditch capacities using a depth of 0.7 feet, shows the ditches to <br />be adequate. The outlet culvert from sedimentation pond #4, which drains <br />approximately 36 acres and extends under the railroad embankment, appears to be <br />undersized and will create a headwater depth of 4 feet at the inlet. <br />Therefore, this set of two culverts should be resized to prevent excessive <br />ponding at the inlet (see "Stipulations" section of this TEA). <br />All ditches will be maintained and operated until the area has been restored <br />and revegetated. After they are no longer required, they will be reclaimed and <br />revegetated (Page IV-74 of the permit application). <br />Stream Channel Diversions (Relocation of Streams) <br />The Scullion Gulch diversion will be constructed concurrently with the D-Portal <br />15 <br />