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• Outfall Slope 15H <br />D50 Size 1.25 feet <br />Invert Eleva [ion 7075.5 <br />25-year, 24-hour Peak Stage 7077.9 <br />Pre-Set[ling Rasin - FHASE IV <br />Eme [q ency SFillway: <br />T}P°- Trapezoidal Channel <br />B~:2 tom 41id[h 1G feet <br />Lengch 20 fee[ <br />Side Slopes 3H:1V <br />glut fa 11 Sl~~pe 3-.54 <br />D50 3i.e 0.7.5 feet <br />In1e[ El e'/a[ion 7116.0 <br />25-year, °4-hour Fea l: Stage 711P.G <br /> Summary <br /> With the phase IV design sediment pond UG6's capacity is attributed entirely to the <br />• emban 4.ment. Du ri nq passage of tt~e 10-year, ''?4-hour storm [he spillway does not discharge <br /> s edimeni downstream not is there any fl cw through the emergency spillway. The pond will <br /> be a l.e rma nent sr. ru cture after mining and therefore will need to be redesigned later on <br /> to safely pass the flow from the 100-year, 24-hour precipitation event. Th=_ embankment <br /> is cens[ruct ed [~~ be stable and provide adequate freeboard. Therefore, based on [he <br /> design, this structure complies with the app rcpriate regulations fc•r a sedimentation <br /> structure. <br />The Pre-Settling Basin is a temporary structure whi r_h will Ge reclaimed once reclamation <br />activi[i es ct the mine area have progressed far enough so that it is no longer required. <br />Friut tc reclamation of the Pre-Settling Basin, Seneca will demo ns[rate Chat this basin <br />is no longer required. Seneca Cual company will pe ricdically inspect both of these <br />st[uc[ures for sediment storage, structu cal integrity and ha za rdeus conditions. <br />Maintenance and remedial wort: will be pe [formed in accordance with the approved mine <br />permit. <br />• <br />9 Revised 03/02/98 <br />