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4 <br />SUN COAL COMPANY <br />MEADOWS N0. 1 <br />IMPOUNDMENT CERTIFICATION <br />Sedimentation Pond 2 (Lower Impoundment) <br />Design Criteria <br />Capable to contain, and treat the peak flow from the 30 year 24 <br />hour storm event and capable to convey the peak flow from the 25 <br />year 24 hour storm event through the combination of the principal <br />and emergency spillway. <br />Design Criteria <br />Ten year 24 hour storm event 1.6 inches <br />Twenty-five year 24 hour storm event 2.0 inches <br />One hundred year 24 hour storm event 2.3 <br />Ten year 24 hour runoff 9.0 cfs-Total flow 0..65 acre feet <br />Twenty five year 24 hour runoff 17.7 cfs-Total flow 1.22 acre feet <br />One hundred year 24 hour runoff-24.3 cfs <br />-Total flow 1.73 acre feet <br />Soil Conservation Service Curve Number 75 <br />Drainage Area 36.4 acres <br />Vegetative Type Grassland <br />Emergency Spillway Design <br />Trapezoidal <br />Spillway Depth 2 feet <br />Spillway Width 10 feet <br />Spillway Sideslopes 2:1 <br />Riprap D-50=6 inches <br />Riprap Channel Length 20 feet <br />Embankment Height 9 feet <br />Embankment Width 15 feet <br />Embankment Length 180 feet <br />Topsoil Depth 6 inches <br />Vegetative Type Grass <br />