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• SEDIMENT CONTROL - TIPPLE AREA <br />Two ponds are located in the tipple area - the west pond (pond A) to <br />control runoff from the emergency coal storage area and the truck dump, <br />and the east pond (pond B) to control runoff from the conv eyors, <br />crushers, and train loadout area. The ponds and their storage - dis- <br />charge curves are shown in figures 1 - 3. <br />Design criteria are shown below: <br />Area (Acres) <br />Soil Type (Class) <br />Land Use (cn) <br />Flow Length (ft) <br />Elevation Change (ft) <br />Tc <br />o,..,.~ e <br />10.9 acres <br />Routt (c) <br />Dirt Road (87) <br />750 <br />10 <br />0.08 hrs (4.8 min) <br />Pond B <br />30.2 acres <br />Routt (c) <br />Dirt Road (87) <br />2100 <br />45 <br />0.22 hrs (13 min) <br />• Required Pond Capacity <br />10 yr 24 hr runoff (1.8" rainfall) <br />1.8" ranfaill ~ 0.75" runoff <br />0.75 x acres = acre ft capacity <br />-IZ- <br />0.68 acre Ft <br />Peak Flow <br />25 yr 24 hr storm (2.1" rainfall) <br />Use moderate slope, type II storm 18 cfs/in 32 cfs/in <br />2.1" rainfall ~ 0.99" runoff <br />0.99 s cfs/in = peak flow 17.8 cfs <br />12 <br />Ref: Peak Flows in Colorado <br />Soil Conservation Service 1977 <br />1.89 acre Ft <br />31.6 cfs <br />• <br />