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<br />Sediment Volume <br />Land slopes: The shop area is predominately flat ( 2$ slopes). The <br />topsoil pile has 2:1 side slopes and a flat top. The same erosion rate as <br />found at the explosives storage is used 0.004 Ac. ft. <br />Ac. Ft. <br />For 3 years Vs = (0.004) (3) (20.6) = 0.25 Ac. Ft. <br />Total req'd volume =water + sediment <br />= 1.48 + 0.25 = 1.73 Ac. Ft. <br />• <br />Emergency Spillway: <br />Direct Runoff = 1.11" <br />For 4$ slopes <br />Q 25 Yr = (1.11) (25) = 27.8 cfs <br />1 - 24" 0 cmp is now in place which flows full <br />cfs is needed. Use two additional 24" Q crop's <br />storage capacity. <br />10 cfs. An additional 18 <br />to help maintain maximum <br />Temporary Diversion Ditch Along West Side of County Road 53 <br />This ditch drains 2 acres. One area is the 243 acres in the watershed <br />above the shop and ancillary facilities. The other area is the 190 acres <br />above the county road on the west side. <br />The ditch starts with a cross-sectional area sufficient for the 10 year-24 <br />hour flow from the 243 acre drainage and then increases to handle the <br />peak flow from both drainages. <br />243 acre drainage: <br />CN = 68 Ave. slope 10$ <br />Note: No reduction in area was made for the areas which have their own <br />settling ponds -shop, landfill, and explosives storage. <br />Q 10 Yr = (155) (0.13) (0.86) = 17 cfs <br />190 acre drainage <br />CN = 68 Ave. slope 25$ <br />Q 10 Yr = (130) (0.13) (1.15) = 19 cfs <br />Using Manning's formula with n = 0.035 So = 0.03 <br />Upper Section: <br />Q req'd = 17 cfs <br />Q=21 cfs <br />V = 5.4 Ft.lSec. <br />• <br />Lower Section: <br />Qreq'd=17+19=36 cfs <br />Q = 55 cfs <br />V = 6.9 Ft./Sec. <br />1981 (Year 3) <br />Design of sedimentation pond HG-lA <br />Review caIcuIations prepared by S. Banerjee <br />