PERMFILE66875

• Permit No: C1981016
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Sedimentation Control & Diversion Structure Calculations
• Section_Exhibit Name: APPENDIX XXI to Section XXI.8
• Media Type: D
• Archive: No

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• U.S. STEEL SEDIt1EPJTATION POND
Flow Desion Calculations
1. Determine drainage area (Exhibit _).
Area 4 = 2.78 acres = 35.9°%
Area 4A = 3.33 acres = 43.0%
Area 48 = 0.57 acres = 7.4%
Area 4C = 0.53 acres = 6.8%
Area Highway = 0.54 acres = 7.0%
Total Area = 7.75 acres = 100.1%
2. Determine weighted curve number (Pp2-5,23-SCS)(Ah1C II)
• Area 4 = 35.9% * 89CN = 3195.1
Area 4A = 43.0% * 79CN = 3397.0
Area 46 = 7.4% * 79CN = 584.6
Area 4C = 6.8% * 89CN = 605.2
Area Highway = 7.0% * 98CN = 686.0
8467.9
_> 84.68
_> 85 CN
3. Determine precipitation
l0yr -- 24 hr = 1.6"
25yr -- 24 hr = 1.8"
4. Determine volume of runoff for CN85 (Pp65,SCS)
l0yr -- 24 hr = 0.52 inches ~ 7,75 acres
• = 4.03 acre inch
= 0.34 acre foot