PERMFILE137872

• Permit No: C1982055
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: LOADOUTS SMALL AREA EXEMPTIONS
• Media Type: D
• Archive: No

November 1993 Ratan Crcek * Sma!! Area E.remption • 1
• 1.3 Hydrology Results
Peak Discharge
10-year,24-hour event
Lease Area 1 1.6 cfs
Lease Area 2 3.3 cfs
1.4 Ditch and Berm Design
The ditch and berm for Lease Area 2 were designed using Mannings equation for open
channel flow assuming a V-shape channel. The results are summarized as follows:
Berm
Q 3.3 cfs
Berm slope: 0.5
Sideslopes: 2H:1 V
Mannings n: .035
Depth of flow: 1.0 feet
Veloci[y: 1.7 fps
Berm height: 1.3 feet
Freeboard: 0.3 feet
(Note: The berm design is considered conservative as it assumes a two sided v-ditch. In
• reali[y, it is only a on.
Collection Ditch
Q
Channel slope:
Sideslopes:
Mannings n:
Depth of Flow:
Veloci[y:
Total Depth:
Freeboard:
:-sided ditch).
3.3 cfs
0.5
2H:1 V
.035
1.0 feet
1.7 fps
1.3 feet
D.3 feet
1.5 Sediment Fence Requirements
Given the peak discharge and the permissivity of the sediment fence, the amount of sediment
fence surface area required to safely pass the peak discharge from a 10-year, 24-hour event was
determined as follows:
Sedimen[ Fence permissivity: 15 gal/min/ftz or 0.033 cfs/ft= {Manufactures Quote)
Required Surface Area:
Lease Area 1 1.6 cfs/0.033 cfs/ft' = 50 ft'
Lease Area 2 3.3 cfs/0.033 c{s/ft' = 100 ftZ

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