PERMFILE113133

• Permit No: C1981014
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 19 APPENDIX C SMALL AREA EXEMPTION HYDROLOGIC DOCUMENTATION
• Media Type: D
• Archive: No

2.0 Run-off Collection Berm Sediment Fence
2.1 Hydroloeic Inputs
All hydrology inputs are shown on the SEDCAD+ computer printouts.
The CN numbers used for the berm watershed were obtained from Procedures for
Determining Peak Flow in Colorado and Technical Released No. 55 (USDA-SCS, ]980).
Based on soil type and vegetation cover, curve numbers were determining using Table 2-
2a and 2-2d, USDA-SCS TR-55, for the following conditions:
Disturbed
Soil Type: B
Ground Cover: <3090. Poor
Cover Type: Wild grasses
CN: 82
2.2 Hydroloey Results
Peak Discharge
10-year, 24-hour event 0.10 cfs
2.3 Berm Design
The berm was designed using Manning's Equation for open channel Flow assuming a V-
shaped channel. The results are summarized as follows:
Channel slope: 1.0 90
Side slopes: 2H: I V
Manning's n: 0.035
Depth of Flow: 0.3 ft
Velocity: I.0 fps
Berm height: 0.6 ft
Freeboard: 0.3
2.4 Sediment Fence Requirements
Sediment Fence Petmissivity
Required Surface Area:
IS gaVmin/fC or 0.033 cfs/ft'
0.10 cfs/0.033 cfs/ft' = 3.1 ft''
2.5 Rock Dam Requirements
Rock Dam Permissivity:
Required Surface Area:
0.069 cfs/fr
0.10 cfs/0.069 cfs/ft'-= I.5 ft'
Discharge through the rock dam was determined using a flow velocity of 0.069 fps. This
. velocity was derived from data obtained from the U.S. Department of the Interiors' Engineering
and Design Manual for Disposal of Excess Spoils.