2011-11-28_PERMIT FILE - C1992081 ‎(30)‎

• Permit No: C1992081
• IBM Index Class Name: Permit File
• Doc Date: 11/28/2011
• Doc Name: Small Area Exemption SEDCAD Information
• Section_Exhibit Name: Tab 12 Appendix 12-2
• Media Type: D
• Archive: No

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Small Area Exemption Demonstration
Water Pipeline
The following EEDCAD demonstration documents that the Water Pipeline corridor
located in NW/9 of Section 14 and E/2 of Section 15 meets the intention of
Rule 9.05.2(3).
Peak runoff and sediment calculations were estimated using the SEDCAD 4
computer model. The analysis was conducted using the 10-year, 24-hour storm
event (1.7 inches).
Hydrology Inputs
The area calculation is based on a 15 foot wide by 3,000. foot long
disturbance corridor.
The time of concentration inputs were digitized from Exhibit 12-1.
The curve number (CN) value was calculated based on the following conditions.
• Soil Type - Morapos Silty Clay Loam, 5 - 15$ Slope (from Routt County
Soil Survey)
• Hydrologic Soil Group - C (from Routt County Soil Survey)
• Cover Type - Pasture, grassland or range-continuous forage for grazing
• Hydrologic Condition - Good
• CN = 74
Sedimentology Inputs
• K factor: 0.29 (from Rou tt County Soil Survey)
• Average slope: 7.5$
• Average length: 15 £eet
• C: 0.092 (no canopy, 60~ ground cover)
• P: 0.65 (moderate roughness)
Hydrology Results
• Peak discharge:
0.26 cfs
Sedimentology Results
• Peak sediment concentration: 1,174 mg/1
• Peak settleable concentration: 0.46 ml/1
TR-07
12-2.91
Revised 03/06