PERMFILE131331

• Permit No: C1981014
• IBM Index Class Name: Permit File
• Doc Date: 6/3/2002
• Section_Exhibit Name: Exhibit 19 Attachment 2 SAE Documentation
• Media Type: D
• Archive: No

HYDROLOGIC DOCOtdENTATION
SMALL AREA E7CE~STION
YARD AREA
The following calculations demonstrate the amount of sediment fence, straw
bales or gravel berm surface area required to adequately handle the runoff from
the Yard Area SAE.
Runoff volume and peak discharge calculations were performed utilizing the
SEDCAD 4 computer model consistent with the methodology previously discussed in
this Exhibit. The sediment control structure was designed to handle the peak
discharge from a 10-year, 24-hour storm event.
1 Hydrology Inputs
All hydrology inputs are shown on the SEDCAD 4 computer printouts.
The CN numbers used for the SAE watershed were obtained from Procedures
for Determining Peak Flows in Colorado and Technical Release No. 55
(USDA-SCS, 1980). Based on soil type and vegetation cover, curve numbers
were determined using Table 2-2a and 2-2d, USDA-SCS TR-55, for the
following conditions:
Reclaimed (< 2 years)
Soil Type: B
Ground Cover: <30~, Poor
Cover Type: Herbaceous
CN: 80
2 Hydrology Results
Peak Discharge In
10-year,24-hour event
0.91 cfs
3. Sediment Fence Requirements
Sediment Fence Permissivity:
Required Surface Area
10 gal/min/ft~ or 0.022 cfs/ft~
0.85 cfs / 0.022 cfs/ft~ = 39 ft~
The silt fence should be installed in accordance with the manufactures
recommendations. Design assumes regular inspections and maintenance.
4. Straw Bale Requirements
Straw bale Permissivity:
Required Surface Area:
14 gal/min/ftZ or 0.031 cfs/f tZ
0.90 cfs / 0.031 cfs/ftz = 29 ftZ
5. Gravel Berm
Gravel Berm Permissivity:
270 gal/min/ft~ or 0.60 cfs/ft2
Required Surface Area: 0.91 cfs / 0.60 cfs/ft~ = 1.5 ft~