2010-05-25_REVISION - C1981008 ‎(37)‎

• Permit No: C1981008
• IBM Index Class Name: Revision
• Doc Date: 5/25/2010
• Doc Name: Response 1 Revised Pages Section 2.05.3‎(3)‎ Attachment 2.05.3‎(3)‎-22
• Type & Sequence: PR6
• Media Type: D
• Archive: No

2. Runoff
Return Period:
Rainfall, P:
Runoff, Q:
Runoff Volume
10 -Year
2.00 in
0.3498 in
4.5316 Acre -Ft
The pond volume below the emergency spillway will be comprised of three design needs:
1) 10 year storm inflow of 4.5 acre feet, as described above
2) 3 year sediment delivery of 0.02 acre feet, as based on the calculations shown below.
Therefore, the total design volume below the emergency spillway is 4.5 + 0.02 ac -ft which is
4.52 acre feet. As is shown in the SEDCAD details, the bottom of the emergency spillway is
5616.0', which has a volume of 12.3 acre -ft at this elevation.
Pond Volume Calculation based on Universal Soil Loss Equation (SurvCAD)
Input Data
Landuse Area Rainfall Erod- Length Slope Ls Cf Pf
(ft ^2) Factor ability (ft) N
Pasture 6770530.8 50.0
Runoff = 1.000 inch.
Sediment Density = 175.000
Time = 1.0 years
Drainage Ratio = 0.37
Total Area = 155.430 acres
Gross Erosion = 159.846 tons /yr.
Total Yield = 59.143 tons /yr.
Runoff Volume = 12.953 acre -ft
0.37 2121.0 4.1 1.39 0.04 1.00
Sediment Volume = 0.016 acre -ft (3 -year total)
Total Volume = 12.968 acre -ft
* The Cf factor is determined from the chart on the following page, shown in Design Hydrology
REVISED AUGUST 2009 Attachment 2.05.3(3) -14 -6