2008-12-04_PERMIT FILE - C1994082

• Permit No: C1994082
• IBM Index Class Name: Permit File
• Doc Date: 12/4/2008
• Doc Name: Part I Pond 010 Postmine Storage Capacity Addendum ‎(TR37)‎
• Section_Exhibit Name: Tab 13 Attachment 13-3A.1
• Media Type: D
• Archive: No

• 10-year, 24-hour event: 1.7 inches
• 25-year, 24-hour event: 2.1 inches
• 100-year, 24-hour event: 2.5 inches
Sedimentology• To determine the sediment loading to the pond, the average
annual "R" method was used. The amount of sediment storage is determined for
a defined length of time and is based on the design storm R, design storm
sediment load, average annual R, and the number of storage years (Y) . R is
the rainfall erosivity factor. The equation for required sediment storage
is.
Required Storage = (Annual R)(# years)(Storm Sediment Load)
Storm R
The TR-37 SEDCAD4 demonstration used the same annual R value (10) as was used
in the TR-30 P.s-Built Report demonstrations. The R value was obtained from.
Figure 8A.1, Isolines of R factor for Western U.S., which was taken from
Design Hydrology and Sedimentology for Sma11 Catchments (Haar., et. al.,
1993).
A sensitivity analysis wars conducted varying the number of storage years (Y)
to maximize sediment storage capacity and maintain compliance with the
applicable rules and regulations. The number of storage years (Y) was
increased in the Sedimentology sub-routine until the effluent settleable
solids concentration in Pond 010 discharge exceeded the water quality
criterion (0.5 milliliters per liter [ml/1]), or the model indicated there
was between 0.5 and one (1) foot of storage room in the pond (the elevation
difference between calcul;sted top of sediment storage and principal spillway
invert elevation), as recommended by Warner et a1 (1998). The SEDCAD4 model
results present the maximum sediment storage while retaining capacity to
store the design storm runoff and maintain compliance with applicable rules
and regulations.
Reclaimed Condition Storage CapacitV• Results of the TR-37 SEDCAD4
demonstration show the storm runoff volume for the entire watershed from the
10-year, 24-hour event to be i.9 acre-feet (ac-ft). The following summarizes
Pond 010 storage capacity for the TR-37 10-year, 24-hour event SEDCAD4
demonstration.
Principal spillway invert elevation (ft msl) _
Total pond storage capacity (at principal spillway elev.) _
Storm predicted effluent peak settleable concentration =
Predicted annual sedimf=_nt loading =
Predicted sediment storage capacity =
Predicted maximum sediment storage elevation (ft msl) _
Number of storage years (Y) _
6,784.0 ft
9.4 ac-ft
0.0 ml/1
0.01 ac-ft
2.2 ac-ft
6,783.1 ft
>200 years
TR-37 13-3A.1-3 Revised 02/08