2009-02-06_PERMIT FILE - C1980005A

• Permit No: C1980005A
• IBM Index Class Name: Permit File
• Doc Date: 2/6/2009
• Doc Name: Stock Pond Design
• Section_Exhibit Name: Tab 13 Appendix 13-9
• Media Type: D
• Archive: Yes

POND DIMENSTIONS
The dimensions and capacity of permanent stock ponds are shown on the attached stock pond as-built
drawings. As shown, all embankments are less than five (5) feet in height as nwa,urud froiu the
upstream toe of the dam to the invert of the emergency spillway. The combined slope of all the
embankments is less than SH:1 V with no slopes greater than 2H:1 V. All the capacities are less than
two (2) acre-feet. All stock ponds have emergency spillways that consist of a single open channel.
None of them have a principal spillway or dewatering pipe.
SPILLWAY CAPACITIES
The stock ponds were analyzed to determine if the spillways for the permanent stock ponds have the
capacity to safely pass the peak discharge from the 25-year, 24-hour storm event. In addition, rock
riprap requirements were also evaluated.
The peak discharge, spillway capacity and rock riprap requirements were determined using
SEDCAD4. The peak discharge was determined using the same methodologies and assumptions
outlined in the postmine channel SEDCAD demonstrations. A curve number of 71 was used for
this evaluation which represents a hydrologic soil group B with a fair herbaceous cover. All hydrology
inputs and results are shown on the attached SEDCAD4 computer printouts.
To determine spillway capacity, capacity tables were developed based on the existing spillway
dimensions using the pond subroutine in the SEDCAD model. The SEDCAD results are attached.
Using these tables and the peak flow from the 25-year, 24-hour storm event, the depth ul~ 1]uw and
freeboard were determined for each stock pond. The results are shown on the table below.
Rock riprap requirements were determined using either the PADER or OSM method found in the
channel utility subroutine of the SEDCAD model. The results are summarized on the following
table.
STOCK POND SPILLWAY SUMMARY

Pond 25
Year

Flow
(cfs
Width

(ft) Invert
Elev. of

Spillway
ft) Depth
of

Flow
ft Peak
Flow

Elev.
ft
Top of
Embankment
(ft)
Freeboard

(ft)
Ri ra
p p
Dso
(inches)
T-3 14.3 12 7,460.5 0.6 7,461.1 7,464.0 2.9 Ve
T-4 17.4 6 7,096.0 1.1 7,097.1 7,102.1 5.0 12
T-8 13.5 8 7,318.5 0.7 7,319.2 7,321.6 2.4 6
T-16 6.0 10 7,464.6 0.5 7,465. l 7,469.0 3.9 6
T-17 12.5 20 7,135.0 0.4 7,135.4 7,138.0 2.6 9
T-20 6.4 20 7,202.0 0.4 7,202.4 7,204.3 1.9 6
T-26 32.2 18 7,333.3 0.9 7,334.2 7.336.4 __2.2__ _ 9
T-28 24.4 20 7,502.6 0.8 7,503.4 7,505.0 1.6 9
T-29 30.9 18 7,403.8 0.9 7,404.7 7,406.0 1.3 12
T-30 19.0 18 7,674.0 0.7 7,674.7 7,675.8 1.1 9
T-31 8.9 I S 7,818.0 0.8 7,818.8 7,820.3 1.5 6
T-32 7.3 12 7,812.5 0.5 7,813.0 7,814.8 1.8 6
T-33 10.3 17 7,512.0 0.8 7,512.8 7,513.8 1.0 9
TR-46 2 Revised 09/08