February 2014
1
113-82323
Sediment Pond Catchment
Area (ac)
10-Year Event
Volume (ac-ft)
1
Sediment Storage
Volume (ac-ft)
2
Total Pond
Volume (ac-ft)
3
Pond 1
104.5
14.5
8.7
23.2
Pond 2
143.8
19.9
12.0
31.9
Pond 3
211.7
29.3
17.6
46.9
Environmental Flows 249.1
32.4
20.8
Pit Dewatering
-
4.4
7.4
PUG Plant Pond
45.1
6.3
3.8
10.1
Notes:
3. Total pond volume represents a neatline volume and does not include the required freeboard.
2. The annual volume of sediment generated was assumed to be equal to one inch of runoff from
the entire catchment area. This corresponds to 3,630 ft
3
/acre.
Table C1: Sediment Pond Sizing Summary
Waste Rock Facility
Pit Pond
65.0
PUG Plant
1. In accordance with the Wyoming Department of Environmental Quality Water Quality Rules and
Regulations, Chapter 11, Section 31, the sediment ponds are sized to accommodate the 10-year 24-
hour runoff event. The design storm event was modeled using the Hydrologic Engineering Center's
HEC-HMS program. Additionally, the ponds must be sized to accommodate the expected sediment
J:\11JOBS\113-82323 Bear Lodge Mine\Surface Water\H&H calculations\Bear Lodge H&H v4.11Rev E.xlsm
