_PERMIT FILE - C1981008A ‎(13)‎

• Permit No: C1981008A
• IBM Index Class Name: PERMIT FILE
• Doc Name: Sedimentation Pond 004
• Section_Exhibit Name: Tab 13 Attachment D
• Media Type: D
• Archive: Yes

DESIGN ANALYSIS
GENERAL
Sedimentation Pond 004 was evaluated and constructed to meet or exceed the
design and performance requirements of the Colorado Mined Land Reclamation
Division while utilizing as much of the existing structure and topography
as possible. Pond 004 was designed to adhere to the following
specifications:
1. Provide storage for the runoff from the 10-year, 24-hour
storm event without experiencing any discharge through the
emergency spillway (0.19 ac-ft. ) .
2. Provide an emergency spillway capable of passing runoff from
the 25-year, 24-hour storm event (0.25 ac-ft. ) .
3. Provide adequate storage for the sediment generated from the
10-year, 24-hour (MUSLE) storm event (3.1, 10-year, 24-hour
MUSLE storm events or 0.035 ac-ft. ) .
4. Provide a nonclogging dewatering device and principal spillway
that will provide adequate detention time for the 10-year,
24-hour storm event and still allow a method to dewater the
pond to the 100 percent sediment storage level in a reasonable
amount of time.
HYDROLOGY
The hydrology of the watershed was, analyzed by utilizing the SEDIMOT II
computer modeling program. In performing this analysis, the
characteristics of the minesite and reclamation procedures along with
onsite sediment control procedures were considered. Addendums A, B, and
C contain complete listings of the SEDIMOT II inputs and outputs for the
10-year, 25-year, and 100-year design storms, respectively. Table 1 is
a summary of these results.
TABLE 1
Design Hydrology and Sedimentology Summary
Structure 004
DESCRIPTION 10yr-24hr 25yr-24hr 100yr-24hr
Precipitation Depth 1.60-in. 1.80-in. 2.40-in.
Inflow Runoff Volume 0. 19-ac-ft 0.25-ac-ft 0.45-ac-ft
Pond Volume at Peak Stage 0.29-ac-ft 0.34-ac-ft 0.48-ac-ft
Peak Stage 7.07 -ft 7.89-ft 9.42-ft
2