2012-02-28_REVISION - M1980244 ‎(65)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 2/28/2012
• Doc Name: VOL 5, Facility Design, Part 1: Table of Contents & Summary
• From: CC&V
• To: DRMS
• Type & Sequence: AM10
• Email Name: TC1
• Media Type: D
• Archive: No

Storm Frequency - Duration
100 - year /24 -hour Storm
Storm Depth
3.5 inches
SCS Storm Type
II
SCS Weighted Curve No.
See Table 6
Time of Concentration
Basin Dependent: 0.1 hours minimum
Travel Time
Basin Dependent: 0.1 hours minimum
Sub - Watershed Area
Drawings A500 (Phase 1), A510 (Phase 2)
and A610 (Post Closure)
Cripple Creek & Victor Gold Mining Company Squaw Gulch Valley Leach Facility Design
6.0 Surface Water Control
6.1 Site Surface Hydrology
Project No.: 74201125G0
1 September 2011
Surface flows resulting from storm events will be controlled and routed around the VLF
using surface water diversion structures. Surface water flows from portions of the
mine areas and VLF will be routed along the margins of the VLF and into Squaw Gulch
or minor tributaries adjacent to the VLF. The VLF diversion structures will also route
surface water flows from the upgradient SGOSA.
The size and geometry of the surface water control structures are based on
stormwater flows from the 100 - year /24 -hour storm event for both the operational and
post closure VLF configuration.
HEC -HMS software was selected to estimate flow volumes and peak flows throughout
the site. The total catchment area for the ultimate configuration during operations was
divided into three sub - watersheds, while the total catchment area for Phase 1 of the
VLF was divided into five sub - watersheds. Hydrologic parameters for the operational
model (Phase 2, ultimate configuration) are summarized in Table 6 and presented in
Appendix F.2. Operational e sub - watershed areas and diversion channel flow paths
for the models are shown on Drawings A500 and A510 for Phases 1 and 2,
respectively, and on Drawing A610 for post closure.
Mining is a dynamic activity, and the topography within the contributing basins may
change daily. From time to time, it may be necessary for CC &V to re -grade areas,
super - elevate haul roads, and redirect runoff to other areas. These activities will
cause the operational surface water drainage patterns to be different from those
shown on the drawings. The operational sediment detention structures were not
incorporated into the surface water models for sizing the diversion ditches because the
addition of the detention ponds will tend to reduce both the peak discharge and runoff
volumes. Therefore, the diversion channel sizing is considered conservative.
The data listed in the following table provide a summary of the general hydraulic input
parameters used in the HEC -HMS model for derivation of design storm runoff flows:
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