2018-10-19_REVISION - M1980244

• Permit No: M1980244
• IBM Index Class Name: Revision
• Doc Date: 10/19/2018
• Doc Name: Adequacy Review Response
• From: CC&V
• To: DRMS
• Type & Sequence: TR101
• Email Name: TC1
• Media Type: D
• Archive: No

Knight Piesold
CONSULTING
Environmental Department, Meg Burt, Senior Manager October 8, 2018
Cripple Creek and Victor Gold Mining Co. (Newmont)
5.0 ECOSA FACILITY TOE BERM DESIGN UPGRADES
This section presents the civil design upgrade that was completed for the ECOSA facility toe berm. The
total impoundment volume was increased to comply with the storage design criterion by increasing the
height of the existing berm in a localized area.
5.1 Hydrologic Analyses
The hydrologic analyses methodologies and associated input parameters that were used are described in
Section 2.3. The results of the analyses to estimate 2x the runoff volume generated from the
10-year/24-hour storm event per the storage design criterion are presented in Table 2.7. The required
storage volume for the ECOSA facility toe berm is approximately 35,800 ft3.
5.2 Civil Design
The modified embankment design is presented on Drawing 220. A localized area approximately 150 feet
long was raised to provide the required storage capacity. The maximum fill height is approximately 4 feet
and has been designed with a top width of 7 feet and side slopes of 1.25H:1.OV. The top width and side
slopes were both estimated based on the existing berm topography and are thus assumed stable. Knight
Piesold recommends the fill material consist of large angular cobbles of competent rock consistent with
the material used to construct the existing toe berm.
6.0 CLOSING REMARKS
This document presents Knight Piesold's final SWMP evaluation findings and the required design
upgrades to EMP 22 and the ECOSA facility toe berm. By way of summary, the following additional
design upgrades/additions are required per facility (reference Table 3.1):
• EMP 6
- Impoundment volume capacity increase via the addition of a second Non jurisdictional Size
Dam downstream of the existing EMP impoundment.
- Existing spillway chute capacity and riprap increases required. In addition, a full spillway design is
required for the second impoundment.
• EMP 8a
- Impoundment volume capacity increase via excavation to increase the footprint area and depth,
and a Non jurisdictional Size Dam.
- Spillway does not currently exist; a single, full spillway design is required.
- An inflow diversion channel does not currently exist but is needed to reduce the contributing area to
EMP 9a-d such that its existing capacity will be sufficient. A full channel design is required.
• EMP 8b
- Existing spillway inlet weir and chute capacity increases required.
- Existing inflow diversion channel riprap increase required.
• EMP 9a-d
- Existing EMP 9a spillway inlet weir capacity and chute capacity and riprap increases required (i.e.,
full redesign).
- Spillways do not currently exist for EMPs 9b-d; full spillway designs are required.
• EMP 13
- Impoundment volume capacity increase via the addition of a second Non jurisdictional Size
Dam downstream of the existing EMP impoundment.
- Spillway does not currently exist; a full spillway design is required. In addition, a full spillway design
is required for the second impoundment.
- Existing inflow diversion channel riprap increase required.
11