2018-04-27_REVISION - M1980244 - Laserfiche WebLink

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Knight Piesold CONSULTING Environmental Department, Meg Burt, Senior Manager April 27, 2018 Cripple Creek and Victor Gold Mining Co. (Newmont) 4.3 Civil Design The designs presented on Drawings 000 through 215 were completed to an FS-level and are not for construction. The pertinent design data are presented on the drawings themselves via tables and notes. The existing impoundment is denoted as EMP-22 on the design drawings. The new second impoundment, located downstream of EMP-22 and denoted as EMP-22b, has been designed to be constructed entirely in cut with side slopes of 2.OH:1.OV. Plan and profile views of EMP-22/22b are presented on Drawing 200. The new spillway connecting EMP-22 to EMP-22b is also designed to be constructed entirely in cut. The spillway is to be constructed and lined with riprap and nonwoven geotextile to the bottom of EMP-22b to prevent erosion in the spillway and on the impoundment slopes. Plan and profile views of the upstream spillway, along with a design cross section is presented on Drawing 210. The new spillway connecting EMP-22b to the downstream environment, designed entirely in cut, will be located at the northwest corner of the EMP-22b impoundment. The spillway will discharge into an existing channel that serves as a bypass to reduce the contributing area to EMP-22. The entirety of the spillway is to be lined with riprap and nonwoven geotextile. The plan, profile, and design cross section are presented on Drawing 215. 5.0 CLOSING REMARKS This document presents Knight Piesold's final SWMP evaluation findings and the required design upgrades to EMP 22. By way of summary, Knight Piesold will develop and provide CC&V the following additional FS-level design upgrades, per Table 3.1: • Diversion channels: — DC-EMP8a(new-capacity and riprap) — DC-EMP8b(riprap,which may affect capacity) — DC-EMP13(riprap,which may affect capacity) — DC-EMP16(capacity) — DC-EMP17a (absent - riprap, which may affect capacity), which will also serve as the spillway for EMP 16 — DC-EMP18N (absent-riprap,which may affect capacity) — DC-EMP18W(capacity and riprap) — DC-EMP20N (absent-riprap,which may affect capacity) — DC-EMP20S (capacity and riprap) • Spillways: — EMP 6(outlet channel [i.e., chute]capacity and riprap),two spillways in series required — EMP 8a(absent-inlet weir, chute capacity, and riprap) — EMP 8b(inlet weir and chute capacity) — EMP 9a-d (absent-inlet weirs,chute capacities, and riprap), four spillways in series required — EMP 13(absent-inlet weir, chute capacity, and riprap),two spillways in series required — EMP 16(chute riprap, which may affect capacity),which will be DC-EMP17a — EMP 17(absent-inlet weir, chute capacity, and riprap) — EMP 17a(chute capacity and riprap) — EMP 17b(chute capacity) — EMP 18(absent-inlet weir, chute capacity, and riprap) 10