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Knight Piesold Knight Nisold and Co. <br /> C O N S U L T I N G 1999 Broadway, Suite 600 <br /> Denver, Colorado 80202-5706 USA <br /> Telephone: (303)629-8788 <br /> Facsimile: (303)629-8789 <br /> April 27, 2018 <br /> Cripple Creek and Victor Gold Mining Co. (Newmont) KP Project No.: DV101-00408/03 <br /> 100 North 31 Street KP Doc. No.: DV-18-0450 <br /> PO Box 191 <br /> Victor, Colorado 80860 <br /> Attn: Environmental Department, Meg Burt, Senior Manager <br /> Subject: Cripple Creek and Victor Mine <br /> Stormwater Management Plan Evaluation—Review Findings, EMP 22 Design Upgrades <br /> Revision 2 <br /> Dear Meg: <br /> This letter presents the findings of the Stormwater Management Plan (SWMP) infrastructure review <br /> performed by Knight Piesold and Co. (Knight Piesold) for Cripple Creek and Victor Gold Mining Co. <br /> (CC&V), a subsidiary of Newmont Mining Corporation (Newmont). The review was performed based on <br /> observations made during the site visit, information provided by CC&V, and analyses performed by Knight <br /> Piesold. The emphasis of the review was focused on the enhanced management practices (EMPs), or <br /> engineered stormwater management ponds, and the associated spillways and contributing diversion <br /> channels(DC). Specifically, the following aspects of the SWMP infrastructure were evaluated: <br /> • Facility layouts: Locations, alignments, profiles, and cross-section dimensions. <br /> • Design criteria: Stormwater conveyance and storage recurrence interval storm events. <br /> • Hydrologic analyses: Stormwater peak flow rates and volumes. <br /> • Hydraulic analyses:As-built capacities and erosion protection measures. <br /> The analyses performed by Knight Piesold were used to evaluate if the existing SWMP infrastructure <br /> adheres to the design criteria. This evaluation compared the peak flows and runoff volumes estimated by <br /> Knight Piesold (based on the established design criteria)to the as-built hydraulic capacities. Where it was <br /> found that a structure is undersized (i.e., identified design gap), Knight Piesold will provide an updated <br /> feasibility study(FS) level design to CC&V that adheres to the design criteria. <br /> The required design upgrades are currently underway and will be presented to CC&V in a separate <br /> design report. However, this document describes the required design upgrades for EMP 22, also known <br /> as the Chicago Tunnel Site Detention Pond, and includes FS-level design drawings for this structure. This <br /> specific design is included herein because CC&V committed to this work as part of the Permit No. M- <br /> 1980-244 Amendment 11 process with the Colorado Department of Natural Resources Division of <br /> Reclamation, Mining and Safety(DRMS). <br /> 1.0 SITE VISIT <br /> Knight Piesold performed a site visit on February 20, 2018 with CC&V personnel. The visit was hosted by <br /> Katie Dehlin, Justin Bills, and Ron Parratt of CC&V and attended by Bryan Fahl, Rowan Sauer, and <br /> Thomas Jamieson-Lucy of Knight Piesold. It included a kick-off meeting to align both companies' teams <br /> and a tour of the relevant water management structures at the mine. <br /> fArnageme•I syclen re^fief�y <br /> 110 <br /> ISO T1,N71-E"S 585661 <br /> OHSAS i800,-OHS 585663 <br />