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ALEcological Resource Consultants, Inc. <br /> 35715 US Hwy.40,Suite D204^'Evergreen,CO^ 80439^ (303)679-4820 <br /> Technical Memorandum <br /> Date: December 21, 2016 <br /> To: Erik Munroe, Newmont <br /> E�PDO L <br /> Cc: Jay Janney-Moore, NewFields THa4;tis <br /> From: Troy Thompson, ERC <br /> 32913 =� <br /> .., <br /> Re: Chicago Tunnel Hydraulic Evaluation �pNAL ' <br /> Adequacy Items 53 and 57 for AM-11 <br /> Introduction <br /> Ecological Resource Consultants, Inc. (ERC) was tasked with evaluating sizing for the inlet channel, <br /> sediment pond and outlet channel at the Chicago Tunnel area of Newmont Mining Corporation's <br /> (Newmont) Cripple Creek&Victor(CC&V) gold mine. Our evaluation considered whether the previously <br /> constructed channels were sized adequately and whether the sediment pond spillway has capacity to <br /> safely pass the 100-year design flow. ERC utilized past SEDCAD analysis by Steffens and Associates, Inc. <br /> (Steffens)as the basis for our assessment. <br /> Hydrology <br /> ERC's assessment was based on the 100-year design storm event, which has a depth of 3.5 inches at this <br /> site (Steffens 2016). For the inlet channel to and the outlet channel from the sediment pond, peak flow <br /> values were provided by Steffens. The 100-year design flow for the inlet channel (Structure#5)was 7.04 <br /> cfs while the design flow for the outlet channel (Structure #4) was 43.26 cfs (Steffens 2016). For the <br /> sediment pond itself(Structure #6), the Steffens evaluation routed the design storm through an empty <br /> pond and determined that there would be no outflows. ERC conservatively assumed that the pond was <br /> full at the start of the event and that the pond didn't provide any reduction in peak flows. We therefore <br /> assumed that the sediment pond spillway would need to be able to safely pass the 100-year flow from <br /> the inlet channel of 7.04 cfs. Locations of Structures#4,#5 and#6 are called out below based on mapping <br /> generated by Steffens. <br />