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The WRL is designed to allow the infiltration of stormwater so that it safely flows out to the North <br /> Fork of Clear Creek as it does currently. No diversion structures will be installed around the <br /> WRL as it is designed to safely pass surface water runoff. At each active lift, water will be <br /> retained behind a stormwater berm to allow infiltration and evaporation. Once a lift is completed <br /> (graded and capped with coarse blasted rock) stormwater will be able to freely flow and infiltrate <br /> down the slope. During mining, CDPHE discharge points will be present at the toes of the WRL <br /> where it drains towards the North Fork of Clear Creek. <br /> The revised Exhibit G contains additional detail and design calculations on this topic. <br /> 55. On Page G-4, the application states "discharge points will be monitored and located as <br /> shown on map G-1". However, the Division was unable to locate any discharge points on <br /> this figure. Please be sure any proposed discharge points are clearly labeled on this <br /> figure. <br /> Please refer to Map G-1 for added discharge locations. <br /> 56. On page G-4, the application states larger rock will be needed at the toe of the <br /> embankment in each of the two main drainages in which the waste rock will be placed. <br /> Please explain the purpose of this proposed(rock) feature and how the rock size was <br /> chosen. Additionally, please provide a schematic plan view and a generalized cross- <br /> section of the toe of each waste rock landform, showing any proposed <br /> structures/features to be constructed in these areas. <br /> The WRL is designed to safely convey water both through it (infiltration) and atop it (runoff). To <br /> this end it is capped with rock of sufficient size to allow safe runoff flow, see Exhibit G maps for <br /> specific design criteria. The sizing of the cap rock is determined by treating the WRL slope as <br /> the bottom of a steep channel with the existing natural slopes of the drainage as the channel <br /> side slope. Rock size is then selected to ensure that the post mine discharge is at an equal or <br /> slower velocity as the pre-mine drainage discharge. This ensures that the discharge will not <br /> increase erosion downstream of the discharge point. Since the channel widens going up the <br /> WRL slope, the minimum size of slope armoring rock decreases. <br /> Cross sections and other details showing the design for the WRL cap and toe rock can be found <br /> in the revised Exhibit G. SEDCAD design reports are also included in Exhibit G. These reports <br /> show the hydraulic calculations used to determine the necessary size of rock that will be placed <br /> as the WRL cap. The rock size determined in SEDCAD will act as a guide for sizing the broken <br /> rock placed as the WRL cap. Treating the WRL slope, particularly at the toe, as an armored <br /> channel provides the operator with a simple construction guidance tool when placing rock <br /> armoring. The placement of vegetation will further enhance the stability of the slope and its <br /> resistance to erosion, <br /> Blasted, broken rock placed at a 1.01-1:1.0V slope without any intentional vegetation planting has <br /> shown to maintain its stability in the various road fills of the Central City Parkway. The WRL will <br /> have a shallower slope, more controlled material placement, and vegetation planting. Given the <br /> general stability of the CCP fill slopes the Applicant is confident in the long-term stability of the <br /> WRL. <br /> 57. The toe of the proposed waste rock landform (in the east drainage) appears to be <br /> located within 300 feet of North Clear Creek. Please describe how the creek will be <br /> December 2021 19 a Lewicki& Associates <br />