2016-11-07_REVISION - M1980244 (2)

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Response 1: Any commitments made are considered commitments by Cripple Creek & Victor Gold Mining Company (CC&VGMC). I I Comment 2: Page 2, Storm water controls. Specific to Comment 41 above, this paragraph states "Newmont will commit to operational maintenance of the check dams in ensuring they function as designed. "Please change%onfirm this is a CC&V commitment Response 2: Please see Response 1. Comment 3: Figure 1. Proposed surface roughening and Note 5. According to the figure and Note 5 (and further explained in Detail C Figure 2), a 100 foot wide strip of the Phase II subgrade upgradient and adjacent to the haul road will be roughened, presumably for assistance in erosion control. As the upgradient slope length is generally between 800 and 1,200 feet, the Division is uncertain as to how effective this roughening will be. Please provide rationale as to why this surface roughening is only to be applied to the last 100 feet above the haul road V-ditch. Response 3: The Phase 2 area has been graded to proposed grades, however the area has been left in rough condition, not smoothed/finished, to promote infiltration and to reduce stormwater runoff velocities. The proposed surface roughening applied upgradient of the v-ditch will provide additional infiltration and reduction of stormwater velocities prior to entering the v-ditch. To assist slowing stormwater velocities on Phase 2, sediment logs are planned to be constructed on the 9850, 9950, 10050, and 10150 foot elevations (Figure 1). Comment 4: Figure 2. Note 3 and Detail B. a. Note 3 indicates the roadside V-ditch is designed to convey the runoff from the 5-year, 24-hour storm. Runoff collected by the roadside ditch is conveyed to the Phase I sediment pond(a.k.a. EMP 008c) which is designed to store two times the 10 year, 24-hour storm runoff volume (ref. Note 6, Figure 1). As such, it would appear more appropriate that the roadside V-ditch have the capacity to convey the 10 year, 24-hour peak flow. Please provide the Division with adequate rationale for designing the roadside ditch with a conveyance capacity less than the 10 year runoff for which the downgradient sediment pond is designed. Response 4a: A 5-year,24-hour storm event=2.2 inches of precipitation while the 10-year,24-hour storm event=2.4 inches of precipitation. The 5-year,24-hour storm water design was choosen for the sizing of the v-ditch to accommodate Newmont's internal haul design criteria and minimize grading and rock basting in the Phase 2 area. Due to the two percent backslope of the haul road back toward the storm water drainage ditch there is additional capacity to convey storm water to the Phase I sediment pond.