2016-07-28_REVISION - M1980244 (2)

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• Page 9: Under Item#4 - Overburden moisture content has largely returned to field capacity,the text states"The rapid response to the 2015 spring flooding suggests that much of the overburden in the district has now reached field moisture capacity, and no longer is as effective in attenuating sudden flow events as it was in the prior decade." Considering this statement, do you expect the response time of Carlton Tunnel flow to be more rapid (similar to spring 2015 flooding)and variable moving forward? If so,does the current water treatment facility have the ability to accommodate such flows? RESPONSE: It is expected that the moisture space in the overburden rockmass in the Cripple Creek District is approaching the field capacity for much of the material that was emplaced in the prior mining periods. This refilling of pore space is expected to reduce the attenuation of flow exiting the Carlton Tunnel, creating small surges in the flow, of the kind shown during the 2015 thaw period referenced in the report. The sedimentation ponds at the Carlton Tunnel portal were expanded in 2007, in fulfilment of a settlement agreement between Cripple Creek and Victor Gold Mining Company(CC&V) and the Colorado Department of Public Health and Environment(CDPHE). CDPHE requested a minimum 15% increase in capacity to achieve conformance with standards, but CC&V opted to increase the capacity by 42.5%, thereby creating a substantial factor of safety against future sedimentation failures'. Thus the treatment facility has adequate capacity to treat the flow from the Carlton Tunnel portal during period flow peaks that may occur in the future due to the approach of the overburden rockmass to field capacity. 3.4.2 Water Table • Page 10: At top of page under"The water table illustrates the groundwater flow system", Item#2,the text states"The water level in the eastern overflow apron in the diatreme appears to remain at approximately the original level,which is substantially below the original (and proposed) ground surface, indicating that the hydraulic conductivity is sufficient for vertical flow away from the surface,but only capable of carrying a moderate amount of water into the eruptive centers of the diatreme." Considering this statement, is it safe to assume that all water infiltrating this area (including the ECOSA)will eventually enter the Cell 3 saturated bedrock acid neutralization zone? RESPONSE: Since Amendment 11 was submitted, a substantial amount of work has been performed to support changes to the water rights augmentation plan for the project. This work has demonstrated that in the vicinity of the eastern fringe of the eastern overflow apron of the diatreme, the original and current water table is at or close to the ground surface, as shown on the single hatched area on revised Plate 9 (Rev.1), which is included in Attachment 1. Groundwater that infiltrates in this area emerges in Grassy Valley close to the diatreme/Precambrian interface. The groundwater heads and flow behavior in this area have not changed as a result of any mining-related activity, including installation of the district drainage tunnels, as also shown in Plate 9 (Rev.1). As no proposed Amendment 11 mining activity is located within the diatremal infiltration area which provides flow to Grassy Creek, it follows that water infiltratingfrom areas affected by mining under this amendment will eventually enter the Cell 3 saturated bedrock acid neutralization zone. • Is there potential for impacted water from the northern portion of ECOSA or WHEX to enter the Grassy Valley drainage system? 1 ABC,2007. Carlton Tunnel Pond Capacity and Aeration Engineering Report. Report prepared for Cripple Creek& Victor Gold Mining Company by Adrian Brown Consultants, Inc.,dated October 1,2007 Page 3 of 28