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Cross Gold Mine <br />December 2024 G-3 <br /> <br /> <br /> Comstock Area <br />The disturbance area around the Comstock shaft and structures will be contained by stormwater control <br />berms to prevent sediment discharge. Map G-1 shows the drainage areas, and the Exhibit C maps <br />show stormwater control berm locations. An uphill diversion structure will also be used to reroute offsite <br />water flows around the disturbed area. Designs and hydrology for this diversion structure can be found <br />in Appendix G-1. Prior to any mining of the pre-law waste piles in this area, a stormwater control plan <br />will be designed and provided to CDRMS in a technical revision. Currently the Comstock Area is used <br />only for storage. <br /> Stormwater Discharge Permit <br />The Cross Gold Mine discharges stormwater under Permit #COR 040242. The mine submits annual <br />reports on our Surface Water Management program (SWMP). As required by regulation, the current <br />SWMP containing sediment and erosion BMPs, are maintained on site for use and inspection. <br />Appropriate BMP storm water controls will be implemented during the proposed construction and <br />reclamation activities. The BMPs include the stormwater control measures described in this exhibit. <br />Copies of the stormwater management plan can be provided to CDRMS on request. <br />2. Groundwater Resources <br />Groundwater at the site is controlled by drainage out of the existing mine adits which report to ponds <br />and then discharge to Coon Track Creek through a permitted discharge point. The improved water <br />handling system will eliminate the need for ponds that can freeze during the winter and will maintain the <br />discharges to Coon Track Creek. Groundwater wells within two miles of the site are shown on Map C- <br />1A. These wells are clustered around the west side of the Town of Nederland and the Eldora Ski <br />Resort. The geology and groundwater hydrology in and around the mining complex can be seen on <br />Map C-1B. <br />Waste rock analyses previously performed, and part of the Division's existing permit file indicate the <br />host rock and ore are non-acid generating. Ground water pH based on three quarters of analysis has <br />been between pH 6.4 and 7.6 in the three-baseline ground water monitoring wells: Cross Well, Cabin <br />Well, and Caribou Well. Groundwater data can be found in Exhibit U. <br /> <br />The groundwater beneath and adjacent to the Cross Mine is present in a single aquifer, the Mountain <br />Crystalline Bedrock Aquifer as mapped in the ON-010 Colorado Groundwater Atlas (Barkmann et al., <br />2020). Unlike sedimentary rock aquifers, igneous and metamorphic crystalline rock aquifers have little <br />primary porosity; water is stored in fractures and underground mine excavations like stopes and <br />workings. Frequently, old mine workings have not been mapped. Groundwater flow proximal to and <br />within the compliance boundaries is within the Idaho Springs Gneiss and the Caribou Monzonite Stock <br />geologic units. Within the subalpine and alpine basins of the facility area ground water use is restricted <br />to private wells that intercept fracture sets (Flynn, 2003, Bruce and O’Riley, 1997). Other than the <br />onsite wells there are no state-permitted wells within one mile of the compliance boundary. The closest