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Cross Gold Mine <br />December 2024 G-2 <br /> <br /> <br /> <br />As with groundwater, surface water quality impacts are not expected. Surface water flows uphill of the <br />mine portals and disturbed area will either pass through the site without contacting disturbance, be <br />rerouted around disturbed areas, or will be collected and passed through stormwater control measures <br />to prevent offsite pollutant discharge. The two principal areas of activity, the Operations Area and the <br />Comstock Area, each have their own stormwater control measures. <br />Mine stormwater control and discharge are covered under CDPHE discharge permit #COR 040242. <br />The mine submits annual reports on our Storm Water Management program (SWMP). As required by <br />regulation, the SWMP containing sediment and erosion Best Management Practices (BMPs), are <br />maintained on site for use and inspection. Appropriate BMP storm water controls will be implemented <br />during the proposed construction and reclamation activities. <br />GIR currently manages one permitted mine water discharge point, which discharges directly into Coon <br />Track Creek under Colorado Department of Public Health and Environment (CDPHE) Water Quality <br />Control Division (WQCD) Colorado Pollutant Discharge Elimination System (CPDES) Permit CO- <br />0032751. Storm water control measures will adhere to SWMP for all construction activities, on-going <br />mining, and final site reclamation operations. This is an underground mining operation, and all mine <br />waters will be treated to meet applicable water quality standards. These measures will ensure the <br />protection of the prevailing hydrological conditions in the area. <br /> Operations Area <br />The Operations Area surface water will be managed with diversion structures, berms, and a sediment <br />pond. Diversion structures will be used to divert water around the mine disturbance area above the <br />Cross Mine and Idaho Tunnel portals. This will reduce the quantity of water that passes through the <br />disturbed area around the portals and reduces the inflow into the portals themselves. The net result will <br />be less mine affected water being managed. The diversion structures are shown on the Exhibit C maps <br />and Map G-1. The hydrologic calculations for all drainage areas can be seen in Appendix G-1. <br />Diversions structure designs can also be found in Appendix G-1. <br />Stormwater control berms will be used in the Operations Area to prevent surface water from storm <br />runoff from departing the Operations Area uncontrolled. These berms will be constructed as shown on <br />Exhibit C maps. A sediment pond will be installed at the toe of the waste rock landform to collect <br />sediment from surface runoff and to control the discharge of surface water from the waste rock <br />landform area. Along the toe of the Cross Mine side of the Operations Area, another stormwater control <br />berm will be used to collect sediment. Given the limited area along the Cross Mine side, the stormwater <br />berm will be able to function as a filter and sediment can accumulate along its inner side while water <br />seeps through without a sump or sediment pond. <br />The limited disturbance area around the Potosi Shaft Area means that a stormwater control berm will <br />be sufficient to control stormwater and prevent sediment discharge. Exhibit C maps show the berm <br />location and Map G-1 shows the drainage basins that drain to the Potosi Shaft area.