2025-06-23_REVISION - M1980244 (99)

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• SSR MINING 8 SURFACE WATER CONTROL AND CONTAINMENT INFORMATION Stormwater for the Cresson Project is managed under the Stormwater Management Plan (SWMP), which is reviewed and updated annually. The SWMP details mining activities, effluent limitation guidelines, stormwater management controls, identification of potential pollutant sources, best management practices, schedules and procedures, and comprehensive inspection requirements. As designated by this plan, all stormwater management features are inspected on a quarterly basis and following significant precipitation events. The SWMP is provided in Appendix 3. In 2018, an evaluation of the SWMP and stormwater control features was completed by Knight Piesold Consulting, as approved under TR-101. Outcomes of this evaluation included: • Updated design event precipitation values (National Oceanic and Atmospheric Administration (NOAA) 2013 Atlas 14, Volume 8). • Updated curve number assignments per the Natural Resources Conservation Service (NRCS) SCS curve number runoff method. • Recommended improvement of some stormwater management features to comply • with updated curve numbers and design events. Improvements for several features will be completed in 2019 and the SWMP will be updated to reflect these changes. Enhanced management practice (EMP) ponds have been configured to be less than 10 feet in height when measured from the existing grade at the downstream toe to the spillway, and excavated an additional five feet below grade to provide the optimum depth of 15 feet. Embankments of less than 10 feet in height are not regulated by the Division of Water Resources, Office of the State Engineer under the Dam Safety Regulations. 8.1 Surface Water Quality Data Regionally, surface water flows from the Cresson Project area are tributary to the Upper Arkansas River basin. Surface water flows into Grassy Valley, a tributary to Beaver Creek on the north side. Surface water flows into Theresa Gulch and Bateman Creek, both tributaries to Wilson Creek, which flows into Fourmile Creek on the south. The drainages flowing west are Poverty Gulch, Maize Gulch, and Arequa Gulch, from north to south. These streams are all tributaries to Cripple Creek, which also flows into Fourmile Creek. A discussion of surface water quality is provided in Exhibit G and supporting data is provided in Appendix 6. These data include at least five successive calendar quarters. Figure G-2 in Exhibit G shows the surface water rights for a two- mile radius around the Affected Lands boundary.• Cripple Creek&Victor Gold Mining Company Exhibit U Cresson Project Amendment 14 13