2025-03-03_PERMIT FILE - M2024056 (2)

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5. Aquifers The only identified aquifer located at the site is the shallow alluvial aquifer of the South Platte River. The depth to this aquifer varies throughout the year but is typically five feet below surface. According to the U.S. Geological Survey's Ground Water Atlas of the United States', the underlying bedrock aquifer is the Laramie Fox Hills Aquifer of the Denver Basin system. The entirety of the Evans Mining Resource operation will take place in the overlaying alluvium above a shale/siltstone layer; the Laramie Fox Hills Aquifer will not be mined. 6. Surface Water The mining operation will impact surface water in the area through the stormwater runoff that enters the site. Map G-1 shows the drainage patterns and how they are affected throughout the life of the mine. The maps include information on the drainage basins currently, during mining, and post reclamation as well as the drainage directions throughout these stages. The primary concern for surface water protection at the site is preventing the discharge of sediment, oil, and/or hydraulic fluids from the operation areas. Oils and hydraulic fluids are stored on site following the standard best management practices. These practices include the use of secondary containment at fluid storage and transfer points, spill kits, and employee training regarding safe handling practices. Sediment is trapped onsite using controls and best management practices by directing and controlling surface water runoff that enters the disturbed areas. More information on sediment and surface water control is provided below. 6.1 . Surface Water Handling One drainage basin collects all stormwater runoff on and around the Evans site. This is shown on the Drainage Map. 6.1.1. Mining During all phases of mining, surface water runoff will drain to the active pit or reclaimed reservoir. Water collected in the active mining pod will be allowed to evaporate or will be discharge via the approved CDPHE outfall once sediment has settled out. 6.1.2. Post Reclamation The drainage patterns during mining will be retained following reclamation of the site. Any surface water runoff will collect in the reclaimed reservoir. There is enough storage capacity above the anticipated reservoir level and the top of the shore to store the 100-year storm events. 6.1.3. Flood Protection Mining will extend to within 150 feet from the South Platte River as shown on the Drainage Map. Due to this proximity to the river, measures will be taken to protect the riverbank from erosion https://pubs.usgs.gov/ha/ha730/ch—c/ Evans Mining Resource G-5 Lewicki&Associates February 2025