2024-12-19_PERMIT FILE - M2024059 (6)

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sediment, oil, and/or hydraulic fluids from the operational areas. Oil and hydraulic fluids are contained on the site using standard best management practices related to the storage and transfer of such fluids. These include the use of secondary containment around storage and transfer points, spill kits, and employee training on safe handling practices. Sediment is trapped onsite using controls and best management practices related to directing and controlling surface water runoff that enters disturbed areas. Appendix G-1 contains all surface water runoff calculations for the North Hangs Mine. 6.1 . Surface Water Handling — Mining Surface water runoff will be handled the same way throughout North Hangs Mine's mine life: water from all mining disturbance areas will drain into the active mining and processing areas. The mine's drainage basin and drainage directions are shown on Map G-1. The majority of the disturbed area drains into the mining pits. The processing area runoff will drain internally against the stormwater control berm that rings the processing area. A stormwater management plan (SWMP) as part of the CDPHE discharge permit for the operation, will be strictly enforced onsite. This includes the proper maintenance of stormwater controls such as berms, the proper storage of potential pollutants such as diesel fuel, and the proper sampling and documentation of sampling from discharge points. The active pit will drain internally and the processing area will drain internally. Grading of the site to drain internally, along with the buffers of undisturbed ground between each mine pit and the Colorado River will ensure that no sediment laden water flows enter the river. Undisturbed areas will continue to drain in the same manner as prior to mining. Once surface water is collected within the mining pit it will be collected in the pit floor perimeter ditches and be routed to the pit dewatering pump. The pit dewatering pump will then pump into existing drainage swales in undisturbed ground onsite to return to the river. The pit pump will always be located at least two feet below the active mining floor to ensure clean water pumping. Pit pump discharge will be regulated as a National Pollution Discharge Elimination System (NPDES) discharge point under an approved CDPHE discharge permit for sand and gravel mining. Such permits monitor, limit, and enforce potential pollutants in water discharge to ensure downstream water quality is protected. 6.2. Surface Water Handling — Reclamation Following reclamation, drainage patterns will be established that are permanent. These are shown on Map G-1. The post-reclamation drainage patterns will consist of areas of the reclaimed mining pit(s) that drain into the reclaimed ponds, the processing area drainage which will continue to drain internally and against the stormwater control berm, and the undisturbed portions of the site which will drain as they had prior to mining. Dewatering activity will cease following final reclamation. North Hangs G-3 Lewicki&Associates December 2024