2022-07-29_REVISION - M2006084 (3)

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Gravel stockpiles will be next to the crusher and screener throughout the life of the pit. Since the crusher and screener will never be placed in a mining phase containing a wetland footprint, and the phases are all in excess of 9.5 acres, no gravel stockpile will be near or within any wetland footprint. Dozers may also be used to move topsoil or gravel. There will be no blasting as part of this operation. Mining and screening/washing activities are expected to occur at intervals during the year. Mining will proceed in general from east to west through the phases numerically. At any one time, there may be portions of two mining phases active. No stockpiling will take place within the northwest portion of the mine to ensure that the wetland footprints are unaffected. Also, the site manager will have a GPS unit with the delineated wetlands loaded onto it. This will allow the site manager to continuously review the operation and ensure that there is no material place in any wetland footprint. The overburden from Phase 1 will be permanently stored in the staging area, as shown on Map C-2. Topsoil and overburden will be stored in Phases 1-3 during mining. Overburden and excess topsoil from future phases will be used to backfill selected locations within the pit to create a sinuous and pleasing lake edge and wetland shelf once the area is reclaimed. See Map F for details of the final lake configuration. Flood event run-off will be contained within the mining pit allowing the pit to serve as the sediment detention structure. Due to wet conditions, the pit will need to be pumped. The pit dewatering ditches will flow towards the pit low point in the northwest corner. From there it will be pump to a sediment sump on the buffer between the pit and the river. See Map C-2 for details. The in-pit dewatering pump will have a berm surrounding it to detain fines. The sump will allow for all sediments to settle out of the discharged water. The sediment sump will be approximately 90 feet wide and 160 feet long. From the sump, the water will overflow into the White River and the nearby wetlands. An NPDES permit is in place for the operation currently, and it will be updated with new discharge points. Selenium concentration in the discharge water will not be monitored as it is not required for the NPDES permit. Selenium has not been a problem in this part of Colorado. Pumping will take place at a rate of 500 gallons per minute. All of the pit water will be pumped into the White River or wetlands during mining. Wetlands within the disturbance area as seen on Map C-2 will be excavated under the USACOE Tulloch Rule. Therefore, no fill of any kind will be placed within the wetland footprint area at any time. This includes backfill, topsoil, and/or stockpiles. A Gravel Well Permit will be applied for with the Colorado Division of Water Resources. No augmentation plan is needed since this area has under appropriated water available. The mining of the deposit will occur to the limits shown on Map C-2 with slopes no steeper than 2H:1V around the perimeter of the pit. The interior slopes however, may be mined using a 0.5H:1V to near vertical slope on active mining faces. Highwall mining will progress to the final 3H:1 V&6H:1 V slopes. The 6H:1 V slopes will be mined to along the north and west sides of the pit down to 10 feet below the water level. The remainder of the perimeter will be 3H:1 V to 10 feet below the water level. Below this the slopes may be up to 2H:1 V. The 6H:1 V slopes will reduce erosion if the water over tops the buffer, and will facilitate the return of vegetation without topsoil in reclamation. This slope will revegetate as a wetland. Overburden occurs in sufficient quantities on the site to create the wetland shelf as designed. The slopes are expected to be stable, as it is used at similar sites in the area with White River City D-2 ®Lewicki&Associates July 2022