2011-12-22_REVISION - M1982155 - Laserfiche WebLink

Home Browse Search

Water - General Requirements In the valley floor, beyond the edge of the pit boundaries, small, very subtle drainages that tend to connect with gullies on the side slopes of the valley are evident. As water flows off the top of the land containing the gravel deposits, it encounters the steep valley edge that is composed mostly of highly erodable gravel exposures. When water reaches the more level valley floor, sediment from the steeper slopes above is deposited in small alluvial fans that are mostly covered with a dense growth of vegetation. As these fans develop, the drainages across and between them change, but the entrance to this zone from the steeper slopes above stays fairly constant over time. Although the pit floor will have a subtle rolling topography as described above, discharge from the pit to the Rock Creek valley will still occur. Since the retention of water in the pit is not allowed under Colorado water law without prior approval, it is important to create configurations that keep the water draining without reaching high velocities that can cause rapid erosion. However, only during final reclamation will the mine pit area be graded and stabilized to allow surface drainage off of the permit area. During most of the mining and reclamation period, stormwater from the pit will not flow off of the permit area. At all times, the appropriate stormwater discharge permit will be obtained from the Colorado Department of Public Health and Environment and the associated monitoring and stormwater management plan will be followed for surface water discharges. The discharge from the pit will be intentionally directed into existing drainageways in the valley floor. Thus, the edge of the pit will likely have not only a horizontal blending to produce smooth slope transitions, but it will be vertically variable to match rises and falls in the topography just beyond the pit edge. Initially, silt fence or other sedimentation best management techniques should be installed in all drainages within about 50 feet of the edge of the affected land. Until the vegetation develops on the pit floor there will be a fair amount of sediment discharge from the regraded and seeded pit floor. These best management practices will aid in reducing the amount of sediment that leaves the affected land. No irrigation will be used in establishing the vegetation, so no water rights are required for those purposes. No water storage will occur in the pit. Water - Groundwater Specific Requirements No groundwater is expected to be encountered in the mining and therefore the groundwater in the valley floor should not be affected. Test holes during resource evaluations confirm that the groundwater table will not be encountered during mining. Mining at the Fountain Pit immediately east of the amendment area also confirms that the groundwater table is below the depth of mining. Fountain Pit M -1982 -155 DRMS 112 Permit Amendment Revised in Response to Adequacy Review Comments Page 15