2011-03-21_PERMIT FILE - C2009087A (2)

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RULE 2 - PERMITS impacts. The waste rock disposal area will be reclaimed as soon as operationally practical after it is • no longer required to support ongoing mining and related operations. The initial step in reclamation of the coal stockpile will involve removal of any remaining stockpiled coal materials and associated structures. Subsequent reclamation activities will involve regrading the disturbance areas to the final post- mining design configuration, replacement of soil and substitute materials, and revegetation. These activities are designed to establish effective surface drainage, stabilize the affected areas, and develop a self- sustaining vegetative community. Generally, ground water inflows to active mine workings are captured and routed to underground sumps which serve as operational water supplies for underground operations. Under normal operations, any accumulations of mine water which exceed the available capacity of underground sumps and cannot be recycled to the mine water system will be pumped to the surface for discharge to sedimentation ponds, which ultimately discharge to Little Grassy Creek through an approved CDPS discharge point. Based on historic data and preliminary estimates of mine inflow volumes and mine water use requirements, it is anticipated that most if not all mine inflows can be either recycled through the operational mine water system or stored underground. Based on available sampling data for groundwater likely to contribute to mine water inflows, any potential mine water discharge is not expected to result in a significant water quality impact, and will actually be of better (lower TDS) water quality than that of the lower Little Grassy Creek / Pond 002, as discussed in the Probable Hydrologic Consequences. Mining and related support activities will require a consistent water supply with adequate capacity • to meet all operational mine water supply requirements. Potable and sanitary water requirements for the mine, as well as mine use requirements, are addressed through a well completed in the Trout Creek Sandstone. Use of the Trout Creek Sandstone as a water supply source has minimal potential to affect surface water or other groundwater aquifers, because the Trout Creek member is hydraulically isolated by low- permeability shales. The PSCM drainage and sediment control network is designed to function as the primary mitigation system to prevent significant impacts on surface water quality. Disturbed area runoff from precipitation events and snowmelt is intercepted and routed through sedimentation ponds with sufficient detention time to provide effective solids settling. Operation of the sedimentation ponds may result in some delay in water discharge to the receiving drainages, potentially altering discharge volume and consequently streamflow downstream from these structures and may show slightly increased concentrations of TDS and other constituents in the runoff retained in the pond due to evaporation. Significant overall increases in TDS and other chemical constituents for the receiving drainages are not expected because runoff volumes from disturbed areas will be limited by upstream diversion of undisturbed drainage, and surface disturbance areas will be of limited size (6.1% of the Little Grassy Creek watershed, as discussed in the Probable Hydrologic Consequences section). PSCM will monitor sedimentation pond discharge under its CDPS permits (Ponds 002, 003, and 004), in order to detect any significant changes in surface water quality. If significant changes are noted, PSCM may, with consultation from CDMG, develop and implement appropriate water treatment • plans. PSCM will adhere to the requirements of the CDPS permit, including monitoring and reporting. Both delays in discharge and potential evaporative effects and related mitigation PSCM Permit App. 2.05 -98 Revision 12/17/09