2018-01-31_PERMIT FILE - C2009087A (3)

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RULE 2 - PERMITS structures. Subsequent reclamation activities will involve regrading the disturbance areas to the filial post- ininln`g, 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 \ \atcr iiiflo\\s to active Illllle \vorkillgs are Captured and routed to llllderground sumps \\Inch serve as operational water supplies for unLler( round operations. Under normal operations. ally aCCU111l11ations of Illllle \\atcr \\hlch exceed the avallable capacity Of 1111dCrgrOUnd SuIllps and cannot be recycled to the ]Mille \\ater s }'stern \\111 be plllllped to the SUI'IaCC for discharge to sedimentation ponds. \\h1Ch ultimately discharge to Little Grass\ Creek through all approved CDPS discharge point. Based oil historic data and preliminary estimates of Millie IllflOw \OIL1111cs and mine \\ater use requirements. It is anticipated that most if not all Illllle inflo\\S can be either recycled thr01.1`,T,11 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 Iydrologic Consequences. Mining and related support activities will require a consistent water supply \\nth adequate capacity to meet all operational mine \water supply requirements. Potable and sanitary water reglllrelllellts for the Illllle. as well as Illllle use requirements, are addressed thrOUgh a ,Nell completed 111 the Trout Creek Sandstone. Use of the Trout Creek Sandstone as a \\ater supply source has minimal potential to affect SllrfaCe water or other groundwater aquifers. because the Trout Greek inelllber is hvdraulically isolated by lo\\- permeability shales. The PSCM drainage and sediment control network is designed to function as the primary mitigation systeinl to prevent significant impacts oil surface water quality. Disturbed area runoff from precipitation events and sno\vnlelt 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 streamflo,, 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 considerations are also discussed under Ground Water Protection Measures, as these effects also apply to alluvial aquifers in hydrologic connection with the surface streams. Midterm Review 2.05- y6 Revision 04/2013