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S~iar - 2.05.6 <br />Both delays in discharge and potential evaporative effects and related mitigation considerations are <br />• discussed in detail under Ground Water Protection Measures. Significant overall increases in TDS <br />and other chemical constiruents for the recetvutg drainages are not expected because runoff volumes <br />from disturbed areas will be limited by upstream diversion of undisturbed drainage, surface <br />disturbance areas will be of limited size, and reclamation of disturbance azeas will be occurring. OMI <br />will monitor all discharges from sedimentation structures to ensure compliance with ®PS <br />requirements. If problems are noted with TDS or any other discharge constiruent, OMI will initiate <br />measures as appropriate to effectivelycontrol and mitigate the problem <br />Mute disturbance areas will be reclaimed on completion of mining or when they are no longer <br />required to suppon ongoing mining and related operations. Reclamation, reestablishment of <br />vegetative cover, and restoration of effective surface drainage will rtwtitrtvx disturbed area runoff to <br />the sedimentation ponds, limiting the potential effects of surface leaching and evaporation. <br />Restoration of natural drainage and direct discharge to the receiving drainages once the sedimentation <br />ponds are removed at the end of the extended liability period will effectively eliminate any potential <br />surface water impacts related to the sedimentation ponds. <br />Protection of Ground Water Quantity and Quality - OMI has incorporated specific control and <br />mitigation measures in the proposed minting and reclamation plans to effectively prevent or m~nim~~r <br />significant mining related impacts on ground water quantity, quality, and recharge, storage and <br />discharge relationships. Ground water systems will be protected by limiting surface disturbance and <br />mining-related subsidence both of which can alter runoff and infiltration characteristics; conuolling <br />mine drainage and recycling any significant mine inflow volumes in the operational mine water <br />system; handling earth materials, mine drainage, and runoff in a manner that ntutirnizes acidic, toxic, <br />or other harmful infiltrations to groundwater, and managing excavations and other disturbances to <br />prevent or control discharge of pollutants to the ground water system <br />• OMI's mining operations and related activities have the potential to effect ground water quantity <br />through inflows to the mine workings from the water table aquifer which may reduce the amount of <br />water available in portions of the water table aquifer and result in temporary localized depression of <br />the water levels in small overlying perched aquifers; and alteration of surface infiltration <br />characteristics. Muting and related operations tray also affect ground water quality by modifying <br />ground water chemistry, altering pH, and increasing concentrations of TDS and specific chemical <br />corrstituents. Specific activities which may potentially impact ground water quantity and quality <br />include the following: <br />• Mme dewatering <br />• Underground coal removal <br />• Surface placement of coal (stockpiling) and mine development waste <br />• Retention of drainage in sedimentation pond structures <br />Operational measures that will be implemented to mitigate these impacts are discussed in the <br />following sections. <br />In conjunction with mine development activities for the Elk Creek Mine in the D-Seam, OMI will use <br />a series of shallow dewatering wells to create a temporary localized cone of depression in the water <br />table in the immediate vicwty of the mine development entries. The intent of this shoe-term <br />dewatering effort is to dewater both the alluvium/colluvium and the D Coal Seam in the itruntediate <br />vicinity of the proposed development entries so that the materials to be excavated are not saturated <br />and ground water inflows to the excavarion are min;m~~rd. It is anticipated that once constntction of <br />• the development entries, ventilation shafu, and planned underground sump are completed, <br />dewatering in the initial development area can be discontinued and that any subsequent mine water <br />inflows will be handled through the underground sump. Any excess mine water accumulations in <br />either the existing Sanborn Creek Mme sump or the proposed Elk Creek Mute sump will be <br />transferred to the surface and discharged through a ®PS discharge point. <br />PR04 2.05-84 Revised August 2000 <br />