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<br />• In the unlikely event that longwall development and initial operations result in large <br />volume aune inflows, Oxbow could utilize the existing seven million gallon sump to the C- <br />Seam, existing inactive mine workings, the mine water storage and treatment pond, and any <br />existing excess storage capacity in the sedimentation ponds for temporary water storage, <br />treatment, and dischazge. <br />63. Pages 2.05-41 and -41a discuss the mitigation of impacts of mining with the additional facilities <br />and refuse pile proposed in this technical revision. There is no mention of any impacts to surface <br />water. OCM should include a discussion of what, ijany, impacts are anticipated, and propose <br />appropriate mitigation measures. <br />Response: Potential surface water impacts associated with the mine expansion activities <br />proposed under TR-29 will be limited to minor increases in surface disturbance area and <br />associated disturbed area runoff, temporary culverting of an additional 650 feet of Elk <br />Creek, drainage modifications in the area of the West Valley Fill, and minor reductions in <br />consumptive water use. <br />Changes in disturbance areas, disturbed area runoff, and drainage configuration are <br />addressed in Appendix B, Protection of Hydrologic Balance. The Elk Creek culvert <br />extension, filling of the lower portion of the West Valley ephemeral drainage, and minor <br />changes in consumptive use are addressed by a U.S. Army Corps of Engineers 404 Permit. <br />On completion of operations, the Elk Creek culvert will be removed, the Elk Creek <br />channel restored, and the associated disturbance areas reclaimed. Section 2.05.6 has been <br />• reviewed and revised co briefly summazize and reference the proposed hydrologic <br />protection/mitigation measures. Please see accompanytng revtstons. <br />64. Map E-3214 also shows ditches and berms which divert flow out of the Elk Creek channel. All <br />ditches and berms must be removed once the disturbed areas no longer contribute sediment in <br />excess of pre-mine levels or that of adjacent undisturbed lands. OCM should clarify that all berm <br />and ditches will be removed <br />Response: The noted temporary ditches and berms are specifically designed as small <br />drainage features to prevent disturbed area runoff from entering Elk Creek until sufficient <br />vegetative establishment occurs to effectively control runoff and erosion. It is anticipated <br />that these drainage features will silt in during [he reclamation liability period, effectively <br />resulting in natural removal and reclamation. In the unlikely event that these features are <br />not eliminated through natural siltation, they will be removed utilizing hand methods or <br />other methods designed to minimize additional disturbance. Section 2.05.4 and Appendix <br />B were reviewed and revised as appropriate to clarify the commitment to remove the <br />temporary ditches and berms. <br />65. It appears, based on a review of Map E8.3286, that the proposed West Valley Fil[ will be <br />downstream of the downstream monitoring site on the North Fork. Please submit a plan for a <br />new downstream monitoring site. <br />Response: Oxbow will establish a new monitoring station NF-3 on the North Fork of the <br />Gunnison River downstream of the West Valley Fill and will add this station to the <br />• hydrologic monitoring network for ongoing mine monitoring. The new monitoring <br />station will be downstream of the Town of Somerset. <br />The possibility exists that leakage from old piping for the Town of Somerset sanitary sewer <br />system may be entering the river and surface runoff from the town may carry other <br />