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conduct upstream and downstream water sampling to determine acceptable discharge <br />rates to maintain the sulfate levels below the 250 mg/1 in-stream standard. This standard <br />applies year round to this reach due to drinking water usage. Modeling indicates <br />conductivity (964 umhos/cm and SAR 2.4 highest modeled) should not be a problem. <br />Yampa River - Below Trout Creek - Increases in both TDS and sulfate will occur in the <br />Yampa River due to mine water discharges. The applicant predicts an increase in both <br />dissolved solids and sulfate of approximately 9% over ambient levels. This increase <br />would not affect any current uses or exceed the in-stream standards. <br />Detention of surface water runoff in sedimentation ponds and related evaporation loss <br />Treatment of disturbed area runoff will cause a decrease in peak flows in the Fish Creek and <br />Foidel Creek watersheds. However, any decrease due to retention in sedimentation ponds <br />will be more than offset by increased water downstream due to mine water discharge from <br />the underground workings. Increased levels of suspended solids will be minimized due to <br />sedimentation ponds and NPDES effluent limitations established for each point-source <br />discharge from the mining operation. <br />Diversion of overland flow with ditches <br />Diversions will deprive small areas of water but will not significantly reduce flows <br />downstream. <br />Induced recharge or discharge by underground mine dewatering <br />Mine dewatering can cause changes in the natural process of stream discharge and recharge. <br />Mine dewatering and gradient reversal may cause small decreases in Fish Creek and Foidel <br />Creek stream flows in and around the mined area. Increased or modified recharge is also <br />possible due to subsidence. Due to the small areal extent and the shale aquitards between <br />the Wadge coal and the streams, increased recharge would likely not be significant. <br />Subsidence impacts on Foidel Creek, Middle Creek, and Fish Creek <br />Subsidence of portions of Foidel Creek, Middle Creek, and Fish Creek will cause gradient <br />changes in these streams. These gradient changes will result in ponding and channel <br />incision controlled by the streams' relationship to orientation of longwall panels and <br />gateroads. Subsidence cracks in the near surface also have the potential to disrupt the <br />streamflow. Based on the presence of fine-grained alluvial material, any disruption of <br />stream flows would be temporary. Site-specific experience from Foidel Creek resulted in a <br />complete loss of streamflow for approximately 24 hours followed by recovery over the <br />subsequent months. <br />See section B, part III B of this document for more information concerning the surface and <br />ground water monitoring plan. <br />The Division has evaluated each of these impacts and finds that the operations proposed <br />Foidel Creek Mine 22 June 4, 2010