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be exceeded. Therefore, the mine will adjust discharge levels to prevent exceedance <br />during this period in the same way conductivity levels will be regulated on Lower Fish <br />Creek. The mine demonstrated that sulfate levels could be accurately determined by the <br />existing relationship with conductivity (sulfate/conductivity--0.32). When conductivity at <br />the upstream site on Trout Creek (site 301) equals or exceeds 740 umhos/cm, discharge <br />from site 109 will cease entirely. <br />Lower Trout Creek — Below Fish Creek — Flow rate and water quality will be affected by <br />mine water discharge from site 115 and site 109 (Portal discharge). Modeling performed <br />by the applicant (TR -32) indicates that during low flow, the sulfate standard of 250 mg/l <br />could be exceeded due to mine water discharges. The applicant has committed to <br />conduct upstream and downstream water sampling to determine acceptable discharge <br />rates to maintain the sulfate levels below the 250 mg/l 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 />Foidel Creek Mine 23 February 25, 2016 <br />