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Lower Trout Creek – The mine does not affect Trout Creek waters above the confluence <br />of Trout Creek with Middle Creek, but the flow rate and quality of Trout Creek is <br />affected by site 109 (portal area) discharge into Foidel Creek. Foidel Creek flows into <br />Middle Creek upstream of the confluence of Middle Creek and Trout Creek. Modeling <br />submitted during the TR-32 review indicates the potential for significant impact over the <br />lower Trout Creek from the confluence with Middle Creek to the confluence with Fish <br />Creek due to mine water discharges. Conductivity over this reach should not be a <br />problem, as the highest modeled value was 970 umhos/cm, which would not preclude <br />irrigation usage. The sulfate limit of 250 mg/l over the period of June to February could <br />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 /> <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 /> <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 /> <br /> Detention of surface water runoff in sedimentation ponds and related evaporation loss <br /> <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 /> <br /> Diversion of overland flow with ditches <br /> <br /> Diversions will deprive small areas of water but will not significantly reduce flows <br />downstream. <br /> <br /> Induced recharge or discharge by underground mine dewatering <br /> <br /> Mine dewatering can cause changes in the natural process of stream discharge and recharge. <br /> <br /> <br />20 <br /> <br /> Foidel Creek MineOctober 8, 2013 <br /> <br />