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TSS concentrations of streams should not increase because flows from disturbed and reclaimed areas will be treated <br />in sedimentation ponds to meet NPDES effluent limits. The effects of leaching in exposed spoil and waste rock <br />plies, detention of water in sedimentation ponds, and pumping water out of pits and underground mine workings <br />have the potential to increase TDS concentrations and change ionic composition of surface waters. <br />The planned underground mining activities have the potential of creating changes in the existing surface water <br />quantity in terms of runoff flows and flow rates including changes in peak flows and low flow conditions. <br />Likewise, the planned underground mining activities have the potential of producing changes in the existing surface <br />water quality in terms of conductivity, total dissolved solids (TDS), total suspended solids (TSS), ionic <br />composition, sodium adsorption ratio (SAR), pH, and trace metals with iron and manganese, the primary indicators. <br />Water quality impacts will be addressed for all seasonal conditions including both high and low flow conditions. <br />The underground mining and related activities that have the potential of impacting surface water flows and water <br />quality are described below along with an assessment of the nature and magnitude of potential impact. The primary <br />surface water impact will result from the discharge to Foidel Creek and Fish Creek of mine inflows that are <br />collected in sumps and pumped to sedimentation ponds and settling ponds for treatment prior to release or <br />discharged directly to these drainages <br />Impacts of Direct Disturbance of Surface Flow Channels <br />Direct disturbance of surface flow channels may occur either when temporary construction activities require a <br />stream crossing for installation of pipelines or other utilities, or for long-term road or railroad crossings. In both <br />cases, normal streamflows will not be interrupted and any stream channel disturbance will be mitigated through <br />reconstruction of the natural stream channel and floodplain configuration. <br />Normally, any disturbance in stream channel areas will occur during low-flow periods to minimize disruption of <br />flow. If flow characteristics of the affected channel are ephemeral or intermittent, it may be possible to complete <br />work in the stream channel when there is little or no flow. If any significant flow is occurring during the <br />construction period, flows will be temporarily diverted around the disturbance area during construction using a <br />pump(s) and pipeline. Normal flow will be restored, once construction is completed and the affected channel areas <br />restored. <br />For temporary construction disturbance, the effective disturbance area will be minimized to the extent reasonably <br />feasible, and the affected stream channel, banks, and any affected floodplain areas will be restored to their original <br />configuration through backfilling, compaction, grading, and placement of armoring (as appropriate). Disturbance <br />areas will be reseeded with TCC's standard riparian seed mix. <br />For long-term road or railroad crossings, culverts or other appropriate designed flow structures will be installed to <br />safely pass the design flows in compliance with applicable provisions of Rule 4.03, and inlets will be armored to <br />protect against erosion. If the road/railroad is approved as a permanent postmining feature, the associated drainage <br />structures will remain in place. If the road/railroad crossing is to be removed as a part of mine reclamation, the <br />affected stream channel, banks, and floodplain areas will be restored at that time, as previously described. <br />Impacts of Mine Water Discharge <br />The relatively continuous discharge of anticipated mine water to Foidel Creek constitutes a significant proportion of <br />total streamflow during low flow periods. This will result in perennial flow in Foidel Creek, while the mine is <br />discharging to Foidel Creek. When the Fish Creek dewatering site is operating it can represent a significant portion <br />of the Fish Creek flow. Runoff flows in Foidel Creek should increase during the period when the mine is <br />discharging. Projected mine inflows through the life of the mine have been re-estimated based on current data and <br />are discussed in the Ground Water PHC section, Ground Water Inflow to the Mine. The maximum discharge to <br />Foidel Creek from Pond D and the IORT Boreholes is expected to be approximately 1,000 gpm on a temporary <br />basis, and approximately 400-600 gpm on an annual basis. Maximum discharge from the Fish Creek Boreholes and <br />Site 115 will range up to 1,200 gpm, however, average annual discharges will range from 55 to 300 gpm. <br />MR08-230 2.05-151 09/05/08 <br />