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s• <br />Discharge of mine inflow water to surface water drainages <br />Mine water discharged to the surface system will increase the conductivity, total dissolved <br />solids (TDS), sulfate, and iron concentrations in the streams receiving the discharge. Total <br />suspended solids, SAR, and pH could also increase due to these discharges. SAR may reach <br />up to 6.2 in Fish Creek and 3.0 in Trout Creek. Sulfate and conductivity impacts are <br />predicted for various segments of the stream system to be affected. TR-32 approved a plan <br />which will allow the mine to discharge considerable volumes of degraded water during high <br />flow (high dilution capacity) and lesser or no discharge during periods of low flow (minimal <br />dilution capacity). <br />Lower Middle Creek - Impacts in this segment will be pronounced due to relatively small <br />instream flows. There is no sulfate or irrigation standard over this reach. However, due <br />to standards on Trout Creek immediately below this segment, impacts will be minimized <br />during most times of the year. <br />Lower Fish Creek - The potential for significant impacts to lower Fish Creek, from mine <br />water discharge site 115 (Fish Creek dewatering facility) downstream to the confluence <br />with Trout Creek, exists. Although no sulfate standard applies over this reach, Fish <br />Creek and adjacent alluvial valley floor areas are held to a 1500 umhos/cm material <br />damage standard for irrigation waters. Modeling indicates that during low flow periods, <br />the instream conductivity limit of 1500 umhos/cm could be exceeded. Therefore, the <br />applicant has committed to maintain its mine water discharge rate from site 115 at a level <br />which would prevent material damage (<1500 umhos/cm) by measuring upstream flow <br />and quality and computing a discharge rate which would prevent downstream exceedance <br />of the conductivity limit for irrigation waters. The sulfate standard for drinking water of <br />250 mg/1 does not apply over this reach. <br />Lower Trout Creek - The mine does not affect Trout Creek waters above the confluence <br />with Middle Creek, but the flow rate and quality of Trout Creek is affected by site 109 <br />(Portal area) discharge into Foidel Creek. Foidel Creek flows into Middle Creek <br />upstream of the confluence of Middle Creek and Trout Creek. Modeling submitted <br />during the TR-32 review indicates the potential for significant impact over the lower <br />Trout Creek reach due to mine water discharges. Conductivity over this reach should not <br />be a problem, as the highest modeled value was 970 umhos/cm, which would not <br />preclude irrigation usage. The sulfate limit of 250 mg/1 over the period of June to <br />February could be exceeded. Therefore, the mine will adjust discharge levels to prevent <br />exceedance during this period in the same way conductivity levels will be regulated on <br />Lower Fish Creek. The mine demonstrated that sulfate levels could be accurately <br />determined by the existing relationship with conductivity (sulfate/conductivity--0.32). <br />When conductivity at the upstream site (site 301) equals or exceeds 740 umhos/cm, <br />discharge 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/1 <br />could be exceeded due to mine water discharges. The applicant has committed to <br />Foidel Creek Mine 21 June 4, 2010