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Total suspended solids, sodium adsorption ratio (SAR), and pH could also increase due to <br />these discharges. SAR may reach up to 6.2 in Fish Creek and 3.0 in Trout Creek. Sulfate <br />and conductivity impacts are predicted for various segments of the stream system to be <br />affected. TR -32 approved a plan which will allow the mine to discharge considerable <br />volumes of degraded water during high flow (high dilution capacity) and lesser or no <br />discharge during periods of low flow (minimal dilution capacity). <br />Lower Middle Creek — Impacts in the Lower Middle Creek from the confluence with <br />Foidel Creek to the confluence with Trout Creek will be pronounced due to relatively <br />small instream flows. There is no sulfate or irrigation standard over this reach. However, <br />due to standards on Trout Creek immediately below this segment, impacts will be <br />minimized 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 />of Fish Creek with Trout Creek, exists. Although no sulfate standard applies over this <br />reach, Fish Creek and adjacent alluvial valley floor areas are held to a 1500 umhos/cm <br />material damage standard for irrigation waters. Modeling indicates that during low flow <br />periods, the instream conductivity limit of 1500 umhos/cm could be exceeded. <br />Therefore, the applicant has committed to maintain its mine water discharge rate from <br />site 115 at a level which would prevent material damage (<1500 umhos/cm) by <br />measuring upstream flow and quality and computing a discharge rate which would <br />prevent downstream exceedance of the conductivity limit for irrigation waters. The <br />sulfate standard for drinking water of 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 />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/1 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 />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 />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 />Foidel Creek Mine 21 August 10, 2018 <br />