Laserfiche WebLink
Surface water <br />Several possible effects on the surface water system have been identified: <br />Discharse of mine inflow water to surface water draina:es <br />Ivtine water discharged to the surface water system will increase the conductivity, total dissolved solids (TDS), <br />sulfate, and iron concentrations in the streams receiving the discharge. Total suspended solids, SAR, and pH could <br />also increase due [o these discharges. SAR may reach up to 6.2 in Fish Creek and 3.0 in Trout Creek. Sulfate and <br />conductivity impacts are predicted for various segments of the stream system to be affected. TR-32 approved a <br />plan which will allow the mine to discharge considerable volumes of degraded water during high flow (great <br />dilution capacity) and lesser or no discharge during periods of low flow (minimal dilution capacity). <br />Lower Middle Creek -Impacts in this segment will be pronounced due [o relatively small instream flows. <br />There is no sulfate or irrigation standard over [his reach. However, due to standards on Trout Creek <br />immediately below this segment, impacts will be minimized during most times of the year. <br />Lower Fish Creek -The potential for significant impacts to lower Fish Creek, from mine water discharge site <br />115 (Fish Creek dewa[ering facility) downstream to the confluence with Trout Creek, exists. Although no <br />sulfate standard applies over this reach, Fish Creek and adjacent alluvial valley floor areas are held to a 1500 <br />umhos/cm material damage standard for irrigation waters. Modeling indicates that during low flow periods, the <br />instream conductivity limit of 1500 umhos/cm could be exceeded. Therefore, the applicant has committed to <br />maintain its mine water discharge rate from site ] I S at a level which would prevent material damage (<1500 <br />umhos/cm) by measuring upstream flow and quality and computing a discharge rate which would prevent <br />downstream exceedance of the conductivity limit for irrigation waters. The sulfate standard for drinking water <br />of 250 mg/I does not apply over this reach. <br />Lower Trou! Creek- The mine does not affect Trout Creek waters above the confluence with Middle Creek, <br />but the flow rate and quality of Trout Creek is affected by site 109 (Portal area) discharge into Foidel Creek. <br />Foidel Creek flows into Middle Creek upstream of the confluence of Middle Creek and Trout Creek. Modeling <br />submitted during TR-32 review indicates the potential for significant impact over the lower Trout Creek reach <br />due to mine water discharges. Conductivity over this reach should not be a problem, as the highest modeled <br />value was 970 umhoslcm, which would not preclude irrigation usage. The sulfate limit of 250 mg/I over the <br />period of June to 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 Lower Fish Creek. The <br />mine demonstrated that sulfate levels could be accurately determined by the existing relationship with <br />conductivity (sulfate/conductivity=.32). When conductivity at the upstream site (site 301) equals or exceeds <br />740 umhos/cm, discharge from site 109 will cease entirely. <br />Lower Trou! Creek -Below Fish Creek- Flow rate and water quality will be affected by mine water discharge <br />from site 1 I S and site 109 (Portal discharge). Modeling performed by the applicant (TR-32) indicates that <br />during low flow, [he sulfate standard of 250 mg/I could be exceeded due to mine water discharges. The <br />applicant has committed to conduct upstream and downstream water sampling to determine acceptable <br />discharge rates to maintain the sulfate levels below the 250 mg/I in-stream standard. This standard applies year <br />round to this reach due to drinking water useage. Modeling indicates conductivity (964 umhos/cm and SAR <br />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 Yampa River due to <br />mine water discharges. The applicant predicts an increase in both dissolved solids and sulfate of approximately <br />C:\JHB\C82056\PROS\PR05 FINDINGS 62800.doc <br />14 <br />