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RAG Empire Corporation, Eagle Mine Water Quality Assessment CO-0034142 Q3 =Downstream flow (Qt + Qz) M1= In-stream backgound pollutant concentrations M2 =Calculated maximum allowable effluent pollutant concentration M3 =Maximum allowable in-stream pollutant concentration (water quality standazds) For non-conservative parameters and ammonia, the mass-balance equation. is not as applicable and thus other approaches are considered where appropriate. Note that conservative pollutants aze pollutants that are modeled as :if mass is conserved and there is no degradation, whereas non- coriservativepollutants i3egade and sometimes aze created within a receiving stream depending on stream conditions.;. A more detailed discussion .of the technical analysis for these parameters-is provided in the pages that follow. _ -~ • ~. Pollutants of Coacern -. ' . The following parameters were identified by the WQCD as pollutants of concern fortliis facility: • Fecal Coliform - - • Total Residual Chlorine ` • Total Recoverable Iron • Dissolved Zinc. .During assessment ofthe facility, neazby facilities, and receiving stream water.quality, dissolved Iron was also identified as a pollutant of concern. Nearbv Sources ~. An assessment of neazby facilities based on EPA's Permit Compliance System (PCS).database found 17 dischazgers in the Moffat County area. More than one-half of the facilities were discharging to another watershed. Several.facilities conducted construction-related operations (e.g., sand and gave]) and thus had no pollutants of concern in common with Eagle Mine. Other facilities were located more than twenty miles from the Eagle Mine and thus were not considered. `:, , The closest facility is the Williams Fork Mining Co. (COG500062), located. approximately. 4 miles upstream of the confluence of the Yampa River with the Williams Fork River. Tri-State and Trapper Mine are the next two closest facilities. These facilities dischazge to tributaries to the Yampa River, which aze located between 10-1 S miles upstream of the confluence of the Yampa River and the Williams Fork River. There were no facilities identified that discharged upstream in the Williams Fork River. No downstream discharges were identified within 20 stream miles of the Eagle Mine. The nearby dischargers were evaluated to determine their impacts on this WQA. Ultimately, these dischazgers were not found to affect the assimilative capacity calculations for the Williams Fork River neaz the Eagle Mine. Based on available information, tl•,ere~is no indication that non-point sowces were a significant source of pollutants of concern. Thus; non-point sources were not considered in this assessment. Appendix A Page 9 of 13