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Blue Mountain Energy, Tnc. WWTP Water Quality Assessment CO-0038024 chlorine, and ammonia as unique pollutants of concern. The design flow of Outfall 004 is 0.042 MGD (0.065 cfs). The technical analyses that follow include assessments of the assimilative capacities based on the appropriate design capacity for the applicable pollutants o£ concern. More detailed explanations accompany the calculations for the specific pollutants of concern. Nearbv Sources An assessment of nearby facilities based on EPA's Permit Compliance System (PCS) database found 24 dischazgers in the Rio Blanco County azea, including the subject facility. None of the 23 remainingfacilitieshadpollutantsofconcernincommonwithB]ueMountainEnergy,Inc. WWTP. Several facilities were located more than twenty miles from the Blue Mountain Energy, Inc. W WTP and thus were not considered. The neazest dischazgers were: • Town of Rangely WWTP (COG-584044), which discharges to the White River north of town, a distance of approximately 10 miles downstream from the points of confluence between Red Wash and Scullion Gulch with the White River. This facility shazes no pollutants in common other than total residual chlorine, fecal colifonn, and ammonia that the Blue Mountain Energy, Inc. Outfall 004 may dischazge. However, due to the distance and the lazge dilution in the White River, no impact is expected. • Sheli Frontier Oil & Gas, Inc. operates several coalbed methane wells in the general vicinity ofthe subject facility under multiple general permits. None of the discharges are believed to be in the immediate vicinity; none dischazge to Red Wash or Scullion Gulch or their • tributaries. Further, these wells produce no pollutants in common with the subject facility other than iron. Although they produce methane gas from coal seams, the coal is not disturbed in the process of gas extraction. Because of the distance between the subject facility and any of Shell Frontier's dischazges and because of the lazge dilution in the White River, no impact is expected. The ambient water quality background concentrations used in the mass-balance equation account for pollutants of concern contributed by upstream sources [o the White River, and thus it was not necessary to model upstream dischazgers together with the Blue Mountain Energy, Inc. W WTP when determining the available assimilative capacities in the White River. There aze no dischazgers, upstream or downstream, to Red Wash or Scullion Gulch or their tributaries. Due to the distance traveled and the significant dilution of the receiving stream, modeling downstream facilities in conjunction with Blue Mountain Energy, Inc. W WTP was not necessary. Based on available information, there is no indication that non-point sources were a significant source of pollutants of concern. Thus, non-point sources were not considered in this assessment. Chlorine: The mass-balance equation was used to determine the assimilative capacities for chlorine for Outfa11004, which is the only outfall expected to contain total residual chlorine. There are no point sources discharging total residual chlorine within one mile ofthe Blue Mountain Energy, Inc. W WTP. Because chlorine is rapidly oxidized, in-stream levels ofresidual chlorine are detected only for a short distance below a source. Ambient chlorine was therefore assumed to be zero. There are no total residual chlorine standards for segment ] 3a. Thus, the assimilative capacities will be based on the downstream standazds and low flows for segment 12. Additionally, because total • Appendix A Page 11 of 1S