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Mountain Coal and Beaz Coal Water Quality Assessment CO-0038776 and CO-0044377 It is the standazd approach of the WQCD to perform amass-balance check to determine if fecal coliform standards aze exceeded. WQCD procedure specifies that checks are conducted using only the chronic low flow as set out in Section III. Using the mass-balance equation provided in the beginning of Section IV, the background concentration contained in Section II, and the in-stream standazds for fecal coliform shown in Section II, checks for fecal coliform were conducted. The effluent flow, Q2, reflects the design flow from Outfal] 004 and Internal Outfa11007 in the respective calculations. The data used and the resulting calculations of the allowable dischazge concentration, M2, aze set forth below. Nnrth Fnrknfthe runni.cnn River -'-'--- -~-- --- --- Parameter -----~----- Q I (cfs) Q 1 (cfs) Q j (cfs) MI (#/100 ml) M#/100 3 ( ml) M#/100 1 ( ml) Fecal Coliform 43 0.28 43.28 4 200 30,300 Outfa11007 Parameter Qt (cfs) Q1 (cfs) Q3 (cfs) MI (#/100 ml) M3 (#/100 ml) M2 (#/100 ml) Fecal Coliform 43 0.016 43.016 4 200 526,950 Metals: Metals may occur naturally in rock. azound eoalseams. Earth disturbances, such as mining operations, expose rock to air and water creating a potential for these elements to be present in elevated concentrations. Thus, arsenic, cadmium, copper, chromium, iron, lead, manganese, mercury, nickel, selenium, silver and zinc, which have been identified as pollutants potentially present in mine water discharges, are evaluated in this assessment. According to the Agency for Toxic Substances and Disease Registry, chromium in the trivalent form occurs naturally in the environment whereas hexavalent chromium is produced by industrial processes. Industrial processes at this facility would not generate hexavalent chromium and therefore the evaluation for chromium is limited to the trivalent form. Using the mass-balance equation provided in the beginning of Section N, the low flows provided in Section III, the background concentrations contained in Section II, and the in-stream standazds for metals shown in Section II, assimilative capacities were calculated. 'The effluent flow, Q2, reflects the combined design flow of 0.28 cfs resulting from Mountain Coal W WTFs Outfalls 004 and 016 and Beaz Coal WWTF Outfa11001, thereby resulting in the calculation of an allowable dischazge concentration, M2, applicable to all three outfalls. The data used and the resulting calculations ofthe allowable dischazge concentrations, M2, are set forth in Table A-9 for chronic assimilative capacities and in Table A-10 for acute assimilative capacities. Appendix A Page 15 of 20 Last Revised 3/9/2004