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Mountain Coal and Beaz Coal Water Quality Assessment CO-0038776 and CO-0044377 Table A-10 Acute Assimilative Capacities for Metals Mountain Coal Ontfalls 004 and 016 Bear Coal Outfall 001 As, Trec (ug/1) 32 0.28 32.28 0 50 5,764 1 Cd, Dis (ug/I) 32 0.28 32.28 0 1.8 208 2 Cr+3, Trec (ug/1) 32 0.28 32.28 4.0 50 5,307 1 Cu, Dis (ug/1) 32 0.28 32.28 0 7.3 842 2 Pb, Dis (ug/I) 32 0.28 32.28 0.54 31 3,512 3 Mn, Dis (ug/1) 32 0.28 32.28 4.2 2401 276,321 Ni, Dis (ug/1) 32 0.28 32.28 0 269 31,012 4 Se, Dis (ug/1) 32 0.28 32.28 0 18 2,075 Ag, Dis (ug/1) 32 0.28 32.28 0 0.66 .. 76 4 Zn, Dis (ug/1) 32 0.28 32.28 0 67 7, 724 Note 1: No current or historical ambient back~ound data were available for toW recoverable As or CN3. However, total As and toW Cr data were available and thus were used as the background concentration. Because the low flow for Sylvester Gulch, West Sylvester Gulch, the Dry Fork of Minnesota Creek and Lone Pine Gulch is zero, the assimilative capacities aze equal to in-stream water quality standards, respectively. These values, as shown in Tables A-3 and A-5, aze: • Total Recoverable Arsenic acute = 50 ug/1 • Dissolved Cadmium acute = 19 ug/1 • Dissolved Cadmium chronic = 6.2 ug/1 • Total Recoverable Trivalent Chromium acute = 50 ug/1 • Dissolved Copper acute = 50 ug/1 • Dissolved Copper chronic = 29 ug/1 • Dissolved Iron chronic = 300 ug/1 • Total Recoverable Iron chronic = 1000 ug/1 • Dissolved Manganese acute = 4738 ug/1 • Dissolved Manganese chronic = 2618 ug/1 • Total Mercury chronic = 0.01 ug/1 • Dissolved Nickel acute = 1513 ug/1 • Dissolved Nickel chronic = 168 ug/I • Dissolved Selenium acute = 18 ug/1 • Dissolved Selenium chronic = 10.6 u~l • Dissolved Silver acute = 22 ug/I • Dissolved Silver chronic = 3.5 ug/1 Appendix A Page 17 of 20 Last Revised 3/9/2004