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Mountain Coal and Beaz Coal Water Quality Assessment CO-0038776 and CO-0044377 <br />Table A-5 <br />TVS-Based Metals Water Quality Standards for Sylvester Gulch, West Sylvester Gulch, <br />the Dry Fork of Minnesota Creek, and Lone Pine Gulch <br />Based on the Table Value Standazds Contained in the Colorado Department of Public Health <br />and Environment Water Quality Control Commission Re lation 35 <br />Calculated Using the Following Value for Hazdness as CaCO3: 400 mg/1 <br />Parameter In 3'tream Wafer ~ t <br />,; .,_,.,; ~ __ ! ,Quality'Standard •_, Formula Used ; <br />Acute 19 ug/1 [1.13667-0.041841x(l~ardness)][e(1.128(]n(bardness)}3.6867)] <br />Cadmium, Dissolved (o.7asz(In(barane5s>}z.~ls>] <br />Chronic 6.2 ug/1 [l.1016~-o.oalsam(bardne55)][e <br />Hexavalent Chromium, Acute 16 llg/1 Numeric standards provided, formula not applicable <br />Dissolved Chronic 11 ug/1 Numeric standazds provided, formula not applicable <br />Acute 50 ug/1 e (o.sazzpn~,araness>}l.~aos} <br />Copper, Dissolved <br />Chronic 29 ug/1 e(o.ssaspn(baraness>}l.~azs> <br />Acute 4738 ug/1 e(0.3331(]n(hardness)}+b.4676) <br />Manganese <br />Chronic 2618 ug/1 a (0.3331(in(hardness))+s.s7a3> <br />Acute :,1.513 ug/1 a [o.6a6(]n(baniness)}~z.zs3) <br />Nickel, Dissolved <br />Chronic 168 ug/1 a (o.sa6(ln(bardness>}ro.ossa) . <br />Selenium, Dissolved Acute 18 ug/1 Numeric standards provided, formula not applicable <br />Acute 22 ug/1 '/: e (1.7z(lu(hardness)}6sz> <br />Silver, Dissolved (1.7z(ln(nardness>}9.o6> <br />Chronic 3.5 ug/1 e <br />Acute 379 ug/1 e(o.sa~3(m(baraness>)+o.s61s> <br />Zinc, Dissolved <br />Chronic 382 ug/1 e(o.sa~3pn(baranes:)}ro.a699) <br />Ambient Water Quality <br />The WQCD evaluates ambient water quality based on a variety of statistical methods as prescribed in <br />Section 31.8(2)(a)(i) and 31.8(2)(b)(i)(B) of the Colorado Department of Public Health and <br />Environment Water Quality Control Commission Regulation No. 31. Ambient water quality is <br />evaluated in this WQA for use in determining assimilative capacities and in completing <br />antidegradation reviews for pollutants of concern. <br />North Fork of the Gunnison River: To conduct an assessment of the ambient water quality of the <br />North Fork ofthe Gunnison River upstream ofthe Mountain Coal and Beaz Coal W WTFs, datawere <br />gathered from USGS water quality station 09132500 (North Fork of the Gunnison River neaz <br />Somerset, CO) and from the permittee's Upper North Fork station, both located at the same point <br />approximately 1 mile upstream from the nearest dischazge. Data for the USGS station were available <br />for a period of record from October 1996 through August 2001, except for total ammonia and total <br />chromium data, for which recent data were not available. Thus, historical data for a period ofrecord <br />from October 1977 through August 1982 were used. Data from the permittee's Upper North Fork <br />Appendix A Page 8 of 20 Last Revised 3/9/2004 <br />