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Mountain Coal and Bear 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 Standards Contained in the Colorado Department of Public Health <br />and Environment Water Quality Control Commission Regulation 35 <br />Calculated Using the Following Value for Hardness as CaC03: 400 mg/1 <br /> In-Stream Water <br />Parameter ,Quality Standard: Formula Used <br /> <br />i <br />d Aeute 19 Ug/1 [i.13667-0.041841n(hardness)][e (1.128(In(hardness)}3.6867)] <br />ssolve <br />Cadmium, D ChiOn1C 6.2 ug/1 [1.10167-0.041841n(hazdness)][e (0.7852(In(bardness))-2.715)] <br />Hexavalent Chromlum, Acute 16 llg/1 Numeric standards provided, formula not applicable <br />D1SSO1Ved C11rOn1C 11 llg/1 Numeric standards provided, formula not applicable <br />l Acute $0 ug/1 e(o.9azz(mp,araness)}l.7aos> <br />Copper, Disso <br />ved <br />Chronic <br />29 ug/1 <br />e (o.BSasQn(haraness)}l.7az8> <br /> Acute 4738 ug/1 e(0.3331(In(hardness)}F6.4676) <br />Manganese <br />Chronic <br />2618 ug/I (0.3331(ln(hardness))*5.8743) <br />e <br /> <br />k <br />l <br />i <br />l <br />d ACnte 1$13 Ug/1 e (0.846(ln(hardness))+2.253) <br />e <br />, D <br />sso <br />ve <br />Nic ChrO1llC 168 ug/1 - e (0.846(In(itardness)}M.0554) <br />Selenlum,D1SSO1Ved ACUte 18ug/1 Numeric standards provided, formula not applicable <br />~ <br />i <br />l <br />d n ....~ <br />"`'"`e ~ 7 <br />~2 ug/. r~ (1.72(L~(hardness))-6.52) <br />,_ e . <br />ve <br />Si]ver, D <br />sso ChronlC 3.$ llg/1 e (1.72(in(hardness))-9.06) <br /> <br />i <br />d ACUte 379 ug/1 e(0.6473(In(hardness))+0.8618) <br />Zinc, D <br />ssolve Chrome 382 ng/1 e(0.8473(In(hardness)}+0.8699) <br />Ambient Water Quality <br />The WQCD evah:a±es ambient water quality based or. 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 P/ater Quality Control Commission Regulation No. 3i . Ambient wafer 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 ofthe ambient water qualityofthe <br />North Fork ofthe Gunnison River upstream ofthe Mountain Coal and Bear Coal WWTFs, datawere <br />gathered from USGS water quality station 09132$00 (North Fork of the Gunnison River near <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 discharge. 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 />