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Twentymile Coal Company Water Quality Assessment 000042161 <br />Because there were no current data from USGS Flow gages immediately upstream of the Twentymile <br />• Coal Company, several USGS gage station were evaluated as part of this assessment. <br />• <br />Table A-3 <br />Site-Specific Water Quality Standards For Fish Creek <br />Based on the Table Value Standards Contained in the Colorado Department of Public Health <br />and Environment Water Quality Control Commission Regulation Nos. 32 through 38 <br />Calculated Using the Following Value for Hardness as CaC03 400 mg/1 <br />Parameter . Calculated ln-Streara Water <br />Quaky S[andard Formula .Used <br />~~ <br />Cadmium, Dissolved Trout 19 ug/1 a l'.1za~ n 055 }3.aze) <br /> Chronic 3.4 ug/1 a f0' e55 ."'° <br />Trivalent Chromium, Acute 5405 ug/1 a o.a1 " e55 7.688 <br />Dissolved Chronic 644 ug/1 e ° 19~" e55 '. <br />Hexavalent Chromium, Acute 16 ug/I Numeric standards provided, formula not applicable <br />Dissolved ChrOn1C 11 Ug/1 Numeric standards provided, formula not applicable <br />Copper, Dissolved Acute 65 ug/1 a o. 4 z " a e55 1.463,) <br /> Chronic 39 ug/1 a o. 4 " , 055 1.465) <br /> <br />Lead, Dissolved <br />Acute <br />899 ug/1 1.616 a ss 2.8 36 <br />e <br /> Chronic 28 ug/I a ''q' 055 .167 <br />Nickel, Dissolved Acute 2653 ug/1 a ~0 ass .73 <br /> Chronic 274 ugJl e ° e== 1.06 <br /> <br />Manganese, Dissolved <br />Acute <br />9034 ug/I . 69 n ass q.q <br />e <br /> Chronic 3105 ug/1 a °34 " ' °:: 4.~esa <br />Selemum, D1SSO1Ved Acute 20 Ug/l Numeric sandards provided, formula not applicable <br /> ChrOn1C 5 Ug/1 Numeric standards provided, formula not applicable <br />Silver, Dissolved Acute 22 ug/I e z " e55 .ZI <br /> Trout 0.81 ug/1 a t. "' lo. <br />Zinc, Dissolved Acute 379 ug/1 e ' q 3 `~' <br /> Chronic 343 ug/1 a C53 <br />To develop representative low flows for Fish Creek for use in the Twentymile Coal Company <br />assimilative capacity evaluation, data from USGS Gage Station 09244100 (Fish Creek neaz Milner, <br />CO) located approximately three miles upstream in Fish Creek were evaluated. Daily flows from the <br />USGS gage in Fish Creek neaz Milner were obtained and the annual 1 E3 and 30E31ow flows were <br />calculated using U.S. Environmental Protection Agency (EPA) DFLOW software. To calculate the <br />low flows upstream of Outfall 001, the watershed area ratio was multiplied by the low flow <br />calculated at the Gage Station 09244100. The output from DFLOW corrected-to Outfall 001 by <br />watershed area ratios provides low flows calculated by month, and these are presented in Table A-5. <br />Note that because data from USGS gage station 09244100 were available from a period of record <br />. (POR) from 1955 through 1972, other USGS gage stations were evaluated to help correlate these <br />older data to current data. Downstream USGS gage station 09239500 (Yampa River Above <br />Appendix A Page 5 of 12 <br />