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COLORADO DEPARTMENT OF IILAL'f!i <br />Water Qualify Control Uivisinu <br />Rationale - Page 7 <br />Permit No: CO-0033553 <br />APPENDIX 2 <br />GVALUATCON Oh' PERMIT LIhLITS FOR 004 <br />Total Iron: <br />Annual Effluent Concentration = (Q7-10 + Qmf) Cs - (Q7_10) Ca <br />Qmf <br />Where: <br />Q7-10 = the annual 7 day-10 year low flow value which has been <br />determined by the Division: 1.6 cfs <br />Qmf = maximum mine water flow from tfte facility = 0.29 cfs (or 130 <br />gpm) <br />Cs = stream sta~ldard for total iron: 1,0 mg/1 <br />Ca = ambient upstream concentration of total iron, assumed <br />maximum: 0.5 mg/1 <br />Thus, the total iron effluent concentration was determined from the mass <br />balance equation as follows. <br />(1.6 + 0.29) (1..0) - (1.6) (0.5) = 3.76 mg/1 total iron <br />0.29 <br />Thus, the federal limit for total iron for coal mine facilities of 3.5/7.0 <br />mg/1 is appropriate for discharge point 004. <br />LimiCS applicable to discharge point 004 include: <br />Parameter Limitation Basis Monitoring Frequency <br />Total Suspended Solids, mg/1 .35/70 a/ BPT Monthly <br />Total l.ron, mg/1 7.5!7.0 a/ BAT/BPT Monthly <br />pli, s.u. (i. 5; 9.0 b/ WQS Weekly <br />011 and Crease, mg/1 IO.U c/ SES Weekly <br />a/ 3U day average/daily maximum <br />b/ minimum/maxiioum fur any snmp.L~ <br />c/ maxiowm for auy sample <br />