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COLORADO DEPARTMEM OF PUBL[C HEALTH AND ENVIRONMENT, Wafer Quality Comrol Division <br />Rationale. -Page 10, Permit No. CC-0000221 <br />The term MjQt represents the Total Maximum Daily Load (TMDL) of a, pollutant that can be carried ~yy the <br />receiving stream withatt violating the stream standards. The term MtQI represents the pollutant load that alr~ <br />exists inrtream above t,4e discharge point in question. The difference between the two loads, which it M3Qj - MtQ/ <br />represents the loading that can be allocated to the discharge. <br />Jt may be appropriate in certain situations to perform a more detailed analysis that would identify, quaruify and <br />develop comrol strategies for additional individual po[httant sources that might exist above and below the <br />perminee's discharge points. /n this case, it was determined [hat limitations for these two discharge lroints can be <br />calculated independemly from arty other pollutant source. However, the two outfalls are considered as one combined <br />source for this purpose. <br />This rationale and accompanying permit serve as a Total Maximum Daily Load (TMDL) under Section 303(d) of the <br />Clean Water Act, and this TMDL will be submitted to the US EPA Region VI/I for review and approval. For this <br />jaci[iry, total recoverable iron is the only parameter of concern. Values for effluent Jlow are shown in Table VI-8 in <br />section V7.3.d)4) and law flaws (30E3) are shown in Table 117-2. In this case, because the upstream 1~ackground <br />concemration is significantly greater than the stream standard, the result is a negative number. The c!efault is the <br />stream standard, which becomes the effluent limitation. <br />Table V[-6 -Summary of TMDL Based Mast Balance Calcalattonr <br />Upstream WQS/TMDL-Based . <br />Ambient Mean Stream Standmd,. Effluent;Concentryrlion, <br />Period Con_tentration Chronic Chronic.: <br />(MI) (M3) (M2) <br />Because of the mathematical relationship between Jlow, pollutant concemration and pollutant mass, concentrat' <br />[imitations calculated using this method implicitly limit insrream polluraru mars to the maximum allowcble level. <br />Also, only flow and concentration limitations need to be specified in she permit. Mass limitmions are not required. <br />3. Discussion of Effluent Limitations: The basis jot the effluent limitations for TSS, pH and oil & grease is unchanged <br />from the presdous permit. Please see previous rationale jot the discussion. <br />a) Rerularions for Effluent Limitations: The Regulations jot Effluent Limitations (10.1.0), apply to the' conventional <br />poiiutams. For this jnciliry the limitations for Oi! and Grease are based on this regulation. <br />- 6) Aoolicable Federal EfRuem Guidelines and Standards: The federal guidelines which apply to this r,pe of facility <br />are found under 40 C'FR 434, titled Coal Mininz Point Source Effluent Guidelines. The limitations which apply <br />area <br />Table VI-7 -Federal Standards (40 CFR 434) <br />Parameter Limitations <br />30 Day Avg Daily Max. <br />pH, s. u. (minimum -maximum) ---ti.0 - 9.0--- <br />Toral Suspended Solids, mg/P* 35 70 <br />Total /rmt, mg/i* <br />BAT** 3.5 7.0 <br />NSPS*** 3.0 6.0 <br />Settleable Solids, mP/P* N/A 0.5 <br /> <br />• Thesr paramnrrs subie[r ro Burden of Proof Rrquiremrnts, rrr nm section <br />8esr A~ailablr Trchnotogy -app Les to rhosr ponds abeadv consrrutted <br />•'• New Sourer Performance Standards - appli[s to those ponds conrrrutted afrer S/1/84 <br />