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COLORADO DEPARTMENT OF HEALTH, Water Qunliry Control Division <br />Rationale -Page 9, Permit No. CO-0032638 <br />1Vhere: <br />Qt =Upstream Iow flows from Part (II.B.2 <br />Qt =Average doily effluent flow (nrazimunr reported flow) <br />Qj =Combined downstream flow (Qt + Q~ <br />Mt = Upstream 6ackgrourui pollutant conceruratian from I!/. B.1 (Leto) <br />M1 = Unlntown; Maximum allowable effluent pollutant concentration calculated using mass balance equntiorr <br />M~ =Maximum downstream allowable pollutant concentration (stream standard) <br />Because of the mathematical relationship between )low, pollutant concentration and pollutant mass, concerrration <br />limitations calculated using this method implicitly limit irtstream pollutant mass to the maximum allowable level. <br />Also, only flow and cartcentratian limitations need to be specifred in the permit. Mass limitations are not required. <br />A summary ojthe mass balance calculations are shown and discussed in VLA.3. <br />3. Discussion of Effluent Limitations <br />aJ Reeulations (or EBluent Limitations: The Regulations for Effluent Limitations (10.1.0), apply to the <br />conventional pollutants. For this facility, the limitations for Oil and Grease ore based on this regulation. <br />bJ Apolicnble Federal E/fluerrt Guidelines and Standards: The federal guidelines which apply to this type of facility <br />ore f<tund under 40 CFR 434, titled FfBueru Guidelines For Coa! Mininx Facilities. The limimtions which apply <br />ore shown in the following table. <br />Table VI-4 -- Federal Standards <br />Paiamerer 30:Doy Avg Concentration Deily Max.:.Concenlratiori <br />pH, s. u. (minimum - mcuimumJ ---6.0 - 9.0--- <br />Totnl Suspended Solids, mg/P* 35 <br />Tole! hart, mg/P* 3.5 <br />70 <br />7.0 <br />Settleable Solids, mP/P* N/A 0.5 <br />77rese paranmmrs subject m Burden of Proof Requiremenu, see Wert secfian. <br />Alternate Lirnirmion Burden of Proof Remrirernents: In conformance with 40 CFR 434.63, the permiuee has the <br />burden of proof when seeking reliejfrom fatal suspenuled solids (TSSJ, total iron and/or settleable solids (SSJ <br />limitntiars for surface runoff only. <br />Reliejnmy be granted for each discharge occurrence only when necessary and shall not be granted when dre <br />permirree has contra! over the discharge. The pernittee should endeavor to meet the primary limitntinrrs <br />rrhenerer possible. The pernhtee will need to show that eueedence of the applicable limirntinru was causer! by <br />precipitation and no other source and rhnr the discharge was beymul their control. For ourfnfls 002, 003 cord <br />004, the permirree will need to demonstrate rhnr the erceedence was caused by surface runoff: Because no <br />surface runofjis discharged drrough autjnll006, this reliejis not available to rhnr ou fall. <br />/J Far rnbr(all, to waive 7SS oral torn! iron limitntiotrs, it is necessary to prove that discharge occurred within <br />48 hours after measurable precipitation has stopped. /n addition, to waive settleable solids limitations, it is <br />necessary to prone rhnr discharge occurred within 48 hours after precipitation greater than the 10-yem~, <br />24-hoary event hat stopped. <br />2J Far snowmelr. ro waive TSS and total irors limitations, it is necessary fo prove rhnr discharge occurred <br />wiNvin 48 hours after pond inflow has stopped. In addition, to waive settleable solids limitnrionc, it is <br />necessary to prone that discharge occurred within 48 hours nfier pond inflow volume greater dmn the <br />10-year, 24-hour everu has stopped. <br />Should n precipimrion eveer or snon•nte(r occur, the perniuee shall submit adequate proof iu order for mr <br />exemption ro be c(ninted. Said proof shall 6e submitted ns an attachment to the Discharge Monitoring Report <br />(DA9RJ for the appropriate period. 7Sre Division shot! determine the adequacy of proof. <br />