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General Minimal Discharge Permit Rationale <br />• Permit No. COG-600000 <br />Pagc II <br />V TERMS AND CONDIITONS OF PERMIT (cou.) <br />B. Water Dualirv Standard Based Effluent Limitations <br />Tonal Residual Chlorite: The mass balance equation is: <br />M= _ <br />MiQr - MiQ~ <br />Qr <br />A7tere: Q, =Chronic low flow (30E3), MGD or Acute low flow IE3, MGD. <br />Qr = 30 day outrage or daily maximum efjlttent flow, MGD. <br />Q, =Combined downstream flow (Q, + Q~. <br />M, = 7RC, Bromine, (mg/P) or Fecal Coliform (#/100 ml) ambient rnstream <br />concentration. <br />M= TRC, Bromine, (mg/P) or Fecal Coliform (#/100 ml) ejf tlttent <br />ltmitafiaR. <br />M3 =Water Quality Standard for 7RC, Bromute, (mg/P) or Fecal Colifatm <br />(#/100 m!). Set rationale Part V.B.1. (IRC), Pan V.D.3. (Bromine), <br />or Pan V.B.2. (FCoG.). <br />• For discharges to waters not classiked as Use Protected (waters subject ro antiderradationl. <br />the chlorine limits, set in the method described above, are set w the maximum level at which <br />further review is not necessary. The ejjluent limitation necessary to ensure compliance with <br />the tnstream level of 0.0054 mg/P (acute), and 0.0042 mg/P (chronic), is determined from the <br />previous mass balance equation using the following numbers for Mr : WQS for TRC, 0.0054 <br />mg/P (ague), 0.0042 mg/P {chronic). <br />lh< TRC limitations have been bared on the following assumption. In order for the discharge <br />to be "considered not to resuk in significant degradation', the amount of assimilative <br />capadry allocated to the disdrarge must be limited through section 3.1.8. (3) (c) (iii) of 'The <br />Basic Standards" (Ref. A). Thin section spectfits that the increased loading consumed, after <br />mixing with the receiving strewn, ttmst be less than !S% of the available increment between <br />the low-flow pollutant concentrations and the relevant standards. Assuming the low flow <br />pollutant concentrations are currently equal to the previous stream standard of 0.003 mg/P, <br />as allowed in the general permit, IS% of the increment between 0.003 mg/[ and the new <br />(aatte) standard of 0.019 mg/P is equal to 0.15 ~ (0.019-0.003) = 0.0024. Therefore, the <br />new acute (daily marimum) permit limitation will be calculated using the mass balance <br />equation wet a maximum allowable ittrtream concentration of 0.003+0.0024 = 0.0054 mg/P. <br />For Nvonic conditions, the corresponding maximum allowable rnsmam concentration is <br />0.0042 mg/P (30-day Average), using the same method of calculation as the acme. <br /> <br />