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COLORADO DEPARTMENT OF HEALTH, Wares Quality Control Division Rationale -Page 17, Permit No. CO-0043tW8 Table VI-S - Fedeml Effluertt Limitations Max. Cadmium, mg/l 0.05 0.10 Copper, mg/l 0.1 S 0.30 Lead, mg/l 0.3 0.6 Mercury, mg/[ O.ODI 0.002 Zinc, mg/l 0.75 LS For 7SS, the federal guidelines supersede State Irmiu, and will therefore be the ones applied to the appropriate discharge points. For the metals listed, in all cases, limits based upon water quality standards are mare stringent than the federat guidelines. Therefore, the water quality based limits will 6e the ones applied. d. Pollurants Limi[ed 6v Water Ouality Standards For pH, cyanide and metals, the limits that are included in the perntit are based upon stream water quality standards. ALso, while ammonia it not expected to be present in significant concentrations in any discharge at the present time, it will eventually be produced during the detoxificatior of the leach heap. Therefore, in future renewals of this permit, it is expected that ammonia limits based upon water quality standards will be applied. In order to insure that this rs not overlooked during the renews( of the permit, the potential need for ammonia limits at a future date will be noted in the effluent limit tables in both the rationale and the permit. The basic premise used throughout this permit is that there is supposed to be "no discharge". The major emphasis of the permit is therefore upon the verbcation of whether or not any discharge actually occurs. Still, in order to provide a bash for comparing analytical results with maximum allowable pollutant levels, and provide a mechanism for controlling any discharges should they occur, effluent limits have been incorporated into the permit. Some of the potential discharges identified in this permit are isolated from the receiving stream, and the mass balance equation presented in section V/. A. 2. can be used in a standard fashion to calculate water qualin~ based effluent limits. Since the upstream low flow in all cases is equal to zero, the effluent limits calculated using the mass balance procedure are equal to the stream standards. Some ojthe other potential discharges identified in this permit, such as seepage from existing tailings or from the leach heap that will 6e constructed, cannot practicably be isolated from the receiving stream. !n such cases, the stream that may receive the discharge will be what it monitored. Then, since the upsrremn low flow is zero, effluent limits which are equal to the stream standards will be applied to 1lte receiving stream. This will effectively limit the actual point source discharge of pollutants to the some limits. It .should be noted that the limits determined as described al.+ove do not take into account antidegradatian concerns. Should any discharge actually he identified, the permit may be reopened to revise appropriate limits. It is likely that those limits would be lower than those initially imposed. For several parameters, the analytical methods used in the definition of effluent limits are different titan those used in the deftnition of the corresponding stream standard.