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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Permit Number CO-0032751 Page 6 . <br />LIMITATIONS AND RATIONALE: (Continued) <br />Table 2 - Permit Limitations and Monitoring Requirements (Continued) <br />Monitoring <br />Parameter Limitations Rationale Frequency <br />P.D. Copper, mg/1 0.015 - 0.044 ~ <br />o.oz2 - 0.11 J <br />P.D. Lead, mg/1 0.0049 - 0.014 ~ <br />0.12 - 0.61 J <br />P.D. Mercury, mg/1 0.000013-0.000037 J <br />0.0029 - o.ols J . <br />P.D. Zinc, mg/1 0.056 - 0.17 J <br />0.13 - 0.69 ¢/ <br />pH, s.u. 6.5 - 9.0 J <br />Oil 6 Grease, mg/1 10; No Sheen <br />WET Testing, Acute Report - See Part I.B.3 <br />WET Testing, Chronic Report - See Part I.B.10 <br />WQS Weekly <br />WQS Weekly <br />WQS Weekly <br />WQS Weekly <br />WQS Weekly <br />WQS Weekly <br />WQS Weekly <br />WQS Weekly <br />WQS Weekly <br />SES Weekly <br />Permit Regulations Quarterly <br />Permit Regulations Semiannually <br />a/ 30 day average (limits range for metals) J Allowable range <br />J 30 day average/Daily maximum J Daily maximum (limits range <br />for metals) <br />See permit pages la, lb, and lc for the individual monthly metals limits. <br />P.D. - Potentially Dissolved <br />BAT/BPT - Federal limitations: Best Practical Control Technology and Best <br />Available Technology Economically A~:hievable <br />WQS - Water Quality Standard-based Limits <br />SES - State Effluent Standards limitations <br />DISCUSSION: <br />A. Limitations for TSS. oH. Oil an~i Grease. and Flow: The effluent <br />limitations for Total Suspended Solids (TSS), 20/30 mg/1, are based upon <br />the federal BPT effluent regulations (40 CFR 440.102). The limitation for <br />Oil and Grease, 10 mg/1, is based on the State Effluent Standard <br />Regulations (SES). Limitations for pH, 6.5 to 9.0 s.u., are from the <br />Water Quality Numeric Standards (WQS) for the applicable stream and <br />downstream segments. Because the WQS range for pH is more restrictive <br />than that specified under BPT ox SES, the WQS-based limit for pH is <br />applicable. Since the metal limitations were determined from water <br />quality standard based mass balance equations,, three seasonal discharge <br />flow limits are applicable as based upon estimated maximum levels. <br />B. Effluent Limitations for Cadmiurn Cd Conner (Cu). Lead (Pb) Mercury <br />(Hg). and Zinc (Zn): <br />The effluent limitations for thfase metal parameters are based upon the <br />water quality standards for segment 3, since the standard-based limits are <br />more stringent than what is spec;ified for BPT/BAT (40 CFR, Part 440.102 <br />and 103) federal limits for the:;e parameters. The water quality standards <br />n <br />