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COLORADO DEPARTMENT OF HEALTH, <br />Permit Number CO-0032751 Page <br />Water Quality Control Division <br />14. <br />CHANGES TO PERMIT AND RATIONALE FOLLOWING PUBLIC NOTICE PERIOD: (Continued) <br />Flow Measuring Device: {Cont.) a measurment range of 0 to 300 gpm) is <br />available and will be installed for effluent flow measurement probably during <br />1991. The permittee should notify the Division in writing when the flow meter <br />has been installed. <br />Change in Permit Metal Limitations to Potentially Dissolved: Since this <br />permit went to public notice, some of the metal water quality standards for <br />the South Platte River Basin (Reference 4) changed from total recoverable to <br />dissolved. In segment 3, the metal water quality standazds for cadmium, <br />copper, lead, mercury, and zinc are specified as TVS (Table Value Standards). <br />The standards for Cd, Cu, Pb, and Zn are based on equations which are hardness <br />dependent as specified in Tab Le III of the Basic Standards and Methodolo ies <br />for Surface Water (3.1.0) (reference 1); the standards for mercury, which are <br />not hardness-based, are also indicated in Table III. The total hardness (as <br />CaCOg) used for calculations for this permit was 100 mg/1, since this is the <br />hardness level which has been found in samples submitted by the permittee for <br />Coon Track Creek in the vicinity of the discharges. These hardness-based <br />values are expressed as the potentially dissolved fraction for effluent <br />limits. Since the original public notice, based upon permittee comments, the <br />Division has determined that monthly metals limitations are now applicable for <br />this facility. The calculated and applicable standards are indicated in <br />Appendix A, and the mass balance equations for determining the limitations are <br />in Appendix C. <br />Facility Flaw: Three seasonal facility flow limits were included in this <br />permit, as indicated on page la of the permit and which is previously <br />discussed. However, the water quality standard based limits for the five <br />metal parameters in this permit are based upon the total seasonal facility <br />flows from both the Caribou Mine and the. Cross Mine. These flow values (for <br />the WQS mass balance equations included in Appendix C) that were determined <br />for both facilities are indicated below: <br /> Caribou Mine Cross Mine Total of Both <br />Season: Discharg e Fl ow Discharge Flow Discharg e Flows <br /> . <br />January - March 0.0864 MGD (60 gpm) 0.036 MGD (25 gpm) 0. 1224 MGD <br />April thru June 0.0936 MGD (65 gpm) 0.1224 MGD (85 gpm) 0. 2160 MGD <br />July 1 -July 31 0.0576 MGD (40 gpm) 0.0929 MGD (64. 5 gpm) 0. 1509 MGD <br />August - Sept. 0.0576 MGD (40 gpm) 0.036 MGD (25 gpm) 0. 094 MGD <br />Octob. - Decemb. 0.036 MGD (25 gpm) 0.036 MGD (25 gpm) 0. 072 MGD <br />Public Notice Requirements: This will be the second public notice for this <br />renewal permit. Since the time of the first public notice, there have been <br />enough significant changes affecting the: limitations and monitoring in the <br />permit which have resulted in the need ro send this permit to public notice <br />again. <br />Don Halmer <br />June 11. 1991 <br />