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COLORADO DEPARTMENT OF HEAL• Water Quality Control Divisio• <br />Rationale - Page 7 Permit No. CO-0043168 <br />Table VI-2 -- Summary of Mass Balance Calculations (Continued) <br />Upstream Stream WQS <br />Background Standard Effluent <br />Parameter Concentration Acute/Chronic Concentration <br />(mg/1) (M1) J (M3) (M2) <br />Total Mercury 0 0.00001 0.00001 <br />Dissolved Nickel 0 0.15/1.5 J 0.53/7.2 <br />Dissolved Selenium 0 0.017/0.135 J 0.016/0.14 <br />Dissolved Silver 0 0.00022/0.0059 J 0.00023/0.0062 <br />Dissolved Zinc 0 0.74 0.78 <br />a/ - The acute standard is indicated. All other single WQS values are chronic. <br />J -When "0" is indicated, the concentration is assumed to be zero. Although <br />some ambient data exists for Gregory Gulch (two samples of Suaerfund data: <br />6/19;89 and 9/18/89) which are included in the permit application, this data <br />b/ - was not used due to the variability of the two samples and the higher <br />detection levels used for some parameters. Since the calculated (M2) <br />effluent concentrations are approximately the same as the water quality <br />stan~iarc;s (M3), the assumed background (M1) value of 0 mg/1 is used. <br />c/ - The chronic and acute aquatic life calculated numeric standards, based <br />upon a total hardness value of 185 mg/1 as CaC03 for North Clear Creek. <br />Since there is no hardness data available for Gregory Gulch, the hardness for <br />Nor til Clear Creek is used. <br />- The chronic rater quality standard value for total ammonia of 8.55 mg/1 <br />was established from the Black Hawk-Central City Sanitation District permit <br />(CO-D023949) for the August through October season, as based upon a pH of <br />6.9 s.u. and a temperature of 16.0 degrees C (see page 10 of this permit's <br />previous rationale, dated July 16, 1987). <br />2. ~plicable Federal Effluent Guidelines and Standards: The federal <br />BPT and BAT technology-based effluent limitations which apply to <br />this type of facility are found under the Copper, Lead, Zinc, Gold, <br />Silver, and Molybdenum Ores Subcategory of the Ore Mining and <br />Dressing Point Source Category (40 CFR, Part 440.102 and 103). The <br />guidelines and standards which apply are in Table VI-3 below and on <br />the next page. <br />Table VI-3 -- Federal Standards <br />Parameter <br />30 Day Average Daily Maximum <br />Concentration Concentration <br />pH, s.u. <br />Total Suspended Solids, mg/1 <br />Total Cadmium, mg/1 <br />20 <br />0.05 <br />6.0 - 9.0 a/ <br />30 <br />0.10 <br />~ - range <br />