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<br /> <br />• <br />COLORADO DEPARTArrNT OF HEALTH <br />Water Quality Control Division <br />Rationale - Page 2 <br />Permit No. CO-0036021 <br />FACILITY DESCRIPTION: <br />By letter of Sanuary 29, 1985 and telephone conversation of May 17, 1985, the <br />permittee has requested that limitations for outfall 001 be changed to reflect <br />post-mining conditions. The area served by the pond has been backfilled, <br />graded and returned to the desired contour. <br />Because the above changes will require extensive permit modifications and <br />because the current permit will expire on December 31, 1985; the permit will <br />instead be renewed at this time. Upon the effective date of the renewal <br />permit, the requirements of this permit will supercede the conditions of the <br />old permit. <br />Outfall 001 is the only discharge from this facility. The mine has ceased <br />active mining. Outfall 001 is shown in Figures 1 and 2 in the permit. <br />APPLICABLE RULES AND REGULATIONS: <br />Federal BPT (Hest Practicable Control Technology) and BAT (Best Available <br />Technology Currently Achievable) recently promulgated specify the following <br />effluent limitations for reclamation areas: <br />TABLE 1 <br />Parameter BPT BAT <br />pH, s.u. 6.0 to 9.0 NA <br />Settleable Solids, ml/1* 0.5 0.5 <br />*This parameter does not apply to discharges caused by precipitation greater <br />than the 10-year, 24-hour event (or equivalent snowmelt volume). <br />State Lffluent Standards (SES) dictate the imposit'_on of an Oil and Grease <br />limitation of 10.0 mg/1 for all discharges not otherwise limited. <br />Additionally, State Eater Quality Standards (:;QS) dictate a pH limitation of <br />6.5 to 9.0 s.u.. This supersedes the BPT limitation for pH shown in Table 1. <br />Because discharge will be intermittent and will normally occur only duri.^.g <br />precipitation events (periods when receiving water flows will be high) no <br />water quality standard-based effluent limitations are appropriate other t:~an <br />pH . <br /> <br />