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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale - Page 13. Permit No. CO-0027154 <br />VI. TERMS AND CONDITIONS OF PERMIT <br />A. Effluent Limitations (continued) <br />1. Applicable Federal Effluent Guidelines and Standards: There are federal <br />guidelines applicable to all outfalls. The applicable limitations follow. <br />Table VI-7 -- Federal Standards <br />Parameter <br />30 Day Average Daily Maximum <br />Concentration Concentration <br />pH, s.u. (minimum - maximum) 6.0 - 9.0 N/A <br />Total Suspended Solids, mg/1* 35 70 <br />Total Iron, mg/1* 3.5 7.0 <br />Settleable Solids, ml/1 N/A 0.5 <br />* Apply to active areas only, not post mining areas <br />Total Suspended Solids Limitations - EPA promulgated BPT regulations on <br />November 26, 1982, but BCT (Best Conventational Pollutant Control <br />Technology) has been reserved pending finalization of EPA's BCT cost <br />methodology. Therefore, BPT shall apply to the outfalls serving active <br />mining areas. These outfalls are 002 - 008. The State Effluent <br />Standard-based limitations are not applicable for these outfalls pursuant <br />to Section 10.1.3(3) of the State Regulations for Effluent Limitations, <br />which states that when EPA effluent guidelines exist for the industry, the <br />federal limitations shall take precedence. Although outfall 001 serves a <br />post mining area in addition to a spoils spring, the Division is using <br />best professional judgment to apply the BPT limitations to this outfall <br />instead of State Effluent Standard-based limitations because the treatment <br />facility was designed to meet BPT. <br />Total Iron Limitation - The Colorado Mined Land Reclamation Division and <br />the State Engineer's Office require ponds to be dewatered within 36 to 72 <br />hours after a precipitation event. On this basis, the division believes <br />that discharges will occur when stream flow is well above the 7-day, <br />10-year low flow. Thus, technology based limitations (federal BAT) for <br />outfalls 002 - 004, 006 and 008 will adequately protect instream water <br />quality standards. The federal BAT limitations for this parameter are not <br />applicable to outfalls 001, 005 and 007. These outfalls normally <br />discharge continuously; therefore, the applicable water quality standards <br />apply. <br />