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Mine Water Quality Assessment <br />CO-0034142 <br /> <br /> <br />Fe, Trec (u 20 6.2 26.2 1595 1000 - <br />Zn, Dis (u 20 6.2 26.2 25 234 908 <br />Table A-10 <br />Acute Assimilative Capacities for Metals <br />- - Based.on Future TVS Standards <br />°~... <br />~'a ~,~n~re'c,~. ~ -. ate,. ~ `~~~{~ ~' :_ ~ s ~ ~: s ~ "1C:^- . t~,1Y1 <br />~ <br /> <br />' <br />~~ <br />. > : 3 ~, h <br />Zn, Dis (u 11 " 6:2 17.2 25 232 599 <br />Based on these calculations, the dash under MZ indicates that there is no assimilative capacity <br />available in the Williams Fork River for total recoverable iron. According to WQCD standazd <br />procedure, the WQCD Assessment Unit investigates issues ofwater quality standard exceedances. <br />The Assessment Unit is tasked with determining if the exceedances aze valid and placing the <br />receiving stream onthe Clean Water Act Section 303(d) list ofimpaired waters, ifappropriate. Ifthe <br />receiving water is placed on the State's 303(d) list, the Assessment Unit is tasked with developing <br />ttre Total Maximum Daily Loads (TMDLs) and the Waste Load Allocations (WLAs) to. be <br />distributed to the affected facilities. Where an assimilative capacity is calculated to be a:negative <br />number and interpreted to be zero, the-WQCD standard procedure is 4o allocate the water quality <br />- standard to prevent further degradation of the receiving waters until the Assessmenti'Unthas <br />completed its evaluation of the receiving stream and determined TMDLs-and WLAs, where <br />appropriate. = <br />V. Antidegradation Review <br />As set out in The Basic Standards and Methodologies of Surface Water, Section 31.8(2)(b), an <br />antidegradation analysis is required except in cases where the receiving water is designated as "Use <br />Protected:' Note that "Use Protected" waters are waters "that the Commission has determined do <br />not warrant the special protection provided by the outstanding waters designation or the <br />antidegradation review process" as set out in Section 31.8(2)(b). The antidegradation section of the <br />regulation became effective in December 2000, and therefore antidegradation considerations are <br />applicable to the Eagle Mine permit issuance. <br />According to the Classification and Numeric Standazds for Lower Colorado. River Basin, stream <br />segment COLCLY13b is Use Protected. Because the receiving waters are designated as Use <br />~- Protected, no antidegradation review is necessary in accordance with the regulatigns. Thus, for <br />purposes of this WQA, antidegradation review requirements have been met for the Eagle Mine <br />permit issuance process. <br />Appendix A Page 12 of 13 <br />