The provisions of C.R S. 25-8-202 (1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; provide the specific statutory authority for adoption of these regulatory amendments. The Commission also adopted in compliance with 24-4-103(4) C.R.S. the following statement of basis and purpose.
BASIS AND PURPOSE
Upper Gunnison River Basin Segment 12:
Pursuant to tine requirements in tine Basic Standards (at 31.7(3)), tine Commission reviewed tine status of temporary modifications sclneduled to expire before December 31, 2014, to determine winetlner tine temporary modification sinould be modified, eliminated or extended.
During tine September 10, 2012 Rulemaking, tine Commission adopted Type B Temporary Modifications for cinronic cadmium, cinronic copper and cinronic zinc witin expiration dates of June 30, 2013. Since tinat time, U.S. Energy Inas worked witin tine Division and interested parties to develop a sampling plan to identify the natural and human-induced sources of cadmium, copper and zinc in the portion of the Coal Creek watershed affecting water quality in Segment 12 and to assess the extent to which human-induced sources are reversible, including measurable loads from wasterock piles and exploration shafts. U.S. Energy will evaluate a range of alternatives including treatment of contaminated water, whether surface or groundwater, including collection and treatment at the Keystone Mine site. Among other possible metals loading sources, the sampling plan includes a preliminary investigation of groundwater that may be originating from flooded workings within the historic Keystone Mine. The sampling plan includes efforts to evaluate the extent to which metals concentrations in groundwater within and immediately downgradient of the flooded mine workings are being affected by historic mining activity. If such effects are identified, or if preliminary results are inconclusive as to the effects of the flooded mine workings, U.S. Energy will develop plans for further investigation and characterization of metals loading to Segment 12 from the mine area. The Commission believes the sampling plan is sufficiently detailed and othen/vise adequate to support extension of the Temporary Modifications until June 30, 2016. This should provide sufficient time to complete the proposed sampling and data analysis and to develop the other information needed (including a use attainability analysis) to set site specific water quality standards within a reasonable period. This will also ensure that progress towards (i) completing the initial investigation of the flooded mine workings, (ii) developing and implementing plans for further study of potential loading to Segment 12, and (ill) collecting sufficient information to support adoption of site-specific water quality standards in 2016 will be reviewed in the annual Temporary Modification hearings in December 2014 and December 2015.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-35.35