5 Colo. Code Regs. § 1002-33.60
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
Blue River Segment 14: Temporary Modification of the chronic molybdenum standard for water supply.
Climax Molybdenum Company presented evidence that progress has been made on its plan to eliminate the need for a temporary modification and to resolve uncertainty associated with the underlying molybdenum standard of 210 µg/L on Segment 14.
Three studies sponsored by the International Molybdenum Association (IMOA) on the health effects of molybdenum were completed and full reports were made available for consideration in a hearing originally scheduled for December 12, 2017. The hearing was to consider revisions to both the water supply and agriculture molybdenum standards in Regulations 31 and 33, as well as to resolve the temporary modification to the molybdenum water supply standard on Blue River Segment 14.
At the prehearing conference on November 29, 2017, the Commission hearing chair heard arguments regarding a Climax request to continue the rulemaking hearing. These arguments centered on the Division's position in rebuttal that the Commission should not consider any revisions to the water supply molybdenum standard until the most recent IMOA study was peer-reviewed and published as a technical journal article, and until the Agency of Toxic Substances and Disease Registry (ATSDR) considers the recent IMOA study results in the updated version of its draft toxicological profile for molybdenum. The Division presented evidence at the prehearing conference that ATSDR planned to revisit the draft profile in spring 2018, and that an updated version could be expected in approximately one year.
On December 1, 2017, the Commission issued its Prehearing Order, continuing the consideration of water supply and agriculture molybdenum standards in Regulation 31 and Regulation 33 until November 2019. The Commission also continued the rulemaking until January 8, 2018, for the limited purpose of considering an extension of the temporary modification of the water supply standard in Blue River Segment 14. The Commission established additional filing deadlines for Climax to submit additional information to support the extension of the temporary modification.
In this hearing, the Commission considered the additional information presented by Climax in support of the extension of the temporary modification on Segment 14, and found that nonattainment of the underlying standards was demonstrated, there was predicted non-attainment of a water quality based effluent limit, and there was uncertainty regarding the water quality standard necessary to protect current uses. There is also uncertainty regarding the extent to which existing quality in Blue River Segment 14 is the result of irreversible human-induced conditions. The Commission accepted Climax's revised plan to resolve the uncertainty associated with the underlying standard of 210 µg/L with some additional considerations. Climax's plan includes publication of the third IMOA study, awaiting publication of the ATSDR revised Toxicological Profile for Molybdenum, continued water quality monitoring of effluent and Tenmile Creek, source identification, potential additional monitoring, and updates to stakeholders. Furthermore, in order to resolve the uncertainty as to whether attainment of the underlying standard is feasible, in addition to what is outlined in Climax's plan, Climax will conduct investigations for molybdenum including identification of sources, influent control measures, investigation of potential treatment alternatives and treatment optimization, and available blending. Climax will identify treatment options, source control and water management alternatives, the expected effluent quantity and quality that could be achieved with each alternative, and an estimated cost for each alternative.
Given the continuation of the Commission's consideration of revised molybdenum standards until November 2019, which is after the expiration date of December 31, 2018 of the current temporary modification, the Commission extended the "current conditions" temporary modification in Segment 14 to June 30, 2020. "Current conditions" will preserve the status quo. As expressed by the Commission in a previous rulemaking, "current conditions" recognizes that during the term of the temporary modification, variability in a permitted discharger's effluent quality may occur. See Reg. 31, Section 31.53(V)(B).
The Commission also heard evidence that Climax is committed to continuing to resolve outstanding issues associated with the agriculture standard during the pendency of the continued standards rulemaking.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-33.60