5 Colo. Code Regs. § 1002-41.25
The provisions of sections 25-8-202(1)(b); 25-8-204; 25-8-402, C.R.S., provide the specific statutory authority for adoption. The Commission also adopted, in compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE:
In this rulemaking, the Commission adopted revised and new organic chemical standards in section 41.5 . In an effort to keep ground water and surface water organic chemical standards consistent, the changes to section 41.5 were considered during the same hearing that addressed changes to the statewide surface water organic chemical standards in Regulation No. 31 (Basic Standards and Methodologies for Surface Water).
In adopting these new and revised organic chemical standards, the Commission continued to rely on its past policy decisions and precedence documented in Commission Policy 96-2. Additionally, as per Departmental policy the Commission has relied on the United States Environmental Protection Agency's (EPA) Integrated Risk Information System (IRIS) as its first tier source of toxicological data. Review of the IRIS data that had been updated since the last revisions to 41.5 indicated that the water quality standards for two organic chemicals, toluene and 1,2-dibromoethane, needed to be revised.
At the last hearing addressing section 41.5(C)(3), in September 2004, during which the Commission adopted water quality standards for several carcinogenic compounds, EPA had requested that a future rulemaking consider water quality standards for non-carcinogenic compounds. For this hearing the Commission reviewed several non-carcinogenic compounds that lacked water quality standards. This review identified four pesticides that the Commission elected to adopt water quality standards for: acetochlor, dicamba, metribuzin, and prometon. The Commission also corrected several typographical errors and added common synonyms for some of the organic chemicals.
The Commission elected to adopt EPA's maximum contaminant level (MCL) for arsenic and uranium as Domestic Water Supply - Human Health Standards (Table 1). EPA promulgated a MCL of 30 µg/l for uranium in December of 2003, and a MCL of 10 µg/l for arsenic in January of 2006. The Commission has previously adopted these MCLs as surface water-water supply standards, and in an effort to keep the surface and ground water standards consistent, now adopts them as ground water standards.
The Commission received testimony regarding the association of molybdenum as a ground water contaminant in several uranium and vanadium processing and mining sites throughout the Colorado. During the 1990 hearing (q.v. section 41.14), the Commission had elected to delete the molybdenum standard until additional scientific data was available. In August of 1993, IRIS published additional findings and finalized an RfD for molybdenum. During this hearing the Commission elected to adopt a Domestic Water Supply - Human Health Standards (Table 1) for molybdenum based on this updated toxicological data, as well as testimony regarding both existing and planned uranium and vanadium mining and milling activities throughout the State.
The Water Quality Control Division submitted testimony regarding its efforts to update and issue new general ground water discharge permits, and during that process requested additional clarification regarding the existing fecal coliform standard. The Commission updated the fecal coliform standard to clarify both the averaging period and the allowable maximum over that same averaging period. In determining the appropriate maximum and averaging period the Commission relied on EPA's water reuse guidance (EPA/625/R-04/108) for unrestricted urban reuse.
During the Issues Formulation and Informational Hearing the Commission received testimony regarding the Agricultural Standards (Table 3) and the implementation of the manganese standard. The original agricultural manganese standard was derived from EPA's 1972 Water Quality Criteria ("Blue Book"), and addressed crop toxicity in acidic soils. In order to remain consistent with the 1972 criteria, as well as with Regulation No. 31, the Commission elected to add a footnote to specify that the agricultural manganese standard is only applicable in those areas where acidic soils exist.
During the Issues Formulation and Informational Hearing an issue was raised regarding activities that increase naturally occurring contamination, with the intent at that time being that revisions to section 41.5 , the narrative standards, would address this issue. Additional investigation into the issue discovered that the narrative standards, as currently adopted in Regulation No. 41, are only implemented during a ground water classification hearing. The Commission believes that this poses two problems. First, as written, the narrative standards did not apply to all State waters which conflicts with the intention of the Colorado Water Quality Control Act (CWQCA). Second, the narrative standards have not been specifically adopted for all of the current ground water classifications.
One purpose of narrative standards is to provide general qualitative guidance for situations that lack quantifiable, or scientifically predicted, outcomes. Narrative standards define broad guidelines that are intended to meet general water quality goals. For these reasons, narrative standards are applicable when numeric criteria cannot be established, or applied, to a specific discharge or release. Additionally, narrative standards are critical for addressing emergency circumstances when the dynamics of the situation prevent timely scientific review or the normal Commission procedure.
For these reasons the Commission believes that applying the narrative standards to all ground water is appropriate and effectively solves the issues before them. By making the narrative standards statewide standards the Commission fulfills the intent of the CWQCA, implements the narrative standards for all existing ground water classifications, and addresses the issue of anthropogenic increases to naturally occurring ground water contamination.
The Commission revised the paragraph regarding "implementing agencies" to recognize the recent reorganization of the Division of Minerals and Geology into the Division of Reclamation, Mining, and Safety. The Commission also changed the reference to the agency responsible for the Resource Conservation and Recovery Act to recognize that both the Hazardous Materials and Waste Management Division and the Department of Labor and Employment implement different aspects of this statute.
In the 2004 hearing the Commission adopted footnote 7 which included a total trihalomethane (TTHM) standard applicable to existing aquifer storage and recovery (ASR) facilities that use potable finished water. The Commission's intention in doing so was to assure that the ground water organic chemical standards did not limit continued ASR at existing facilities. ASR has been identified by the Colorado General Assembly and the Colorado Water Conservation Board as a potential way to maximize use of aquifers through conjunctive use of surface and ground water resources. ASR has also been identified by the South Platte River Task Force as a potential tool to address water issues in the South Platte River Basin.
In order to assure that the ground water quality standards do not limit future use of ASR, the Commission adopted changes to footnote 7 deleting the reference to facilities that existed as of September 14, 2004, thereby applying the TTHM standard to all ASR facilities using finished potable water that meets all applicable federal and state drinking water requirements. In addition, the Commission adopted a new provision that applies the maximum containment level (MCL) as the standard for ground water that must be met by ASR facilities using finished potable water.
PARTIES TO THE RULEMAKING
5 CCR 1002-41.25