5 Colo. Code Regs. § 1002-41.17
The provisions of section 25-8-202(1)(a), (b) and (2); 25-8-203; and 25-8-204; C.R.S., provide the specific statutory authority for adoption of the attached regulatory amendments. The Commission also adopted, in compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.
ADDITIONAL ORGANIC CHEMICALS - TABLE A
In 1991, Table A, Ground Water Organic Chemical Standards, was updated to set health risk-based standards where MCLs had been established earlier. In this rulemaking, the same policy was followed for forty-five additional organic chemicals that have been promulgated by EPA in the National Primary Drinking Water Regulations as Maximum Contaminant Levels (MCLs), either in EPA's Phase II Rule (Fed. Reg. Jan. 30, 1991), or the Phase V Rule (Fed. Reg. July 17, 1992). Rather than establish the MCL as the standard, however, the Commission chose to continue with its policy to set a health risk-based standard at the 1:1,000,000 level using the same rationale as it did in 1991. That rationale is that MCLs are inappropriate as stream or ground water standards because they include economics and technical feasibility of removal in their development, whereas a standard is designed to fully protect the use of the water. Since dilution is present to temper the effect of applying the health-based standards to dischargers, along with the PQL, the net effect should not be overly burdensome on the regulated community. Where the necessary information in the integrated Risk Information System (IRIS) was not available to establish the health risk-based standard, the MCL was adopted as the standard. As more information becomes available over time, the Commission intends to convert all standards to the health risk-based level.
For benzene, the policy outlined above was not followed. At the informational hearing in February, 1993, the Commission heard considerable testimony concerning the implications that the health-based benzene standard of 1 ug/1 had been having on remedial activities associated with fuel contaminated areas. The MCL level of 5 ug/1 appears to provide sufficient health protection while recognizing the practical difficulties of removing benzene contamination to levels below that concentration.
The organic chemicals chlorophenol and phenol were moved from Table 1 (Human Health Standards) to Table 2 (Secondary Drinking Water Standards), and the proposed standards were set equal to the Ambient Water Quality Criteria for the chemicals. The reason for the change is that although the two chemicals pose a significant health risk at much higher concentrations, taste and odor considerations are a concern at lower concentrations.
PQL's for the organic chemicals proposed in this rulemaking were provided by the Colorado Department of Health Laboratory, and were calculated by multiplying the Method Detection Limit ("MDL"), Estimated Detection Limit ("EDL"), or other detectable level as published by EPA by a factor of ten (10).
It was determined during this rulemaking hearing that PQL's in the Basic Standards for Ground Water, and also in the Basic Standards and Methodologies for Surface Water, will receive further consideration by the Commission and the Division in the next year.
ADDITIONS TO TABLE 1
Four metals standards were added to Table 1 of the Basic Standards for Ground Water. The basis for the addition was the federal Phase V Rule, published in the Federal Register on July 17, 1992. All additional standards were set at the MCL level. Cyanide, one of the Phase V MCLs, was not changed since Table 1 already contained a cyanide standard at a level more stringent than the MCL.
During the rulemaking hearing, the Metro Wastewater Reclamation District pointed out that there is no laboratory test for free cyanide, and that the acid dissociable should be used. Since this proposal was not part of the public notice and was raised so late in the process, it was determined that the Division would address the issue in a rulemaking proposal during the next year.
CHANGES TO 3.11.5 (C)(5)(c)
The change in wording made in the section referenced above was necessary to update the statutory reference for the Storage Tank program in the Hazardous Materials and Waste Management Division. This change will allow a consistent regulatory approach by the Storage Tank program to ground water contamination caused by either underground or above-ground tanks.
CHANGES TO 3.11.6(A)
The change to 3.11.6(A) has been made for purposes of clarifying that the Division has existing authority to consider ground water standards when setting limits for surface water discharges which impact ground water.
A party to the proceeding is in a position where it has alluvial wells in close proximity to a proposed surface water discharge to a frequently dry stream. This party has raised the issue that the sole biological standard of total coliform bacteria may be inadequate to protect public health from direct or indirect discharges to ground water, and that this is particularly the case in instances where a surface discharge impacts ground water.
PARTIES TO THE DECEMBER, 1993 RULEMAKING HEARING
5 CCR 1002-41.17