5 Colo. Code Regs. § 1002-31.35
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 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.
BASIS AND PURPOSE
The current Colorado aquatic life table value for manganese of 1,000 µg/l is based on limited laboratory toxicity test data generated by the Colorado Division of Wildlife (CDOW) in the 1970's (Davies and Goettl 1976). The revised table values adopted in this hearing are based on more recent data obtained from several sources (i.e., CDOW, ENSR, et al.) providing greater insight into the toxicological properties of manganese to aquatic organisms. The database, upon which the new table values are based, contains more than 25 acute and chronic toxicity data points representing approximately eight freshwater quality species. The USEPA has not developed national ambient water quality criteria for manganese. The new state table value criteria are based on the USEPA's guidance for deriving ambient water quality criteria, i.e., Guidelines for Developing Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses (USEPA 1985).
Laboratory test results indicate that manganese toxicity is affected by water hardness - an observation consistent with many metals included on Table III of the Basic Standards. The proposed acute and chronic revisions to the table values are water hardness-based equations rather than the current single value, reflecting the mitigating effect of water hardness on manganese toxicity and the differences in toxic effects resulting from acute (short-term) and chronic (long-term) exposures.
The listings of standards for the following organical chemicals were revised in this hearing, to correct previous typographical errors: Chlorethyl ether (BIS-2) c ; Chloroisopropyl ether (BIS-2); 4-Chloro-3-methylphenol; Chlorophenol 2; Di-n-butyl phthalate; Dinitrotoluene 2,6; Nitrosodiphenylamine N 2 ; and Trichlorobenzene 1,2,4.
As the result of a 1994 rulemaking hearing, the Commission repealed the aquatic life chronic and chronic (trout) table values for silver that had been contained in Table III of this regulation, but also readopted these same table values, with a delayed effective date of March 2, 1998. The Statement of Basis and Purpose for that rulemaking action stated in part: "The Commission has determined that this is an appropriate policy choice to encourage efforts to reduce or eliminate the current scientific uncertainty regarding in-stream silver toxicity, and to assure that Colorado aquatic life are protected from chronic silver toxicity if additional scientific information is not developed."
In the present rulemaking proceeding, the Silver Council, the City of Colorado Springs, the City of Fort Collins, Climax Molybdenum Company, and Kodak Colorado Division proposed that the Commission should delete the chronic and chronic (trout) silver table values from Table III, arguing (among other things) that there is no need for these table values. As an alternative proposal in this rulemaking, the Division of Wildlife proposed that the Commission should replace the existing chronic and chronic (trout) table values for silver with a single new chronic table value (in the form of a new hardness-based equation) that in general would be more restrictive than the previous table values. The Water Quality Control Division proposed that the Commission should take no further action regarding aquatic life chronic table values for silver at this time, thereby allowing the previous table values to go back into effect.
After consideration of the extensive information presented in this hearing on this issue, the Commission has decided to take no action regarding aquatic life chronic table values for silver at this time, with the result that the previously adopted chronic and chronic (trout) table values will go back into effect on March 2, 1998. The Commission finds that the record of this rulemaking proceeding, taken as a whole, demonstrates the need for chronic silver table values (and, correspondingly, chronic water quality standards) to protect aquatic life. The evidence submitted does not demonstrate that Colorado aquatic life would be protected from silver toxicity in the absence of chronic standards, or that the adoption of more restrictive standards is appropriate at this time.
The Commission rejects the Silver Council's argument that the presence of low levels of silver in ambient waters in Colorado is grounds for the deletion of the chronic and chronic (trout) table values. Table values (and corresponding segment-specific standards) are established to protect beneficial uses from the adverse effects of pollutants that are currently or may in the future be discharged to Colorado streams. It is undisputed that silver is present in current point source discharges to Colorado waters. Therefore, it is appropriate to establish table values that will assure that such discharges do not in the future cause elevated levels of in-stream silver that would cause toxicity to aquatic life, even if in most instances current ambient concentrations are not at a level anticipated to cause impacts. The evidence in this hearing does not demonstrate that silver is removed or bound by either inorganic or organic complexing material (ligands) and/or sediments to the extent necessary to eliminate chronic toxicity to aquatic life.
The Commission has considered the factors enumerated in section 25-8-204(4), C.R.S., and believes that they support the decision not to delete chronic table values for silver.
The evidence demonstrated that cities such as Golden, Colorado Springs and Fort Collins have successfully established pretreatment programs that achieve compliance with silver effluent limits in their discharge permits. Moreover, if ambient standards resulting from these table values would result in a substantial economic impact to a particular discharger on a site-specific basis, a number of options may be available in establishing appropriate site-specific standards, as provided in section 31.7 of this regulation. As a policy matter, the Commission believes that it is appropriate to consider any such site-specific economic impacts in a site-specific hearing, rather than by deleting a table value that has been shown to be necessary to avoid chronic toxicity. Based on these considerations, the Commission believes that the decision not to delete the previously adopted chronic table values for silver also meets the "economic reasonableness" goal set forth in section 25-8-102(5), C.R.S.
Contrary to the assertion of the Silver Council, and in accordance with its established interpretation of this legislative provision, the Commission does not believe that the provisions of section 25-8-202(8)(a), C.R.S. are applicable to the issue of whether to retain previously adopted table values for silver. This provision applies only in the situation where there are "corresponding enforceable federal requirements" in place. There are no federal requirements establishing enforceable silver standards in Colorado. Moreover, even if section 25-8-202(8)(a) were applicable to this proceeding, the Commission finds that the evidence in the record of this hearing includes sound scientific and technical evidence that chronic table values for silver are necessary to protect beneficial aquatic life uses of Colorado waters.
Although the Division of Wildlife presented evidence in this hearing which suggests that more stringent chronic table values than those previously adopted for silver may be necessary to protect aquatic life, the Commission believes that it would be premature to adopt more stringent table values at this time. Testimony presented indicated that there are issues regarding the derivation of the specific equation recommended by DOW that warrant further review before revising the table values. The Commission encourages the parties to this hearing to work with the Water Quality Control Division and any other interested persons in a collaborative effort to determine whether the existing chronic table values for silver should be modified to more accurately reflect potential toxicity effects. The Commission also encourages future collaborative efforts to further assess the potential economic and environmental costs and benefits of chronic silver table values, including consideration of how such table values may influence effluent limits in discharge permits.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-31.35