Code of Colorado Regulations
1000 - Department of Public Health and Environment
1002 - Water Quality Control Commission (1002 Series)
5 CCR 1002-31 - REGULATION NO. 31 - THE BASIC STANDARDS AND METHODOLOGIES FOR SURFACE WATER
Section 5 CCR 1002-31.31 - STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY, AND PURPOSE: JULY 11, 1994 HEARING

3.1.8 Antidegradation Rule

Changes were made to several portion of the rule to clarify that the basis for designating waters and making determinations whether significant degradation will occur were the chronic criteria or standards except in those instances where the parameter of concern had only an acute criteria or standard.

One party requested an amendment to §3.1.8 , asserting that the current language did not comport with C.R.S. § 25-8-209(4). However, given the fact that this particular provision was recently adopted in response to a 1992 legislative change, and in view of the fact that the Basic Standard changes under review at this time focus upon numeric criteria, it was decided to defer this particular issue. It may be considered at the next Basic Standards triennial review, or prior to that time if a separate rulemaking addressing antidegradation is noticed by the Commission.

3.1.11 Basic Standards applicable to Surface Waters of the State

The Commission updated the organic chemical table to reflect new chemicals and revised numeric standards and criteria contained in revisions to the Federal Drinking Water Standards and/or updates to the 304(a) criteria for pollutants that have occurred since the 1991 Basic Standards rulemaking.

During the hearing, a number of parties raised concerns about the basic standards applicable to the water supply and water plus fish classifications for chloroform, bromoform, bromodichloromethane and dibromochloromethane. These substances are collectively known as total trihalomethanes (THMs) and are found in most treated drinking water supplies. The substances are contained in drinking water as a result of chlorination of raw water supplies in water treatment facilities. As a result of the discharge of treated drinking water, after use, into wastewater treatment systems, untreated and treated wastewater may contain the substances, particularly chloroform, in excess of the established basic standards levels.

The rationale for limiting trihalomethanes in waters of the State is to protect human health from adverse effects when water is ingested. The existing standards for the four substances were based on calculations from the EPA's Integrated Risk Information System ("IRIS"). The Safe Drinking Water Act and the implementing regulations set a maximum contaminant level (MCL) in finished potable water for total THMs at 100 ug/l, which is significantly higher than the current basic standard of 6 ug/l for chloroform. No maximum contaminant levels have been established for the four individual substances. The Commission recognizes that continued chlorination of drinking water supplies is necessary to control water-borne bacteria and to provide a safe drinking water supply. The Commission also recognizes that to meet the established standards for the four chemicals wastewater treatment works could be required to treat their wastewater at very significant costs to levels below that allowed in drinking water. In general, the Commission's policy has been to limit the occurrence of pollutants in state waters to the lowest feasible levels, consistent with the latest available information regarding full protection of public health. In this instance, in view of the fact that these pollutants may be present due to necessary water supply chlorination, and in view of the potential treatment costs and the existence of the total THM drinking water standard, the Commission has decided to replace the water supply and water plus fish standards for chloroform, bromoform, bromodichloromethane and dibromochloromethane with a total trihalomethane standard of 100 ug/l. This change is being made due to the unique circumstances pertaining to these chemicals, and should not be interpreted as a precedent for other instances where health-protective standards are more stringent than adopted MCLs. The Commission also anticipates that the standard now being adopted may be tightened in the future if, as currently expected, EPA revises the current total THM MCL to make it more stringent. The aquatic life standards for bromodichloromethane and chloroform have not been changed.

A determination was made that the practical quantitation limits (PQL's) were more appropriately addressed in the Regulations for the State Discharge Permit System in order to allow more flexibility in their application in permits and the PQL column and all footnotes referencing them were removed from the table.

Other changes to the table were to expand upon the footnote concerning the application of the water and fish ingestion standards to class 2 aquatic life segments and to correct typographical errors in the spelling of several chemicals.

3.1.16 Tables

Changes to this section included revising and updating the references, and adjusting the water supply criterion for asbestos in Table II and cadmium, nickel, selenium, and thallium in Table III to reflect updated standards in the National Primary Drinking Water Regulations. No revisions to the aquatic life table values for selenium were made as a result of this hearing. A separate rulemaking hearing to consider these issues has been scheduled for October, 1994.

A new class of criteria for metals which address water + fish ingestion was also added to Table III. Water + fish criteria were adopted for antimony and thallium that were equivalent to their respective drinking water supply criteria since their human health based water + fish values were slightly higher. The specific drinking water criteria used are the current "maximum contaminant level goals" for these two metals. As a result of issues raised during this hearing, the Commission intends to review the policy issues related to selecting the basis for human health-based table values and water quality standards. Should the Commission adopt an approach to such table values and standards in the future that differs from that applied in this hearing, the Commission may adjust these antimony and thallium table values at a future hearing. Footnotes concerning application of these criteria as standards to segments were adopted verbatim from the organic chemical table in 3.1.11.

The Commission considered the proposal of various parties to delete the chronic and chronic (trout) table values for silver. The evidence demonstrated that ionic silver causes chronic toxicity to fish at levels below that established by the acute table values. It was undisputed that silver is present in Colorado streams and in the effluent of municipal and industrial dischargers in Colorado. The evidence also demonstrated that the removal of silver from wastewater can be costly. However, there was strongly conflicting scientific evidence regarding the degree to which silver does, or could in the absence of chronic standards, result in actual toxicity to aquatic life in Colorado surface waters. In particular, there was conflicting evidence regarding the degree to which the toxic effects of free silver are mitigated by reaction with soluble ligands to form less toxic compounds and by adsorption to particulates and sediments.

The Commission believes strongly that there is a need for additional analysis of the potential chronic toxicity of silver in streams in Colorado. The Commission encourages the participants in this hearing, and any other interested parties, to work together to develop additional information that will help resolve the differences in scientific opinions that were presented in this hearing. The Commission believes that it should be possible to develop such information within the next three years.

In the meantime, the Commission has decided as a matter of policy to take two actions. First, the chronic and chronic (trout) table values for silver are repealed for the next three years. The Commission intends to implement this action by also repealing for the next three years, in a separate rulemaking hearing to be held later this year, all current chronic table value standards for silver previously established on surface waters in Colorado. Any acute silver standards and any site-specific silver standards not based on the chronic table values would remain in effect. The Commission intends that any discharge permits issued or renewed during this period will not include effluent limitations based on chronic table value standards, since such standards would not currently be in effect. In addition, at the request of any discharger, any such effluent limitations currently in permits should be deleted.

The second action being taken by the Commission is the readoption of the chronic and chronic (trout) table values for silver, with a delayed effective date of three years from the effective date of this final action. The Commission also intends to implement this action by readopting chronic silver standards with a corresponding delayed effective date at the same time that such standards are deleted from the individual basins as described above. 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. If the current scientific uncertainty persists after three years, the Commission believes that it should be resolved by assuring protection of aquatic life.

In summary, in balancing the policy considerations resulting from the facts presented in this hearing, the Commission has chosen to provide relief for dischargers from the potential cost of treatment to meet chronic silver standards during the next three years, while also providing that such standards will again become effective after three years if additional scientific information does not shed further light on the need, or lack of need, for such standards.

The Commission also has revised the drinking water supply table value for silver, to reflect the current secondary drinking water standard, since EPA has deleted the previous maximum contaminant level for silver.

At the hearing, Coors requested that the Commission consider adopting language stating that the Division should not use secondary drinking water standards as the basis for discharge permit limits if the background levels exceed those standards and if there are no site-specific numeric standards based upon ambient data adopted for the constituents in questions. Coors and the Division have discussed the issue and have resolved it for the time being without the need for Commission action on the request at this time. Coors agreed not to pursue this issue in the current rulemaking, but anticipates that its concerns will be addressed in a subsequent hearing that will consider the adoption of site-specific standards on Clear Creek.

Other

Changes were made to section 3.1.7 which specify procedures appropriate in the development of site-specific standards and to section 3.1.14 to allow the adjustment of effluent limits for metals if a site-specific relationship can be shown for instream dissolved and total recoverable metals. Both these changes are being made in response to recent EPA policy concerning the development and application and of metals standards.

The definition of created wetlands was changed to clarify that compensatory wetlands were not included in this class of wetlands.

PARTIES TO THE JULY 11, 1994 HEARING