Overview: Assigning or changing a standard or granting, removing before its expiration, or extending a temporary modification or variance shall be accomplished by a rule after a rulemaking hearing. The procedures for taking such action shall be the same as the procedures for assigning or changing classifications. See section 31.6(3)(a)(i).
(1)Assigning StandardsThe Commission is responsible for promulgating water quality standards as set forth in section 25-8-204, C.R.S. Standards may be narrative and/or numeric and include the following:
(a)Basic StandardsThe basic standards in section 31.11 shall apply to all state surface waters at the effective date of the regulation.
(b)Numeric StandardsA numeric standard may be assigned by the Commission either to apply on a statewide basis or to specific state surface waters. A numeric standard will be assigned by the Commission when it is presented with evidence that a particular numeric level for a parameter is the suitable limit for protecting the classified use. A numeric standard consists of a numeric level and may include a description as to how that numeric level is to be measured. Numeric standards will include appropriate averaging periods and appropriate frequencies of allowed excursions. A numeric standard may be exceeded due to temporary natural conditions such as unusual precipitation patterns, spring runoff or drought. Such uncontrollable conditions are not cause for changing the numeric standard.
A temporary modification of a numeric standard may be granted by the Commission if the numeric standard is not being met at the present time, but such numeric standard is necessary to allow the full attainment of the classified use.
Numeric standards will be assigned based on the evidence presented at the classification and numeric-standard-setting hearings. Numeric standards may not necessarily be assigned for all constituents listed in the tables. In making this determination, the Commission will consider the likelihood of such constituents being present in the waters in question naturally or due to point or nonpoint sources, and shall consider the significance of the constituents with respect to protection of the classified uses. Entities having specific water quality data for the waters being classified, such as 208 agencies, local municipalities and industries, and citizens' groups, the Water Quality Control Division, state and federal agencies, environmental organizations, and other interested persons are encouraged to present such information.
The Commission may use any of the following approaches to establish site-specific numeric standards, as it determines appropriate with respect to specific state surface waters. Existing site-specific standards shall remain in effect until superseded by revised standards promulgated pursuant to this section:
(i)Table Value StandardsThe Commission may apply the numeric levels set forth in tables I, II, and III as site-specific standards when those levels are determined to be appropriate to protect the applicable classified uses, and the available site-specific information does not indicate that one of the following alternative approaches to numeric standards would be more appropriate. Acute and chronic standards may be adopted. Numeric standards may not necessarily be assigned for all constituents listed in the tables. Standards for metals may be established by site-specific adoption of the hardness-dependent equations in table III, instead of single-value numeric standards. The numeric levels for various parameters in tables I, II, and III, are levels determined by the Commission after careful analysis of all available information and are generally considered to protect the beneficial use classifications. They are intended to guide the Commission and others at the use classification and numeric-standard-setting hearings.
(ii)Ambient Quality-Based Standards(A) Where ambient water quality levels are worse than specific numeric levels contained in tables I, II, and III, but are determined adequate to protect the highest attainable uses, the Commission may adopt one of the two following types of site-specific ambient quality-based standards:(I) Feasibility-based Ambient Standard: Where water quality can be improved, but not to the level required by the current numeric standard, a feasibility-based numeric ambient standard may be adopted based on available representative data.(II) Natural or Irreversible Ambient Standard: Where no improvement is feasible, or sources and causes are natural, a site-specific numeric standard may be adopted at existing quality based on available representative data. Site-specific acute standards for parameters in Table III shall be based on the 95th percentile value of the available representative data.(B) Ambient quality-based standards are authorized only where a comprehensive analysis and review is conducted: (I) Which identifies the sources and causes of the elevated levels and characterizes existing conditions, including spatial and temporal variation;(II) Where sources and causes are not natural, a comprehensive alternatives analysis identifies the improved water quality conditions (if any) that could result from feasible pollution control alternatives;(III) Which includes a rationale for either retaining or revising the current use classification(s); and(IV) Which characterizes the highest attainable use.(iii)Site-Specific Criteria-Based StandardsFor state surface waters where an indicator species procedure (water effects ratio), recalculation procedure, use attainability analysis or other site-specific analysis has been completed in accordance with section 31.16 , or in accordance with comparable procedures deemed acceptable by the Commission, the Commission may adopt site-specific standards as determined to be appropriate by the site-specific study results. For segments assigned aquatic life classifications, where factors other than water quality substantially limit the diversity and abundance of species present, the Commission may adopt site-specific acute or chronic standards as determined to be appropriate based upon available information regarding the waters and the habitat. Recurrence intervals for site-specific-criteria-based standards may be determined on a site-specific basis.
Site-specific criteria-based standards and ambient quality-based standards for metals shall be based on dissolved metals whenever the Commission determines that the evidence presented is adequate to justify such standards. Site-specific standards for metals in effect prior to July 31, 1988 were generally based on total recoverable metals. Those standards shall remain in effect until superseded by revised standards promulgated pursuant to this section.
(iv)Standards For Surface Waters In Wetlands(A) Tributary wetlands to which the interim classifications referenced in section 31.13 apply, shall be subject to the following interim standard:(1) Until such time as the Commission adopts site-specific standards for the tributary wetland, water quality in the wetland shall be maintained for each parameter at whichever of the following levels is less restrictive: (b) that quality which meets the numeric standards (except for numeric standards for pH, dissolved oxygen, and any standard established for the protection of a domestic water supply use) of the tributaries of the surface water segment to which the wetland is most directly hydrologically connected. Where the applicable numeric standard is based on section 31.16 , table III, of this regulation, the numeric standard applicable to the wetland may be implemented taking into account the water effect ratio of the pollutant.(2) Ambient quality shall be determined in accordance with section 31.7 and shall take into account the location, sampling date, and quality of all available data. Ambient quality shall be determined as of the time the first regulatory action is undertaken which requires the identification of water quality standards for wetlands. If available information is not adequate to otherwise determine or estimate ambient quality, the interim standard set forth in section 31.7 (b) (iv) (A) (1) (b) shall apply.(B) Wetlands for which the Commission has adopted a site-specific "wetlands" classification described in section 31.13 , shall be subject to numeric standards and designations adopted by the Commission. The Commission shall adopt any numeric standards and designations determined to be appropriate in view of the functions and values to be protected for the wetlands in question.(C) Created wetlands shall be subject only to the narrative standards set forth in section 31.11 , unless the Commission has adopted the wetlands classification and appropriate numeric standards. All created wetlands will have a use protected designation unless determined otherwise as a result of a site-specific hearing.(D) Compensatory wetlands shall be subject to the standards of the segment in which they are located, unless the Commission adopts a wetlands classification and appropriate numeric standards.(E) All other wetlands which are state waters shall be subject only to the narrative standards set forth in section 31.11 , unless the Commission has adopted the wetlands classification and appropriate numeric standards.(F) The issuance and use of site-specific or individual permits under section 404 of the Clean Water Act, is not precluded by the provisions of sections 31.7 , 31.11 or 31.13 , except as provided in the 401 certification process under section 25-8-302, C.R.S.(G) Wetlands water quality standards and classifications shall not be interpreted or applied in a manner that is inconsistent with sections 25-8-102(5) and 25-8-104, C.R.S.(c)Site-Specific Narrative Standards(i) Narrative standards may be assigned by the Commission to apply on a specific state surface water where numeric criteria are not required under federal law. Narrative standards will be assigned based on the evidence presented at the classification and numeric-standards-setting hearings, and must protect the classified uses.(ii) The Commission may adopt a site-specific narrative standard where water quality currently is degraded as a result of historical mining activities and improvement is likely within 20 years, if it determines that such a standard is the most appropriate option to protect existing uses and to promote water quality improvement efforts for the segment(s) in question due to uncertainty regarding what water quality is attainable. Unless the Commission determines that a different approach is appropriate on a site-specific basis, it shall use a statement that the standard(s) for the pollutant(s) in question shall be the chemical concentrations, biological conditions, and/or physical conditions identified by a structured scientific use attainability analysis, or table value standards, if the use attainability analysis is not completed and submitted by a specified date and approved by the Commission. Generally, a numerical temporary modification based on existing ambient quality will also be adopted for the segment(s) and pollutant(s) in question.(3)Granting, Extending, and Removing Temporary Modifications to Numeric StandardsWhere non-attainment of underlying standards has been demonstrated or predicted, the Commission may grant a temporary modification to a numeric standard upon a showing that the conditions in subsection (a), below, exist, provided that adequate supporting information described in subsection (b), below, are submitted. The presence of a temporary modification will be indicated in the appropriate water quality standards basin regulation by listing the parameter, the operative value, and the expiration date. A temporary modification may be granted to an entire stream or waterbody or to any portion thereof. It may be granted at the time a numeric standard is assigned or at any later time. When the temporary modification expires or is removed by the Commission, the underlying numeric standard will be in full effect. In every case, the modification to the numeric standard shall be temporary. All temporary modifications must be reevaluated not less than once every three (3) years.
In general, requests for a temporary modification are preferred over a more permanent downgrading of a present classification where it appears that the conditions causing the lower water quality might be temporary within a twenty (20) year time frame. The adoption of a temporary modification recognizes current conditions while providing an opportunity to resolve the uncertainty.
For the term of a temporary modification, regional wastewater management plans (208 plans) and plan updates, wasteload allocations, and planning, design, and construction of new, enlarged, or improved facilities and management practices shall be geared toward fully attaining the classified use and underlying numeric standard and assist in eliminating the need for the temporary modification. Discharge permits shall be implemented such that, at a minimum, status quo is maintained, and effluent quality is maintained at the best level reasonably achievable in a manner consistent with the provisions of subsection 31.9.
The subsections below provide requirements for the adoption, extension, review, and implementation of temporary modifications.
(a)Conditions Justifying a Temporary ModificationThe Commission may grant a temporary modification of a numeric water quality standard for a waterbody where all of the following apply:
(i) Non-attainment of underlying standards has been demonstrated or predicted(ii) Such non-attainment co-occurs spatially and temporally with an existing permitted discharge that has a demonstrated or predicted problem complying with a water quality-based effluent limit with which:(A) the discharge must currently comply, or(B) the discharge must comply within the next five years, or(C) the discharge must comply in more than five years, and evidence shows significant investment in facility infrastructure would be required before the uncertainty is resolved.(iii) At least one of the following is shown to exist:(A) there is significant uncertainty regarding the water quality standard necessary to protect current and/or future uses.(B) there is significant uncertainty regarding the extent to which existing quality is the result of natural or irreversible human-induced conditions.(b)Adequate Supporting Information for Original Adoption of a Temporary Modification Adequate supporting information must be submitted including all of the following: (i) Characterization of the waterbody and effluent including:(A) raw data describing the waterbody and effluent and characterization of the status quo, or, absent adequate data, a plan to collect data representative of quality as close in time as practicable to the temporary modification adoption, and(B) documentation of waterbody non-attainment and an effluent compliance problem, as required in section 31.7(3)(a).(ii) Documentation of uncertainty pertaining to the underlying water quality standard for the waterbody and/or the extent to which existing quality is the result of natural or irreversible human-induced conditions.(iii) A plan for resolving the uncertainty and eliminating the need for the temporary modification that includes, for each type of uncertainty, a detailed, site-specific approach expected to result in sufficient information to resolve the uncertainty within the term of the temporary modification. The plan shall also include a schedule of timelines for key deliverables, including, but not limited to, annual reporting on progress to the Division. Additionally, the plan shall include activities to ensure that, at a minimum, status quo is maintained, and effluent quality is maintained at the best level reasonably achievable, in a manner consistent with the provisions of subsection 31.9(4). Implementation of nonpoint source strategies for improving waterbody quality can also be considered, as appropriate.(iv) A justification for the narrative or numeric operative value, as defined in section 31.7(3)(d).(v) A justification for the proposed expiration date, consistent with section 31.7(3)(e).(c)Adequate Supporting Information for Extension of a Temporary ModificationIn addition to the information required for adoption of an original temporary modification, a proposed extension of a temporary modification shall be supported by:
(i) Justification for why the time allotted under the previous temporary modification term was not sufficient to resolve the uncertainty and eliminate the need for the temporary modification, and(ii) Demonstration that status quo has been maintained. If waterbody quality status quo is shown to have been degraded, justification that the degradation was not due to the effluent in question shall also be provided.(d)Operative Value during the Term of a Temporary ModificationIn order to ensure that, at a minimum, status quo is maintained, the operative value during the term of the temporary modification will be set to represent the current condition of the waterbody and effluent by either:
(i) Numeric values representing the status quo, or(ii) A narrative "current condition" that represents the status quo; the numeric values representing status quo shall be documented in the Statement of Basis and Purpose.(e)Term and Review of a Temporary Modification(i) When a temporary modification is granted, the length of term of the temporary modification will be set by the Commission. The term granted shall be the shortest possible to resolve the uncertainty. The term of a temporary modification shall be determined on a case-by-case basis, based upon all relevant factors, including, but not limited to: (A) the degree of uncertainty pertaining to the justification regarding the need for and length of the original temporary modification or extension, and(B) how soon resolving the issues that necessitated adoption of the temporary modification is deemed feasible.(ii) In making a decision as to whether a temporary modification should be removed or extended, the Commission will consider all relevant factors, including, but not limited to, whether: (A) the temporary modification still qualifies under 31.7(3)(a),(B) there is an adequate plan to resolve uncertainty for eliminating the need for the temporary modification and substantial progress has been made under the plan,(C) status quo has been maintained, or if status quo in the waterbody, alone, has not been maintained, whether degradation of the waterbody quality status quo is due to factors other than the effluent in question, and(D) there has been no, or minimal, impact from the temporary modification on the uses of the stream in the area of the temporary modification and upstream and downstream of that area. A temporary modification shall not be extended if the proponent did not substantially comply with all conditions of the temporary modification, including, but not limited to, submission of annual progress updates and supporting documentation.
(f)Frequency of Commission Review(i) The Commission will hold, at a minimum, a biennial (i.e., every other year) public rulemaking hearing to review all temporary modifications. As a result of the hearing, the Commission may:(A) Delete the temporary modification and allow the existing underlying standards to go into effect;(B) Delete the temporary modification and adopt a revised underlying standard;(C) Extend the expiration date of the current temporary modification, with or without a revised underlying standard; or(D) Adopt a revised temporary modification with an appropriate expiration date.(ii) Annual progress updates must be submitted to the Division. As a result of the review of the annual progress updates submitted during years with no scheduled formal public rulemaking hearing, the Division may propose that the Commission schedule a rulemaking hearing prior to the regularly scheduled biennial hearing to review and consider revisions, deletions, or extensions of temporary modifications.(4)Granting, Extending and Removing Variances to StandardsA variance to a water quality standard may be granted by the Commission to establish a temporary water quality standard that represents the highest feasible degree of protection of a classified use when the criteria in this subsection are met. Variances approved by the Commission shall be incorporated into the relevant standard tables, and the presence of the variance will be indicated in the appropriate water quality standards basin regulation. When the variance expires or is removed by the Commission, the underlying standard will be in full effect. In every case, the variance to the standard shall be temporary and must be reevaluated during each basin triennial review for the segment, unless the Commission requires a more frequent review when adopting the variance.
(a)Criteria for Granting a Discharger-Specific VarianceVariances to standards are authorized only where a comprehensive alternatives analysis demonstrates that there are no feasible alternatives that would allow for the regulated activity to proceed without a discharge that exceeds water quality-based effluent limits. In addition, an applicant for a variance must satisfy both of the following criteria.
(i) Tests to Determine the Need for a Variance(A) Limits of Technology: Demonstration that attaining the water quality standard is not feasible because, as applied to the point source discharge, pollutant removal techniques are not available or it is technologically infeasible to meet the standard;(B) Economics: Demonstration that attaining the water quality standard is not feasible because meeting the standard, as applied to the point source discharge, will cause substantial and widespread adverse social and economic impacts in the area where the discharge is located. Considerations include such factors as the cost and affordability of pollutant removal techniques; or(C) Other Consequences: Human caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place.(ii) Evaluation of the use of other regulatory tools, including compliance schedules, use attainability analyses to determine whether a change in uses or standards could fully protect actual and potential classified uses on the segment, and temporary modifications, and an explanation for how these other tools are not appropriate or would not result in water quality-based effluent limits that are feasible for the discharger to achieve within the required timeframe.(b)Selection of Alternative Effluent Limits for Discharger-Specific VariancesThe Commission's decision on whether to adopt a variance shall be based upon an evaluation of a comprehensive alternatives analysis and consideration of the impact of the variance on the uses of the waterbody at the discharge location and downstream of the discharge.
(i) Variances adopted by the Commission for a specific discharger shall include alternative effluent limits (AELs) that: (A) represent the highest attainable condition by requiring the highest degree of protection of the classified use that is feasible for the specific discharger named in the variance, and(B) reflects the greatest pollutant reduction achievable throughout the term of the variance while taking into consideration the factors in subsection 31.7(4)(a), as appropriate, and(C) do not result in any lowering of the currently attained ambient water quality, unless temporarily necessary for restoration activities.(ii) To ensure all feasible water quality improvements are implemented throughout the term of the variance, the Commission shall adopt one of the following: (A) An effluent-based AEL, expressed as an effluent concentration, load, pollutant percent removal, or other quantifiable expression of effluent quality and quantity. At its discretion, the Commission may additionally require the adoption and implementation of a Pollutant Minimization Program.(B) An action-based AEL with a quantifiable expression of the specific pollution control requirements to be completed by the discharger and the adoption and implementation of a Pollutant Minimization Program. An action-based AEL may only be justified when no additional feasible pollution control technology can be identified which could achieve a predictable, quantitative improvement in effluent quality.(iii) The Commission will adopt a minimum of two AELs: (A) an initial AEL that applies from the onset of the variance to ensure the discharge does not contribute to any lowering of currently attained ambient water quality, and(B) a final AEL which represents the highest attainable condition that is feasible to achieve during the term of the variance.(iv) The underlying standard is the applicable standard for assessing attainment for a waterbody and the development of effluent limitations for all other dischargers to the waterbody segment not named in the variance.(c)Conditions on Discharger-Specific VariancesA discharger-specific variance applies only to the point source discharge and pollutant(s) specified in the variance. In all permit actions issued to implement a discharger-specific variance:
(i) At the time the variance is implemented in the permit, compliance with the initial AEL will be required. Where necessary and appropriate, the permit may include a compliance schedule for the achievement of any interim and final AELs adopted by the Commission, which may include interim milestones towards achieving the applicable AEL.(ii) Ongoing investigation of treatment technologies, process changes, wastewater reuse, or other controls that may result in improvement in effluent quality, and reports regarding such investigations should be submitted with adequate time to allow for consideration of the information during the scheduled review of the variance by the Commission.(iii) Any limitations and requirements necessary to implement the variance shall be included as enforceable permit conditions, including but not limited to additional monitoring requirements.(iv) The discharge permit effluent limitations shall be established using the least stringent of the water quality-based effluent limits based upon the underlying standard or the AEL(s).(d)Term and Review of a Discharger-Specific VarianceThe Commission will set the term of a variance, on a case-by-case basis, to be only as long as necessary to achieve the highest attainable condition, including the time needed to plan, implement, or evaluate the outcome of the activities. In every case, the variance to the standard shall be temporary and must be reevaluated at a minimum during each basin triennial review for the segment. The specific timing of reviews shall be specified in the variance and comply with all requirements in this section. If the term of the variance is greater than five years, the variance must be reviewed at least every five years after EPA's approval.
The Commission will conduct a reevaluation and submit the results of its reevaluation to EPA within 30 days of the completion of the reevaluation process. If the Commission does not fulfill this requirement, the DSV will no longer be the applicable water quality standard for purposes of the Clean Water Act.
If, as a result of the reevaluation process, the Commission determines that it is possible to achieve a more stringent AEL or highest attainable condition than was originally required by the variance, then the Commission will revise the variance to incorporate the more stringent AEL in that hearing and submit the reevaluation results to EPA. Similarly, if the Commission determines a less stringent AEL is necessary, a revised variance must be submitted to EPA.
When the variance expires, a subsequent variance shall only be adopted if the permittee completed the ongoing investigation of pollution control alternatives and substantially complied with all other conditions of the variance.