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 1002-31.24 - STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE (1988 REVISIONS-MISCELLANEOUS ISSUES)
Current through Register Vol. 47, No. 17, September 10, 2024
The provisions of sections 25-8-202(1)(a),(b) and (2); 25-8-203; 25-8-204 and 25-8-207; C.R.S., provide the specific statutory authority for adoption of the attached regulatory amendments. The Commission also adopted, in compliance with sections 24-4-103(4) and 24-4-103(8)(d) C.R.S., the following statements of basis and purpose and fiscal impact.
BASIS AND PURPOSE:
A. TEMPORARY MODIFICATIONS
Several changes have been adopted to the temporary modification provisions in section 3.1.7 . Several of these changes were recommended by EPA, to ensure compliance with EPA's water quality standards regulations. The Commission agreed to delete certain language relating directly to taking the availability of public and private funds into account in granting or determining the duration of a temporary modification. However, the Commission has added new language providing that the need for time to take the necessary actions to come into compliance with an underlying standard will be taken into account in deciding whether to grant temporary modifications. This provision is meant to take into account the practical realities of implementing new treatment or other control measures, while at the same time assuring reasonable progress toward the improvement of water quality where existing conditions are correctable.
In addition, the Commission has added new language providing that temporary modifications will have a definite expiration date, while retaining flexibility as to the duration of specific temporary modifications. The purpose of this change is to avoid the possibility of a temporary modification simply remaining in place indefinitely without close reexamination, while retaining the flexibility to respond to individual circumstances. For example, the time that it will take to implement corrective measures, as well as the timing of discharge permit expiration and renewal, may be taken into account in determining the appropriate duration of a specific temporary modification.
B. USE ATTAINABILITY ANALYSIS
EPA recommended that new language be added to the regulation stating a requirement that a "use attainability analysis" be conducted in certain instances to assess the attainability of "fishable/swimmable" uses. The Commission has added language to section 3.1.6 requiring that a use attainability analysis be conducted in appropriate instances, and has added a definition of this term to the regulation (section 3.1.5). The Commission declined to make several changes relating to this issue recommended by EPA. For example, EPA recommended that the definition of "beneficial uses" be expanded to differentiate among existing uses, designated uses, and attainable uses. The Commission decided that these changes were unnecessary because there has not been a problem with the current definition, and EPA's changes may generate confusion.
The Commission is aware that certain guidance documents and technical support manuals are available from EPA that may assist in performing use attainability analyses. However, to preserve flexibility, the Commission declined to reference any such specific documents in the regulation. A full biological, chemical, and physical assessment is not a necessary minimum requirement for each and every use attainability analysis. Only those evaluations necessary to determine the attainability of a use for a particular water body need be performed.
In addition, the Commission rejected EPA's recommended change to the definition of "water quality standard." EPA recommended that "standard" be defined to refer both to a designated use and related water quality criteria. In Colorado, the established practice is that classifications specify the designated use and "standard" refers to what EPA calls "criteria." There is no need for the change recommended by EPA, and it would result in considerable confusion.
The EPA recommended that two additional items be added to the list in section 3.1.6 of considerations in assigning classifications. There is no need to adopt the language relating to "waste transport or waste assimilation" because the Commission has never considered adopting such a classification for any Colorado streams. In addition, the requirement that flows resulting solely or principally from effluent discharge be taken into account in classifying ephemeral or intermittent streams would be inconsistent with Colorado's water rights system. Because water rights changes may result in changes in discharge points, it would be inappropriate to rely on effluent flows in classifying streams.
C. TOXICS CONTROL AND WATER QUALITY STANDARDS
The adoption of new statewide basic standards for organic pollutants was proposed in the notice for this hearing. That proposal is being addressed at a separate hearing scheduled for December, 1988, and action on that proposal will be taken separately at a later date. The Commission revised the introduction language in section 3.1.11 to help clarify the application of the narrative basic standards. The Commission rejected a recommendation by EPA that this Regulation reference a separate policy for implementation of the narrative "free from toxics" standards. The Commission has scheduled a separate hearing to consider the adoption of biomonitoring regulations relating to the "free from toxics" standards.
D. GROUND WATER REFERENCES
Because the Commission has adopted separate Basic Standards for Ground Water (3.11.0), the Commission has generally deleted references to ground water in this Regulation. In addition, the name of the Regulation has been changed to "The Basic Standards and Methodologies for Surface Water." A few references to ground water were retained, where ground water quality is a relevant factor in determining appropriate surface water classifications and standards. In addition, as provided in sections 3.1.1 and 3.1.11 , until issues relating to proposed new statewide ground water standards for organic pollutants and radioactive materials are resolved following a December, 1988 hearing, certain basic standards set forth in section 3.1.11 will continue to apply to State ground waters.
E. LOW FLOW CRITERIA
Section 3.1.9 has been revised to change the low flow criteria used for permitting and other purposes. The revised criteria are based on the "biological" approach of establishing a 3-year recurrence interval for water quality standards exceedences, to allow adequate time for aquatic life to recover. This biologically based method is an empirical approach recommended by EPA based upon the available historical data. One example of how to calculate an empirically based flow is contained in "Technical Guidance on Stream Design Flow for Steady-State Modeling," USEPA (1986). This approach is preferable to the prior "7Q10" low flow criterion, which has no biological basis. The revised criteria preserve flexibility to determine on a case-by-case basis the best way to calculate low flows meeting these requirements, depending on the data available in a specific case.
The revised low flow criteria will be applied in conjunction with the new frequency and duration provisions added to the regulation. (See the discussion in the following subsection of this Statement of Basis and Purpose.) This overall approach will provide flexibility for the Division and permittees in the permitting process to assure that water quality standards are met during all appropriate periods, whether resulting from, e.g., flow, pH, or temperature conditions. The second sentence of section 3.1.9 also provides flexibility for the use of periodic low flows whenever warranted due to seasonal variations in critical parameters, such as pH or temperature.
The Commission deferred for later discussion the proposal by the Denver Board of Water Commissioners that certain future water uses be taken into account in calculating a low flow, since the future actual use of conditional water rights often is unpredictable. The Commission believes that this type of proposal warrants further consideration in the future, when it can be more fully and directly analyzed. A Colorado Springs proposal to add language stating that there is no guarantee of low flows used in permits was rejected because it presents a legal issue beyond the scope of this Regulation. The Commission notes that section 25-8-104 precludes the Commission and Division from requiring minimum stream flows.
The Commission has also added a new section 3.1.14 to clarify that these revised low flow criteria are to be used in the discharge permitting process.
F. FREQUENCY AND DURATION PROVISIONS
Language has been added to section 3.1.7 to state that numeric water quality standards will include appropriate averaging periods and frequencies of allowed excursions. Averaging periods are specified in the definitions of "acute standard" and "chronic standard" (sections 3.1.5), in section 3.1.16 and in Tables I, II and III.
The Commission declined to add language to section 3.1.16(1) stating that discharge permit limits are to be based on the more stringent of an acute or chronic standard. Generally, effluent limitations based on chronic standards will be more stringent than those based on acute standards. For now, any exceptions to this rule are to be dealt with by the Water Quality Control Division on a case-by-case basis, using best professional judgment. It is anticipated that this issue will be addressed further in a wasteload allocation/total maximum daily load guidance document being developed by the Division.
Frequency of allowed excursions is addressed in section 3.1.7 . The new low flow criteria in section 3.1.9 also are consistent with these averaging period and frequency of excursion provisions. New section 3.1.14 assures that these provisions will be implemented in translating water quality standards into discharge permit effluent limitations. The Commission believes that these provisions will help clarify the proper interpretation and application of water quality standards.
G. USE CLASSIFICATIONS
The introductory language of section 3.1.13 has been revised to clarify the applicability of the use classifications described in that section. The reference to ground water has been deleted. Consistent with the Water Quality Control Act, the language now specifies that these classifications may be applied to any State surface waters except those in ditches and other manmade conveyance structures. The Commission does not intend any change in its prior practice of applying use classifications to rivers, streams, lakes and reservoirs.
The aquatic life use classification descriptions have been substantially revised. Definitions of "cold water biota" and "warm water biota" have been added to section 3.1.5 to help implement these revised classification descriptions. The changes are intended to more clearly and accurately describe the distinctions that are intended by the Commission among the various aquatic life classifications.
The Commission intends the reference to "diversity" of species to be general, with the appropriate means of assessing diversity to be determined on a case-by-case basis. This reference is not intended to rely on any specific aquatic diversity index. The Commission also notes that a proposal by the Colorado Mining Association to adopt a "stocked segment" qualifier was rejected as unnecessary and potentially confusing. The Commission already has flexibility under section 3.1.7 to take site-specific circumstances into account in determining appropriate numeric standards.
Although existing classifications will be reviewed for consistency with the new aquatic life classification provisions during the next round of triennial reviews, the Commission does not anticipate that wholesale revision of existing aquatic life classifications throughout the State will be necessary.
The previous domestic water supply class relating to ground water has been deleted, since ground water classification is now addressed by The Basic Standards for Ground Water. Also, the previous high quality water classification provisions have been deleted here, since they have been moved-in a revised form- into section 3.1.8.
H. SECTION 25-8-207 IMPLEMENTATION
Both procedural and substantive provisions regarding hearings pursuant to section 25-8-207, C.R.S., have previously been located in the Commission's Procedural Regulations. In response to a recommendation made at the July, 1987 triennial review hearing, the Commission has added the substantive provisions relating to "section 207 hearings" to this Regulation (section 3.1.6), and has simultaneously deleted the corresponding provisions from the Procedural Regulations. The Commission also has added several clarifying revisions to these provisions, in part to make the language more consistent with that in the statute. In addition, the Commission has added language to section 3.1.6 to clarify that in appropriate circumstances revisions to classifications pursuant to a "section 207 hearing" should not be considered downgrading.
I. INNOVATIVE SOLUTIONS OR MANAGEMENT APPROACHES
The Commission seeks to encourage innovative solutions and management approaches to achieve compliance with water quality standards. A new subsection 3.1.14 has been added to clarify that such techniques may be incorporated into discharge permits to achieve compliance with standards. In addition, new language in section 3.1.3 notes that, where appropriate, control regulations can be adopted to require such techniques.
J. MISCELLANEOUS WATER QUALITY STANDARDS REVISIONS
The new table values for metals contained in Table III are based on equations that are dependent on hardness. Footnote (3) specifies how to select hardness values for use in the equations. Footnote (3) as previously adopted (relating to use of the lower 25th percentile of hardness values) has resulted in some confusion regarding its application. The revised footnote is intended to clarify selection of an appropriate hardness value, and to specify that a regression analysis may be used to select hardness values in appropriate circumstances.
The phrase "representative regional data" will need to be interpreted on a case-by-case basis. It is intended to provide flexibility to use data from adjacent streams or geographically and hydrologically similar streams in appropriate circumstances.
The restrictions on use of regression analysis-use of the lower 95 per cent confidence limit and prohibiting extrapolation beyond the data base-are intended to help minimize the risk of developing a regression-based hardness value that may be unrepresentative of actual conditions. The adopted language also is intended to preserve flexibility for the Division to determine where regression analysis may be inappropriate, requiring use of an alternative site-specific method. As one example, regression analysis may be inappropriate where there is a poor statistical fit.
The Commission considered at the hearing whether the fecal coliform standard currently contained in Table I should be changed to a standard based on a different type of bacteria. Recently available EPA criteria documents suggest that standards based on E. coli or enterococci may be appropriate. The Commission declined to make any change in the standard at this time. The major concerns expressed regarding the proposed change were the increased cost of analysis and the lack of a standard analytical methodology for E. coli. The Commission intends to give further consideration to a possible change in the indicator bacteria as more information becomes available to address these concerns. The Commission has requested the Division to provide a status report regarding these issues to the Commission in approximately one year.
Table I has previously specified that dissolved oxygen conditions be maintained as "aerobic" for several classifications. This standard was imprecise and led to some confusion. Therefore, a specific numeric value for dissolved oxygen has been added to replace the previous "aerobic" standard. The intent of the 3.0 mg/l criterion is to reduce the potential for anaerobic conditions downstream from discharges to segments not classified for aquatic life.
The table value for fluoride for domestic water supply in Table II has been revised to be consistent with EPA's revised drinking water standards. Consistent with past practice, EPA's "secondary drinking water standard" has been adopted as the table value.
Notations have been added where appropriate to the text and footnotes of Tables I, II, and III to clarify which standards are intended as thirty-day, chronic standards and which are intended as one-day, acute standards. In addition, footnotes 1, 2 and 3 to Table I now specify that certain criteria are intended as one-day or instantaneous maxima or minima.
The Commission has deleted the previous footnote (1) from Table III. This footnote, relating to alkalinity, has not been applied in practice and has created confusion as to its intent and applicability.
As previously drafted, the new ammonia equations in Table II could under some circumstances result in an acute value that is less (i.e. more stringent) than the chronic value. A clarification has been added to provide that in such circumstances the chronic value would be used as the acute standard.
Clarifications have been added to the equations contained in Table II, footnote (5) to specify the upper limits for chloride ion concentration for application of the respective equations.
K. OTHER REVISIONS
A new subsection has been added to section 3.1.6 to specify the criteria used by the Commission in determining the appropriate segmentation of streams and other water bodies for classification and standard-setting purposes. These criteria are the same as have been used by the Commission for the last several years, and they are simply being added to the text of the Regulation to assure that the public is aware of the Commission's policy in this regard.
A new subsection has been added to section 3.1.7, to reference the statutorily required considerations in assigning water quality standards. This change was recommended at the July, 1987 triennial review hearing, so that the public will be more clearly on notice of the factors relevant to setting water quality standards.
Several references in the regulation to specific EPA guidance documents have been deleted. While these guidance documents, along with other relevant guidance materials, may be used by the Commission and the Division when applicable, the Commission decided that references to the guidance documents in the regulation are inappropriate, because such reference could be interpreted to suggest that the provisions of the guidance documents are intended to have binding regulatory effect. However, the list of references in section 3.1.16 has not been revised, since this list is intended as background information to identify the source of numeric values in Tables I, II and III.
EPA recommended a change to the mixing zone provisions in section 3.1.9 , to require no acute lethality in the mixing zone. The Commission has adopted changes providing that there shall be no acute lethality in the mixing zone except where there is significant dilution and mixing is rapid. The Commission believes that this change should protect aquatic life while avoiding the need for increased treatment where that is unnecessary to protect the classified uses.
In addition to the substantive changes described above, numerous editorial changes have been made in the Regulation in an attempt to make the Regulation as a whole more readable. Several minor changes were made to conform the overall Regulation with the recent changes to the antidegradation provisions. In several instances terminology has been revised to be more consistent with that in EPA regulations- e.g. changing "areawide" to "widespread" -where the Commission felt that this would minimize unproductive semantic disputes with EPA, while not changing the substantive intent of the State regulation. In addition, several typographical errors in Table III and elsewhere in the Regulation have been corrected.
FISCAL IMPACT STATEMENT
The changes taken as a whole are not expected to have major new fiscal impacts over the long run. These changes are in the nature of clarifications and refinements of a system that has already been adopted. It is expected that there will be significant "start-up costs" for both public and private entities, including the Water Quality Control Division, to become familiar with the revised classification and standards system resulting from the combination of these changes and those adopted on June 2, 1987. These costs, which cannot be quantified at this time, would result from any substantial revisions to this system.
It is possible that specific changes may result in marginally less stringent or more stringent standards applying to specific entities, with associated differences in cost of compliance. At this time it is not possible to predict whether the net cost impact on regulated entities will be positive or negative; nor can such impacts be quantified at this time. Overall, the Commission finds that the revisions adopted constitute improvements in the current classification and standard-setting system which will minimize the potential for over-protection (saving the resources of dischargers) and minimize the potential for under-protection (reducing unwarranted impacts on the State's water quality resources).
PARTIES TO MARCH, 1988 HEARING
