6. Narrative Criteria for Mixing Zones Historically, States have relied on narrative criteria as a means to provide baseline protection for water quality, to address toxicity from combinations of pollutants or unknown pollutants through whole effluent toxicity testing and limits, and to control pollutants for which there are no chemical specific criteria available. EPA has consistently maintained that prevention of nuisance conditions ( e. g., materials that will settle to form objectionable deposits, floating debris, oil, scum, foam and other matter, toxic conditions, etc.), through the application of narrative criteria, apply to all waters, at all times, including mixing zones. Despite this long standing policy, EPA is unaware if, in practice, States and Tribes have had any difficulty ensuring the maintenance of these narrative criteria within mixing zones. EPA is interested in comment which might identify any instances where the application of narrative criteria has created difficulties for States and Tribes implementing these provisions in mixing zones. In addition, EPA has traditionally interpreted these narrative `` free froms'' as including a prohibition against lethality in all waters, including within mixing zones. However, lethality is a non conservative endpoint for measuring toxicity. Section 101( a)( 3) of the CWA establishes a goal of prohibiting `` the discharge of toxic pollutants in toxic amounts'' which could be interpreted as applying to chronic as well as acute toxicity. EPA guidance on appropriate water quality within mixing zones also recommends that `` the total time toxicity exposure history must not cause deleterious effects in exposed populations of important species, including postexposure effects'' ( EPA, 1973). EPA is considering how such an interpretation ( i. e., applying chronic toxicity endpoints to water quality within a mixing zone) could be implemented in the context of the application of narrative criteria within a mixing zone. Guidance developed by EPA in 1985 ( TSD) established a rationale for allowing zones of initial dilution ( ZIDs) or acute mixing zones. That guidance limited the use of ZIDs to extremely small areas of the receiving water under limited conditions and to discharges using rapid diffusers which produce effluent discharge velocities exceeding 10 feet per second. That guidance was premised on the rationale that organisms would be physically precluded from maintaining a position within the ZID, thus preventing lethal exposures. Benthic and sessile organisms were also protected where ZID placement was controlled and directed away from such critical areas ( e. g., near shore, shallows, etc.). In addition, EPA reasoned, high rate diffusers achieve compliance with both acute and chronic criteria within a smaller area, utilizing less receiving water volume for dilution than other discharge designs. Consequently, high rate diffusers are believed to provide greater protection of water quality by their rapid dispersion of effluent within a smaller volume of surface water. Where acute criteria are not applied at the end of pipe, current EPA guidance provides for a number of alternative means of protecting against lethality in a mixing zone, even in situations that do not rely on high rate diffusers. Alternatives to requiring compliance with acute criteria at the end of pipe or employing a high rate diffuser to ensure compliance `` within a very short distance from the outfall'' require a significant amount of site specific data. Such site specific data could be requested of NPDES permit applicants. It is EPA's experience that the collection of this kind of data does not occur on a routine basis. EPA is interested in public comment on the relationship between ZIDs or acute mixing zones and narrative criteria prohibitions against lethality and States' and Tribes' experiences with the application of acute mixing zones under varying sitespecific and discharge specific conditions. EPA is also interested in comments on whether the water quality benefits of using high rate diffusers justify potentially detrimental effects on stream bed or shore line habitat.

7. Mixing Zones for Bioaccumulative Pollutants States and Tribes should exercise caution when evaluating whether a mixing zone is appropriate in cases where bioaccumulative pollutants are present. The impacts of bioaccumulative compounds may extend beyond the boundaries of a given mixing zone with resulting impairment of a water body's designated uses, particularly where stationary species ( e. g. shellfish) are present, where uncertainties exist regarding the assimilative capacity of a water body or where bioaccumulation in the food chain is known to be a problem. Sediment contamination has also become a major concern in both flowing and non flowing water bodies. Concerns about sediment contamination require additional attention since typical mixing zone evaluations focus only on water column toxicity. The effects of persistent and bioaccumulative pollutants may not be detected for some distance from the point of discharge, well outside the mixing zone, or possibly not in the water column at all. Some members of the public have expressed concern regarding the use of mixing zones in situations where bioaccumulative pollutants are present in a discharge and have urged EPA to develop specific regulatory requirements prohibiting the use of mixing zones where these pollutants are present. Mixing zone policies are developed to address complete and incomplete mixing conditions associated with point source discharges. These policies identify whether mixing zones are allowed and define how a State or Tribe will limit the amount of surface water allocated to mixing under a variety of circumstances. These circumstances include considerations specific to the effluent and pollutants discharged ( e. g., toxicity, solubility) and to the water body receiving the waste ( e. g., shallow, flowing or non flowing, high flow or low flow, critical habitat). The potential for bioaccumulation problems can depend on a number of site specific factors and the use of mixing zones for bioaccumulative pollutants may be best dealt with on a site or basin specific basis. EPA's mixing zone guidance emphasizes that the determination by a State or Tribe that a mixing zone is appropriate must be preceded by a separate determination that there is available assimilative capacity in the receiving water. Localized water quality concerns are to be balanced with the larger scale issue of overall pollutant loading to the entire water body or segment. Perhaps concerns about the fate and transport of bioaccumulative pollutants are more effectively addressed under total maximum daily load ( TMDL) development and determinations of assimilative capacity which incorporate information on water 36792 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules column, sediment and tissue contamination. EPA is considering the appropriateness of using mixing zones when controlling for bioaccumulative pollutants. As discussed in more detail in Section C of this Notice, EPA has recently developed methodologies for deriving sediment quality criteria for non ionic organics and metals and has proposed sediment quality criteria for five organics. In addition, EPA is working on implementation procedures or a `` user's guide'' for these sediment criteria which will address risk management decisions such as the application of mixing zones. The regulatory impact of special restrictions on mixing zones for a particular family of pollutants is largely determined by how that family of pollutants is defined within the regulation. The issue of definition of bioaccumulative pollutants is also addressed in the discussion of water quality criteria in Section C of this notice. In its Great Lakes Guidance, EPA established a twelve year phase out of mixing zones for existing discharges of bioaccumulative chemicals of concern ( BCCs) in the Great Lakes Basin and a ban on such mixing zones for new discharges ( effective March 1997). The Great Lakes Guidance also allowed States and Tribes to establish limited exceptions to the mixing zone phase out for existing discharges based on water conservation or economic and technical considerations. The general prohibition on mixing zones for BCCs was established largely because of the persistent and toxic nature of even minute amounts of BCCs in the environment; an effect amplified in the Great Lakes by the tendency of the Lakes to act as `` sinks'' for pollutants discharged to the Great Lakes Basin. In addition, there are documented problems with effects of BCCs in Great Lakes waters ( e. g., contamination of Great Lakes salmonid sport fisheries with PCBs and Basin wide mercury contamination). The Great Lakes Guidance provision phasing out mixing zones for BCCs reflected the Agency's thinking that, in general, mixing zone allowances for BCCs are not appropriate. On June 6, 1997, the United States Court of Appeals for the District of Columbia Circuit issued its decision in American Iron and Steel Institute, et al. v. EPA, 115 F. 3d 979 ( D. C. Cir. 1997). The Court's decision upheld the Great Lakes Guidance on all but three issues. One of these three issues was the phase out of on mixing zones for BCCs. Specifically, the Court vacated the final Guidance insofar as it would eliminate mixing zones for bioaccumulative chemicals of concern ( BCCs). While the Court acknowledged the possibility of environmental benefit of the mixing zone provisions, the Court found that EPA failed to show that the provisions were justified in light of the costs. EPA continues to support elimination of mixing zones for BCCs within the Great Lakes Basin wherever it is technically and economically feasible to do so. Thus, EPA intends to propose reinstating this provision in the near future.

8. Stream Design Flow Policies States and Tribes typically identify, within their water quality standards, stream design flow conditions to implement numeric water quality criteria. The stream flow conditions are typically expressed as predictable low flow conditions below which numeric water quality criteria do not apply. Examples of commonly used stream design flows include: the lowest seven consecutive day average stream flow that has the annual probability of occurring once in ten years ( 7Q10); the lowest single day stream flow that has the annual probability of occurring once in ten years ( 1Q10); and the harmonic mean stream flow. The stream design flows typically employed with aquatic life criteria ( i. e., 7Q10 and 1Q10), sometimes referred to as critical low flows or drought flows, are intended to define stream flow conditions at and above which the designated uses are presumed to exist and applicable numeric water quality criteria must be met in order for those uses to be attained. The underlying concept is that these low flow events are a part of the dynamic hydrologic character of all flowing water bodies. Low flow conditions present special challenges to the integrity of the aquatic community. Even under these low flow conditions, however, the long term beneficial use could be maintained unless toxic conditions stress the aquatic community beyond its ability to tolerate and recover. In practice, stream design flows serve several purposes in addition to defining the minimum stream flows below which numeric water quality criteria do not apply. Many States and Tribes have used the stream design flows, or fractions thereof, to define the amount of stream flow that can be assumed to always be available to dilute effluent. Under rapid and complete mixing conditions, the entire stream design flow is used as the basis for determining permit limits. That is, no mixing zone is necessary. Under slow or incomplete mixing conditions, where a mixing zone is necessary, fractions of stream design flow are used to calculate assimilative capacity on which permit limits can be based; in other words, to crudely define the mixing zone. Often this default approach is used by regulatory agencies in response to limited resources, lack of site specific information and the time pressures of permit reissuance. This default approach to defining the mixing zone is, in EPA's view, acceptable as long as the mixing of the effluent in the receiving water occurs away from critical areas and the amount of dilution provided is conservative for a broad range of possible effluent/ receiving water dilution scenarios. However, where a complete mixing assumption does not hold true, such as where an effluent plume does not disperse quickly, and too much of the receiving water is allocated for dilution, this default assumption approach will not ensure attainment of water quality standards because numeric water quality criteria will be exceeded in a larger area than anticipated ( outside the regulatory mixing zone). The default use of fractions of stream design flows instead of more exacting mixing zone determinations is not always appropriate. In some instances, the effluent plume may never fully mix with the specified amount of receiving water, resulting in plumes where criteria are exceeded extending far beyond what may be considered protective of designated uses or allowed under standards. EPA has recommended that site specific information on the mixing characteristics of a discharge be collected to verify the level of protection assumed to be provided to a water body using default mixing zone provisions. EPA believes it is important for individual States and Tribes to make consistent dilution allowance decisions from one site to the next. Requiring States and Tribes, as part of their water quality standards, to specify how dilution allowances under complete and incomplete mix situations will be established may be an appropriate way to ensure consistent decision making. To best define dilution allowances for implementing water quality standards, it is useful to define both stream design flows and effluent design flows. In particular, a distinction should be made between the stream design flows to be used for different ambient water quality criteria ( e. g., aquatic life acute, aquatic life chronic, human health carcinogen). In addition, effluent design flows may vary in some cases based upon seasonal changes or production cycles. Stream design flows may be applied as a maximum dilution allowance or adjusted in individual cases based on 36793 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules any stream specific or pollutant specific considerations. Stream design flows, if they are used, must correspond to the duration and frequency components of the ambient water quality criteria contained in the State or Tribal water quality standards. Currently, States and Tribes must justify the scientific validity of their stream design flow policies where they differ from EPA's recommendations. States and Tribes may also establish specific guidelines for restricting dilution allowances in individual cases ( e. g., States and Tribes may adopt special restrictions on dilution allowances for human health criteria where a discharge is within 2 miles of a drinking water intake). EPA's Great Lakes Guidance and its Technical Support Document for Water Quality Based Toxics Control identify acute and chronic stream design flows to be utilized in drafting permit limits. The Guidance establishes a 7Q10 or 4 day, 3 year biologically based stream design flow for implementation of the aquatic life criterion continuous concentration ( chronic criteria); a 1Q10 for the implementation of the aquatic life criterion maximum concentration ( acute criteria); harmonic mean flow for implementation of human health criteria; and a 90Q10 for the implementation of wildlife criteria. In cases where complete and rapid mixing of effluent with receiving water does not occur, site specific mixing determinations must be made. Although the selection of fractions of stream design flows for the assignment of available dilution for point source discharges does affect the size of the regulatory mixing zone, such default assignments are not hydrologically linked to the actual behavior of the effluent plume in the receiving water, may not protect swimming and drifting organisms or sessile or benthic organisms and are not equivalent to a mixing analysis. There may be other instances where the reliance on a fixed percentage of flow or cross sectional area of the receiving stream in lieu of an actual mixing analysis may not reflect the mixing behavior of an effluent. In some high dilution situations, there may be more rapid dilution occurring than is assumed in dilution calculations. If complete and instantaneous mixing actually occurs, using less than 100% of the design flow can be a means of accounting for situations where the actual assimilative capacity of the water body is unknown. States and Tribes typically determine water body assimilative capacity based on ambient background concentration of a pollutant, when data on such concentrations is available. The assimilative capacity is the difference between the background level of a pollutant and the highest level that would comply with the water quality criterion. Where information on all sources of a given contaminant to a specific water body is incomplete, or where the State or Tribe wishes to reserve assimilative capacity for the future, States and Tribes should allocate less than 100% of the assimilative capacity of that water body at design flow by utilizing less than 100% of the design flow for dilution. EPA is interested in comment addressing the use of these stream design flows or fractions of stream design flows in setting mixing zones and in reserving assimilative capacity in a water body. The Great Lakes Guidance allows States and Tribes to use default assumptions for available dilution in the absence of site specific mixing data. The default dilution assumption for open waters ( e. g., lakes) provides for ten toone dilution. The Guidance also allows for a demonstration to determine actual mixing zone water quality, size, placement and behavior. Under the Guidance, for open waters, in no case can mixing zone size exceed that area in which discharge induced mixing occurs. As a default, the Guidance restricts the mixing zone for protection of aquatic life from acute effects ( i. e., the dilution allowed in calculating limits based on an acute aquatic life criterion or CMC) to 2 parts receiving water to 1 part effluent, at water body design flow or volume. As a default for implementing criteria for the protection of aquatic life from chronic effects ( CCC) in flowing waters ( e. g., rivers and streams), the Great Lakes Guidance allows States and Tribes to use up to 25% of the design flow for dilution. If a site specific mixing analysis is performed, a larger mixing zone may be established. Mixing zones for acute aquatic life criteria in flowing waters are limited to the final acute value or FAV ( 2 ´   the acute criterion) just as in open waters. EPA is interested in comment on whether this FAV default `` cap'' approach is appropriate for waters outside the Great Lakes Basin. As stated above, the Great Lakes Guidance allows increases above the default mixing zone allowances when site specific mixing zone analyses are conducted. These demonstrations compile data on the mixing behavior of the effluent at a particular site ( e. g., the size, shape and location of the mixing zone). The Guidance also required that mixing zones maintain existing and designated uses and comply with narrative water quality criteria ( e. g., `` free froms''). The Great Lakes Guidance also specifies that mixing zones may not jeopardize the existence of threatened or endangered species or their critical habitat. EPA advocates the watershed approach to water quality protection. For the water quality standards program, the emphasis has been toward refinement of designated uses and incorporation of new and emerging sophisticated and integrated analytical tools as a means to better characterize the ecological condition of water resources and more effectively protect designated uses ( see section I( A) `` General Purpose and Vision'' of this document). The development and implementation of mixing zone policies by States and Tribes constitutes risk management at the sub watershed level. EPA has consistently emphasized the need to ensure that State and Tribal mixing zone provisions protect the designated uses of receiving waters. Site specific data collected through a mixing zone analysis will ensure that designated uses will be protected the loss of ecological integrity from the discharge of effluents will be prevented. An emphasis on the protection of designated uses and maintenance of ecological integrity is essential to the watershed approach. The watershed approach requires increased sitespecific information on local aquatic systems and an assessment of the impact of all discharges to local ecosystems. The watershed approach also depends upon the meaningful involvement of local communities in risk management decision making. Explicit, clear implementation policies provide the public with the information necessary to understand decisions being made by regulators and the impact of those decisions on local resources.

Request for Comments on Mixing Zone Policies and Implementation Procedures EPA requests comment on the following questions: 1. Should the regulation be changed to expressly require States and Tribes to include a statement in their water quality standards indicating whether mixing zones are allowed? 2. Should the regulation be changed to expressly require States and Tribes to specify procedures by which mixing zone decisions for individual discharges would be made? 3. Should the regulation be modified to identify the minimum requirements or elements for State and Tribal mixing zone policies ( including size, location, and methodologies)? 36794 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules 4. Consistent with current EPA policy, should the regulation explicitly require narrative criteria to apply in mixing zones? 5. Should the regulation require States and Tribes to identify in their mixing zone provisions what minimum water quality conditions are required within mixing zones? 6. Are there any circumstances, types of pollutants or water body types ( e. g., wet weather discharges) where mixing zones should be restricted or prohibited? 7. Should mixing zones for bioaccumulative pollutants be prohibited? If so, under what circumstances? Should such prohibitions be addressed on a water body or basin specific basis? Should EPA allow exceptions to any such prohibitions? 8. Should the regulation require States and Tribes to specify procedures and decision criteria for evaluating complete and incomplete mixing? 9. Should the regulation require different mixing zone/ dilution procedures for complete and incompletely mixed situations? 10. Should an assumption of rapid and complete mixing within State and Tribal implementation procedures be prohibited except where a defensible technical rationale is included in each site specific determination? 11. Should the regulation explicitly allow the use of default mixing zone assumptions based on fractions of stream design flow in the absence of site specific data? 12. Should the regulation be clarified, consistent with current EPA policy, to require States and Tribes to identify the water body design flows or volumes upon which their water quality standards are based?

F. Wetlands as Waters of the United States The current water quality standards regulation contains no definition of `` waters of the United States,'' although this term is used in the definition of `` water quality standards.'' The phrase `` waters of the United States'' has been defined elsewhere in Federal regulations, including regulations governing the National Pollutant Discharge Elimination System ( NPDES). That definition at 40 CFR 122.2 includes wetlands whose use, degradation or destruction could affect interstate commerce and wetlands adjacent to other waters of the U. S. However, because this definition does not appear in 40 CFR 131, some have questioned whether Part 131 applies to wetlands. EPA's position is that the Part 131 regulations do apply to wetlands. EPA is considering including the definition for `` waters of the United States'' under the standards regulation as well, or, at a minimum, cross referencing the definition at 40 CFR 122.2 as a means of clarifying that the existing regulation applies to wetlands that fall within the definition of waters of the United States. Currently, EPA plans no review or revision of the existing definition of `` waters of the United States'' as part of any revision of the water quality standards regulation. Therefore, under the ANPRM, EPA is interested in comment limited to whether the existing definition should be included within the standards regulation in some form. EPA believes that some States or Tribes may not be providing the same protection to wetlands that they provide to other surface waters, including designation of attainable uses consistent with the CWA and assignment of protective water quality criteria. Therefore, EPA wishes to emphasize that wetlands require the same protection under water quality standards as other waters of the U. S. Section 303 of the CWA requires the protection of all `` waters of the U. S.'' under standards. Addition of the definition of `` waters of the U. S.'' under a revision of the regulations would not constitute an expansion of authority or application, but merely a clarification of those requirements already contained within the CWA. Treatment of jurisdictional issues would not be affected by such a revision, including treatment of waters constructed as waste treatment systems ( e. g., wetlands constructed for wastewater treatment). Notwithstanding protection of wetlands under other provisions of the CWA ( e. g., Section 404), Section 303 clearly establishes a baseline level of protection applicable to all waters. Further, it is this treatment under water quality standards which provides for protection of wetlands as applied under Section 404. Necessary components of water quality standards for wetlands are designated uses and criteria, as defined in 40 CFR 131.6. EPA recognizes that uses and criteria should reflect the unique physical, chemical and biological characteristics of wetlands. States and Tribes are encouraged to develop and adopt appropriate classification systems which provide protection of beneficial uses of wetlands through the application of physical, chemical and biological criteria. EPA also recognizes that certain parameters, conditions or even pollutants may be most appropriately addressed by criteria which specifically reflect differences between wetlands and other surface waters.

Request for Comments on Wetlands EPA requests public comment on the following questions: 1. Should `` waters of the United States'' be defined in the water quality standards regulation? 2. Should EPA provide explicit reference in the regulation to the applicability of water quality standards to wetlands? 3. Do the current regulation and existing guidance provide the necessary regulatory clarity, technical tools, and incentives for States and Tribes to develop appropriate standards for wetlands? 4. Are specific programmatic changes needed to facilitate the development of water quality standards for wetlands?

G. Independent Application Policy 1. Introduction Section 101( a) of the Clean Water Act states: `` The objective of this Act is to restore and maintain the chemical, physical, and biological integrity of the Nation's waters.'' To this end, States and Tribes designate single or multiple uses for their waters including aquatic life protection. For the purposes of assessing the extent to which aquatic life is protected and whether actions to protect aquatic life are needed, the CWA requires that States and Tribes adopt water quality criteria necessary to support designated uses. For waters where aquatic life protection is an applicable designated use, the extension of the CWA requires States and Tribes to adopt criteria protective of aquatic life. Taken together, chemical, physical, and biological integrity define the overall ecological integrity of an aquatic ecosystem. Over the years, EPA, States and Tribes have developed various tools to assess the extent to which water quality attains this objective. These tools have been developed to build on and support the capabilities of each other and provide a comprehensive set of elements necessary for implementing water quality standards and achieving the objective of the CWA. EPA policy and guidance recommends that States and Tribes use chemical specific, toxicity, and biological criteria to monitor and protect designated uses. In 1991, EPA established its policy on independent application ( U. S. EPA, transmittal memorandum of final policy on biological assessment and criteria from Tudor Davies to Regions, June 19, 1991). EPA's independent application policy speaks to how assessments based 36795 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules on these three kinds of criteria are to be integrated into all forms of water quality management decision making. EPA's independent application policy and the ensuing discussion here address the issue of how the three different kinds of assessments are interpreted only in the context of protection of aquatic life and aquatic life uses and not in the context of protection of human health or wildlife. With the advent of different ways of assessing the health of aquatic systems comes the possibility of conflicting results. To address such conflicts, EPA developed the policy of independent application. Independent application states that where different types of monitoring data are available for assessment of whether a water body is attaining aquatic life uses or for identifying the potential of pollution sources to cause or contribute to non attainment of aquatic life uses, any one assessment is sufficient to identify an existing or potential impact/ impairment, and no one assessment can be used to override a finding of existing or potential impact or impairment based on another assessment. The independent application policy takes into account that each assessment provides unique insights into the integrity and health of an aquatic system. In addition, each assessment approach has differing strengths and limitations, and assesses different stressors and their effects, or potential effects, on aquatic systems. For example, while biological assessments can provide information in determining the cumulative effect of past or current impacts from multiple stressors, these assessments may be limited in their ability to predict, and therefore prevent, impacts. While chemical specific assessments are useful to evaluate and predict ecosystem impacts from single pollutants, chemical specific methods are unable to assess the combined interactions of pollutants ( e. g., additivity). Similar to biological assessments, toxicity testing provides a means of evaluating the aggregate toxic effects of pollutants, and like chemical assessments, can also be used when testing effluent to predict single chemical impacts. One of the limitations of toxicity testing, however, is that the identification of pollutants causing toxicity is not always possible or costeffective Each of these three assessment approaches relies on different kinds of water quality data, measures different endpoints and, in practice, will be interpreted in the context of implementing a water quality management program that includes assessment and pollution control. EPA's policy on independent application is based on the premise that any valid, representative data indicating an actual or projected water quality impairment must not be ignored when determining the appropriate action to be taken. Independent application recognizes the strengths and limitations of all three assessment approaches. The next three sections briefly describe three assessment approaches ( biological, toxicological and chemical) one could likely be evaluating when using independent application. Those three sections are then followed by two parallel discussions on different uses of water quality data. One use relates to the NPDES permits program to determine whether a permit must contain water quality based chemical or toxicity limits, and what those numeric limits should be. The other relates to the use of such data to evaluate the quality, or condition, of waters under the CWA section 305( b) and 303( d) programs. At the core of both of these contexts is the question `` are the present applicable water quality criteria complete and appropriate for the water body, and how are we to measure attainment of the present or future criteria that apply to any water body in question?'' Thus, in its most basic sense, independent application remains a water quality standards question. Any changes to or clarifications of the policy on independent application must therefore be considered first under the rubric of water quality standards and then in the separate contexts of permitting and water quality evaluation which are based on water quality standards. States and Tribes routinely determine whether water bodies are attaining their designated uses and whether existing pollution controls adequately protect those uses. Some States and Tribes have recommended to EPA that it modify the independent application policy. Currently, EPA's policy of independent application is the same for both NPDES permitting and water quality assessment programs. However, EPA recognizes that each of the programs has somewhat different data needs and attributes. Therefore, today's notice separates the two distinct uses of independent application to better focus the discussion. a. Biological Assessments. Biological assessments are based on quantifying differences between expected biological community attributes such as structure, function and condition ( known as a reference condition) and the biological community attributes found at a specific site being evaluated. The extent to which the community at the site deviates from the reference conditions is indicative of the degree of impairment at the specific site. The strength of biological assessments is their ability to provide a direct measure of the health of aquatic ecosystems. Biological assessments are also able to detect nonchemical impacts ( e. g., habitat loss, sedimentation, temperature effects) in addition to chemical toxicity problems. States and Tribes that use biological assessments, use them primarily to evaluate the ecological condition of water bodies and to determine whether a water body is healthy, threatened, or impaired ( i. e., aquatic life use attainment decisions). In some instances, States and Tribes have used biological assessments to establish monitoring requirements in an NPDES permit, but generally, most use bioassessments to make non regulatory, general, water resource management decisions. Data from a biological assessment can be compared to a gradient that shows the reference ( expected) conditions without impairment on one end and the worst situation on the other. States and Tribes generally use the results to determine whether additional measures are needed to protect the water segment, or determine how close to attainment an impaired system is. Biological assessments can also play a role in linking impairment to causative agents. This link is often not definitive, but can be very useful in helping to identify the causes and sources of many impairments. Some States and Tribes have used indicator species or groups to distinguish effects of toxicity from effects of organic enrichment. For example, one State documented that a midgefly larvae is found to be predominant in areas contaminated by electroplating or metal wastes. Although biological assessments cannot be used to predict conditions in a mathematical modeling sense, over time they can be used to indicate the direction of change, and the degree of that change, in the condition at a particular site. This information, where it is based on enough data using relatively sensitive appropriate metrics, can be very valuable in deciding whether the current condition is likely to be maintained under similar conditions in the future, or whether there are early warning signs of biological impacts giving reason to believe that additional regulatory actions may be needed to prevent water quality standards impairment. Regulatory actions that are a response to measured change in biological condition will tend to be restorative more than preventative ( i. e., 36796 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules once biological impact is measured, by definition, that impact was not prevented). Although, slight changes that are not sufficient to render a water in non attainment of its aquatic life use, can provide early warning of potentially more significant future changes. In contrast, as noted above, regulatory actions based on impairment predicted, for example via a chemical specific modeling analysis, tend to be preventative. To the extent that conditions in a water body do change ( e. g., flow), biological assessments do not reveal potential future impacts under other exposure conditions ( e. g., low flow conditions). Programmatically, there are concerns regarding quality assurance and quality control for various biological assessment techniques since they have yet to be promulgated, or standardized, in any EPA programs. This is mainly due to the site specific nature of biological assessments. Implementation of biological criteria is also discussed in section ( B) of this notice. b. Toxicological Assessments. Toxicological assessments are conducted by exposing aquatic organisms to effluent or ambient water samples or sediment samples in a laboratory and determining the effects on the exposed organisms. Because toxicity assessments evaluate the overall effects of the entire suite of constituents in a sample, they are ideal for identifying interactions between chemicals that can alter the expected effects of individual chemicals on exposed organisms. Toxicity assessments also capture the toxic effects of chemical compounds not commonly monitored for or for which chemical specific criteria are lacking. In addition, because it can be manipulated in the laboratory, toxicity testing can predict the likelihood of ecological impacts before they occur. This allows safeguards to be put into place before an actual ecological impact occurs. Toxicity assessments are usually limited by the variety of species that can be cultured in the laboratory. While numerous test species can be used to evaluate the toxicity of individual samples, typically only two or three species are used for such tests. By comparison, eight different families are required to develop chemical specific criteria. For some toxicants, the broader sensitivity range provided by testing eight different families is particularly important, for example, where the mode of toxicity action is specific ( e. g., pesticides). Identifying the cause of toxicity can, in some situations, be a difficult, expensive, and lengthy process. Another consideration is that toxicity testing does not detect habitat perturbations which can greatly limit a water resources aquatic life use. Finally, toxicity assessments are only valid for as long as all the sample testing conditions remain the same. Ambient conditions affecting toxicity may change over time necessitating additional testing. c. Chemical Assessments. Chemical assessments measure individual chemical constituents ( e. g., copper, lead) or chemical conditions ( e. g., pH, temperature, hardness, organic content) in a medium. Chemical assessments may be performed on effluent or ambient water samples or sediment samples. Chemical analyses are usually simpler to conduct and generally less expensive than toxicity assessments or bioassessments, particularly if there are only a few chemicals of concern, but the information from these tests may provide limited insight into the ecological condition of the water body. If information is available on pollutant persistence and degradation, modeling can be used to predict pollutant fate and transport under a variety of exposure scenarios. Further, chemical specific assessments are ideal for predicting the likelihood of ecological impacts where they may not yet have occurred either because a proposed activity affecting water quality has not been implemented or critical exposure conditions have not yet been experienced by the aquatic community. For these reasons, regulatory actions based on chemicalspecific assessment can be preventative as well as restorative. Basing regulatory and management decisions on chemical assessment of water quality is an important and proven aspect of water quality assessment and protection. However, as an indirect measure of aquatic health, one of the principal limitations to chemical assessments is dependence upon chemical specific benchmarks ( such as chemical water quality criteria) for determining whether water quality is suitable or unsuitable for attaining and maintaining aquatic life uses. As noted elsewhere in this notice, stressors other than specific chemicals in a water body are often a significant or even predominant cause of nonattainment of aquatic life uses. EPA's current thinking is that complete reliance on chemicalspecific assessments of water quality is too narrow of a focus and fails to provide information on other important ecosystem stressors. In addition, as noted elsewhere in this notice, there are currently water quality criteria for the protection of aquatic life for 31 chemicals. There are tens of thousands of chemicals discharged into surface waters. ( Note, however, that the chemicals for which there are criteria tend to be the most frequently discharged). Thus there is the added problem of too few criteria and too many chemicals, making it inappropriate to rely exclusively on the chemical specific approach. Another substantial limitation of chemicalspecific benchmarks is that for a given site, the benchmarks that are used, may not be the best that are available to reflect the level of protection applicable at the site. For example, site specific aquatic life criteria are generally different ( higher or lower) than the national recommendations for the same chemical. And yet absent site specific criteria, the national recommendations are often used.

2. Independent Application and Water Quality Assessments a. Independent Application. States and Tribes often collect or have access to monitoring data that measure the concentration of specific chemicals in an effluent or water body, the level of toxicity present in ambient water or discharges to a water body and/ or the biological community composition within a water body. These data are then interpreted by comparing them to reference conditions or criteria to determine whether or not aquatic life uses are attained. EPA's 1991 policy on independent application was explicit about the use of independent application in water quality programs: `` This policy, therefore, states that appropriate action should be taken when any one of the three types of assessment determines that the standard is not attained. States and Tribes are encouraged to implement and integrate all three approaches into their water quality programs and apply them in combination or independently as sitespecific conditions and assessment objectives dictate.'' In implementing this policy, EPA recommends that data from the three assessment approaches be applied independently in water quality programs since each method provides unique and distinct information on the characteristics of the water body. In other words, EPA recommends that differences in assessment results be resolved in one of two ways: either presume an adverse impact when any one source of data indicates an adverse impact, or reevaluate the complete data set and modify the applicable criteria to account for the new site specific information. Given EPA's mission to protect the environment and absent definitive data to demonstrate that an assessment is in error or otherwise biased, EPA presumes 36797 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules where an assessment indicates impairment, that assessment is valid. In the context of applying the independent application policy to the assessment of water bodies, there are two distinct CWA provisions to consider: ( 1) section 305( b), which requires States and Tribes to report to EPA and EPA to report to Congress a description of the quality of the Nation's waters; and ( 2) section 303( d), which relates to identification of waters where technology based limitations and other required controls are not stringent enough to ensure that applicable water quality standards will be attained and maintained. With respect to the section 305( b) Report, the CWA broadly calls for States and Tribes to assess water quality conditions in a biennial report. EPA transmits these reports to Congress, together with an analysis of the reports describing water quality conditions. Because these are water quality assessment reports that States and Tribes submit to EPA, and not specific regulatory decisions, there may be sufficient flexibility in the interpretation of data to allow a more integrated approach to evaluating limitations and inconsistencies in the interpretation of data produced under various approaches. For example, direct assessments of the condition of the waters ( e. g., biological assessment) could be weighted more heavily than indirect measurements ( e. g., chemical and toxicity). With respect to section 303( d), the CWA and EPA's implementing regulations require States and Tribes to identify those waters for which technology based limitations and other required controls are not stringent enough to achieve water quality standards applicable to such waters. See 303( d)( 1)( A), 40 CFR 130.7( b)( 1). When identifying waters pursuant to 303( d), the methods used to determine nonattainment of standards for water quality reporting under 305( b) should also be used. However, water bodies are eliminated from 303( d) list consideration if technology based controls or other required Federal, State, Tribal or local requirements will result in the attainment of applicable water quality standards. TMDLS developed to secure restoration of designated uses are largely dependent upon chemical criteria and assessment to define acceptable pollutant loadings. The question arises as to whether States and Tribes have the flexibility to exclude a water body from 305( b) reports and 303( d), i. e., conclude that the designated use was protected, even in the face of data indicating one or more excursions of the applicable chemical specific water quality criteria. EPA would like to consider possible mechanisms under the existing CWA and the legal theories supporting them to address these questions. As with determining the need for regulatory controls ( permit limits), similar data evaluation issues face States, Tribes and EPA in performing water body assessments for purposes of sections 303( d) and 305( b) of the CWA. With respect to such assessments, EPA's goals for States and Tribes are twofold: ( 1) to encourage the use of chemical, toxicological, physical and biological data in making water body assessments; and, ( 2) to ensure that the data are interpreted and reported in a consistent and scientifically defensible manner so that documents such as the 305( b) report to Congress provide valid and useful information on the status of the Nation's waters as a whole, irrespective of State or Tribal boundaries. EPA recognizes that there may be instances where these goals appear to be in conflict. It is possible that as States and Tribes implement biological assessment programs, they may identify new areas of impact that were previously undetected using other assessment techniques and that this may lead to a reluctance on the part of States and Tribes to develop the expertise necessary to conduct biological assessments. Although this tendency is contrary to the goals and objectives of the CWA, the fact is that addressing new and previously unaddressed threats to surface water quality places additional strain on already limited State and Tribal resources. Some also feel that adherence to a strict independent application policy for assessment purposes discourages the use of more data than minimally needed to make an aquatic life use assessment. In most cases, the minimal amount of data would be a chemical grab sample for a few water quality characteristics such as temperature, pH, BOD, or dissolved oxygen. Collecting minimal data for assessment reporting is much easier and less resource intensive for States and Tribes that are required to increase their reporting coverage, and these States and Tribes would not have to deal with differing interpretation of assessment results. However, EPA believes that placement of waters on section 303( d) and section 305( b) lists should be based on broad thorough assessment data, not on limited and narrow data. The former will help ensure that targeted water quality controls and management actions are appropriate and will result in water quality standards attainment; the latter can result in significant outlays of State and Tribal resources targeted on waters where water quality problems are not well understood. EPA is considering how best to obtain accurate, high quality assessment data and how to reconcile differences between assessments conducted using different techniques in a manner that fosters consistency and remains scientifically defensible. b. Alternatives to Independent Application. There is considerable sentiment among various stakeholder groups that there is a need to better incorporate more comprehensive data, particularly biological data, into the water quality assessment framework described above and that doing so will facilitate collection and use of more integrated and insightful water quality data. EPA shares this view. Some have used the term `` weight of evidence'' to describe an alternative to the present EPA policy of independent application that could facilitate integration of chemical, physical, toxicological and biological data into the assessment program. However, EPA recognizes that individuals' views about the meaning of the term `` weight of evidence'' vary considerably and this variation should be addressed. The term `` weight ofevidence has been interpreted by some to mean that one approach to assessment, e. g., biological, could routinely be used to override conclusions drawn using another assessment technique, e. g., chemical. EPA believes that approach is hierarchical, not a weight of evidence approach. EPA's position is that each approach, chemical, toxicological, physical and biological has inherent strengths and limitations and that all valid water quality assessment data generated under any of these approaches should be used in assessing the health of aquatic ecosystems, in ways that adequately take into account the strengths and limitations of each approach. EPA's current thinking is that as forms of water quality assessment data have become broader ( chemical, physical, biological and toxicological), and as the amount of such data increases, the water quality standards and assessment programs need to facilitate continued collection and use of such data, and that doing so will lead to more thorough water quality assessments, more insightful water quality criteria, and better descriptions of aquatic life designated uses. EPA would not support an approach that could lead to collecting fewer and narrower water quality data by States, Tribes and dischargers. On the contrary, 36798 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules EPA's current thinking is that to employ a weight of evidence approach, a State or Tribe ( or EPA) would need to have a comprehensive set of water quality data to evaluate the chemical, physical, toxicological and biological conditions in a water and to conduct ecological impact assessment to determine the precise causes of impacts ( chemical, physical, biological, and toxicological) and how best to address them. EPA's current thinking is that the most appropriate context for using a weightof evidence approach would be in establishing criteria. In addition, as discussed below, EPA is interested in evaluating the use of a weight ofevidence approach for assessment and reporting under section 305( b) of the CWA. However, once the criteria are established for a water body, the assessment for purposes of listing under section 303( d) of the CWA and permitting under NPDES, must be based on all applicable water quality criteria. EPA's 305( b) reporting guidelines interpret the independent application policy to apply to aquatic life use assessments for State 305( b) reports, not just to permitting for protecting waters due to reasonable potential to violate water quality standards. This policy helps protect against dismissing valuable information when evaluating aquatic life use attainment, particularly in detecting impairment. This approach is most protective when there is limited data available and when there is no documentation on the rigor of the assessment. EPA is concerned that lack of information can provide false confidence about the health of the nation's water bodies. However, EPA is now developing a comprehensive approach for conducting aquatic life use assessments which integrates chemical, toxicological, physical and biological data, and includes consideration of the strengths and limitations of the assessment methods and the data. This shift toward more integrated assessments is reflected in EPA's most recent guidance to the States and Tribes on conducting 305( b) assessments, particularly in determining nonattainment ( EPA's Guidelines for Preparation of the 1996 State Water Quality Assessments ( 305( b)) reports, EPA 841 B   95   001) and is the primary focus of the Office of Water's Criteria and Standards program Plan. The 1996 305( b) guidelines are consistent with the Policy on Independent Application while incorporating a weight ofevidence approach in determining the degree of impairment ( partial or nonsupport). The 1996 guidelines do not allow for a finding of full support, or attainment, of aquatic life use when there are differences in assessment results. Under certain circumstances, however, the guidelines allow for the possibility of a finding of partial support, even where results of different assessments are not fully consistent. Generally, in assessing severity of impairment, assessments based on data with high levels of information, or rigor, should be weighted more heavily than those based on data with low levels of information, and, rigorous biological data should be weighted more heavily than other data types. EPA recommends that the results of biological assessments, especially those with high levels of information, be the basis for the overall aquatic life use support ( ALUS) determination if the data indicate impairment. This is because rigorous biological data provide a direct measure of the status of the aquatic biota and detect the cumulative impact of multiple stressors on the aquatic community, including new or previously undetected stressors. Determining the level of information or rigor for each assessment is a critical component of the 305( b) guidelines on making an ALUS determination. The levels of information allow characterization of the quality and the temporal and spatial coverage of the data States and Tribes utilize to conduct their use assessments. Levels of information are identified for assessments based on biological, physical, chemical and toxicological data. For example, measures of the condition of the aquatic community using indices incorporating multiple assemblages of aquatic organisms based on a regional reference approach would rate higher than a measure of a single organism or single metric or annual fixed station monitoring for chemical contaminants. Likewise, three years of bi monthly fixed station monitoring for chemical contaminants would rate higher than annual fixed station monitoring for the same chemicals or a biological measure of a single organism or metric. Understanding the breadth and robustness of the assessment methods used in evaluating whether a water body is attaining its designated aquatic life use is important information for EPA, the States, and the public. In the future, EPA will be evaluating possible scenarios where a finding of full support could be justified despite differences in assessment results. For example, a finding of full support based on rigorous biological data may be justified despite differences with chemical specific assessment results depending on the magnitude and frequency of the chemical exceedances and the applicability of the chemical benchmark to the site. It will be important for EPA to carefully evaluate such potential scenarios and to define the adequate data requirements and level of rigor necessary to support a determination of full support despite differences in assessment results. Equally important, EPA will need to carefully consider the ramifications of such determinations on other parts of its water program. Another permutation of the weight ofevidence approach to aquatic life use assessment is to establish a hierarchy in which the results of one method could always override the other methods should there be difference in assessment results. Most frequently, it has been argued that biological assessments could always override chemical assessments in determining whether the designated aquatic life uses are being attained. Some prefer this approach because a rigorous biological assessment provides a direct measure of existing ecosystem health and have expressed concern that the policy of independent application oversimplifies the relationship among different data sets used to assess current water quality conditions. Proponents of this approach contend that biological assessment is an integrated assessment that incorporates the information that would be provided through either chemical or toxicological assessments into a single, comprehensive measure of aquatic ecosystem health. Some advocate the acceptance of rigorous biological data as the ultimate arbiter of aquatic life use attainment. They also suggest that, at least with respect to current aquatic life condition assessments, chemical, toxicological, and biological assessments are not independent; each measures the same assessment endpoint, but from different stressors. These proponents say that biological assessment is the only assessment approach available to integrate and reflect current effects from chemical, toxicological, physical, and nonpoint source stressors. Because of this they suggest that rigorous data based on biological assessments and criteria should automatically supersede data from other sources when determining aquatic life use attainment. Some contend that if biological data demonstrate that biological criteria are attained, then the water body is attaining its designated use, even if other monitoring data such as toxicological or chemical data demonstrate an excursion, or potential for an excursion, above a water quality criterion. Some also contend that rigorous biological assessments should be used 36799 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules to supersede assessments based on predicted impacts such as water quality modeling and wasteload allocations in decision making for aquatic life use assessments. One concern with this perspective is that non rigorous biological assessments could be used in such situations, though EPA has 305( b) reporting guidance which suggest minimum quality of biological assessments that could also be used for these situations. In this guidance, EPA recommends using more than one assemblage ( fish and/ or macro invertebrates/ and or algae), several index values or metrics ( multiple metrics), an index period for sampling, and ecoregional or other biogeographic regional calibration. EPA agrees that rigorous biological assessment based on adequate sitespecific data is a direct assessment of aquatic ecosystem health, unlike chemical and toxicity assessments. However, biological assessments are less well suited for use in preventing water quality impacts and will only reflect impacts once they have occurred. Though this may be less of a concern in waters with a relatively constant level of discharge where there has been ongoing biological assessment. A second objective of water quality assessment under the CWA, beyond assessing when the aquatic life use is impaired, is assessing when stressors, if left unchecked, will cause impairment. As discussed above, the chemical specific approach is especially strong for use in identifying and predicting impacts before they happen. EPA is concerned that the use of a hierarchical approach may ignore or undermine valuable information, whether that information is biological, physical, chemical, or toxicological, and not trigger the appropriate action to address the inconsistency ( e. g., evaluation of existing criteria and development of site specific criteria). Therefore, EPA does not support such an approach. EPA has a number of concerns with any approach wherein data from certain assessment techniques may be automatically superseded by those from others. A primary concern is the failure of such a system to make use of all valuable information. In all cases, criteria, whether chemical specific, toxicological, physical or biological, are derived with the intent of identifying a threshold beyond which unacceptable impacts to aquatic ecosystems are expected to occur. In most cases, it is expected that when different assessment techniques ( i. e., chemical and biological) are used for determining attainment of aquatic life uses, the techniques will yield similar results if all are done rigorously. In addition, it is expected to be rare for chemical assessments to indicate nonattainment where biological assessment indicate attainment; analyses conducted by the State of Ohio confirm this. ( See Yoder, C., `` Answering Some Concerns about Biological Criteria Based on Experiences in Ohio.''). However, it is also expected that in certain cases, different assessment techniques will result in different determinations of aquatic life use attainment due to the fact that each technique evaluates aquatic life use attainment differently, and some take into account safety factors for ensuring future attainment while others focus on the current status of the condition. When different assessment techniques that are intended to measure similar environmental endpoints and yield comparable results fail to do so, it may be an indication that assumptions underlying the criteria are not valid for a particular site, or that the data were not rigorous. While in some cases it may be appropriate to weigh one set of data more heavily than another in making a use attainment determination, in others it may be preferable to take advantage of such circumstances as opportunities to validate and cross check criteria, making adjustments as indicated by the data. This could result, for example, in an adjustment to a specific chemical criterion in a particular water if rigorous biological assessment indicated that such an adjustment is appropriate. Such information is also useful to EPA in improving national criteria development methodologies. Lack of comparability in assessments is also a concern for either a weight ofevidence or a hierarchical approach to aquatic life use assessments. Therefore, it is important that there be a common understanding between States, Tribes and EPA as to how conflicts in data interpretation will be resolved in evaluating and reporting water quality. Developing comparable methods to handle data conflicts will make comparisons between States and Tribes more useful, such as in 305( b) reports. Without a consistent approach to resolving data conflicts, assessments of water quality data at the national level becomes problematic. EPA's policy of independent application is one way of providing a consistent and defensible framework for data evaluation in order to minimize this problem.

Request for Comments on integration of data in water quality assessments EPA is interested in comment on how chemical, physical, toxicological, and biological assessments can be effectively incorporated and implemented in State and Tribal water quality standards programs to achieve the goals of the CWA. EPA requests comments on the following questions: 1. How can conflicting interpretations of water quality assessment data be reconciled in a scientifically defensible manner? Should each kind of water quality information stand alone as a scientific measure of current water quality conditions and ecosystem health? Alternatively, are there situations where one type of data should be given more weight than another in determining use attainment? 2. How should States and Tribes evaluate water quality information generated using chemical, toxicological, physical, and biological methods when determining use attainment status? 3. When interpretation of water quality data indicate inconsistent results, what factors ( i. e., data richness), if any, should EPA consider relevant to determining `` appropriate actions''? 4. Should EPA explicitly address in the water quality standards regulation the evaluation assessments using chemical, toxicological, physical and biological assessment methods? 5. Should an approach be instituted where independent application may be relaxed for water quality assessment strategies and decisions when a State or Tribe has established a comprehensive monitoring and assessment program including biological monitoring and assessment? What guidelines should be used to evaluate a State or Tribal biological monitoring and assessment program? 6. How should the policy of independent application address the distinction between situations where adequate rigorous data are available for each assessment technique and situations where available data for one or more of the assessment techniques are limited in quantity or quality? Specifically, should the policy be modified to more explicitly encourage or require, where feasible, additional monitoring, particularly where limited data are to be used as a basis for regulatory action?

3. Independent Application and NPDES Permitting a. Independent Application. Clean Water Act section 101( a) states that ``[ t] he objective of this Act is to restore and maintain the chemical, physical, and biological integrity of the Nation's waters.'' In the context of implementing water quality based pollution controls under the NPDES program, EPA has maintained that independent 36800 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules application of all forms of water quality assessment data ( i. e., chemical, physical, toxicological and biological) is clearly consistent with this objective. In addition to restoring impaired surface waters, water quality based pollution controls are often implemented to prevent water quality standards impairment that projections indicate will occur in the absence of the water quality based controls. Thus, predictive assessment tools are necessary and have proven effective in the NPDES water quality based program. An important question in NPDES permitting that EPA's policy of independent application was specifically developed to address is: how should differences in interpretation of water quality data produced using different water quality assessment techniques for aquatic life uses be reconciled? Upon examination of this question, EPA determined that differences in data interpretation do not necessarily equate to contradictory results. Different assessment results may be complementary since the different approaches can measure different aspects of water quality. For aquatic life uses, all three data types ( chemical, toxicological, and biological) provide useful information and should be used to protect designated uses. Because the different types of assessments often focus on different aspects of aquatic community health and each has different strengths and limitations, it is possible that any one type of assessment may fail to detect impairments, or potential impairments of the designated use. For that reason, EPA's current interpretation of the CWA and its implementing regulations is that all three types of data ( chemical, toxicological, and biological) should be used when evaluating the reasonable potential for a discharge to cause or contribute to an excursion above a water quality criterion and, if one approach indicates that water quality is, or will be, impacted, the results from the other methods could not be used to refute that finding. Under this approach, where `` reasonable potential'' is found, the NPDES permitting authorities must take appropriate `` actions;'' that is, implement water quality based effluent limits that are derived from and comply with the applicable water quality criteria. These `` actions'' may also include additional monitoring to determine whether a problem exists, or to derive site specific criteria if a particular criterion is found to be inaccurate for a site. The policy on independent application is presented in further detail in Chapter 1 of EPA's 1991 Technical Support Document for Water Quality based Toxics Control ( TSD) and in chapter 1 of EPA's Water Quality Standards Handbook   Second Edition, September 1994 ( Handbook) ( both documents cited above). In the Great Lakes Guidance, EPA maintained its policy of independent application with respect to determining the need for water quality based effluent limits, making it an explicit implementation requirement in the Great Lakes States. The Guidance, in Appendix F, Procedure 5, section F `` Other Applicable Conditions,'' states `` When determining whether WQBELs are necessary, information from chemical specific, whole effluent toxicity and biological assessments shall be considered independently.'' ( 40 CFR Part 132, Appendix F, Procedure 5, Section F. 3.). In the permitting context, EPA's independent application policy reflects language in sections 301( b)( 1)( C) and 303 of the CWA and permit regulations implementing these statutory provisions at 40 CFR 122.44( d). Pursuant to section 303 of the CWA, States and Tribes adopt chemical specific numeric criteria and toxicity criteria as part of their water quality standards. Section 303( c)( 2)( B) of the CWA further requires States and Tribes to adopt, as part of their water quality standards, numeric criteria for toxic pollutants for which EPA has published guidance under section 304( a), and whose discharge or presence in State or Tribal waters could reasonably be expected to interfere with the designated uses adopted by the State or Tribe for those waters. ( As discussed elsewhere in this document, all States and Tribes have narrative water quality criteria as well.) Section 301( b)( 1)( C) of the CWA requires effluent limitations in NPDES permits that are `` necessary to meet water quality standards'' or necessary to `` implement any applicable water quality standard.'' Consistent with this provision, EPA's permitting regulations at 40 CFR 122.44( d) require that effluent limits be imposed where the discharge has the `` reasonable potential'' to cause or contribute to an excursion above water quality criteria and specifically describe how those limits are to be expressed ( e. g., chemical specific versus WET limits). Therefore, once a numeric ( or narrative) water quality criterion becomes part of a State's or Tribe's water quality standards, and a permitting authority determines that a discharge of a pollutant would have a reasonable potential to cause or contribute to an excursion above the applicable numeric or narrative criterion, the regulation requires that a limit for that pollutant be established as necessary to meet the water quality criterion. Although the CWA specifies that permit limits must meet water quality standards, it is the permitting regulations that specify the factors that must be considered when determining whether or not there is reasonable potential to cause or contribute to an excursion above a State or Tribal water quality standard, and specifically describe how such limits are to be expressed. EPA regulations at 40 CFR 122.44( d)( 1)( iii)   ( v) describe the conditions under which water qualitybased effluent limits for specific chemicals and for whole effluent toxicity are required in NPDES permits. While these regulations do not specifically use the term `` independent application,'' the concept is expressly laid out. These regulations require chemical specific limits when the permitting authority determines there is a reasonable potential for the discharge to cause or contribute to the excursion above the chemical specific criterion. Likewise, the regulations require limits for whole effluent toxicity if the permitting authority determines there is a reasonable potential for the discharge to cause or contribute to the excursion above the numeric criterion for toxicity or narrative criterion for water quality. Except under limited circumstances ( where the State or Tribe lacks a chemical specific criterion for a pollutant of concern), these regulations do not allow a permitting authority to forgo one type of limit, e. g. a chemical limit, where another type of data, e. g., toxicity, indicate no toxicity. Instead, the two types of data are required to be considered independently. The independent application policy provides a consistent and coherent protocol for resolving conflicts in interpreting monitoring data when determining `` reasonable potential.'' Where such conflicts exist and cannot be reconciled, independent application directs States and Tribes to presume that the data that indicate a current or potential impact are valid and to take appropriate steps to prevent or remediate the impact. The reconciliation phase allows a State or Tribe to gather additional or more detailed data prior to taking regulatory action. Data interpretation conflicts may be best addressed by identifying the cause of the conflict and recalibrating the models and criteria to better reflect the newly acquired site specific information. However, if the causes of the data interpretation conflicts cannot be resolved, under independent application, the State or Tribe must take 36801 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules action based on the data indicating impairment or the reasonable potential for impairment of the water body. EPA believes this procedure for addressing conflicting interpretations of monitoring data is appropriate for a number of reasons. First, as stated earlier, each of the different assessment techniques monitors aquatic ecosystem health from a slightly different perspective. Consequently, it is entirely plausible that only one of the assessment techniques would detect a real or potential impact. Second, assuming that the data generated by the different techniques are of comparable quality and relevance, an indication of a water quality problem using any of the techniques is sufficient reason to implement controls. That being the case, EPA believes the independent application of water quality data in determining when water quality based effluent limits are necessary for individual dischargers is consistent with the CWA. Reconciliation of data interpretation conflicts allows flexible evaluation of data. Once a permit application is received from a discharger, States and Tribes frequently engage in discussions with the discharger over the quality and representativeness of the data. This period of data review and evaluation is also an ideal time for addressing any data interpretation conflicts in order to ensure that permitting decisions are defensible and the permit limits that are imposed are necessary to protect designated uses. States and Tribes, together with permittees, may obtain additional data to verify earlier data or conduct timely studies to support the development of site specific criteria. Ultimately, these site specific criteria may serve as the basis for a permit limit, or a decision that it is not necessary to limit a pollutant in a particular discharge. All of the actions above are consistent with the independent application policy and the CWA. Critics of EPA's policy believe either that data from certain types of water quality assessments have inherently greater value than data obtained by other means or that, in a sense, data quality and ecological significance should be averaged, such that if data obtained from two different assessment methods agree and data from a third disagree with the other two, the two could `` outweigh'' the one. In either case, all of the available data would be considered together, under the assumption that each assessment technique measures a similar endpoint. Under such an approach to data evaluation, limits on effluent toxicity would be appropriate and acceptable as surrogates for chemical specific limits. Similarly, biological assessment data that do not indicate unacceptable levels of impact on the biological community could serve as the basis for a decision not to include either chemical specific or effluent toxicity limits designed to support an aquatic life use in a facility's discharge permit. Proponents of this view argue that independent application forces them to take inappropriate regulatory actions when faced with conflicting assessment data. EPA does not agree in principle with this view. b. Alternatives to Independent Application. States, Tribes, municipalities, and dischargers have expressed concerns that the policy of independent application results in more protection than is necessary to attain and maintain aquatic life designated uses. Many express a preference for an approach which invests data obtained using certain assessment techniques with greater credibility than those obtained in other ways. Such an approach, as discussed above, is sometimes referred to as a weight ofevidence approach. Under such an alternative approach, assuming a high level of confidence in all the available data, one form of data   usually it is argued biological data   would be the ultimate arbiter of whether water quality based effluent limits are needed in a discharger's permit. To determine, for example, whether a water qualitybased effluent limit is needed for a particular chemical pollutant, the risk of adverse impact on the aquatic community would be determined based on all of the available data relying more heavily on high quality, thorough biological data and on the judgment of the individual conducting the evaluation. Several States and members of the regulated community have advanced this approach as preferable to EPA's independent application policy, arguing that such flexibility to exercise judgment is appropriate. EPA's current thinking is that it should not promote an alternative approach to making `` reasonable potential'' decisions that places greater emphasis on biological data. Instead, EPA's current thinking is that such an evaluation of water quality and ecosystem health to determine the appropriate and applicable criteria against which discharges will be evaluated is most appropriately done during the setting of the applicable criteria for a water body. In that arena, it may be feasible to use biological assessment as a basis for determining the appropriate criteria for a given water body. However, once the criteria are set, EPA believes that the current regulation requires `` reasonable potential'' evaluations against all the applicable criteria, and that the policy of independent application in this context is appropriate. If biological data indicate that designated uses are being attained in spite of projected or actual chemicalspecific criteria exceedances, then additional site specific analysis should be done to ensure that controls are developed that are necessary to adequately protect the water body from use impairment. Site specific approaches could include mixing zone studies, more refined water quality modeling to support wasteload allocation, or the development of sitespecific criteria. In any case, chemicalspecific and toxicity criteria are proven and necessary bases of water qualitybased effluent limits. In `` reasonable potential'' analysis, chemical specific monitoring is usually focused on pollutant concentrations in the effluent and the projected ambient result of those concentrations being discharged. Thus, this type of analysis commonly yields projected rather than measured water quality impacts. Where biological impact is not detected using biological assessment methods, it is possible that impairment that is projected and plausible, may simply have not yet occurred. However, where discharges to a stream have been relatively constant over time and there has been ongoing biological assessment, this would be less of a concern. EPA's view is that it would be inappropriate to ignore projected impairment simply because the impairment has not yet been observed in the environment. An additional argument in favor of retaining the independent application policy for `` reasonable potential'' determinations has to do with the suitability of certain types of data and the unsuitability of others for certain applications within the water pollution control program. For example, biological data are not amenable in the same way as chemical specific data for use in waste load allocations, load allocations, total maximum daily load calculations or antidegradation reviews. An approach that would allow biological data to negate a finding of `` reasonable potential'' would suggest possible site specific inadequacies of particular criteria without providing the information needed to determine definitively whether or not the criteria are appropriate or what any alternative criteria should be. As a consequence, a void would be created in the implementation of State or Tribal water quality standards which would render them unable to perform all of their 36802 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules intended functions. Proponents of independent application contend that instead of discarding data and invalidating criteria where conflicting interpretations exist, an effort should be made to determine why the interpretations conflict and to refine the applicable criteria to better reflect the conditions found at the site. Taking this step would ensure that, over time, a full suite of appropriate criteria would be developed for every site and that all appropriate and necessary pollution controls are implemented. In addition, such an approach is consistent with the CWA. Some States and Tribes may be concerned, however, that revising water quality standards, especially where such revision is to deal with a single permitting decision, may be so resource intensive that it is not a realistic option. As discussed above, if numeric water quality criteria exist and are applicable to a water body, permits for dischargers to the water body must ensure that those criteria are met under section 301( b)( 1)( C) and the implementing regulations at 40 CFR 122.44( d). On occasion, States, Tribes and dischargers have asserted that biological and toxicity data from specific waters conflict with chemical data. EPA's current thinking is that instances of clear disagreement between biological and toxicity data and chemical data are infrequent. Based on this belief, EPA would not support a radical shift away from chemical criteria and limits or toxicity criteria and limits. Those tools are simply too important as proven tools for assessing potential impacts to surface waters and improving water quality. EPA's current thinking also suggests that it is important for there to be flexibility to resolve instances of disagreement between different forms of data and that perhaps mechanisms for such flexibility can be clarified or improved. EPA's current thinking is that through collection of broader and more thorough water quality data, EPA, States and Tribes will be able to develop more complete profiles of water body conditions and stressors and that through such evaluation the `` necessary actions'' ( e. g., water quality based effluent limits for one or more pollutants, listing of the water body as not attaining its aquatic life designated use, or best management practices to address nonpoint sources of pollution) to improve water quality in a given water will become more obvious. Disagreement between biological, toxicity and chemical data for the same water is cited by some States and dischargers as a potential situation in which independent application would force unnecessary and burdensome requirements on dischargers. Those opposed to independent application of criteria would like to see States and Tribes given greater latitude to determine when limits based on a given criterion are necessary. They suggest that this could be achieved if States and Tribes were to include, in the chemicalspecific criteria or toxicity criteria portions of their water quality standards, statements explaining circumstances under which the otherwise applicable criteria would not apply at a particular site or would have to undergo some review and revision, while assuring the designated use of the water body would be maintained. Such circumstances could include where the form of the pollutant in the effluent or receiving water is not the form addressed by the chemical criterion in the State or Tribe's standards; or, where a substantial amount of biological and or toxicity data indicate that discharges of the pollutant at levels that would exceed the chemical criteria are not causing the aquatic life use in a particular water body or segment of the water to be impaired. If these conditions could be met, permitting authorities would have the flexibility to determine that a numeric water quality based effluent limit for the pollutant in question is not required, or that an alternate limit should apply. This type of flexibility, to rely on biological evaluations in the criteria setting phase, where data are sufficient to support such flexibility, could be a strong incentive for States and Tribes to develop stronger biological criteria and assessment programs including monitoring reference areas and complete chemical and toxicity monitoring programs, including sitespecific data on most sensitive species to chemical( s) for which flexibility is being sought. EPA approval of water quality standards implementing such an option requires acceptance of an interpretation that sections 301( b)( 1)( C) and 303( c)( 2)( B) of the CWA allow States and Tribes to identify, within their water quality standards, conditions or circumstances which would render specific numeric criteria not applicable to certain waters in specific instances, or alternatively in need of refinement. EPA has significant technical questions about how such an option could be implemented within the context of a State's or Tribe's water quality standards. EPA is especially interested in detailed technical comments describing how such an option would be included in a State's or Tribe's water quality standards, how such an option would ensure protection of designated uses in water bodies where criteria are deemed not applicable. In addition, EPA is soliciting comment on specific procedures that could be used by a State or Tribe to arrive at a decision that a criterion is not applicable at a specific site. In particular, EPA is interested in technical evaluations of what types of data would be necessary to support such a decision, the quantity and quality of the data and how the data would be evaluated. Finally, EPA seeks detailed technical comments indicating how other elements of the water quality standards program would function in situations where chemical or toxicological water quality criteria were adjusted based on biological assessments. For example, if a State or Tribe were to employ the option discussed above, it is not apparent how critical water quality program elements such as determining the need for permit limits or whether or not a new discharge could be allowed to a stream segment could occur absent chemical specific or toxicity based criteria applicable to the water body. To be workable, this option may need to be paired with a scientifically defensible mechanism for making decisions about activities such as permit limits and load increases. Since chemical criteria and chemical specific interpretations of narrative criteria currently are the principal benchmark used for these functions, would pursuing the option discussed above be workable, or would it introduce a level of complexity into State and Tribal water quality standards that could result in slowed or suspended water pollution control programs, and expose aquatic ecosystems to greater risk because of the lack of an identified threshold of impact? EPA's current thinking is that significant flexibility already exists within the current regulatory framework to account for available biological and toxicity data. For example, numeric criteria, once adopted, may be modified to better reflect conditions at a specific site. Bioassessment and toxicity data can play a valuable role in identifying sites where conditions differ sufficiently from those assumed in the calculation of the national or State or Tribe wide criteria to warrant site specific modification of the criteria. Bioassessment and toxicity data can also provide useful information in identifying instances where a given constituent in an effluent is toxicologically distinct from a similar substance for which a criterion is available, indicating the need for a separate criterion for the constituent in 36803 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules question. Establishing site specific criteria would provide relief similar to that contemplated in the option proposed above. Lastly, public participation is a basic tenet of the water quality standards development process. Public participation is also sought in the context of issuing NPDES permits. During standards development, public input is sought to assist the regulatory agency in identifying the appropriate water quality goals for the waters under the jurisdiction of a State or Tribe. During NPDES permit issuance, public input is again sought to verify that the permit proposed to be issued is consistent with the water quality goals. Some assert that these two public participation steps seek input on different questions and are not interchangeable. Does the weight ofevidence option discussed above reduce the opportunity for meaningful public participation in the standards setting process by making it more difficult for the public to determine which water quality criteria will apply to which water bodies, and, as a result, what the water quality goals for an individual water body are? EPA is considering how a weight of evidence approach might be implemented in a manner that does not restrict the opportunities for meaningful public participation in the water quality goal setting process.

Request for Comments on Independent Application EPA requests comment on the following questions: 1. What is the rationale for modifying the independent application policy as it pertains to NPDES permitting? Under what circumstances could it be justified? 2. If there are circumstances where an approach other than independent application is acceptable, should any one type of water quality data receive greater weight and why? 3. How should States and Tribes evaluate effluent data generated using chemical, toxicity and biological methods in determining reasonable potential to cause or contribute to an impairment? 4. Would checks or oversight mechanisms be necessary to ensure that where decisions about reasonable potential are based on chemical, toxicity and biological methods, such decisions are made with integrity? For example, EPA or public oversight? 5. Are there any cases which indicate that either chemical specific, whole effluent toxicity or biological approaches do not legitimately represent some aspect of use attainment? 6. Should EPA explicitly incorporate into the water quality standards regulation the independent application policy? 7. Should independent application be addressed the same or differently for permitting than for assessment and use attainment decisions under 305( b) reporting and 303( d) listing? 8. If EPA were to separate the use of independent application in determining the use attainment status of a water body from the use of independent application when determining reasonable potential for an effluent, what approach, independent application, weight of evidence, or hierarchical, should be used for use attainment decisions? NPDES permitting? What would the implications be if the programs used two different policies? 9. Would a policy allowing numeric criteria to not apply to all waters where supported by scientifically defensible data be workable? Would it unnecessarily complicate the regulatory program, for example by delaying the issuance of permits? Are existing mechanisms of criteria setting and permit issuance sufficiently flexible?

IV. Summary and Potential Program and Regulation Changes EPA believes that the water quality standards program and decisions it yields will continue to be the focus of growing pressure and scrutiny as solutions to remaining surface water quality problems in this country are found to be increasingly elusive, difficult, and/ or expensive. The task set forth by the Clean Water Act is to improve water quality even where it is difficult to do so. To accomplish this task, EPA envisions a national water quality standards program in which: the best possible information on whether designated uses are being attained and how to attain and maintain them is available and used; water quality criteria are selected from a wide ranging menu of scientifically sound criteria and tailored to each watershed; and national norms of consistency and flexibility in State and Tribal water quality standards are clear. With this vision in mind, EPA, through this ANPRM, begins a review of the water quality standards regulation in a public forum in an attempt to identify possible amendments to the regulation and new guidance or policy that may be needed to address three distinct objectives: ( 1) eliminate any barriers to, and otherwise enhance State and Tribal implementation of, watershed based water quality planning and management; ( 2) facilitate use of new, more integrated water quality assessment and criteria science in water quality standards programs, and; ( 3) improve the regulation so that it can be implemented more efficiently and effectively ( including cost effectively). The preceding pages of this ANPRM outline current regulatory provisions, accompanying guidance and policy, and current practices in the core areas of the water quality standards program. Each section of the ANPRM identifies issues that have been raised to EPA that come out of the collective experiences of States, Tribes, cities, industry and environmental advocates, as well as EPA's experience. The issue discussions are followed by specific questions that are intended to elicit focused comments. It is important for commenters to focus on these specific questions as a vehicle for developing comments. It is equally important for commenters to develop ideas that address the three objectives above in a more general sense and to identify the five to seven highest priority issues the commenter believes EPA should address in a follow on regulatory proposal. EPA welcomes ideas on how the water quality standards regulation, policy and or guidance can be revised to facilitate water quality management on a watershed basis. In requesting comment on eliminating barriers to and facilitating implementation of watershed based water quality planning and management, EPA directs commenters' attention primarily to the sections on designated uses, criteria, antidegradation, mixing zones and independent application. In requesting comment on how to facilitate use of new, more integrated water quality assessment and criteria science in water quality standards, EPA directs commenters' attention primarily to the sections on biological criteria, and independent application. In requesting comment on how to improve the efficiency and effectiveness ( including cost effectiveness) of the water quality standards program, all sections of the ANPRM are relevant for review. EPA seeks a water quality standards program that protects the nation's waters as envisioned in the CWA, that establishes requirements that are necessary to attain and maintain healthy and sustainable ecosystems, and that is flexible enough for States and Tribes to protect water quality and at the same time avoid costly requirements that have little or no environmental benefit. Below is a brief summary outline of the potential changes to the water quality standards program and 36804 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules regulation that are discussed and considered in this ANPRM. The list of potential changes includes the potential changes to the program and regulation on which EPA is specifically requesting comment. Each area of potential change is discussed in detail in the specified section of the ANPRM. It is possible that EPA will ultimately propose some of the changes outlined below. It is also possible that EPA will conclude based on the public comments it receives that some or all of the issues presented in the ANPRM can be best addressed through non regulatory mechanisms such as guidance or policy.

A. Uses 1. Refinement of use designations to achieve increased specificity in aquatic life and recreation uses being protected. 2. Minimum elements of a use attainability analysis ( UAA). 3. When is UAA required/ not required? a. UAAs whenever an aquatic life use is designated ( beyond fishable/ swimmable) to see if the use reflects the highest potential for the water body. b. Periodic review of marginal or limited aquatic life use designations. c. When is a use considered attainable? d. Conditions under which refinements in designated uses may be considered actions not requiring analysis to support use removal and alternatively the conditions under which such action is considered a use removal requiring justification under § 131.10( g). e. Circumstances under which UAA is required and circumstances under which UAA must be reviewed. 4. Removal of designated uses. a. Minimum aquatic life uses for all waters, because even degraded water bodies support some form of aquatic life. b. Evaluate use removal provision at § 131.1( 10)( g) allowing removal of a use due to the existence/ operation of a dam. c. Clarify whether the physical factors reason for removing a use includes removal of a recreational use due to poor physical access to the water. Alternatively, the removal of a use for physical factors could be limited to aquatic life uses only. d. Clarify in § 131.10 that at least one of the six use removal criteria must be met to remove any use, not just aquatic life and recreation uses. 5. Alternatives to use downgrade such as variances, temporary standards and ambient based criteria. a. Recognize site specific criteria set to natural background levels as a permissible alternative to use downgrade. b. Recognize site specific criteria set to irreversible anthropogenic background levels as a permissible alternative to use downgrade.

B. Criteria 1. Ambient Water Quality criteria for Aquatic Life Protection. a. Examination and possible interim revisions to EPA recommendations on the duration and frequency of criteria excursions to account for organism response model and population response model. 2. Site specific criteria and procedures. a. Specify that States and Tribes must have regulatory procedures for establishing site specific criteria. b. Minimum requirements for development of site specific criteria. 3. Narrative criteria and interpretation procedures. a. Identify additional methods for implementation of narrative criteria. b. Clarify that States and Tribes are required to adopt narrative criteria for all waters. ( all States already have). 4. Codification of CWA requirement to adopt numeric toxics criteria. a. Define `` reasonable expectation'' under 303( c)( 2)( B). (`` States and Tribes may adopt numeric chemical specific criteria for those stream segments where the State or Tribe determines that the priority toxic pollutants for which EPA has issued CWA section 304( a) criteria guidance are present and can reasonably be expected to interfere with designated uses.'' emphasis added) 5. Chemical criteria beyond priority pollutants. a. Develop and recommend or require criteria for certain non priority pollutants. 6. Numeric values in the absence of criteria or data sufficient for criteria. a. States and Tribes develop method for derivation of alternative values where minimum data requirements for criteria not satisfied. Specific EPA derivation procedure or guidelines. 7. Require or recommend that State and Tribes adopt numeric toxicity criteria. 8. Sediment quality criteria. a. Require or recommend that States and Tribes adopt sediment criteria ( narrative or numeric). b. Specify in regulation that States and Tribes have the flexibility to adopt sediment quality criteria. 9. Biological criteria. a. Require or recommend that States and Tribes adopt biological criteria ( narrative or numeric). b. Specify in regulation that States and Tribes have the flexibility to adopt biological criteria. c. Specify linkage between biological criteria and stressor identification. 10. Wildlife Criteria. a. Recognize in regulatory text that wildlife criteria are valid forms of water quality criteria. b. Recognize in regulatory text that wildlife criteria endpoints other than bioaccumulation endpoints are valid bases for wildlife criteria. 11. Physical criteria: Existing and potential future role of. a. Identify physical criteria such as habitat ( including clean sediment) and hydrologic balance criteria in 40 CFR 131 as valid forms of criteria that States and Tribes can adopt in their water quality standards. 12. Human Health Criteria. a. Higher fish consumption assumptions for site specific or regional situations when subpopulations that are highly exposed have been identified. b. Clarification of the use of MCLs and MCLGs in State and Tribal water quality standards.

C. Antidegradation 1. Minimum elements of State and Tribal antidegradation implementation procedures. a. Revise regulation to include the minimum elements of a State and Tribal antidegradation implementation method. b. Revise the regulation to explicitly say that State and Tribal antidegradation implementation procedures ( in addition to just the policy) must be submitted in triennial review package and are reviewable by EPA. 2. Tier 1 protection ( protection of existing uses). a. Define or clarify what constitutes loss of an existing in stream water use. b. Specify that a clear approach to maintaining and protecting existing uses that may not be adequately protected by strict application of water quality criteria is a required element of an antidegradation implementation procedure. 3. Waters covered by tier 2 level protection. a. Clarify waters subject to tier 2 level protection. b. Clarify tier 2 provision requiring all cost effective and reasonable best management practices for nonpoint sources prior to allowing a lowering of water quality. c. Clarify that States and Tribes are to consider the 303( d) listing status of a water body, and the information supporting that status, when determining whether a proposed activity that is expected to degrade water quality in that water body can be authorized under tier 2 of the State's or Tribe's antidegradation provisions. 36805 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules 4. Outstanding national resource water ( ONRW) classification, level of protection, and public role in nominating. a. Public nomination of ONRWs. b. Level of protection afforded to ONRWs. 5. Creation of Antidegradation tier 2.5. a. Revise the regulation to explicitly recognize tier 2.5 protection.

D. Mixing Zone Policy and Implementation Procedures 1. Specify that, to use mixing zones, States and Tribes must indicate in their water quality standards whether they allow mixing zones, conditions under which mixing zones are allowed, minimum requirements for mixing zones. 2. Procedures and decision criteria used in addressing complete and incomplete mixing. 3. Site specific technical justification for rapid and complete mix assumption. 4. State and Tribe policies and procedures to address rate of mixing. 5. Clarify in regulation that narrative criteria apply in mixing zones. 6. Restrict Mixing zones for bioaccumulative chemicals of concern.

E. Applicability of Water Quality Standards to Wetlands 1. Clarify in 40 CFR Part 131 that wetlands with interstate commerce connection are waters of the U. S. requiring water quality standards.

F. Evaluation of EPA Policy of Independent Application ( IA)

1. Increase use of chemical, toxicological, physical and biological data in making water body assessments in a consistent and scientifically defensible manner. 2. Specify how, and the circumstances under which, different forms of assessments ( chemical, toxicological, physical and biological) can be used together to determine: a. When a designated aquatic life use is or is not attained, b. The type and value of criteria that should apply to a water, and c. When water quality based effluent limits are required in a permit. 3. Specify the adequate data base and level of rigor necessary in biological assessments to support a determination of full use support despite differences in assessment results. In addition to the potential program and regulation changes outlined above, EPA is also requesting comment on the costs and benefits and potential reporting and record keeping requirements that might be associated with these changes. These issues are discussed more fully in the next section.

V. Regulatory Assessment Requirements A. Executive Order ( E. O.) 12866, Regulatory Planning and Review Under Executive Order 12866, [ 58 Federal Register 51,735 ( October 4, 1993)] the Agency must determine whether the regulatory action is `` significant'' and therefore subject to Office of Management and Budget ( OMB) review and the requirements of the Executive Order. The Order defines `` significant regulatory action'' as one that is likely to result in a rule that may: ( 1) Have an annual effect on the economy of $ 100 million or more or adversely affect in a material way the economy, a sector of the economy, productivity, competition, jobs, the environment, public health or safety, or State, local, or tribal governments or communities; ( 2) Create a serious inconsistency or otherwise interfere with an action taken or planned by another agency; ( 3) Materially alter the budgetary impact of entitlements, grants, user fees, or loan programs or the rights and obligations of recipients thereof; or ( 4) Raise novel legal or policy issues arising out of legal mandates, the President's priorities, or the principles set forth in the Executive Order. While this advance notice of proposed rule making establishes no regulatory requirements it could ultimately result in a rule that would satisfy one or more of the above criteria. It has therefore been determined that this action is a `` significant regulatory action'' under the terms of Executive Order ( E. O.) 12866. As such this action was submitted to OMB for review. Changes made in response to OMB suggestions or recommendations have been documented in the public record. Under the terms of E. O. 12866, EPA is to prepare for any significant regulatory action an assessment of its potential costs and benefits. If that action satisfies the first of the criteria listed above, this assessment must include, to the extent feasible, a quantification of these costs and benefits, the underlying analyses supporting such quantification, and an assessment of the costs and benefits of reasonably feasible alternatives to the planned regulation. Because the purpose of this notice is to initiate a structured national debate on a broad set of issues rather than to propose specific regulatory changes, it is not feasible to quantify the costs and benefits of any resulting regulations at this time. The Agency is aware, however, that this notice could lead to a regulatory action for which the preparation of a quantitative assessment of costs and benefits would be appropriate. The Agency is thus requesting comment on the costs and benefits of any of the possible regulatory changes discussed in this notice, as well as on appropriate methodologies for assessing them. The Agency would be particularly interested to hear from States and Tribes that may already have experience implementing some of the measures discussed in this Notice and may already have prepared analyses of the costs and/ or benefits of such measures. Other members of the public are also encouraged to submit any data they may have on the costs and benefits of specific measures ( e. g., conducting biological assessments).

B. The Regulatory Flexibility Act ( RFA) as Amended by the Small Business Regulatory Enforcement Fairness Act ( SBREFA) of 1996 Under the RFA, ( 5 U. S. C. 601 et seq.), as amended by SBREFA, for proposed rules, EPA generally is required to conduct an initial regulatory flexibility analysis ( IRFA) describing the impact of the regulatory action on small entities as part of rulemaking. However, under section 605( b) of the RFA, if the Administrator for the Agency certifies that the rule will not have a significant economic impact on a substantial number of small entities, EPA is not required to prepare an IRFA. The requirement applies to proposed rules only and as this notice is an ANPRM, these requirements do not apply to this notice.

C. Paperwork Reduction Act Under the implementing regulations for the Paperwork Reduction Act, an agency is required to certify that any agency sponsored collection of information from the public is necessary for the proper performance of its functions, has practical utility, is not unnecessarily duplicative of information otherwise reasonably accessible to the agency, and reduces to the extent practicable and appropriate the burden on those required to provide the information ( 5 CFR 1320.9). Any proposed collection of information must be submitted, along with this certification, to the Office of Management and Budget for approval before it goes into effect. Most of the potential regulatory changes discussed in this Notice could entail new reporting and record keeping requirements for States and Tribes and/ or members of the regulated public. EPA 36806 Federal Register / Vol. 63, No. 129 / Tuesday, July 7, 1998 / Proposed Rules is interested in comments on any and all aspects of these potential paperwork requirements, and in particular on how they should be structured to fulfill the requirements that they have practical utility, are not unnecessarily duplicative of other available information, and are the least burdensome necessary to satisfy the purposes of the Water Quality Standards Program.

Dated: June 25, 1998. Robert Perciasepe, Assistant Administrator for Water. [ FR Doc. 98   17513 Filed 7   6   98; 8: 45 am]

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