Key Concepts Module 5: Flexibilities
This module highlights aspects of the water quality standards regulation and guidance that make them flexible enough to accommodate specific water quality-related circumstances, while meeting the requirements of the Clean Water Act (CWA) and the water quality standards regulation.
The module provides answers to the following:
- If a State/Tribe finds that attaining a designated use is not feasible, can it remove or modify the use in its water quality standards?
- Can a State/Tribe's water quality criteria allow for a naturally occurring pollutant concentration in a waterbody segment that exceeds the national criteria for aquatic life uses?
- What if a discharger needs additional time to evaluate its ability to comply with a State/Tribe's standards before putting expensive controls in place?
- Can a permitted discharger be allowed a grace period for complying with a permit limit based on a new or revised criteria?
At the end of the module is a brief quiz intended to touch on some Core Modules regarding water quality program flexibilities that will be further examined in the classroom session of this module.
This module's main pages and brief quiz at the end take about 15 minutes to complete.
Flexibility Mechanisms in Water Quality Protection
States or authorized Tribes have different approaches for addressing particular water quality-related circumstances:
|Need for designated use removal/revision||Standards||Use attainability analysis
If a State/Tribe finds that attaining one of the designated uses in its standards is not feasible, it can be changed or removed based on appropriate analysis and documentation subject to EPA review and approval.
|Need to address waterbody specific conditions||Criteria||Site-specific criteria
In addition to the ability to revise designated uses, States/Tribes may establish site-specific criteria where it identifies conditions in a water body that differ from national criteria (e.g., naturally occurring pollutant concentrations in a stream segment that exceed the national criteria for aquatic life uses). The State/Tribe must follow established protocols/procedures for establishing the criteria, which are adopted then subject to EPA review and approval.
|Need for discharger or State/Tribe to evaluate whether a designated use and associated criteria are appropriate and attainable.||Individual or multiple dischargers||Variance
If an individual or group of dischargers determine they cannot meet their current permit limit immediately but are also uncertain whether they can ultimately meet it, a permitting authority can grant a variance. This temporarily modifies the standards, usually for a specific pollutant with all other underlying standards remaining in place. The State/Tribe must follow its established variance policies, and the variance is then subject to EPA review and approval.
|Need for discharger grace period to meet permit limits based on new/revised criteria||Individual discharger||NPDES permit compliance schedule
If an individual discharger requests additional time to comply with a permit limit based on new or revised criteria, a permitting authority can include a compliance schedule as part of the discharger’s NPDES permit. When deciding to grant the compliance schedule, the State/Tribe’s water quality standards (or implementing regulations) must specifically authorize the use of compliance schedules in NPDES permits and be consistent with EPA's regulations.
A designated use and its supporting criteria can be removed/revised from water quality standards when a State or Tribe determines that attaining the use is not feasible. The revision/removal must be supported with appropriate analysis and documentation for the administrative record. Any such revision to water quality standards must be submitted to EPA for review and approval.
Key Point. When the designated use to be revised addresses the CWA 101(a)(2) goals, the State/Tribe must conduct a formal use attainability analysis (UAA), make it available to the public, and then convene a public hearing. This requirement also applies when establishing subcategories of uses if the criteria become less stringent.
Question. What is a use attainability analysis?
A use attainability analysis (UAA) is a structured, scientific assessment of the physical, chemical, biological, and economic factors affecting whether a designated use can be attained.
Key Point. A UAA is required when a State/Tribe is designating uses for the first time that do not address the CWA 101(a)(2) goals or when removing a CWA 101(a) goal use or adopting subcategories for such uses if the new use or subcategory will require less stringent criteria than those associated with the previously designated use. Such a UAA must demonstrate that attaining the CWA 101(a)(2) goals is not feasible.
Feasibility of Controls
A designated use is considered attainable if:
- It is an existing use, or
- It can be attained with
- technology-based controls for point sources
- cost-effective and reasonable best management practices (BMPs) for non-point sources
A designated use is considered not attainable if:
- It is not an existing use, AND
- Attaining the use is "not feasible" because of at least one of the six factors listed in 40 CFR 131.10(g)
An existing use is defined by the Water Quality Standards regulation as those uses actually attained in the water body on or after November 28, 1975, whether or not they are included in the water quality standards (40 CFR 13 1.3). Refer to Existing Uses in Module 2.)
In developing a use attainability analysis, a State/Tribe must demonstrate that attaining a CWA 101(a)(2) goal use is infeasible due to one of the factors listed (40 CFR 131.10(g)). The State/Tribe should also identify the highest attainable use in its UAA.
- Factor #1
- Naturally occurring pollutant concentrations prevent the attainment of the use; or
- Factor #2
- Natural, ephemeral, intermittent or low flow conditions or water levels prevent the attainment of the use, unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating State water conservation requirements to enable uses to be met; or
- Factor #3
- Human caused conditions or sources of pollution prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place; or
- Factor #4
- Dams, diversions or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the water body to its original condition or to operate such modification in a way that would result in the attainment of the use; or
- Factor #5
- Physical conditions related to the natural features of the water body, such as the lack of a proper substrate, cover, flow, depth, pools, riffles, and the like, unrelated to water quality, preclude attainment of aquatic life protection uses; or
- Factor #6
- Controls more stringent than those required by sections 301(b) and 306 of the Act would result in substantial and widespread economic and social impact.
Key Point. The process of developing a use attainability analysis works best when States/Tribes, Federal agencies, and other stakeholders agree beforehand on key factors that will be presented, what information will be needed, and how data will be interpreted.
Learn More. Additional detail on aspects of the use attainability analysis that should be agreed on up front. Proceed to the Learn More Topic.
The Economic Factor
Many States/Tribes have based their use attainability analyses on factor six, establishing that the imposition of controls beyond the technology-based minimums would result in "substantial and widespread economic and social impact." This language is generally interpreted as addressing affordability.
Key Point. Making the economic case does not call for turning the use attainability analysis into a cost-benefit analysis. Rather, it calls for evaluating (1) the cost of treatment, (2) whether the discharger can afford more stringent controls (i.e., company solvency), and (3) what the effect of higher costs would be on the community (e.g., median household income).
Resources. Listing of guidance from EPA and other sources on use attainability analyses. Proceed to the Resources Topic.
A variety of potential biological, physical, and chemical parameters may be relevant for developing a use attainability analysis to support changing an aquatic life or recreational designated use.
Addressing Local Conditions
EPA develops recommendations for many water quality criteria that individual States or Tribe's adopt into their water quality standards. By establishing limits on particular chemicals or conditions in a water body, the adopted criteria are relied on to support protection of the State/Tribe's designated uses.
However, States/Tribes also have the flexibility to modify criteria recommendations, if necessary, to establish site-specific criteria that reflect local conditions in a particular water body or a waterbody segment.
Key Point. Site-specific criteria are criteria relevant to a given localized site and that reflect local environmental conditions. Importantly, site-specific criteria for a water body do not alter its designated uses.
When developing site-specific criteria, the State/Tribe must follow established protocols/procedures. The criteria are then subject to EPA review before becoming effective for purposes of the Clean Water Act.
When Site-Specific Criteria Are Allowed
Site-specific criteria can be used to address any one or more of the following situations. (Select the linked items listed to view when site-specific criteria are allowed.)
The sensitivities of species at a site differ from those used to develop national water quality criteria.Situation #2
The physical/chemical characteristics of a site alter the bioavailability/toxicity of a pollutant.Situation #3
A State/Tribe wants to establish a criterion equal to “natural background” levels.
Learn More. Protocols/procedures for developing site-specific criteria. Proceed to the Learn More Topic.
Temporary Modification to Water Quality Standards
Situations can arise in which an individual or group of dischargers determine they cannot immediately meet their permit limits but are uncertain if they can ultimately meet them. For example, the discharger may want to more fully assess its ability to operate within a State/Tribe's water quality standards before investing in expensive controls. Or, the discharger(s) may be anticipating a less-expensive control technology becoming available in the near term.
For such situations, the regulations afford the flexibility to adopt a variance that temporarily modifies the water quality standards to the highest use and criteria that are currently available. This varied use and criteria then serve as the basis for the permit limits that a discharger can meet for the duration of the variance.
Key Point. A water quality variance is a temporary change in a State/Tribe's water quality standards and its relevant criteria, usually regarding a specific pollutant. That is, the underlying standards remain in place. In granting the variance, the State/Tribe must follow its established variance policies and the variance is then subject to public and EPA review. Variances should be reviewed on a triennial basis along with the rest of the State/Tribe’s water quality standards.
Concepts Applied. Read how the flexibility to issue variances was written into the Tribal water quality standards for the Pueblo of Acoma. Pueblo of Acoma Water Quality Standards (pdf) (Refer to p. 2-23 (variances) and p. 2-24 (short-term exceedances).)
When Variances Are Allowed
States/Tribes must use one of the six factors listed (listed in 40 CFR 131.10(g)) to demonstrate that the designated use is not feasible to attain in the short term.
- Factors for Establishing the Basis for Granting a Variance
- Naturally occurring pollutant concentrations.
- Dams or other hydrologic modifications.
- Natural, ephemeral intermittent low-flow.
- Natural physical conditions preclude attainment of aquatic life uses.
- Human-caused conditions or pollutant sources that cannot be remedied or would cause more environmental damage to correct than to leave in place.
- Substantial and widespread economic and social impact.
Question. Can you guess which of the six factors is most commonly used to justify a variance?
Answer. While any of the six factors can be used, in practice, the "substantial and widespread economic impact" factor is most commonly used to justify a variance.
Discharger Grace Period
Situations also can arise where an individual discharger requests additional time to comply with NPDES permit limits based on new or revised criteria in a State/Tribe's water quality standards.
The regulations afford the flexibility to address such requests with a compliance schedule as part of the discharger's NPDES permit if the State/Tribe has a provision authorizing the use of compliance schedules. The compliance schedule allows the particular discharger time to meet a permit's limit or limits while taking steps to eventually be in compliance. Typically, the compliance schedule is included as part of the Terms and Conditions in an NPDES permit and includes interim requirements. The requirements for granting compliance schedules in NPDES permits can be found in the permitting regulations at 40 CFR 122.47.
Key Point. The compliance schedule's timetable must require the discharger to achieve the final water quality-based effluent limit as soon as possible.
Key Point. The State/Tribe's water quality standards or implementing regulations must specifically authorize the use of compliance schedules in NPDES permits.
Concepts Applied. Read how the flexibility to use compliance schedules to allow an NPDES permitee time to make treatment facility modifications was written into the Tribal water quality standards for the Pueblo of Acoma.
Pueblo of Acoma Water Quality Standards (pdf)
The water quality program includes mechanisms that allow flexibility in addressing local circumstances that may arise.
For example, a designated use can be removed/revised if the State/Tribe finds that attaining the use is not feasible. If the use addresses the CWA's 101(a)(2) goal, then the change must be supported by a formal use attainability analysis.
Similarly, states/tribes have the flexibility to modify national criteria recommendations in order to adopt site-specific criteria that reflect local conditions in a particular water body.
Also, the regulations afford the flexibility to grant a variance that temporarily modifies the State/Tribe's standards in order to allow a particular discharger (or dischargers) to determine what standards are attainable over the long term. The temporary modification usually regards a specific pollutant. Thus, the underlying standards remain in place. To grant such a variance, the State/Tribe must demonstrate that attaining the currently designated use is not feasible in the short term due to one of the six factors listed in 40 CFR 131.10(g).
If authorized by the State/Tribal water quality standard or implementing regulations, a discharger can also be allowed a compliance schedule to take the necessary actions to come into compliance with permit limits based on new, revised, or newly interpreted water quality standards. This involves establishing a compliance schedule as part of the discharger's NPDES permit and including interim requirements.
To complete your review of the topic in this module, please take the self-assessment quiz by reviewing each question and considering the possible responses.
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For informational purposes only–Not official statements of EPA policy.