This module discusses the requirement that water quality standards include a framework and methodology for deciding if, when, and how water quality that exceeds the CWA 101(a) goal can be degraded by regulated activities and when that water quality must be maintained. Answers to the following questions are provided:
At the end of the module is a brief quiz intended to touch on some Core Modules regarding a State or Tribe's antidegradation program that are 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.
On this page:Under the Clean Water Act (CWA), once the existing uses of a water body have been established—by evaluating the water's quality relative to uses already attained—a State/Tribe must maintain the level of water quality that has been identified as being necessary to support those existing uses.
But what if the water quality is better than what is necessary to support the existing uses? That is, what if progress has been made toward attaining the CWA 101(a) goal uses?
Question. Can the State/Tribe then allow a degradation of water that is better than that necessary to protect CWA 101(a) uses? What if the degradation would provide economic or social development opportunities or other benefits to the State or Tribe?
The answer is yes. However, in order to effectively address the considerations involved in making such decisions, EPA's regulations require the State/Tribe to have established an antidegradation policy as part of its water quality standards.
In essence, a State or Tribe's antidegradation policy provides a framework for weighing the pros and cons of a proposed activity that could degrade water quality and for involving the public in the decision-making (40 CFR Section 131.12(a)).
Key Point. Within limitations established by EPA's regulations, the State or authorized Tribe has the discretion to permit activities that degrade water quality to a minimum level—that is, to the level of quality identified in the State or Tribe's water quality standards as being necessary to support the water body's existing uses.
Antidegradation policy can apply to both point and non-point source activities.
Key Point. Before permitting degradation for point sources, the State/Tribe must ensure that the most stringent technology-based controls required by statute and regulation will be implemented.
Because the Clean Water Act does not authorize regulatory non-point source control programs, EPA cannot require States/Tribes to implement such programs. States/Tribes, of course, are free to adopt requirements for non-point sources that exceed those of the CWA. Nonetheless, where States/Tribes have established an approach for evaluating non-point sources, the process must be followed before allowing degradation of water quality.
Key Point. Before allowing an increase in pollutant loads by non-point sources, the States/Tribes with a non-point source control program should ensure that reasonable and cost-effective best management practices for control will be implemented.
Along with an antidegradation policy, States/Tribes also are required to identify their implementation method. In so doing, the State/Tribe establishes how and when the policy will be applied and what criteria will be used in its decision-making.
Key Point. An essential requirement of antidegradation policy implementation is to allow for public involvement in the decision-making. In all cases, the State/Tribe must pose the question to the community and other stakeholders: Do we want to allow the quality of this water body to degrade?
A State or Tribe's policy must be neutral regarding such questions, allowing the State/Tribe to decide about the degrading water quality based on implementation criteria.
Key Point. Taken together, the antidegradation policy and the policy's implementation method constitute the State or Tribe's antidegradation program.
Some EPA Regional Offices provide guidance on developing implementation methods.
The general parameters of a State or Tribe’s antidegradation program must address three categories.
Tier 1. Protection of water quality for existing uses. Tier 2. Protection of high quality waters. Tier 3. Outstanding National Resource Waters.
Key Point. For all tiers, a State or Tribe's review of activities that raise antidegradation considerations should be documented and subject to public review and comment.
At a minimum, States/Tribes must apply their antidegradation program to activities that are regulated under State, Tribal, or federal law, including:
Key Point. Federal antidegradation requirements do not create State/Tribal regulatory authority over otherwise unregulated activities.
Tier 1 of the State or Tribe’s antidegradation program must protect existing uses by maintaining the water quality necessary to support those uses. Tier 1 is applicable to all surface waters.
Existing uses are determined by considering data on both the use that has occurred and the water quality that has been achieved to support the use.
Tier 2 of the State or Tribe's antidegradation program protects "high quality" waters—that is, water bodies where existing water quality conditions are better than necessary to protect CWA 101(a) uses.
High quality waters must be addressed by the State or Tribe's antidegradation program because of the importance of such waters as a resource with economic, public health, and ecological value.
Key Point. Trade-offs must be carefully considered before a high quality water resource is allowed to be diminished in any way through degradation of water quality. The State or Tribe's antidegradation program must identify a procedure to be followed and questions to be addressed when confronting such issues.
Learn More. Two ways to identify high quality waters. Also, information about antidegradation review for high quality waters. Proceed to the Learn More Topic.
Tier 3 of the State or Tribe's antidegradation program protects outstanding national resource waters (ONRWs)—waters that have unique characteristics to be preserved (e.g., waters of exceptional recreational, environmental, or ecological significance).
Key Point. No degradation is allowed in an ONRW, except on a short-term basis—meaning weeks or months rather than years. An example of an allowable temporary degradation might be during repairs of a facility.
While States/Tribes are required to have provisions in their antidegradation policy that address ONRWs, it is left to the State/Tribe's discretion to identify waters as ONRWs.
Many States/Tribes have levels of protection that are similarly protective but may allow more flexibility when making water quality determinations. Examples of such designations include "Outstanding Natural Resource Waters," "Outstanding State Resource Waters," or "Exceptional Waters."
EPA Regional Offices review new and revised antidegradation policies and antidegradation procedures developed by States and Tribes.
EPA’s key considerations for reviewing antidegradation programs:
Consideration A
Does the antidegradation policy protect existing uses, high quality waters, and ONRWs?
Consideration B
Are implementation methods identified?
Consideration C
Do protections for high quality waters apply to a broad spectrum of waters rather than just a narrow subset?
Consideration D
Is the wording used to describe the program consistent with CWA Section 131.12 (a)(1)-(4)?
Consideration E
the identified implementation methods consistent with EPA’s antidegradation provisions?
To complete your review of the topic in this module, please take the self-assesement quiz by reviewing each question and considering the possible responses.
A note about the quiz:
Your answers will NOT be scored or recorded. However, selecting the Submit button for each question will provide you with the correct answers on screen.
At the end of the quiz is a Get Password button. Select this after you have completed the quiz to obtain one of the six passwords you will need to obtain your Certificate of Completion at the end of the course.
Disclaimer:
For informational purposes only–Not official statements of EPA policy.
Although the Clean Water Act does not specify an approach for identifying high quality waters, EPA provides guidance on two approaches that are generally in use.
This approach to identification of high quality waters is typically conducted as part of the permit review process. The basis for the determination can be chemical data as well as biological data or indices. The approach involves the following steps:
This increment — termed the "assimilative capacity" of the water body — is considered the resource to be protected.
This approach to identification of high quality waters is usually based on monitoring data collected either prior to or as part of the permit review process. This so-called "designational approach" involves the following:
The State or Tribe's determination about whether to authorize a degradation of high quality waters should involve the following questions:
Is it necessary?
That is, are cost-effective alternatives available that would eliminate or reduce the reduction in water quality?
Does the activity associated with the discharge support important economic or social development?
That is, what benefits are forgone if the reduction in water quality is not allowed?
That is, what benefits are forgone if the reduction in water quality is not allowed? Has the public been involved?
Public participation—as well as intergovernmental review—generally takes place through comment on the draft permit.
Public participation—as well as intergovernmental review—generally takes place through comment on the draft permit. Will existing uses be protected?
Degradation can only be allowed if existing uses are protected.
For example, assume a State or Tribe has classified a water body for "fishable/swimmable" uses and has identified a criterion of 5.0 mg/L for dissolved oxygen (DO) as protective of that use. If the DO level is subsequently found to be better than identified as protective for the use, the State/Tribe could consider allowing a use that would degrade water quality back to the criterion level. However, it could not allow the level of DO in the water body to degrade any further than that established by the criterion. Also, the State or Tribe must follow its established procedures when allowing the use.
Some States/Tribes do not require an antidegradation review if the lowering of water quality will be "de minimis"—that is, if the reduction would be so small as to be considered insignificant. Such a policy can enable States/Tribes to focus resources on questions involving the potential for more significant degradation.
Key Point. For point sources, the State/Tribe must ensure that the most stringent technology-based controls required by statute and regulation will be implemented.
Key Point. The danger of such a policy can be the potential cumulative effect on a water body’s assimilative capacity of allowing a number of de minimis degradations of the same pollutant. Hence, EPA recommends that where de minimis exclusions are allowed that a cumulative cap on these degradations be applied to a waterbody's assimilative capacity.
Generally, antidegradation reviews for high quality waters take place when a point source discharger requests a new National Pollutant Discharge Elimination System (NPDES) permit or an increase in allowable loadings under an existing permit. The discharger generally submits the analyses needed for the State/Tribe to weigh considerations and make a determination.
Key Point. For point sources, the State/Tribe must ensure that the most stringent technology-based controls required by statute and regulation will be implemented.
Because the Clean Water Act (CWA) does not authorize regulatory non-point source control programs, EPA cannot require States/Tribes to implement such programs. Nonetheless, where States/Tribes have established an approach for evaluating non-point sources, the process must be followed before allowing degradation of high quality waters.
Key Point. For non-point sources, the States/Tribes with a program should ensure that reasonable and cost-effective best management practices for control will be implemented.
Resource. Enforceable State Mechanisms for the Control of Nonpoint Source Water Pollution (Environmental Law Institute, 1997) (Note: 1998 and 2000 editions also extant.)
If the antidegradation review involves the dredging or filling of a wetland, Section 404 of the CWA requires that any permit issued be consistent with the State or Tribe's water quality standards and antidegradation policy.
The U.S. Army Corps of Engineers reviews Section 404 discharge permit applications to avoid "significant degradation" of wetlands, as defined by the regulations (40 CFR 230.10(b))
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