What is the Clean Water Act? Antidegradation

Antidegradation provides a framework for maintaining and protecting high quality waters, controlling degradation of waters currently exceeding minimum quality requirements, and preventing pollution from interfering with uses in all waters. Antidegradation requirements were actually adopted as policy in federal regulation in 1968: several years before the Clean Water Act! When the Clean Water Act was passed, this existing policy became a part of the nation's comprehensive new clean water regulations. Federal regulations for antidegradation policy can be found in 40 CFR 131.12.

What does the Clean Water Act’s Antidegradation policy require?

The federal policy requires a three-tiered approach outlined below:

Tier I Tier II Tier III

Protect existing uses
Permit no activity that would eliminate or interfere with an existing use. This in essence reiterates and reinforces the requirements for designated uses and developing the associated set of water quality criteria for each designated use. Tier I establishes the absolute floor for water quality protection.

Maintain "high quality" waters
Avoid any lowering of the quality of waters that currently meet or exceed water quality standards except under some limited circumstances. The circumstances under which a state can permit the lowering of water quality in high quality waters are defined in detail in the regulations. Again however, all existing uses are to be protected.

Protect "outstanding" waters
Protect and maintain the current water quality in Outstanding National Resource Waters (ONRW). Waterways in National and State parks and wildlife refuges and waters that have exceptional recreational or ecological significance can be designated as ONRW.

Every state must develop and implement an antidegradation policy that is at least as protective as the federal policy. States can develop a policy that is more specific and more protective if they choose to do so. Kentucky's Antidegradation policy (PDF, 158K) is identical to the federal policy. States also must develop a way of assuring the policy is implemented. Implementation should ensure that the state's major water quality programs, decisions and any day-to-day activities affecting water quality and aquatic ecosystem health will be consistent with all three tiers of the antidegradation policy.

What should a protective antidegradation implementation procedure do?  

  • Protect all existing uses with strong use designations and water quality criteria.
  • Trigger a through review of pollution-preventing alternatives whenever a permit for a new or expanded discharge is requested for a "high quality" water (a waterway that has at least assimilative capacity for the pollutant or pollutants referred to in the proposed permit).
  • Provide a system for identifying and protecting "Tier III" waters; and
  • Actively involve the public in decisions about any "Tier II" permits and in the designation of "Tier III" waters.

Questions about Tier II and Tier III waters

Tier II Tier III
What if my waterway is below the criteria limit for most standards but exceeds on fecal coliform? Does a waterway have to be pristine to be designated as ONRW and protected as Tier III water?

If a new or expanded permit activity would lower the water quality in your waterway in any respect in which it currently has assimilative capacity (is below the maximum allowed for a pollutant), Tier II is to apply to the permit. Having too much of one pollutant (in this example, fecal coliform) is not to be used as a justification for allowing more of different pollutant of which there is currently little in the water.

No. Waters of "exceptional ecological significance" are to be given special consideration in the development of a state's ONRW list. The list can also include waters of exceptional recreational value, and waters in National or State Parks or wildlife refuges. All of these waters should be considered for Tier III protection, whether or not their existing water quality is particularly high.

Learn about Kentucky’s Antidegradation Issues!