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Antidegradation provisions describe the conditions under which water quality may be lowered in surface waters. Existing beneficial uses must be maintained and protected. Further, water quality better than that needed to protect existing beneficial uses must be maintained unless lower quality is deemed necessary to allow important economic or social development (existing beneficial uses must still be protected).

Provisions addressing antidegradation are in the Water Quality Standards chapter of the Ohio Administrative Code (OAC Chapter 3745-1). Within that chapter, rule 3745-1-54 addresses antidegradation provisions for wetlands and rule 3745-1-05 addresses antidegradation provisions for other surface waters of the state.


  • OAC 3745-1-05 Antidegradation  - effective July 1, 2003
  • The rule was updated on March 15, 2010, to make submittal, public notice and public hearing requirements for Section 401 water quality certification projects consistent with ORC 6111.30.
  • The rule was updated on March 1, 2011, to clarify rule applicability exemptions for existing sources, assimilative capacity reserve allocations for outstanding state waters and superior high quality waters, and assimilative capacity set-aside revision petition procedures.


What is Antidegradation?

Antidegradation refers to provisions that must be followed before authorizing any increased activity on a water body that may result in a lowering of water quality including an increase in the discharge of a regulated pollutant, or activities that may significantly alter the physical habitat.  The antidegradation rule is required by the Clean Water Act and federal regulations.  Antidegradation must be part of any state’s water quality standards program.  The antidegradation rule, along with water quality criteria and beneficial use designations, provides the overall structure of this water quality standards program.  The antidegradation rule must protect the existing use of the water body, and only allow a lowering of water quality when it is necessary to support important social and economic development.  Simply put, the antidegradation rule establishes a procedure to determine that a discharge is necessary before authorizing it.

The state’s antidegradation rule establishes procedures and requirements to ensure that the concepts outlined by the federal regulations are met.  These requirements include public participation activities, intergovernmental coordination, a determination of important social and economic development, an alternatives analysis and greater protection for exceptional quality streams.

The following materials provide additional information and guidance on how the rule will be implemented.

Supporting Documents

The following documents were made available during the 2002-2003 antidegradation rule-making. They provide additional background and detail.


Walter Ariss 614-644-3075
Anthony Nosko 614-644-1987