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Wet weather events (e.g., rain, snowmelt) can affect publicly owned treatment works (POTWs) operations when excess water enters the wastewater collection system. The increased wet weather flows can exceed the POTW treatment plant's capacity to provide the same type of treatment for all of the incoming wastewater. The treatment plant's secondary treatment units are the most likely to be adversely affected by wet weather because the biological systems can be damaged when too much water flows through them. POTWs employ a variety of operational practices to ensure the integrity of their secondary treatment units during wet weather. This update to the regulations will seek to clarify permitting procedures so as to provide POTWs with separate sanitary sewer systems flexibility in how they manage and treat peak flows under wet weather conditions. These updates will also seek to ensure a consistent national approach for permitting POTWs that allows efficient treatment plant operation while protecting the public from potential adverse health effects of inadequately treated wastewater.

Statement of Need:

This update to the regulations will seek to clarify permitting procedures for POTW treatment plants with separate storm sewer systems under wet weather operational conditions. These updates will also seek to ensure a consistent national approach for permitting POTWs that provides for efficient treatment plant operation while protecting the public from potential adverse health effects of inadequately treated wastewater.

Summary of the Legal Basis:

The rule will be proposed under the Clean Water Act, 33 U.S.C. 1311 and 33 U.S.C. 1314.

Alternatives:

Alternatives have not yet been developed at this time.

Anticipated Costs and Benefits:

A cost analysis analyzing anticipated costs and benefits will be developed for the rulemaking at the time of proposal.

Risks:

The agencies will be able to analyze the risks of the proposed rulemaking once policy decisions have been made.