2025 Triennial Review of the Connecticut Water Quality Standards

The Connecticut Department of Energy and Environmental Protection (Department) is initiating a review of Connecticut Water Quality Standards (“WQS”). This review is being conducted to evaluate the need to update or revise the WQS in order to remain consistent with State and federal law and to ensure that Connecticut’s WQS continue to reflect the best available science and support sound water quality management policies to improve and protect the water resources of the state.

With this notice the Department is requesting input from all interested parties on any aspect of the WQS that a person believes the Department should consider for potential revision. The comment should include the topic of concern, whether it is currently covered by the WQS, and if so where, any suggested revision and the basis for the suggested revision. Any technical information or reports supporting the comment should be included. Comments on the WQS were accepted from July 28, 2025 through August 25, 2025. A public meeting was held via ZOOM on August 14th at 11:00 AM Eastern Time (US and Canada).

While the Department will accept comments on any provision of the WQS, the Department is particularly interested in comments on the portions of the WQS which the Department is evaluating for revision. The need to revise the WQS to address these topics was identified during the previous Triennial Review which was conducted in 2019. Prior to proposing formal changes to the Water Quality Standards, the Department is once again providing an opportunity for public review and comment on the current WQS through this Triennial Review process. After reviewing any comments received during this Triennial Review, the Department will develop recommended updates to the WQS and initiate a formal regulatory revision process which will include a formal public review and comment process.

The topics under consideration for change within the WQS are identified below. Additional topics may be identified during this Triennial Review process and included in subsequent proposed changes to the WQS.

Topics under Consideration for Revision within the WQS Regulations:

Updates to Numeric Water Quality Criteria

Since the WQS were last revised, EPA has updated recommendations for water quality criteria. The Department is currently reviewing the water quality recommendations from EPA and will either propose adoption of the federally recommended criteria or provide a reason for not doing so in accordance with section 304(a) of the federal Clean Water Act. These include updates to federal water quality criteria recommendations for toxics, bacteria and ammonia. Information about the current federal recommendations for water quality criteria can be found on the EPA web site.

1. Low Flow Statistic Applicable to Fresh Waters
   The 7Q10 flow is currently identified as the low flow condition in freshwater rivers and streams. No changes are expected to be proposed to change the low flow condition from the 7Q10 flow to the Q99 flow. CTDEEP has worked with the USGS to update and add 7Q10 flows to StreamStats later this year, making this information easily available.  
2. Extended Disinfection Period
   The current Water Quality Standards contain requirements for disinfection of treated sewage discharge to surface waters at section 22a-426-4(a)(9)(E) of the regulations. This section requires continuous disinfection for all sewage treatment plants located south of Interstate Highway I-95. Disinfection is currently required for all sewage treatment plants north of Interstate Highway I-95 from May 1 to October 1, unless an alternative schedule, including continuous disinfection, is approved to protect those using the waterbody. Based on public comments which identified contact recreational activities within Connecticut that occur outside the current disinfection period, the Department intends to propose an extension of the disinfection period for all sewage treatment plants located north of Highway I-95 to include the period from April 1 through November 1, unless an alternative schedule, including continuous disinfection, is approved to protect those using the waterbody.
3. Downstream Protection
   Water quality in a particular section of a waterbody maybe affected by activities in the upstream watershed which contribute pollutants to the waterbody that are then transported downstream, affecting water quality in that downstream portion of the waterbody. The Clean Water Act requires consideration of these impacts on downstream waters when addressing water quality concerns. The Department believes that this concept is currently included within the WQS but is reviewing federal recommendations and may propose changes to the regulations for clarification, as needed.
4. Water Quality Classification Maps
   The Department is evaluating the need to make changes in order to reconcile the water quality classification designation with shellfishing classification for specific water quality segments, as needed. Additionally, the Department expects to update ground water classification designations for consistency with Aquifer Protection Areas.     

2025 Triennial Review Submitted Comments

Rivers Alliance

U.S. Environmental Protection Agency Region 1

Department of Agriculture Bureau of Aquaculture

Town of Sharon

Triennial Review Archive