Connecticut Department of Energy & Environmental Protection

DEEP headquarters at 79 Elm Street in Hartford has partially re-opened to staff and members of the public as of Tuesday, February 3. The DEEP records room has re-opened. The DEEP Central Permit Processing Unit (CPPU) will be open to the public starting on Wednesday, Feb. 4. For updates, click here

Water Quality

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  • Triennial Review Process for Water Quality Standards

    Explanation of the Triennial Review Process for the Connecticut Water Quality Standards.

  • Archive of Water Quality Standards Documents

    This archive contains copies of Water Quality Standards which were previously adopted in Connecticut.

  • Water Quality (305b) Report to Congress

    The DEEP Water Monitoring Group conducts annual water quality monitoring to evaluate the physical, chemical and biological condition of the State’s waters. Group staff collect a wide variety and large quantity of information each year, including water chemistry data, water temperature data, bacteria data, biological community data (fish, macroinvertebrates, diatoms) and tissue contaminant data.

  • Triennial Review of the Connecticut Water Quality Standards

    Topics under Consideration for Revision within the WQS Regulations 2025

  • Water Quality Classification Maps

    Water Quality Classification Maps by Town.

  • 2013 Proposed Water Quality Standards Regulations

    Previous (2013) proposed changes to the Connecticut Water Quality Standards.

  • Cyanobacteria Blooms

    Cyanobacteria, also known as blue-green algae, occur naturally in lakes and ponds throughout Connecticut.  These microscopic organisms often go unnoticed and cause no harm.  However, excessive nutrient pollution and climate change are causing waterbodies to experience more frequent nuisance cyanobacteria blooms that may produce and release toxins.  When cyanobacteria blooms release toxins, people and animals using the water body for recreation can have health effects.  It is important to note that not all algal blooms are harmful algae blooms (HABs), however it is not possible to determine the level of toxins in the water without a more detailed evaluation. Out of precaution it is best to avoid direct contact with water experiencing a bloom.  When in doubt, stay out!   

  • Water Quality Reclassification

    Information regarding a request to change the surface or ground water quality classification of a property or area

  • Proposed Water Quality Standards

    Proposed amendments to Connecticut’s Water Quality Standards 2009.

  • Fact Sheet for the Water Quality Standards and Classifications

    The Connecticut Water Quality Standards form the foundation of water quality programs in CT. This fact sheet provides a summary of water quality classification definitions and provides general information.

  • Water Quality Standards and Classification

    The Connecticut Water Quality Standards establish the water quality goals of Connecticut's waterbodies and form the foundation of Connecticut's water management programs.

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