Connecticut 303(d) Impaired Waters 2020 is a subset of Connecticut 305(b) Assessed Waters 2020. If any one of the assigned designated uses is categorized as NOT Supporting, the assessed waterbody is included in this subset and is considered impaired. Additional information about Integrated Water Quality reporting is available on the CT DEEP website, Integrated Water Quality Report page. 

Connecticut 305(b) Assessed Waters files includes rivers, lakes and estuaries that have been assessed in compliance with Sections 305(b) and 303(d) of the federal Clean Water Act. Section 305(b) of the Clean Water Act requires each state to monitor, assess and report on the quality of its waters relative to attainment of designated uses established by the State's water quality standards. Section 303(d) requires each State to compile a subset of that list identifying only those waters not meeting water quality standards and assign a Total Maximum Daily Load (TMDL) priority ranking to each impaired waterbody.

This assessment is based on information collected and compiled prior to 2020. It represents conditions at a particular point in time and does not represent current conditions. Depending on the type of waterbody - river, lake, or estuary - this information geographically displays attainment and non-attainment (e.g. full supporting, not supporting, not assessed) for each designated use - aquatic life, marine aquatic life, recreation use, fish consumption, shellfish harvesting, and drinking water supply.