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NYS Section 303(d) List of Impaired/TMDL Waters

The New York State Section 303(d) List of Impaired/TMDL Waters identifies those waters that do not support appropriate uses and that may require development of a Total Maximum Daily Load (TMDL). The Section 303(d) List is updated every two years. The current List in effect is the Final 2018 NYS Section 303(d) List (PDF). Response to public comments received during the public comment period for the 2018 list are summarized here (PDF).


The Federal Clean Water Act requires states to periodically assess and report on the quality of waters in their state. Section 303(d) of the Act also requires states to identify impaired waters, where designated uses are not fully supported. For these impaired waters/pollutants, states must consider the development of a Total Maximum Daily Load (TMDL) or other strategy to reduce the input of the specific pollutant(s) restricting waterbody uses, in order to restore and protect such uses.

The waterbody/pollutant listings in the Section 303(d) List are segmented into a number of categories. The various categories, or Parts, of the list include:

  • Part 1 - Individual Waterbodies with Impairment Requiring a TMDL,
  • Part 2 - Multiple Segment/Categorical Impaired Waterbodies - Includes Acid Rain Waters, Fish Consumption Waters, and Shellfishing Waters,
  • Part 3 - Waterbodies for which TMDL Development May Be Deferred - Includes Waters Requiring Verification of Impairment, Waters Requiring Verification of Cause/Pollutant, and Waters Where the Development, Implementation and/or Evaluation of Other Restoration Measures is Pending.

Impaired Waters NOT Included on the NYS Section 303(d) List

Not all impaired waters of the state are included on the Section 303(d) List. By definition, the list is limited to impaired waters that require development of a Total Maximum Daily Load (TMDL). A list of Other Impaired Waterbody Segments Not Listed (PDF) on the 303(d) List Because Development of a TMDL is Not Necessary is also available. There are three (3) categories of justification for not including an impaired waterbody on the Section 303(d) List:

  • Category 4a Waters - TMDL development is not necessary because a TMDL has already been established for the segment/pollutant.
  • Category 4b Waters - A TMDL is not necessary because other required control measures are expected to result in restoration in a reasonable period of time.
  • Category 4c Waters - A TMDL is not appropriate because the impairment is the result of pollution, rather than a pollutant that can be allocated through a TMDL.

Consolidated Assessment and Listing Methodology

An outline of the process used to monitor and assess the quality of New York State waters is contained in the New York State Consolidated Assessment and Listing Methodology (CALM). The CALM describes the water quality monitoring, assessment and listing process in order to improve the consistency of assessment and listing decisions.

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