303(d) Listing

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Washington State is required to assess if a body of water fails to meet federal standards. Water bodies that fail to meet standards are added to a list, known as the 303(d) list.


  • Ecology describes the listing this way: "The federal Clean Water Act requires states to perform a water quality assessment every two years to track how clean the rivers, lakes, and marine water bodies are. We place assessed water bodies in categories that describe the quality of the water and status of any needed clean up. The assessment helps us to use state resources more efficiently by focusing our limited resources on water bodies that need the most work." (Ecology 2021)
  • Ecology curates a state-wide list a map service.
  • Some bodies of water are subject to a TMDL study. (What determines which water bodies get studied?)