Impaired Waters and TMDLs

The Impaired Waters Restoration Pipeline: Impaired Waters 303(d) Listings

The term "303(d) list" is short for the list of impaired and threatened waters (e.g., stream/river segments, lakes) that have been identified and reported to EPA. The Clean Water Act requires states, territories and authorized tribes to submit impaired waters lists for EPA approval by April 1 of even-numbered years.

The listing process has led to the identification and tracking of over 70,000 impaired waters throughout the United States in the spring of 2014. The 2010 analysis of the TMDL program looked at the progress of national listing efforts within EPA Regional and jurisdiction-specific areas, maps of reporting status and other relevant information.

Over the years, states and EPA have worked together to improve the timeliness of reporting through issuance of guidance. To capture national and statewide listing efforts, EPA uses the Assessment and TMDL Tracking and Implementation System (ATTAINS), an online database that provides integrated state-reported information on water quality assessments, impaired waters and TMDLs to the public. Impaired waters list information is available in tabular form through ATTAINS, as well as in mapped form available as downloadable Geographic Information System (GIS) files.

Reports and Resources