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Water: Total Maximum Daily Loads (303d)

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 (CWA) requires states, territories, and authorized tribes to submit impaired waters lists for EPA approval by April 1 of even-numbered years. For more information on how states identify impaired waters, submit lists, and report on water quality through an integrated reporting procedure, see Overview of Impaired Waters and Total Maximum Daily Loads Program. The listing process has led to the identification and tracking of over 40,000 impaired waters nationally. This page summarizes progress on national listing efforts with EPA Regional and jurisdiction-specific summaries, maps of reporting status, and more resources of interest.

In recent years, states and EPA have worked together to improve the timeliness of this reporting through issuance of guidance (e.g., 2006 Integrated Report Guidance). EPA also developed 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.

Resources of Interest

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

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