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Water: Total Maximum Daily Loads (303d)

What is a 303(d) list of impaired waters?

Overview of Impaired Waters and Total Maximum Daily Loads Program

Overview | Glossary | Example TMDLs | Litigation


What is a 303(d) list of impaired waters?

The term "303(d) list" is short for the list of impaired and threatened waters (stream/river segments, lakes) that the Clean Water Act requires all states to submit for EPA approval every two years on even-numbered years. The states identify all waters where required pollution controls are not sufficient to attain or maintain applicable water quality standards, and establish priorities for development of TMDLs based on the severity of the pollution and the sensitivity of the uses to be made of the waters, among other factors (40C.F.R. §130.7(b)(4)). States then provide a long-term plan for completing TMDLs within 8 to 13 years from first listing.

EPA policy allows states to remove waterbodies from the list after they have developed a TMDL or after other changes to correct water quality problems have been made. Occasionally, a waterbody can be taken off the list as a result of a change in water quality standards or removal of designated uses; however, designated uses cannot be deemed unattainable and removed until a thorough analysis clearly shows that they cannot be attained.

How do states identify impaired waters?

Regulations say states must evaluate "all existing and readily available information" in developing their 303(d) lists (40 C.F.R. §130.7(b) (5)). Usually due to a lack of resources, most state water quality agencies are able to monitor only a small percentage of their waters consistently enough to detect water quality problems. Many state agencies use data collected from outside organizations and the public to compile their lists. There are usually requirements for data collection and submission before state agencies will consider the data.

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How do states submit lists?

In addition to the 303(d) report, the CWA requires that each state report every two years on the health of all its waters, not just those that are impaired. Information from this report, known as the 305(b) report or "biennial water quality report," has historically been used to develop the "threatened and impaired waters" list. Most states compile the data and findings from the 305(b) report and add information from other sources, such as the state's report of waters affected by nonpoint sources (CWA §319), to produce the 303(d) list. EPA recommends that states combine the threatened and impaired waters list, 303(d) report, with the 305(b) report to create an "Integrated Report," due April 1 of even-numbered years.

State Options for Reporting Water Quality Status
Separate 305(b) and 303(d) Reports
(Minimally Required by Regulations)
Integrated Report
(Recommended Reporting Format)
The state's Section 303(d) list is comprised of waters impaired or threatened by a pollutant, and needing a TMDL. States submit a separate 305(b) report on the conditions of all waters. A single state developed report that integrates the reporting requirements of CWA Sections 303(d), 305(b) and 314 EPA's Integrated Report Guidance (IRG) developed for 2002, 2004, 2006 and 2008 reporting cycles (www.epa.gov/owow/tmdl/).
Both are due to EPA on April 1 of every even year. EPA approves/disapproves 303(d) list, uses 305(b) information to prepare biennial report to Congress. EPA approves/disapproves Category 5 of the Integrated Report, uses information to satisfy requirements of 305(b).

EPA then has 30 days to approve or disapprove the 303(d) or Category 5 lists. If EPA disapproves a state list, EPA has 30 days to develop a new list for the state; although historically, EPA has rarely established an entire list for a state. Usually EPA partially disapproves a list because some waters have been omitted and adds these few waters to the state's list.

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