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EPA Environmental Dataset Gateway
EPA Office of Water (OW): Impaired Waters with TMDLs NHDPlus Indexed Dataset
US Environmental Protection Agency, Office of Water
The Total Maximum Daily Load (TMDL) Tracking System contains information on waters that are Not Supporting their designated uses. These waters are listed by the state as impaired under Section 303(d) of the Clean Water Act. The status of TMDLs are also tracked. TMDLs are pollution control measures that reduce the discharge of pollutants into impaired waters. A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources. What is a total maximum daily load (TMDL)? Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use. A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The calculation must include a margin of safety to ensure that the waterbody can be used for the purposes the state has designated. The calculation must also account for seasonal variation in water quality. The Clean Water Act, section 303, establishes the water quality standards and TMDL programs.
The purpose of this application is to provide a summary of the TMDL program that are available for EPA Regions and the states. There are a few ways to access these reports. Go to
to access the tools that provide the TMDL reports for the nation, state, or region.
Time Period of Content
West Bounding Longitude:
East Bounding Longitude:
North Bounding Latitude:
South Bounding Latitude:
None. Please check sources, scale, accuracy, currentness and other available information. Please confirm that you are using the most recent copy of both data and metadata. Acknowledgement of the EPA would be appreciated.
Environment and Conservation, Human Health and Disease, Inland Water Resources
Metadata Reference Information
Metadata Standard Name:
FGDC Content Standards for Digital Geospatial Metadata
Metadata Standard Version:
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