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EPA's Region 6 Office

Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations

Total Maximum Daily Load Program

§ 303(d) Lists ~ TMDL Documents ~ Region 6 TMDL Contacts ~ Definitions

The Clean Water Act requires states to adopt water quality standards to protect the nation's waters. These standards identify the designated uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support, along with the scientific criteria to support that use. Many of our water resources cannot currently meet their designated uses because of pollution problems from a combination of point sources, such as sewage treatment plant discharges, industrial dischargers, and nonpoint sources, such as pollutants carried by rainfall runoff from forests, agriculture lands, abandoned mine lands, etc. A Total Maximum Daily Load (TMDL) 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.

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.

TMDL Documents For Review/Comment (DRAFT):
FINAL TMDL Documents:

CWA § 303(d) Lists and Associated Documents:

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