EPA Office of Water (OW): Impaired Waters with TMDLs by Causes of Impairment and Probable Sources and TMDL Pollutant

Under Section 303(d) of the Clean Water Act (CWA), states, territories, and authorized tribes, collectively referred to in the Act and here as "states," are required to develop lists of impaired waters. A state’s 303(d) impaired waters list is comprised of all waters where required pollution controls are not sufficient to attain or maintain applicable water quality standards. The law requires that states establish priority rankings for waters on the lists and develop Total Maximum Daily Loads (TMDLs). A 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 the load reduction needed from various sources of the pollutant.

Organization Name: U.S. EPA Office of Water (OW)

Contact: US EPA Headquarters, Office of Water (reid.wendy@epa.gov)

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