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Water: Water Quality Standards Academy

Basic Course: Supplemental Topics - TMDL Implementation: Pollutant Source Control Mechanisms

Listing Impaired Waters and Developing TMDLs

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Point Source discharging into water body.

TMDLs are not self-implementing under Section 303(d); however, existing implementation mechanisms vary depending on the source of the pollutant(s):

  • Point sources. Allocations to point sources get implemented through permits that are consistent with the WLA in the TMDL. These permits are enforceable under the Clean Water Act through the National Pollutant Discharge Elimination System (NPDES). Permits are issued by EPA or States/Tribes with delegated authority.
  • Nonpoint sources. There is no federal enforcement program for control of nonpoint source pollution. Nonpoint source controls are primarily implemented through State/Tribal and local nonpoint source management programs. Some of these State/Tribal or local programs have regulatory enforcement authority.
Key Point. Although states are not required under Section 303(d) to develop TMDL implementation plans, many states include them with the TMDL or develop them as a separate document and EPA does not approve or disapprove them. Evaluations of TMDLs with implementation plans have shown greater success in achieving water quality objectives. TMDL implementation plans provide additional information on how point and nonpoint sources are being controlled-or should be controlled in the future-to meet the relevant water quality standards.
Resource. For information about point source pollution and the NPDES permits program, visit EPA's NPDES Web page . See also the NPDES module in this online training.

Resource. For information about nonpoint source pollution, visit EPA's Polluted Runoff (Nonpoint Source Pollution) Web page.

For informational purposes only–Not official statements of EPA policy.

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