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Water: Water Quality Standards Academy

Basic Course: Supplemental Topics - Summary

Listing Impaired Waters and Developing TMDLs

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  • States and Tribes are required under CWA Section 303(d) to identify, prioritize, and establish TMDLs for impaired waters as well as those with water quality that is threatened with impairment. States/Tribes must submit the 303(d) list of impaired/threatened water bodies to EPA every 2 years.

  • In addition, Section 305(b) requires that States/Tribes submit a description of the water quality of all waters in the State/Tribe's boundaries. Further, Section 314 requires States/Tribes as part of their 305(b) report to submit information to EPA on the water quality status of all publicly owned lakes.

  • EPA encourages States/Tribes to submit their list of impaired or threatened water bodies in an "integrated report" that also includes their required submissions under Section 305(b) and Section 314. Using the Integrated Report option to submit this information satisfies the requirements under all three sections of the CWA.

  • States and Tribes must develop TMDLs for each water body/pollutant combination identified on the 303(d) list. The allocations to point and nonpoint sources in the TMDL provide the basis for establishing water quality-based controls that—when implemented — should result in attainment of standards.

  • The TMDL document must include components required by statute or regulation. EPA guidance recommends additional components.

  • TMDLs are not self-implementing. Rather, existing implementation mechanisms vary depending on the source: Point source controls are enforceable under the NPDES permit program. Nonpoint source controls are primarily implemented through State/Tribal and local nonpoint source management programs.

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

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