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Water: Total Maximum Daily Loads (303d)

TMDL Program Results Analysis

The development of Total Maximum Daily Loads (TMDLs) has increased markedly in recent years and over 45,000 TMDLs have now been completed. The TMDL Program Results Analysis Project is a multi-year EPA effort directed at measuring and analyzing programmatic and environmental results from the TMDL Program. What we learn from results analysis helps us understand the strengths and weaknesses of our program and make future program improvements. The goals of this project are as follows:

  • to improve the state of our understanding about how the TMDL Program and closely related activities (e.g., stream restoration projects) lead to varying patterns of results;
  • explain these patterns and, where possible, their causes; and
  • help apply results analysis findings at state, regional, and national TMDL Program levels through technical, programmatic, and policy actions.

The Clean Water Act's impaired waters program pipeline (top of page) is a simplified graphical representation of how impaired waters are restored in a step sequence involving TMDLs and other program actions. Impaired waters are waters too polluted or otherwise degraded to meet the water quality standards set by states, territories, or authorized tribes. TMDL Program Results Analysis has addressed all five pipeline stages in order to understand TMDL results in their broadest context. Click on any of the five stages in the pipeline diagram to learn more about TMDL Program. Or, visit the Overview Page for more about TMDL Program Results Analysis in general.

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