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Water: Total Maximum Daily Loads (303d)


The planning stage involves developing and completing TMDLs, or in some cases TMDL alternatives, for the waters identified during the listing stage. A TMDL is essentially a plan, usually based on monitoring information and scientific modeling, that describes how pollutant loads coming from various types of sources must be reduced in order to meet Water Quality Standards. TMDL alternatives known as "4b Plans" are sometimes acceptable where existing, required activities are expected to lead to full recovery. Both TMDLs and 4b Plans are most often completed by states and others but must be approved by EPA. TMDL Implementation Plans are also part of the planning stage; these plans are more specific than the TMDL in terms of what non-point source and point source pollution control actions will occur in what areas to achieve the goals of the TMDL.

The development of TMDLs has increased markedly in recent years and over 45,000 TMDLs have now been completed. Over 4,000 TMDLs have been developed per year in recent years. The pace of TMDL completion is of high priority to the Agency, with numbers reported quarterly, semiannually, and annually for reports such as the  EPA Office of Water Midyear and End-of-Year Reports.

Resources of Interest:

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