Total Maximum Daily Loads (TMDLs)

The goal of the federal Clean Water Act, found in U.S. Code 33 U.S.C. §1251 et seq., is "to restore and maintain the chemical, physical, and biological integrity of the Nation's waters."  Missouri’s water quality standards establish pollutant limits to protect drinking water supply, fishing, swimming, aquatic life and other designated uses. A total maximum daily load (TMDL) is the calculation of the maximum amount of a specific pollutant that a water body can absorb and still meet water quality standards.

When waterbodies fail to meet the water quality standards, they are considered impaired waters. The Clean Water Act requires states to develop TMDLs for all waters listed on the 303(d) List of Impaired Waters. In Missouri, the Missouri Department of Natural Resources develops TMDLs. The calculated TMDL is allocated among the various pollutant sources in the watershed and becomes the goal to restore water quality. For more information, review the department's What are TMDLs? - PUB2090 fact sheet or visit the U.S. Environmental Protection Agency's Overview of Total Maximum Daily Loads (TMDLs) website. 

Each TMDL document includes allocations of the acceptable load for all pollutant sources. It also includes an implementation plan to identify how the load will be reduced to a level that will protect water quality. All draft TMDLs are made available for review and comment during a 45-day public comment period. Email public comments or questions about TMDLs to tmdl@dnr.mo.gov. 

TMDL Development Prioritization and Scheduling

Water body impairments are ranked as high, medium or low priority for TMDL development. For impairments ranked as high priority, a specific year is given for when a TMDL may be developed. All priority rankings and development schedules are reevaluated with each new 303(d) List. 

• Prioritization Framework for Development of Total Maximum Daily Loads
• TMDL Alternative - Category 5-alt Components

Specific to developing the 2022 303(d) list, impairments identified as high priority and identified on the 303(d) list as scheduled to begin development in 2022 will be provided to EPA for including in the national bridge metric goals. They are called “bridge metrics” because this is just a temporary metric that is bridging the gap between the 2013-2022 and the 2024-2034 metrics. Beginning with the 2024 303(d) list, a more formalized national 303(d) framework will be implemented. For more information, please review 2022 Section 303(d) List - TMDL Bridge Metrics. The Missouri water bodies that are included in the bridge metrics are identified by an asterisk next to the Water Body Identification Number in the TMDLs Under Development table below.

Approved TMDLs

Approved TMDLs are the final TMDL document, as approved by the U.S. Environmental Protection Agency after public notice and comment. Access to final TMDL documents are provided below in two different formats. The only difference is the amount of additional information provided about the impaired water body or lake.

• Missouri Approved or Established Total Maximum Daily Loads - A PDF document containing minimal information about the impaired water body or lake and links to the final TMDL document and implementation document, if available.
• Impaired Waters and TMDL Map Viewer - An online ArcGIS map that shows locational data for the impaired water body or lake. Detailed information about the water body is accessed by clicking on the line or polygon segments on the map. Included in the water body information are links to the final TMDL document and implementation document, if available. Although the department compiled the map information, no warranty, expressed or implied, is made by the department as to the accuracy of the data and related materials.
• Tools and Resources for Watershed Planning and Improvement - A TMDL identifies water quality problems, possible causes and provides targets for restoration. However, actual water quality improvements are often dependent upon voluntary actions and support from local communities and landowners residing within the watershed.