RELATED ECOLOGY PROGRAMS
Total Maximum Daily Load
What is a "total maximum daily load"?
A total maximum daily load (TMDL) is a numerical value representing the highest amount of pollutant a surface water body can receive and still meet water quality standards. Any amount of pollution over the TMDL level needs to be reduced or eliminated to achieve clean water. The Clean Water Act requires that states develop a TMDL for each of the water bodies on the state's 303(d) list. The state sends the finalized TMDL to EPA as part of a water quality improvement report (WQIR) for approval.
TMDL process in Washington State
In general, the TMDL strategy is a common-sense, science-based approach to cleaning up polluted water so that it meets the state water quality standards. Washington State's TMDL process starts with identifying pollution sources within a watershed and determining what needs to change so that pollution is reduced or eliminated.
Pollution sources are broken down into two categories. The first is nonpoint pollution, where the source runs directly off the land into the water. The allowable discharge from all the nonpoint sources is called the load allocation. The second category is point source pollution, which typically flows out of a pipe and is regulated by an NPDES permit. The allowable discharge from a permitted point source is called a wasteload allocation. The water quality improvement report (WQIR) then sets out the actions required for each point source and land use in the project area to ensure TMDL allocations are met.
In short, our TMDL approach:
Elements of a TMDL
Each TMDL project is unique, but there are essential elements to the process. As long as these elements are included, the TMDL project should result in a water quality improvement plan that is complete, acceptable to the public, and approvable by EPA. These elements include:
The TMDL process includes getting feedback from watershed residents, local governments, and other stakeholder groups. Ecology makes every effort to include local input regarding the development of a specific TMDL project. If the parties disagree, they should first try to resolve differences by working with the regional TMDL lead and Water Quality Program regional office supervisor. Should these options not settle the issue, then the local entity or citizen can use the procedures in WQP Policy 1-25 to invoke a formal request for dispute resolution. Causes for dispute could include a technical or procedural disagreement of the TMDL project.
If the local entity or resident does not first attempt to resolve the issues with the regional Water Quality Program office, they will be referred to the regional office before a dispute resolution process can be initiated.
Once the water quality improvement plan is approved by EPA, the next step is to put the TMDL implementation plan into action. Community members and organizations can participate in TMDL projects in a number of ways.
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Last updated June 2013
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