The TMDL development process is a problem solving approach that results in a framework for water quality improvement. DEQ is responsible for completing Total Maximum Daily Load studies. In Montana, the geographic scale for this process includes the complete watershed area of contribution for a pollutant. A TMDL is developed for a single pollutant, such as a metal or sediment. A river, lake, or stream may have multiple pollutants, each with its own TMDL study.
The State of Montana develops reports that may contain multiple TMDLs at a watershed scale. During the TMDL process, waters may be found to be healthier than originally thought, or healthy because of recovery from past polluting practices. These waters are taken off the impaired waters (303(d)) list and do not have a TMDL completed for that pollutant.
Steps in the TMDL Development Process
Each TMDL study is somewhat different because impairments to natural systems of rivers, lakes, and streams vary. However, the process of diagnosis, setting amounts of pollutant reduction, and recommended strategies for repair is very similar.
What is the extent of the problem?
In order to fully evaluate the extent of the problem for each pollutant, a set of parameters to characterize water quality is first identified. Then more detailed information is gathered, focusing on these factors. In addition, numeric targets are developed for many of these parameters. These represent compliance with the applicable Water Quality Standard. The gathered information is compared to the targets to assess the severity of the problem.
Which human activities are contributing to the problem? How much is being contributed?
Human activities that contribute to pollutant loads are identified. The magnitude of contributions from source categories such as crop irrigation, septic systems, and wastewater treatment plants is quantified. As part of this effort, natural background pollutant loading is also quantified.
What is the acceptable total load of pollutants?
The maximum acceptable daily load is identified. Amounts of total pollutant loading above the total maximum daily load (TMDL) need to be reduced in order to solve the problem.
How can this problem be solved?
The amount of reduction needed from each source category is determined to satisfy the TMDL. These are called the allocations. Determining allocations includes social and economic considerations and an assessment of overall feasibility. The goal is to develop a fair and reasonable suite of achievable allocations.
The TMDL Report
The results of these steps are incorporated into a final TMDL report. This provides a planning framework for additional local water quality protection and restoration projects.
What to Expect from a Completed TMDL
A completed TMDL provides information on water quality problems and strategies to reduce pollutants by changing land and water management activities. Implementation to meet a TMDL is voluntary for most activities. A TMDL does not create new regulations, but may affect how existing regulations are implemented.
DEQ Role in TMDL Implementation
Montana DEQ does not implement TMDL pollutant reduction projects for most activities, but can provide technical and financial assistance for stakeholders interested in improving water quality in their areas. DEQ staff:
- Work with participants to use the TMDLs as a basis for developing locally-driven, comprehensive Watershed Restoration Plans.
- Administer funding specifically earmarked to help fund water quality improvement and pollution prevention projects, and can help identify other sources of funds.
Read Understanding the Montana TMDL Process to learn more.