Clean Water Legacy Program

Mission: To meet current needs while ensuring a future in which Minnesota's waterways and watersheds remain an abundant source of clean water, provide enjoyable recreation, and support healthy aquatic ecosystems.

Total Maximum Daily Load studies

When do studies need to be done?

A Total Maximum Daily Load study must be prepared for every waterbody on the Impaired Waters List This link leads to an external site.. The study is a detailed assessment that determines how much pollutant is present in an impaired water, the sources of the pollutant, and what pollutant reductions will be needed to restore the water resource to health. The study assesses both those pollutants that come form point sources (an individual business or wastewater treatment plant) and from non-point sources (general land-use activities) to provide a comprehensive picture. The study is prepared by teams whose members may include staff from state and local units of government, watershed districts and water management organizations, environmental groups, fishing groups, and involved citizens — anyone with an interest in the water resource and the desire to participate on the team.

What happens after the study is completed?

Dalen Coulee restoration

After the study has been prepared and approved by the U.S. Environmental Protection Agency, a detailed implementation plan is developed. Depending on the type, severity, and scale of the impairment, restoration may require years or even decades, and several million dollars. Restoration activities often include:

  • improvements to wastewater treatment plants or stormwater systems;
  • upgrading failing septic systems
  • implementing "best management practices" to minimize runoff or soil erosion;
  • changing land-use or business practices where pollution is severe; or
  • restoring stream channels and lakeshore.

The Minnesota Pollution Control Agency publishes lists of both draft This link leads to an external site. Total Maximum Daily Load studies and approved This link leads to an external site. studies with their implementation plans.

DNR staff participates on Total Maximum Daily Load study teams and provides expertise and data collected by the DNR to help develop studies and implementation plans. When water quality is restored, the lake or stream is removed from the Impaired Waters list. Long-term monitoring is continued to ensure standards are maintained.