Skip to main content

Oregon State Flag An official website of the State of Oregon »

Total Maximum Daily Load (TMDL)

Section 303(d) of the Clean Water Act requires states, territories, and authorized tribes to list impaired waters and develop total maximum daily loads (TMDLs) for impaired waterbodies. A TMDL establishes the maximum amount of a pollutant allowed in a waterbody and serves as the starting point or planning tool for restoring water quality1.

DEQ has identified ODOT as a designated management agency for pollutants of concern in over 50 TMDLs statewide. ODOT has implemented a statewide TMDL program focused on managing TMDL pollutants associated with the operation, construction, and maintenance of ODOT roads, highways, and bridges. Major components of its statewide TMDL management plan are executed through the core regulatory programs that ODOT is already required to comply with:

  • MS4 Phase I Individual Permit
  • 1200-CA Permits
  • 401 Dredge & Fill Certifications
  • Underground Injection Control (UIC) Permit
  • Federal Aid Highway Programmatic (FAHP)
ODOT's 2020 Phase I Individual MS4 Permit requires an updated draft TMDL implementation plan by June 2023. This implementation plan will identify ODOT's specific actions to achieve TMDL allocations statewide for all TMDLs in effect at the time the permit was issued. As new TMDLs are implemented, ODOT and Oregon Department of Environmental Quality (DEQ) will review and update ODOT's TMDL implementation plan as necessary to address any basin specific requirements. A link to ODOT's draft TMDL implementation plan will be provided with ODOT's MS4 Annual Report June 1, 2023.

1 Clean Water Act Section 303(d): Impaired Waters and Total Maximum Daily Loads (TMDLs) | US EPA