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Erosion Prevention in the Mercury TMDL Area

On August 26, 2025, the County adopted erosion prevention standards for the Mercury TMDL Area, which covers the Willamette River Basin.

Map showing the extent of the Willamette River Basin in Lane County

These new erosion prevention requirements are a part of the County’s Willamette Basin Mercury Total Maximum Daily Load (TMDL). A TMDL specifies the maximum amount of a pollutant that a water body can receive and still safely meet water quality standards.

The Willamette Basin Mercury TMDL was developed by the Oregon Department of Environmental Quality and approved by the federal Environmental Protection Agency, as authorized through the Federal Clean Water Act (CWA) of 1972.  The Willamette Basin has high levels of mercury, a toxin that threatens not only habitat and fish health, but human health as well. The purpose of the Mercury TMDL is to reduce mercury levels within the Willamette Basin. 


Graphic showing the aquatic mercury cycle
Mercury cycling pathways in aquatic environments are very complex. The various forms of mercury can be converted from one to the next. Most important is the conversion to methylmercury, the most toxic form. Ultimately, mercury ends up in the sediments, fish, and wildlife, or evades back to the atmosphere by volatilization. Reprinted with permission from Mercury Pollution: Integration and Synthesis. Copyright Lewis Publishers, an imprint of CRC Press.


  • These new Mercury TMDL standards are in addition to the erosion requirements within the County-Administered MS4 Area around the Eugene and Springfield urban growth boundaries (the small, bright green areas on the map below).
  • All land-disturbing activities within the Mercury TMDL Area and the MS4 Area must use best management practices (BMPs) to meet the erosion prevention outcomes of Lane Code 9.090.030.
  • Erosion prevention permits are not required within the Mercury TMDL Area, but may be required in the MS4 Area.
  • Development permit applications will need to provide a signed self-certification declaration, stating that erosion prevention methods will be used throughout the course of construction.

  • See the or visit the County's Zone and Plan Maps to determine if your property is in the MS4 Area and/or the Willamette Basin Mercury TMDL Area.


     



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