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Mercury TMDL Area Requirements

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

The County's Mercury TMDL Area is located within the Willamette River Basin, shown in white on the map above. The area covers roughly 76% of Lane County. The County has adopted erosion prevention standards in the Mercury TMDL Area to meet state and federal standards.

Because the Willamette River has high levels of mercury, the federal Environmental Protection Agency (EPA) and the Oregon Department of Environmental Quality (DEQ) have established stormwater requirements that jurisdictions in the Basin must follow to reduce the mercury levels and protect the waters of the state. These requirements were first published by the DEQ in 2019 and were later amended in 2021 by the EPA. Together, the documents are known as the Willamette Basin Mercury Total Maximum Daily Load, or "Mercury TMDL" for short. 

A TMDL is a scientific calculation that specifies the maximum amount of a pollutant (such as mercury) that a water body can receive and still safely meet water quality standards. The purpose of the Mercury TMDL is to reduce mercury levels within the Willamette Basin. 

Erosion Prevention Requirements in the Mercury TMDL Area

See 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.

  • All land-disturbing activities must use best management practices (BMPs) to meet the erosion prevention outcomes of Lane Code 9.090.030.
  • Erosion prevention permits are not required.
  • 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.