The 2006 Willamette Basin TMDL was developed for the mainstem Willamette River and 9 of the 12 subbasins. It includes specific chapters on three primary parameters of concern: bacteria, mercury and temperature. These three chapters contain detailed analyses for each pollutant and focus primarily on the mainstem Willamette River. For bacteria and temperature, these chapters also provide summaries of the Subbasin-level analyses. Specific chapters were created for each of the nine subbasins that were the focus of detailed monitoring and analysis. These provide a local focus of all the TMDL-related issues within a geographic region and address different pollutants depending on the subbasin. These include water quality limited parameters for bacteria (water contact recreation), mercury and temperature as well as DDT, dieldrin, dissolved oxygen, and turbidity. They also address pollutants including total suspended solids, total phosphorus, inorganic suspended solids, ammonium-nitrogen, nitrite + nitrate nitrogen, dissolved inorganic nitrogen, ultimate carbonaceous biochemical oxygen demand, and ammonia as N.
A water quality management plan was also included which provides a framework for the implementation of the TMDL. While the TMDL analysis determines what pollution reductions are needed to achieve water quality standards, the WQMP indicates the strategies needed to make the reductions happen.
Technical appendices were included to provide detailed assumptions, analyses, and other supporting information. These appendices have been designed to enhance the readability of the main chapters by placing much of the detailed technical information in the appendices rather than in the main chapters.
The 2006 TMDLs were approved by EPA on Sept. 29, 2006. Since then, EPA has approved new TMDLs for Mercury and Temperature. The 2006 TMDL and WQMP for Mercury was replaced in 2019. The 2006 TMDL and WQMP for Temperature was replaced in 2025. The 2006 TMDLs and WQMP for Mercury and Temperature are no longer active. However, other pollutants including bacteria that were addresses by the 2006 TMDL and WMQP remain active and are in effect. These pollutants are addressed in Chapters 1, 2, 5-14, and Appendix A.
The 2006 TMDLs for mercury and temperature are no longer in effect and have been replaced. The documentation provided below is for informational purposes only. The 2006 TMDLs for other parameters are still in effect.
Willamette River Basin Temperature TMDL modeling reports from Portland State University and USGS:
Other documents