Title: Willamette Basin TMDL and WQMP
Water Quality Limited Parameters: Bacteria (water contact recreation), DDT, Dieldrin, Dissolved Oxygen, Mercury, Temperature, Turbidity
Pollutants: Heat, Turbidity, Total Suspended Solids, E. coli, Total Phosphorus, Methylmercury, Total Mercury, Inorganic Suspended Solids (ISS), Ammonium-Nitrogen (NH4-N), Nitrite + Nitrate Nitrogen (NO3-4N), Dissolved Inorganic Nitrogen, Ultimate Carbonaceous Biochemical Oxygen Demand (CBODU), Ammonia as N
Status: EPA Approval Letter of Addendum for Temperature Nov. 23, 2011; DEQ Issued Sept. 21, 2006; EPA Approval Sept. 29, 2006
The 2006 TMDL was developed for the mainstem Willamette River and nine of the 12 subbasins and contains the following chapters:
An overview of the Willamette Basin;
Specific chapters on the 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.
A water quality management plan (WQMP) is 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 have been 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.
Temperature, mercury and bacteria are three main pollutants presenting widespread problems in the Basin. These parameters were addressed for specific subbasins. Several additional pollutants including dissolved oxygen, turbidity, and toxics (DDT, aldrin, dieldrin) were addressed for specific waterbodies. The scale of the analysis varies depending on the pollutant.
Three primary areas of concern
Temperature: Applies to 9 subbasins, with a major effort on the mainstem Willamette River. The 9 individual subbasins were covered in a manner consistent with previous temperature TMDLs. The Tualatin temperature TMDL was completed in 2001 (See Tualatin TMDL webpage); the Yamhill and Molalla-Pudding temperature TMDLs were deferred. The Molalla-Pudding TMDL was issued in 2008 (see Molalla-Pudding TMDL webpage).
Bacteria TMDL: Applies to 4 subbasins that have a higher proportion of urban and agricultural land uses (Lower Willamette, Middle Willamette, Upper Willamette, and Clackamas). Bacteria planning targets apply to other five subbasins that have no 303(d) (impaired waterbody) listings yet but have the potential for similar problems.
Mercury: A TMDL was issued in 2006 for the entire basin (mainstem and all 12 subbasins) that was replaced in 2019 (see
2019 Willamette Mercury TMDL web page).
Nov. 23, 2011
Sept. 21, 2006