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Willamette River Mainstem and Major Tributaries Temperature TMDL

Proposed rule

Rulemaking contact: Michele Martin, 503-880-7737

In 2013, the United States Environmental Protection Agency disapproved the Natural Conditions Criterion contained in Oregon's water quality standard for temperature due to the 2012 U.S. District Court decision for NWEA v. EPA, 855 F. Supp. 2d 1199 (D. Or., 2012). This portion of the temperature water quality standard was used in most temperature TMDLs issued from 2003 through 2012. On Oct. 4, 2019, the U.S. District Court issued a judgment for NWEA v. EPA, No. 3:12-cv-01751-HZ (D. Or., Oct. 4, 2019) and required DEQ and USEPA to replace 15 Oregon temperature TMDLs that were based on the Natural Conditions Criterion and to reissue the temperature TMDLs based on the remaining elements of the temperature water quality standard.

A Total Maximum Daily Load is a water quality restoration plan and the calculation of the maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards for that particular pollutant. The maximum amount of loading a waterbody can receive is called the loading capacity. Loading from all pollutant sources must not exceed the loading capacity of a waterbody, including an appropriate margin of safety.

This rulemaking proposes to develop temperature TMDLs for the mainstem Willamette River and all the major tributaries downstream of the dams, except for the McKenzie River which is included in the Subbasins TMDL. The exact extents are described in the Quality Assurance Projects Plans listed on the Temperature TMDL Replacement Willamette River Mainstem and Major Tributaries project page

​DEQ plans to hold two rulemaking advisory committee meetings for the Willamette River Mainstem and Major Tributaries Temperature TMDL. The role of the rulemaking advisory committee is to advise DEQ on the following: 

  • Economic and fiscal impacts of the proposed rules for entities impacted by the proposed TMDL
  • Revision of required TMDL elements with a focus on the TMDL allocations to be updated based on the current temperature criteria for the Willamette River Mainstem and Major Tributaries project area
  • Revisions to the Water Quality Management Plans 

​Meeting 3: July 30, 2024, 9:30 to 11:30 a.m. (PT)

Join via Zoom
Call-in number: 833-928-4608 (Toll-free in the U.S.)
Meeting ID: 865 0658 9804 

Previous meetings

Meeting 2: May 16, 2024

Meeting 1: March. 14, 2024

Public involvement

There are no public events scheduled at this time.

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EQC action

DEQ plans on presenting the Willamette River Mainstem and Major Tributaries TMDL to the Environmental Quality Commission for proposed rule adoption in November 2024 to give EPA a minimum of 30 days for their approval or disapproval by Feb. 28, 2025.