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 (USEPA) 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.