DEQ works closely with local, state and federal agencies as well as the public to improve water quality in the Columbia River and its tributaries. The U.S. Environmental Protection Agency identifies the Columbia as one of the nation’s seven “great water bodies” in need of heightened protection from environmental harm.
DEQ oversees several Total Maximum Daily Load, known as TMDL, plans to help reduce pollution and toxics in the Columbia. TMDLs calculate the maximum amount of a pollutant that a water body can receive and still meet water quality standards.
Total dissolved gas standard modification for mainstem Columbia River
Under Oregon Administrative Rules, the Environmental Quality Commission may modify the total dissolved gas criteria on the mainstem Columbia River for the purpose of allowing increased spill for salmonid migration (OAR 340-041-0104(3)).
On Aug. 31, 2024, the most recent order approving a modification to the total dissolved gas water quality standard on the lower Columbia River expired. In effect for the last five spill seasons (2020 – 2024), the order modified the 110 percent TDG water quality standard to 125 percent during spring spill and 120 percent during summer spill for voluntary spill to benefit juvenile migration past the four lower Columbia River dams: McNary, John Day, The Dalles, and Bonneville.
In July 2024, the U.S. Army Corps of Engineers sent a letter to DEQ requesting a renewal of Oregon's total dissolved gas modification order by January 2025. The Corps expects to continue implementation of spill operations for fish passage as outlined in Appendix B of the U.S. Government Commitments in support of the Columbia Basin Restoration Initiative of the Resilient Columbia Basin Agreement. The Agreement – signed by the whole of the U.S. Government and the Nez Perce Tribe, the Confederated Tribes and Bands of the Yakama Nation, the Confederated Tribes of the Umatilla Indian Reservation, the Confederated Tribes of the Warm Springs Indian Reservation of Oregon, the States of Oregon and Washington, and environmental advocacy groups led by the National Wildlife Federation – specifies that spill up to 125 percent total dissolved gas will continue to be used as a tool for juvenile fish passage.
On Friday, Sept. 6, 2024, DEQ released a draft five-year total dissolved gas modification order for the mainstem Columbia River. The public comment period will be open for 30 days. DEQ will consider and respond to all written comments received by 4 p.m. on Sunday, Oct. 6, 2024.
DEQ plans to hold one public hearing. Anyone can attend a hearing in person, or by webinar or teleconference.
Public Hearing: 2024 Total Dissolved Gas Modification Order
Location: 700 NE Multnomah St., 700 Conference Room, Portland, OR 97232
Date: Sept. 20, 2024
Start time: 10 a.m.
Join Zoom Meeting
Meeting ID: 835 0490 4648
Dail-in: 877 853 5257 US Toll-free
Instructions on how to join webinar or teleconference: Instructions
DEQ will present an informational item including background on total dissolved gas management and the proposed draft modification order at the Sep. 26-27, 2024 Environmental Quality Commission meeting.
Additional documents and resources
EPA approved this TMDL on Nov. 18, 2002
On May 18, 2020, EPA established the Columbia and Lower Snake Rivers Temperature Total Maximum Daily Load.
EPA approved this TMDL, which covers three key waterways in Oregon, TMDL approved by the Environmental Protection Agency on Feb. 25, 1991