Total Maximum Daily Loads

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 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 four Columbia River dams

On Jan. 24, 2020, the Oregon Environmental Quality Commission approved an order  modifying the total dissolved gas water quality standard to allow voluntary fish passage spill by the U.S. Army Corps of Engineers to assist juvenile salmonid migration past four lower Columbia River dams: McNary, John Day, The Dalles and Bonneville. The order is effective 2020 through 2024 and modifies the 110 percent TDG water quality standard to 125 percent for spring spill and 120 percent for summer spill.

For approval of the order, the EQC considered DEQ’s TDG memorandum and its attachments , which include public comments and DEQ’s response to comments. Audio of the EQC TDG agenda item is available at the EQC January 2020 meeting web page  under Agenda Item I.

 

Lower Mid-Columbia River ecological assessment

DEQ completed its “snapshot” ecological assessment of the Lower Mid-Columbia River, which covers 150 miles between Bonneville Dam on the west and McNary Dam on the east. This study –- the first of its kind on this section of the Columbia -- showed that while the river’s fish and bank habitat is degraded, its water quality is generally good, with low levels of metals and organic compounds known as polyacromatic hyrdrocarbons. Unfortunately, bass and largescale sucker fish fillets sampled from the river as part of this study show accumulation of potentially harmful levels of mercury, chlorinated pesticides and other toxic or cancer-causing chemicals, including dioxins, furans, and PCBs.

This assessment fills information gaps and compliments studies conducted by states, tribes, federal agencies and non-governmental organizations to gauge conditions, identify problems and find solutions to pollution issues affecting the Columbia River. The U.S. Environmental Protection Agency listed the Columbia Basin as one of seven Great Water Bodies deserving of special attention and protection from environmental harm.

Total Dissolved Gas TMDL - Lower Columbia River

EPA approved this TMDL on Nov. 18, 2002 

Dioxin Discharges TMDL - Columbia River (as well as Snake and Willamette Rivers)

EPA approved this TMDL, which covers three key waterways in Oregon, TMDL approved by the Environmental Protection Agency on Feb. 25, 1991


 

​Contact

Columbia River Basin Coordinator
Paula Calvert,  503-229-5101