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

The Oregon Environmental Quality Commission approved an order issued to the U.S. Army Corps of Engineers modifying Oregon’s total dissolved gas water quality standard on Feb. 2, 2015. The standard modification will assist juvenile salmonid migration past four lower Columbia River dams: the McNary, John Day, The Dalles and Bonneville. The five-year order modifies the total dissolved gas standard from April 1 through August 31 and is in effect from 2015 through 2019.


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



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