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NW Fishletter #390, February 4, 2019
 Washington, Oregon Initiate Temporary Total Dissolved Gas Changes
Washington Department of Ecology has issued a draft Environmental Impact Statement (EIS) to increase total dissolved gas (TDG) limits in the lower Snake and lower Columbia rivers to 125 percent, while Oregon Department of Environmental Quality officials are preparing to present the same adjustments to the state's Environmental Quality Commission.
The planned change in both states is part of the flexible spill agreement reached by the states, federal agencies and the Nez Perce Tribe in December as a temporary alternative to continued court action for spilling water over the eight dams on the lower Snake and lower Columbia rivers.
The proposed change is not being sought for this spring's spill, but could be implemented in 2020. This year, compared with the 2018 court-ordered spill, the agreement increases spill at these dams for 16 hours each day during the spring spill period when market prices for electricity are lower, and allows federal agencies to spill below 2018 levels for eight hours per day during the spring spill period when prices are high.
Allowing dams to spill water to 125 percent TDG was also one of several recommendations from the Southern Resident Orca Task Force as a method of increasing prey for orcas. Modeling has shown that spilling up to 125 percent TDG will result in higher juvenile fish passage and greater smolt-to-adult return ratios.
Washington state says the purpose of its draft EIS is to evaluate the risks of adjusting TDG to allow more spill in the Snake and Columbia rivers. It is accepting comments on a short-term modification of the standards until Feb. 28.
"This temporary change for the 2019-2021 spring spill seasons at the dams would test the potential benefits for fish passage when higher levels of dissolved gases, mainly oxygen and nitrogen, are allowed," states a news release from Washington Gov. Jay Inslee.
Oregon will consider the changes through an administrative process, said Paula Calvert, Columbia River coordinator for the Oregon DEQ. She said the temporary adjustments to the state's TDG criteria being proposed for the lower Snake and Columbia rivers can be changed by its commission.
Staff intends to present the reasons for the proposed changes to commissioners in March, and is currently aiming for approval in November, she said. -K.C. Mehaffey
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