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NW Fishletter #394, June 3, 2019
 Washington DOE Proposing 125-Percent TDG Rule Change
The Washington Department of Ecology has begun the process for changing some provisions in its water quality rules, including increasing total dissolved gas (TDG) limits at eight Snake and Columbia river dams to 125 percent.
In a May 7 notice, Ecology says it is beginning the rulemaking process for multiple revisions. The agency is now reviewing public comments to determine the scope of an environmental impact statement (EIS) for the potential rule changes. The EIS will evaluate the potential environmental impacts of amendments, and will be used to guide the proposed rule language.
Ecology spokeswoman Colleen Keltz said her agency expects to release a draft EIS for public comment in July, and will likely host a public hearing on the proposed rule changes.
Washington already modified its TDG limits to 120 percent in both the forebays and tailraces at eight dams under a short-term modification of TDG standards during spring spill. The change was made to accommodate this year's flexible spill agreement between three federal agencies, the states of Washington and Oregon, and the Nez Perce Tribe. Next year, the agreement calls for increasing spill to 125 percent TDG for 16 hours a day, prompting Washington's potential rule change.
Oregon will also have to change its dissolved gas criteria before next year's spring spill season in order for the 125 percent TDG limit to go into effect. In a May 10 memo to the state Environmental Quality Commission, Oregon Department of Environmental Quality Director Richard Whitman noted that TDG levels higher than 110 percent can cause gas bubble trauma in fish.
However, additional voluntary spill helps out-migrating juvenile salmon and trout, the memo states. The Commission will be asked later this year to modify the TDG standard to 125 percent at the Columbia River dams for the April 1, 2020, fish migration spill season, it says.
Keltz told NW Fishletter that the modification to 120 percent TDG included an understanding that normal monitoring for gas bubble trauma in fish would continue at the dams by the Fish Passage Center during the 2019 spill season, and that no additional monitoring was required.
She said if the water quality standards are changed to increase total dissolved gas limits to 125 percent TDG at the dams, Ecology would establish biological thresholds that must be met for not only salmon and steelhead, but other aquatic life.
In a follow-up email, she wrote that the proposal to adjusting TDG criteria to 120 percent will also consider additional monitoring requirements. Currently, the Fish Passage Center monitors ESA-listed Chinook salmon and steelhead smolts in the Snake and Columbia rivers. In 2018, the smolt monitoring program collected and examined fish for signs of gas bubble trauma at Rock Island Dam in the middle Columbia above its confluence with the Snake River, and at Bonneville and McNary dams on the lower Columbia, and Lower Granite, Little Goose and Lower Monumental on the Snake River.
"The goal of the gas bubble trauma monitoring program is to sample 100 salmonids each day of sampling at each site," she wrote. "The proportion of each species sampled is dependent upon their prevalence at the time of sampling."
Whitman's memo also noted that DEQ will coordinate with the Washington and Oregon's fish and wildlife departments and other Columbia River partners "to assess physical and biological monitoring that should occur if the 125 percent modification is authorized."
Washington is also tackling three other potential rule changes in its water quality codes, including amendments to meet legal obligations from a 2018 court order; aligning its rule with the Washington Department of Health's shellfish program, and clarifying descriptions of marine water aquatic life use designations.
Keltz said the proposed rule change from the court obligations resulted from Ecology's intervenor status in Northwest Environmental Advocates v. United States Environmental Protection Agency. Ecology is seeking to remove incremental temperature allowance provisions which would only apply to water bodies that were cooler than temperature criteria, and therefore would not have a direct effect on temperature standards at hydroelectric dams. -K.C. Mehaffey
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