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NW Fishletter #391, March 4, 2019

[5] Orca Recovery, Flexible Spill Agreement Among Reasons For Dissolved Gas Proposal

A proposal to modify Washington state's total dissolved gas standards to 120 percent in both forebays and tailraces at eight dams this year would allow for more spill and reduce powerhouse encounters by salmon and steelhead smolts--which should eventually result in more adult returns.

That's according to Michael Garrity, Washington Department of Fish and Wildlife's Columbia River policy manager. Models predict that between 10,000 and 60,000 additional spring Chinook salmon would return to the Columbia Basin or become available for orcas in a few years if a new flexible spill plan occurs, Garrity said. That plan requires changes this year in Washington's total dissolved gas (TDG) standards, which are now under consideration by the state Department of Ecology.

Garrity and Chad Brown, Ecology's water quality management unit supervisor, explained the state's proposal for a short-term modification of TDG standards during an hour-long webinar Feb. 19, followed by questions and a public hearing on the proposal.

Only Jim Waddell--a longtime proponent of Snake River dam removal and retired civil engineer for the U.S. Army Corps of Engineers--commented during the webinar, saying that the extra spill will not do enough to boost Chinook runs and help endangered orcas. "This idea that this is buying us time is not really accurate," he testified, adding, "The only thing that can make a difference is immediate breaching of the dams this year."

Ecology heard others testify at a public meeting in Vancouver, Wash., on Feb. 13, and will also consider written comments submitted by Feb. 28. The agency issued a draft environmental impact statement in January to modify the dissolved gas levels, and expects to make a decision by March 29--in time for the spring spill season, set for April 3 to June 20.

Brown said his agency is considering increasing TDG limits only at the eight lower Columbia and Snake river dams, after receiving formal requests from the Washington Department of Fish and Wildlife, the Columbia River Inter-Tribal Fish Commission, the Northwest Sports Fishing Association, Columbia Riverkeeper and Save Our Wild Salmon.

In addition, the state's Southern Resident Orca Task Force recommended raising TDG levels to allow for more spill, and a flexible spill agreement involving three federal agencies, the states of Washington and Oregon, and the Nez Perce Tribe will require the ability to spill at higher levels.

Total dissolved gas is at 100 percent under normal pressure, Brown said, and rises when air is forced into the water from turbulence, such as at the base of a waterfall or from water spilling over dams. That makes water supersaturated with air--mostly nitrogen and oxygen. Because high levels of dissolved gas have a negative impact on aquatic life, Washington limits TDG to 110 percent throughout the state, except at the eight dams where TDG is currently limited to 115 percent in forebays and 120 percent in tailraces. The standards are higher at these dams because studies have demonstrated that salmon and steelhead smolts have higher survival rates when they migrate downstream over a spillway compared with traveling through the powerhouses, Brown said.

He said that the draft environmental impact statement (EIS) analyzed three alternatives--taking no action, removing the 115 percent TDG in forebays and maintaining a 120 percent TDG standard in tailraces, or removing the 115 percent TDG at forebays and increasing standards in tailraces to 125 percent TDG. The preferred alternative, he said, would remove the 115 percent TDG in forebays and maintain 120 percent TDG at tailraces. If adopted, it would match Oregon's standards, and go into effect for three years unless another action is taken.

The third alternative--raising TDG to 125 percent--is proposed under the flexible spill agreement beginning in 2020. But the state will need to consider that change through a more permanent action, which would likely require a federal Environmental Protection Agency review, Brown said.

He said changing standards through a short-term modification--which is being proposed for this year--is a tool used to temporarily change administrative rules. It's not often used, and when it is, it's usually a modification issued for hours or days, he said. Brown added that it can also apply to longer duration modifications lasting weeks or months, which could be applied annually for up to five years.

Brown said Ecology received 10 comments during its scoping process prior to developing the draft EIS, which are included in the draft. Comments ranged from support for both 120 and 125 percent TDG to help juvenile survival rates and aid southern resident killer whales, to disapproval due to risks from prolonged TDG levels to aquatic life, the cost of the increased spill and the need to assess impacts on carbon emissions.

Ecology's draft EIS notes that scientific support for increased spill is primarily from the Comparative Survival Study, which is a joint multi-year modeling study done by the Fish Passage Center; Columbia River Inter-Tribal Fish Commission; fish and wildlife departments in Washington, Oregon and Idaho; and the U.S. Fish and Wildlife Service. "The CSS predicts steady improvements in juvenile survival and adult returns as spill increases up to at least 125 percent TDG," the EIS says.

The EIS also notes that NOAA Fisheries' COMPASS model "is less optimistic about the benefits of additional spill, largely because it does not factor in the same assumptions about delayed mortality as the CSS model due to powerhouse (i.e. non-spillway) passage routes and different conclusions about the relative benefit of fish transportation as an alternative to spill."

While the Independent Scientific Advisory Board has critiqued both models, it has not directly compared them, the EIS says.

The EIS notes potential negative impacts to juveniles and chum, and says that relatively few studies have focused on TDG impacts on adult salmonids.

In its conclusion, Ecology's draft document states that the agency seeks to weigh the increase in survival of juveniles migrating to the ocean with the risk of adverse impacts to salmon and other aquatic life. "Given that dam and salmon managers have not previously provided voluntary spill to 120 percent due to the potential for higher TDG levels to increase symptoms of gas bubble trauma in juvenile salmon, steelhead, and non-listed aquatic species, continuing monitoring for gas bubble trauma will occur," it says.

The EIS also mentions the "significant regional debate" over the best level of spill at these eight dams, and notes that questions remain about the benefits, "especially when factoring in impacts from elevated TDG levels; uncertainty about the effects of higher gas levels of spill on aquatic life in the river other than salmonids; and concerns about the value of 'foregone' power revenue from spill, given impacts to electricity ratepayers and/or other potential fish and wildlife investments." -K.C. Mehaffey

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NW Fishletter is produced by NewsData LLC.
Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: K.C. Mehaffey
Phone: (206) 285-4848 Fax: (206) 281-8035

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