LONGVIEW — The U.S. Army Corps of Engineers has proposed improving a fish collection trap on the north fork of the Toutle River to help salmon and steelhead rebound from the eruption of Mount St. Helens.
Modifying the trap is $34 million cheaper than replacing it, the agency said in a revised draft environmental impact report on its effort to control volcanic sediment washing out of the Toutle Valley.
Federal fish biologists and the Cowlitz Indian tribe had objected to the Corps 2014 plan, saying it did not adequately consider fish restoration. Engineers hope the new plan will break the stalemate that has delayed sediment control work for years.
Fish planted upstream
The 28-year-old trap sits above the junction of the Green River and the Toutle’s north fork, collecting salmon swimming upstream. Biologists then plant the fish in tributaries of the north Toutle above its 125-foot-tall sediment retaining dam. But the fish collection facility has never worked as well as biologists wanted. In the new report, the Corps weighs replacing the trap or modifying it with new technology.
In the document, the Corps recommends improving the trap rather than replacing it. The agency cites lower cost and less disturbance to the environment for its recommendation.
Possible upgrades include improving water intake, sediment flushing, fish ladder entrances and attraction flows.
The Corps also proposed adding a third upstream fish release spot at Deer Creek, to go along with the two existing sites at Alder Creek and Hoffstadt/Bear Creek. This should increase spawning opportunities for endangered fish that use the Cowlitz, such as Lower Columbia coho salmon and steelhead, according to the Corps.
The Corps will accept public comment on its plan until Nov. 6. Corps Portland District spokesman, Karim Delgado, said the Corps hopes to issue a final environmental impact statement for the project early next year.
“We don’t want to do anything that would adversely affect the various complexities of this environment (or) the people that are affected by it,” Delgado said. “For us to be able to gauge public interest and concerns by opening up comments to the public, they can let us know if anything is missing, or anything (they) feel we didn’t give enough importance to. It’s probably the most critical part of our entire hearing process.”
Other than the changes to the fish collection facility, the plan outlines the same measures to control the flow of silt: raising the sediment-retaining dam in increments, building wooden structures such as weirs in the upper valley and dredging the Cowlitz River if silt clogs the channel.
The Corps has been battling volcanic silt since the May 18, 1980, eruption of Mount St. Helens dumped more than 3 billion tons of debris into the upper valley. If unchecked, it could wash downstream and clog the Cowlitz River, increasing flood risks. However, the Corps recently stated that flood protection levels in Longview, Kelso, Castle Rock and Lexington meet federal requirements.