WALLA WALLA, Wash. -- The U.S. Army Corps of Engineers, Walla Walla District has awarded a $15 million construction contract to Syblon-Reid Co. to build a new fish ladder at the Mill Creek Diversion Dam in Walla Walla.
The current fish ladder at the Diversion Dam, built in 1982, no longer meets the standards set by the National Marine Fisheries Service for successful fish passage – raising concerns for steelhead, Chinook salmon and bull trout returning to spawn in Mill Creek.
The new fish ladder will feature improved attraction flow and passage design, significantly reducing the time fish spend navigating the diversion dam and improving access to critical spawning habitat in upper Mill Creek. In addition, the project includes improvements to the dam’s downstream stilling basin, a bypass channel for juvenile fish traveling downstream, and bypass gates for flushing sediment past the dam.
The project requires replacing a small section of the earthen portion of the diversion dam on the Rooks Park (North) side for the upstream end of the new ladder, as well as replacing a section of the levee in Rooks Park on the downstream end. It also will pave the way for future fish identification, counting and PIT (passive integrated transponder) tag facilities, allowing for better monitoring and management of fish populations.
Construction is scheduled to take place between the summer of 2025 and the fall of 2027. Site preparation work, such as surveying and staging area preparation will begin in September. Closure notifications will be issued in advance of any on-site work impacting public access.
To ensure continued flood risk management and minimize impacts to fish, in-water work will be carefully phased.
Upon completion, the new fish ladder will not only benefit fish populations but also will enhance USACE's ability to manage flows during flood events, improving both fish passage and flood risk reduction for the Walla Walla Valley. This project represents a significant investment in both environmental stewardship and community safety.
For more information you can contact the Walla Walla District at 509-527-7020 or visit us on Facebook at www.facebook.com/WallaWallaUSACE or www.facebook.com/millcreekdam.