The USACOE constructed the flood control project on Mill Creek through Walla Walla includes a diversion dam, storage reservoir, and a 6.7 mile long flood control channel, which includes 263 channel spanning weirs (sills) over a three mile reach.

The flood control channel creates water quality problems and presents a series of complex fish passage barriers. ESA listed steelhead, and bull trout, and reintroduced spring chinook utilize the flood control channel during migrations. Returning adults encounter flow-dependent passage problems associated with channel spanning weirs, light attraction barriers (in the underground sections), and a lack of resting water in the concrete channel section, among other problems. Juvenile fish encounter low spring flows, and high water temperatures in late spring. Often by mid-May adults and juveniles become trapped in the flood control channel where they experience lethal temperatures. Many of these passage issues are considered as imminent threats in the Snake River Salmon Recovery Plan. Mill Creek, upstream of the flood control project, is a critical and under-utilized area for spawning and rearing of ESA listed species, and provides for an important recovery opportunity for those listed fish, as well as good habitat for other native fish and reintroduction efforts for spring chinook.

This project would consider two solutions to improving passage a water quality in the channel including building fish ways and conducting levee set backs. During the pilot phase of this project 4 weirs were fitted with fishways at Tausick Way. Additional 3 weirs were notched as part of the Gose and construct passage improvements at four of the sills. These structures were identified as barriers in the Mill Creek Barrier Assessment completed in 2009. Construction the the four sills was completed in the summer of 2011 and can be viewed at the Tausick Way Bridge adjacent to the Walla Walla Community College Campus.