The U.S. Army Corps of Engineers, Walla Walla District (Corps), in partnership with its non-federal sponsor, Walla Walla County, proposes to conduct a general investigation study on the Mill Creek Flood Control Project (Project) in Walla Walla, Washington. The study includes a modernized reassessment of the overall flood risks Mill Creek presents to the Walla Walla community. The study will consider Project capacity, performance, and reliability of several components through a range of alternatives that could be implemented to reduce risks to the community looking forward.
The Project was authorized in 1938 with the single purpose of reducing flood risk to the City of Walla Walla and surrounding communities.
The existing Project consists of four main components:
1) Bennington Dam, which impounds Bennington Lake, an off-channel reservoir
2) Diversion Dam, which diverts flood water through a channel into Bennington Lake
3) Leveed Channel (upstream and downstream of Walla Walla),
4) The concrete channel through downtown Walla Walla. Since the disastrous 1931 flood, life safety risks have increased.
The Project used to be able to divert floodwaters to Yellowhawk and Garrison Greeks.
The flood risk reduction provided by the Project may be insufficient to address current risks, and the number of buildings in the flood zone has tripled and now includes five elementary schools, two middle schools, two high schools, two colleges, six nursing and assisted-living homes, and three hospitals.
A public scoping period was conducted Oct. 15 through Nov. 16, 2018, including a public meeting held Nov. 1, 2018, in Walla Walla, Washington. Information and comments submitted during the scoping period will be included in the permanent public record, and used to identify issues to address in the study, exploring alternatives and identifying potential environmental effects of possible changes to the system. The study process will include additional outreach activities with citizens and stakeholders across the community to gather their thoughts and ideas related to the way we could manage flood risks and other important water resources considerations.
The Mill Creek GI study will also include coordination and consultation with other federal and state agencies to find ways to minimize potential effects to valuable environmental resources, such as ESA-listed fish, water quality, and cultural and historic resources.
The Corps is committed to working with our non-federal sponsor, Walla Walla County, and the larger community to provide safe and sustainable solutions to reduce flood risk in the City of Walla Walla and surrounding communities.
We will keep the public informed by updating this webpage and distributing information to area news media as the study progresses.