Walla Walla, Wash. – The U.S. Army Corps of Engineers, Walla Walla District, and Mill Creek Flood Control Zone District signed a Project Partnership Agreement for the Mill Creek Section 205 Project on November 21.
The agreement defines the shared responsibilities and cost-sharing commitments of the Walla Walla County and the U.S. Army Corps of Engineers as they jointly design and construct improvements to the Mill Creek Flood Risk Management System over the next few years.
The Mill Creek Section 205 Project is a flood risk management project to improve the performance and reliability of the 6.5-mile stretch of concrete and leveed sections of channel running through the City of Walla Walla. Improvements will include levee raises over six sections, as well as wall and ceiling repairs in other locations.
This project will increase the capacity of the leveed sections of the Mill Creek Channel to 3,700 cubic feet per second (cfs) to match the rest of the system. It will also repair about 300 feet of concrete wall to prevent it from failing, remove or repair failing ceilings within the covered portion of the channel running through downtown, and repair and reinforce a pier that supports structures that span the channel.
Additionally, operations will be modified to delay diversions into Bennington Lake. Currently, diversions into Bennington Lake normally begin at 1400 cfs. The change in operations would increase that flow rate trigger to 1700 cfs to pass more floodwater through the system prior to diverting flows to the reservoir saving space in Bennington Lake for larger or subsequent flood events.
Lt. Col. ShaiLin KingSlack, Commander of the Walla Walla District, and Todd L. Kimball, Chairman of the Walla Walla Board of County Commissioners, signed the agreement on November 21.
Design for the project is expected to begin in 2023, with most construction taking place in 2024 and 2025. The project is expected to be completed by early 2026.
Release no. 22-072