DESCRIPTION
The Mill Creek Flood Control Project was completed by the Corps of Engineers in the 1940s to reduce flooding of the City of Walla Walla. Two miles of the channel consists of a concrete flume. Mid-Columbia Summer steelhead, bull trout, and spring Chinook experience passage barriers over a range of flows in the channel, as identified and described by the Mill Creek Fish Passage Assessment completed in 2009 (06-2203). There are several different channel cross-section types (reach types) in the concrete channel, each having unique hydraulics. This project completed final designs and construct fish passage improvements in a 285 foot long section of what is known as Reach Type 6 identified in the 2009 Mill Creek Assessment.
The Mill Creek Project was completed by the Corps of Engineers in the 1940s to reduce flooding of the City of Walla Walla. Two miles of the channel consists of a concrete flume. Summer steelhead, bull trout, and spring Chinook experience passage barriers over a range of flows in the channel, as identified and described by the Mill Creek Fish Passage Assessment completed in 2009 (06-2203). There are several different channel cross-section types (reach types) in the concrete channel, each having unique hydraulics. This project completed final designs and implemented fish passage improvements in a 350 foot long section of what is known as Reach Type 6. Passage improvements included modification of baffles in the channel to reduce low flow fish passage problems, addition of resting pools to address fish stamina failure problems, and addition of surface roughness to provide low velocity water during high flow. This was the third of several projects to improve passage to high quality habitat in the upper Mill Creek watershed.
