U.S. Army Corps of Engineers Assesses Fish Impact From "Evans Creek Relocation Project" (Part Two)

Upper Evans Creek
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MAP 

The Evans Creek Relocation Project is intended to improve overall riverine processes in the lower portion of Evans Creek, increase habitat complexity within the channel, increase riparian habitat functions, and separate the lower portion of Evans Creek from existing, incompatible land uses. The City addressed potential impacts to Essential Fish Habitat (EFH) due to the project in the November 2020 Biological Assessment that was submitted with the JARPA package:

EFH for Pacific salmon, including Chinook and Coho, is present in the project action area.During construction activities in phase 2 when the new channel is connected to the existing channel, the Project would result in a temporary and localized turbidity plume. Active construction within Coho and Chinook freshwater EFH, dewatering the existing channel, and loss of less than 1 acre of rearing habitat during phase 2 construction activities resulted in an EFH effect determination of “may adversely affect EFH for Coho and Chinook salmon” in the Biological Assessment. This adverse effect is temporary and will only occur during the construction phase, when the newly constructed channel would be connected to the existing creek.

 The new channel that replaces it would actually increase the amount and quality of EFH in this section of Evans Creek. Once water has been diverted into the new channel, the project would benefit EFH, and the addition of fish habitat features, and improved channel characteristics would benefit Coho and Chinook migration and rearing. In particular, the proposed stream relocation would direct Evans Creek through existing wetlands, resulting in a higher-functioning ecological system. 

The proposed relocation would not have an effect on the amount of stream flow associated with peak flow events. Aligning the channel through existing wetland areas would establish a direct connection between stream hydrology and wetland hydrology adjacent to the stream. This connection may enhance the quality and quantity of instream flow during low flow periods.

Overbank flows during periods of moderate flow would enhance off-channel rearing conditions. It is anticipated that the Project would provide improvements to riparian buffer and floodplain connectivity, enhance rearing habitat for Chinook Salmon, steelhead, and other salmonids, and augment fish passage to the upper watershed.

Once completed, the new channel would provide improvements to habitat and water quality in this portion of Evans Creek. 

 

Colleen C. Anderson

Project Manager, Regulatory Branch

U.S. Army Corps of Engineers, Seattle District

Office:  206-764-3262

colleen.c.anderson@usace.army.mil

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