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Mussels get a lift around bridge replacement project on the Mississippi

What do you do with hundreds of thousands of freshwater mussels in the way of an interstate highway bridge over the Mississippi River? You move them. A unique and sizeable mussel bed with a diverse population of freshwater mussels was in the direct impact zone of new pier construction for the I-74 Mississippi River Bridge Replacement project, located in the Quad Cities, in Iowa and Illinois. Based on surveys conducted in 2014, there were likely almost 850,000 mussels representing 25 different species present within the construction area of the new bridge. Among them were three federally listed species, the Higgins eye pearlymussel, the sheepnose and the spectaclecase, along with two state listed mussels, the black sandshell and the butterfly mussel.

Working with the Iowa and Illinois Departments of Natural Resources, the field office developed an Intergovernmental Agreement to facilitate a coordinated approach to the project. The results of that agreement included a relocation plan to avoid and minimize direct impacts to threatened and endangered mussel species. Together with Iowa Department of Natural Resources and Illinois Department of Natural Resources, along with the two states’ Departments of Transportation, we coordinated a robust baseline mussel  study, host fish sampling, and a poolwide survey.. which will make up the required monitoring and mitigation for the project. The monitoring surveys will inform future river construction projects where mussels will be impacted.

Host fish sampling and the poolwide survey are a couple of products which will result from this cooperative effort to create useful mitigation for impacts to this mussel resource. A mussel education and outreach position is also funded by the state transportation departments through the I-74 mitigation. During Phase 1, completed in 2016, more than 140,000 mussels were moved out of the direct impact zone of the new bridge piers in preparation for the new bridge construction, scheduled to start in Spring of 2017. Phase 2, removal of the old bridge, will involve moving additional mussels in 2020.

By Heidi Woeber
Illinois and Iowa Ecological Services Field Office

A diver prepares to search the Mississippi River for freshwater mussels during a relocation project. Photo by Heidi Woeber/USFWS.
“PilotIsland_GreenBayNWR.jpg”: Project Leader Steve Lenz with Pilot Island looming in background. Photo by Tina Shaw/USFWS.

A diver prepares to search the Mississippi River for freshwater mussels during a relocation project. Photo by Heidi Woeber/USFWS.


Last updated: March 15, 2017