Moving mussels proves to be a real workout in Northeast Iowa
Just like your liver filters your blood, mussels in the Mississippi River filter out toxins and help balance the river’s ecosystem. To protect the mussels from damage during the construction process, two recent Mississippi River bridge projects involving the Iowa Department of Transportation have included relocating thousands of mussels, some of which are on the endangered species list.
In 2016, when the Iowa and Illinois Departments of Transportation were building a new river crossing to carry Interstate 74 over the Mississippi River, more than 140,000 mussels were moved out of the way to preserve them. More recently, a new project underway by the Iowa and Wisconsin DOTs to build a new Mississippi River crossing connecting Lansing, Iowa, to Crawford County, Wisconsin, successfully relocated tens of thousands of mussels to preserve them from damage during the construction project.
Jill Garton, from the Iowa DOT’s Location and Environment Bureau, said, “Using some of the lessons learned from the early mussel move for the I-74 bridge, we had a pretty good idea of how best tackle this move and we had great partners to get this accomplished.”
Why did the mussels need to be moved?
When surveys of the area of the Mississippi River where the project was to occur were conducted in 2018 and 2020, researchers found the presence of several varieties of mussels, including the endangered Higgins Eye Pearly Mussel. At that time the U.S. Fish and Wildlife Service issued a biological opinion that the mussels would have to be moved to another location, out of harm’s way.
Garton said, “Freshwater mussels impact water quality. When you have mussels in an area, they filter impurities in the water and improve the health of the ecosystem. Without those filters, the water quality can degrade pretty quickly, putting other species at risk.”
Because mussels are sedentary creatures and can’t move out of the way when something disrupts their bed, they need to be physically moved to save them from being crushed by construction equipment. When the new bridge is in place, they will be relocated back to the area to continue their work as filters for river impurities.
It sounds pretty simple to just pick up a bunch of mussels and move them, but the relocation process involves several federal and state agencies, both in Iowa and Wisconsin. Because at least one species of mussel is on the endangered list, there were other factors at play to be especially mindful of those mussels, as well. Each of the more than 30,000 mussels found in the area of the bridge project needed to be collected, weighed, aged, tagged, recorded, and relocated.
“Strong working relationships with the agencies, our consultants, and our internal Iowa DOT colleagues made preparation for and completion of the relocation possible,” said Garton. “The Iowa bank of the mighty Mississippi River in this area is home to an even larger mussel bed than we anticipated, but with a lot of long hours by all involved, we did it. Completing the successful relocation of the mussels not only met our environmental commitments under law but provided us with the satisfaction that we are protecting the environment that many of us enjoy in our free time outside of work.”
How did the process of relocation work?
Beginning in August, highly skilled divers started along the shoreline to approximately 80 meters into the river. The deepest they dove was approximately 26 feet, but the average depth was approximately 12 feet.
Garton said, “The visibility in the river was very poor most of the time and the divers were working by feel, moving slowly along the riverbed. They slowly and methodically searched the river.”
By November, the project was wrapping up just as the weather turned cold.
Garton said the team was pleased by the number and variety of mussels found, cataloged, and relocated. She said, “The data collected by the dive teams found a density and diversity of mussels that was a bit unexpected and very exciting. We’re looking forward to getting the construction project underway so it can provide a safer crossing for travelers. Once the new bridge is completed and the old one is demolished, we’ll be moving mussels back into the area so they can continue filtering impurities in the river.
Watch for another relocation project this summer near the Lansing marina to allow the contractor to stage construction in the area without damaging the mussels.
This project is making lives better through Transportation by keeping the ecosystem of the Mississippi River healthy allowing everyone to enjoy their time on the river and all it provides to the local area.
This is a wonderful story of great environmental conservation! I had never even thought about this part of new bridge building! Thanks to everyone involved!
Posted by: Stacy Lee | 05/10/2024 at 08:56 PM
I used shell in pool 19 when allowed years back.glad conservation hasn't forgot about them, I always thought someday we were probobly going to cause deplete them at some point especially "washboard."clam.i couldnt crawl around on that river with a garden hose,in my mouth and keg compressor.those were the last money living made from the river.
Posted by: Todd Twidwell | 05/07/2024 at 11:13 PM