This summer, volunteers with the Huron River Watershed Council sloshed into the Huron River in Ypsilanti on a fact-finding mission for threatened and endangered mollusks. It’s required by law before removing a dam, as some mussels are federally protected.
Now, they have plans to move the mollusks out of harm's way.
That's because removing the Peninsular Paper Dam can hurt the mollusks, even if it benefits the river in the long term, said Paul Steen, an aquatic ecologist with the watershed council.
“The biggest change that we see upon dam removal is this initial first few days or weeks after removal, where the river is trying to adjust to the new hydrologic situation,” he said. That change in water flow often moves sediment trapped behind the dam.
And that movement can be disastrous for wildlife that lives downstream.
“Because we are taking [the dam] out, then we have this responsibility to make sure the mussels are not negatively impacted from other activities,” Steen said. The group found wavy-rayed lampmussels and black sandshell mussels. Both species are threatened, according to Michigan’s Department of Natural Resources.
The problem can be both the quantity and the quality of that sediment. Too much flowing down the river at once can suffocate mussels and their food sources.
Contaminants in the river and the sediment – like leftover pollution from the paper factory that used to pull power from the dam – could harm mussels that breathe them in.
“[It’s] just like a human breathing in smog or exhaust from a car,” Steen said. The contaminants can damage mussels' gills and inhibit their ability to breathe.
The watershed council doesn’t expect much sediment to move downstream. That’s based on multiple sediment studies conducted by engineering firms, said Dan Brown, a watershed planner who has been working with the city to plan the dam’s removal.
“The sediment quality is pretty good and the sediment volume is lower than we expected,” he said. “But it's still a lot of sediment to manage.”
The restoration plan includes moving the mussels to another part of the river and removing much of the sediment behind the dam.
“The fastest way to restore a river [and] restore ecological health is to remove a dam,” Brown said. “Dams block essentially all of the ecological functions that a river provides.” That’s the general consensus among scientists and state officials, who overwhelmingly support removing the dam.
But a there are also locals who believe removing the dam will harm the river more than help it. Some residents worry it will disrupt the current ecosystem that has adapted to the impoundment behind the dam, said Tricia Mora, an Ypsilanti resident and board member of Friends of Peninsular Park.
“There is a thriving ecology in the area, which includes many species which do thrive in more of the pond-type, marshy type environment as opposed to fast-flowing water environments,” she said. Friends of Peninsular Park is an Ypsilanti neighborhood group that works to maintain Peninsular Park, which is located next to the dam where the old power house used to be.
The watershed council and Friends of Peninsular Park share a common goal: stewardship of the river and its ecosystems. But on the issue of the dam, they diverge on what is best for the river.
“The benefit is that it's actually eliminating a risk, a risk of damage that you cause by dam removal,” Mora said. Her group is concerned about the impact that moving sediment and changing the water flow will have on fish downstream.
But that risk is being addressed, said Brown, the watershed planner. The sediment will be moved, he said — it’s a major part of the $14 million budgeted for removing the dam and restoring the impoundment behind it.
“Sediment management is really a core task, a core process in dam removal,” Brown said said.
When that sediment is properly managed and the mollusks moved, removing the dam will improve the river’s health more than harm it, said Steen, the aquatic ecologist.
“We don't make rivers healthier by putting in human obstructions,” he said.
Removing the dam will benefit fish as well, according to a statement from the Michigan Department of Natural Resources Fisheries Division.
“This removal would increase river connectivity and provide high quality fish and freshwater mussel habitat,” the statement said. “Dam removal would result in approximately 1.25 miles of impoundment returning to natural stream conditions and over 3 miles of connected river.”
The watershed council plans to move the mussels in summer 2025 to another section of the Huron River. Sediment removal and the gradual demolition of the dam will begin in late 2025, Brown said.
