KATHRYN, N.D. — A potentially deadly low-head dam on the Sheyenne River near here is being eliminated — and in the process, thousands of mussels in the river have been relocated to prevent them from being harmed during demolition of the dam.
A group of volunteers including students from Valley City State University worked for several days in October to collect and move thousands of mussels from a huge mussel bed in the Sheyenne River just east of Kathryn and about 18 miles south of Valley City.
In all, about 10,000 clams out of an estimated 16,000 thought to be in that area of the river were moved out of harm's way prior to the start of demolition of the dam, according to Andre Delorme, a professor of biology at VCSU.
Delorme said most of the collected mussels were relocated to a stretch of the river above the dam, while the remainder were resettled some distance downstream from where the dam is located.
Demolition work on the Kathryn dam is expected to start in early to mid-December, with completion of the project expected in early to mid-2021.
The project involves removal of the dam and replacing it with a mix of boulders and gravel, according to Delorme.
The dam is going away, he said, because of its age and because of the drowning danger low-head dams pose to swimmers.
"They're drowning machines," Delorme said, referring to low-head dams and the deadly, washing machine-like turbulence they create.
A number of drownings have occurred in recent years involving low-head dams on the Sheyenne River, including the 2012 death of a woman who drowned trying to help her dog get out of the river near what is known as "Little Dam" on the southwest side of Valley City.
Also, a man died in 2014 after a rubber raft that he and two friends were riding in went over the same dam and capsized.
Delorme said he wasn't aware of any drownings having occurred at the Kathryn dam, but he said the structure and the dangerous currents it creates are similar to dams where drownings have happened.
He said a survey of mussels in the Sheyenne River near the Kathryn dam done in the summer of 2019 determined the area could be home to as many as 16,000 mussels.
He said the approximately 100-yard stretch of river where the relocation took place represents part of a massive mussel bed in the Sheyenne River that extends for about a half mile to a mile.
He said while the mussel population is fairly healthy today in that region of the Sheyenne, it was much larger as recently as 2009, when a survey of that general area estimated the mussel population at about 100,000.
Delorme said the decline is believed to be tied to increased outflows from Devils Lake, including the impact such flows have on riverbank erosion.
Despite the decline in mussel numbers, Delorme said it is hoped populations are starting to stabilize.
"There are a couple of species that seem to be tolerating it (increased Devils Lake outflows) better than others," Delorme said.
He said during the relocation project, workers identified about six different mussels species, including three species North Dakota Game & Fish views as "species of concern" based on their low numbers.
Delorme said on a good day the relocation effort included 20-25 VCSU students, as well as workers from the U.S. Fish and Wildlife Service hatchery in Valley City and North Dakota Game and Fish.
"It was a pretty broad effort," he said.
Delorme said removal of the dam will encourage wider distribution of both fish and mussels in the river.
He said mussels have been in the Sheyenne River for thousands of years and that they help in filtering water and nutrient cycling.