Zebra mussels continue to expand in the Red River, and it’s just a matter of time before the invasive mollusks affect water infrastructure in Grand Forks, the city’s water treatment plant supervisor says.

“They’re going to start becoming a problem, and we need to figure something out,” said Fred Goetz, supervisor of the Grand Forks water treatment plant. “We need to find some way to mitigate them.

“As of right now, we’re business as normal.”

Larval-stage zebra mussels, called veligers, first were detected in the Red River at Wahpeton, N.D., in 2010 and now are present along the entire river and throughout Lake Winnipeg. The mussels, native to freshwaters of Europe and Asia, likely came to the Great Lakes in the 1980s in the ballast water of large ships from Europe and spread rapidly from there, according to the U.S. Geological Survey.

The veligers, which are microscopic, float downstream and can hitch a ride in bait buckets, livewells and bilges, to name just a few modes of spreading. Adult zebra mussels are about the size of a man’s thumb and are notorious for clinging to hard surfaces, crowding out native mussels, disrupting freshwater ecosystems and clogging infrastructure such as water intakes.

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The city of Grand Forks gets its water from the Red and Red Lake rivers and contracts with divers to check the water intake structures every winter, Goetz said, most recently last February. So far, there haven’t been issues on the Red Lake River – which drains into the Red River at East Grand Forks – but the divers are finding zebra mussels in growing numbers on the Red River intake in downtown Grand Forks, he said.

Divers again will inspect the intakes this coming winter, he said.

“The company that we hire, they also clean the screens off, but all that entails is taking a wire brush and scraping them,” Goetz said. “I’m sure they come back just as fast as you’re taking them off.”

The North Dakota Game and Fish Department also is finding both adult and larval zebra mussels in growing numbers along the Red River, said Jessica Howell, aquatic nuisance species coordinator for the North Dakota Game and Fish Department.

Game and Fish takes monthly water samples from May through October along the river to check for larval zebra mussels in Fargo, Grand Forks and Drayton, N.D., Howell said; she also looks for adult zebra mussels in exposed areas.

“We have been getting more reports all along the Red River,” she said. “There’s been a lot of them on rocks and things exposed at the time we’re there.”

“Unfortunately, we can’t do much about them, but we have noticed an uptick.”

Besides Red River water intakes, small zebra mussels are showing up in the water treatment plant’s sample pumps, which pull untreated water from the river through a raw water line, Goetz said. From there, the water goes into what’s called a pre-treatment basin, where chemicals such as aluminum sulfate used to treat the water apparently kill the mussels before they can go any farther, he said.

“We haven’t found anything in our basins, but we feed chemical prior to that so I would assume it would kill them or do something to them so they aren’t a problem,” Goetz said. “But we are seeing them in our intake building in our sample pumps.”

The city is working with its engineering company to find a solution to the growing zebra mussel population and its potential impact on water infrastructure, Goetz said.

“We have not come up with anything as of yet,” he said. “We’re in very preliminary discussions.”

For now, the best people can do is try to keep invasive species from spreading by obeying state law and following the “Clean, Drain and Dry” principle that North Dakota and many other states and provinces have adopted to educate the public about the risks of spreading invasive species from infested waters to new areas.

North Dakota, Minnesota and most other places now require boaters to pull the drain plugs from bilges, livewells and bait wells in their boats once they leave the water. Zebra mussels can live up to 28 days out of the water if they’re in cool, moist conditions.

“That’s why we recommend ‘Clean, Drain, Dry,’” Howell said. “If they know our laws and they follow our laws, that’s going to stop the majority of risk of moving things.”

Water that’s 140 degrees, or bleach and vinegar, will kill larval zebra mussels.

The Game and Fish Department has a form on its website for reporting suspected zebra mussels or other aquatic nuisance species, Howell said.

More info: gf.nd.gov/ans.

Dokken reports on outdoors. Call him at (701) 780-1148, (800) 477-6572 ext. 1148 or send email to bdokken@gfherald.com.