CHAMBERLAIN — City officials in Chamberlain say they’re working with a private company to remove millions of zebra mussels from the Missouri River that, if left untreated, could cause serious damage to the city’s water filtration plant.

The South Dakota’s Game, Fish and Parks department first discovered the presence of zebra mussels in the water near Oacoma’s Cedar Shore Resort. Migratory patterns and the natural flow of the Missouri River led some zebra mussels to settle across the river near the intake pipes to Chamberlain’s water plant.

Mike Lauritsen, Chamberlain's city administrator, said that while mussels haven’t made their way into the pipes yet, they need to be removed before it becomes a possibility.

“They can end up in there,” Lauritsen said. “They’ll colonize at the end and eventually up into the tubing which would restrict our water flow.”

The city approved a $98,400 contract with Central Divers, a Pierre-based commercial diving service, to remove the mussels.

Though the price tag seems high, the investment is necessary to prevent further expenditures. If the mussels were to clog up the inside of the pipeline, Lauritsen said a process called pigging might be necessary to remove the mussels.

Pigging a pipe involves inserting a device, called a pig, into a pipe and using pressure to force it through, scraping the inside sidewalls and carrying the mussels out of the pipe.

Lauritsen couldn’t give a price estimate, as it varies significantly, but said pigging would substantially increase the cost of the cleaning.

In addition to the divers cleaning the intakes, the contract specifies that the water will be treated with copper sulfate — a substance that the United States Environmental Protection Agency has labeled as hazardous to humans and domestic animals.

Despite this, state and federal governments do have a permitting process for acceptable use, of which the City of Chamberlain is fully cooperating with.

“We had to go through a process with the Corps of Engineers and the Department of Agriculture and Natural Resources to get permits,” Lauritsen said. “It’s less than one part per million that we put in there.”

A study published by the National Institute of Health found that copper sulfate levels of 100 to 300 parts per million in drinking water produce no ill effects .

South Dakota Aquatic Invasive Species Coordinator Tanner Davis said copper sulfate is a common substance used in water filtration systems when zebra mussels are present.

Though Lauritsen said Central Divers is known for quality work, Davis said the problem is still present in other parts of the Missouri River and the state.

“Zebra mussels give off 30,000 to 40,000 eggs per spawn, and they can spawn multiple times each year,” Davis said. “When they develop (from eggs) into veligers, they free float — their only movement is downstream.”

The only way mussels can move upstream is by attaching to watercraft that don’t remove them before changing bodies of water.

“We should be clear on transportation via water with the larval state of zebra mussels,” Davis said. “People still can have the possibility of transporting adult mussels in any situation where there's open water.”

That’s why, Davis said, the Game, Fish and Parks department is so adamant about draining and cleaning a boat every time it’s removed from the water.

“Once again we just really stress: clean, drain and dry,” Davis said. “It's gonna be up to the public to prevent the spread going forward.”

Lauritsen added that it only takes one or two zebra mussels to kick off a breeding population.

“You see the signs at our boat ramps. Make sure that you’re not spreading them around,” Lauritsen said. “That's one of the most important things that we try and push on our sportsmen in the area.”

Zebra mussels lie dormant in water temperatures under 54 degrees, but can still be transported in a dormant state.