A Zebra Mussel that was found in the Kansas River is shown with a dime. Several thousand of these mussels have been found in the river. The species’ rapid reproduction and colonization already force municipalities, utilities and other industrial operations nationwide to spend billion a year on control efforts.

Zebra mussels are in the Kansas River, threatening to clog pipes that carry water into the city’s Kaw Water Treatment Plant.

Employees of the treatment plant discovered the typically dime-sized mussels earlier this month while cleaning out an intake.

While the mussels are not expected to affect the quality or safety of the city’s supply of drinking water — they cannot survive the chlorination process used during treatment — the sharp-shelled bivalves could add to the system’s maintenance expenses, said Megan Gilliland, a city spokeswoman.

That’s because the mussels — already known for coating dock piers, boat hulls and motorboat parts — can cause broader problems by covering and clogging a plant’s intake valves, concrete basins and transport lines.

Lawrence’s treatment plant is the first in the state to report the presence of zebra mussels. The species’ rapid-reproduction and stubborn colonization already generate annual nationwide expenditures of $145 million to control mussels in electric generating plants, according to the Kansas Department of Wildlife and Parks.

While eradication of the invasive species is considered “nearly impossible” by state wildlife officials, the city envisions using high-pressure water to manage the problem, at least for now.

“In the future we may have to look at additional opportunities for cleaning, and utilization of aggressive mechanical methods to lessen the effect of mussels on our operations,” said Charlie Ballenger, manager of the Kaw plant. “The quality and quantity of water produced will not be affected.”

The first report of the mussels in the United States came in 1988, in the Great Lakes. Since then such mussels have spread into the Midwestern, Northeastern and Southeastern United States.

In Kansas, the state Department of Wildlife and Parks has tracked the mussels’ spread into seven different lakes since 2003: El Dorado, Cheney, Winfield City, Marion, Perry, Afton and — also earlier this month — Wilson, which is 55 miles west of Salina.

The Perry discovery came three years ago, after a boater reported a single mussel affixed to the hull of his boat. State divers then found three adult mussels, plus larvae, in the Marina Cove area.

Gilliland said that zebra mussels likely were transported into the Kansas River by a boat that had been in Perry Lake. Zebra mussels’ larvae are both free-floating and microscopic, making it easy for them to be carried — often unknowingly — by boaters who do not properly clean or otherwise rid their equipment of such a threat.

To prevent the spread of zebra mussels and their larvae from infested waters into other water, officials urge boaters and people who fish to:

• Never move fish or water from one body of water to another.

• Empty bait buckets on dry land, not into lakes.

• Inspect boats, trailers, skis, anchors and all other equipment, and remove any visible organisms and vegetation.

• Wash equipment and boats with hot water (at least 140 degrees) or dry for at least five days, to remove or kill species that are not visible.

The Kaw plant is one of two municipal plants that last year treated and pumped out a combined 3.785 billion gallons of water.

Zebra mussels have not yet been discovered at the city’s Clinton Water Treatment Plant, which gets its raw water from Clinton Lake, Gilliland said.

The Lawrence Energy Center, a coal-fired plant that generates 19 percent of all power for Westar Energy customers, also has a water intake in the Kansas River, upstream from the Bowersock Dam.