The lakes in Ramsey County are part of St. Paul's drinking water system. The mussels' presence won't affect quality, officials said.
Zebra mussels have been found in three Ramsey County lakes that are part of the St. Paul drinking water system, city and state officials said Friday.
The fingernail-size invaders were found in Lake Vadnais, Sucker and Pleasant lakes, and in canals and pipes joining them.
But the nearly 420,000 people in St. Paul and seven first-ring suburbs served by the system need not worry, said Steve Schneider, general manager for St. Paul Regional Water Services. The seven are Mendota Heights, West St. Paul, Maplewood, Lauderdale, Falcon Heights, Roseville and Little Canada.
"The presence of zebra mussels does not affect the quality of the water at all," Schneider said.
"This is our raw water reservoir, and all of that water is treated in our water-treatment facilities after it leaves the lakes and before it gets to customers."
However, zebra mussels can clog screens, valves and intake pipes that are part of the system, he said, and removing them may increase maintenance expenses. Most of the system's water is pumped from the Mississippi River through the chain of lakes before it is treated and distributed to communities.
It's the first time that zebra mussels have been found in metro lakes, said Luke Skinner, supervisor of the invasive species program for the Minnesota Department of Natural Resources. "It's certainly a disappointment because we've been working hard to keep them out," he said.
The mussels could have entered St. Paul's system from the river or from boaters or fishermen who brought them into the lakes through bait buckets or aquatic weeds, Skinner said.
No boats are allowed on Sucker Lake and Lake Vadnais, he said, and only boats without motors are permitted on Pleasant Lake, but all three are open to fishing.
The damage they do
Zebra mussel larvae are microscopic and free-floating at an early stage of life, and later latch on to hard surfaces to grow. They proliferate by the millions. Besides clogging pipes, they can litter beaches and shallow areas with sharp shells, smother native mussels and disrupt the aquatic food chain.
Skinner said it's not clear how quickly the mussels will multiply in the three metro lakes or how they may change them. In some cases, the filter-feeding mussels clarify water, he said, which allows more plants to grow and changes fish habitat.
Xcel Energy officials have been dealing with zebra mussels for the past several years at its Red Wing steam plant, the Allen S. King plant near Bayport and especially at the Prairie Island nuclear plant. Brad Geise, environmental analyst for Xcel, said that the company used chemicals twice this year to kill zebra mussels before they got too thick on pipes at Prairie Island, at a cost of more than $100,000.
"It's a nuisance to stay on top of them, but if you ignore it, they have the potential to shut things down," Geise said.
Invaders from Europe
Zebra mussels were discovered in Lake St. Clair between Lakes Erie and Huron in 1988 and probably came from Europe in the ballast water of ships.
They have spread rapidly in the Great Lakes and elsewhere, including Duluth Harbor, the Upper Mississippi River and the Lower St. Croix River. In 2000, they were found in Lake Zumbro near Rochester, and they have also been found in three lakes near Brainerd: Ossawinnamakee in 2003, and Rice Lake and Lake Mille Lacs in 2005.
Tom Meersman 612-673-7388