Formerly a pea-green problem by the end of each summer, the Burnsville-Apple Valley lake now has improved fishing and boating.
"This spring it's as clear as I've ever seen it," said Dave Scheerer, whose family has lived on the 110-acre lake since 1994.
He remembers years ago when algae blooms and curly weeds fouled boat motors and discouraged boaters and water skiers by the end of the summer.
The experts are seeing the same trend: "2011 was the first year we have seen water lab analysis show the lake is meeting [Minnesota Pollution Control Agency] goals," said Jeff Kehrer, natural resources coordinator for Apple Valley.
It took a lot of money and cooperation to restore Alimagnet to health, city officials said. The lake is about 10 feet deep or less and fringed with oak, pine, birch and other trees.
About five years ago, the two cities spent more than $630,000 to dredge out three storm runoff basins leading into the lake. They used state grants and worked with the state Department of Natural Resources (DNR) and lake residents to remove bowheads and other rough fish and invasive weeds, said Daryl Jacobson, water resources specialist for Burnsville.
"So far Alimagnet is one of our more positive stories,'' Jacobson said. "We don't usually see water quality improve that quickly."
The two cities share a huge wooded peninsula park jutting north into the lake. People fished along park shores last week as flocks of mallards paddled about. Apple Valley also has a smaller park on the east side. Burnsville offers two canoe racks by County Road 11 on the lake's west arm.
Alimagnet, carved out by glaciers, is one of hundreds of metro lakes monitored by Metropolitan Council's environmental services division. Council spokesman Tim O'Donnell said in an e-mail that data collected since 2002 shows the lake has more than doubled its clarity to 1.3 meters deep last year, and cut in half the levels of phosphorus -- a nutrient in fertilizers that feeds algae -- and chlorophyll-a, an indication of algae.
The Alimagnet Lake Association, composed of about 60 lakeside homeowners, paid a third of the cost for a winter aeration system in 2005 and stocked the lake with 1,000 large-mouth bass. The DNR netted bowheads and bluegill sunfish. Those species had consumed all native plankton, then stirred up phosphorus in the lake bottom while looking for more food. The stocked bass and channel catfish eat bowhead and other rough fish and improve fishing.
Scheerer, 59, president of the association, said every spring the lake owners also remove curly leaf weeds. The invasive weed normally dies in June, adding unwanted phosphorus and other nutrients that feed algae blooms, Jacobson said. The removal makes room for native aquatic plants that benefit the lake, he said.
"It used to look like pea soup by September," Scheerer said. "We are trying to get an equilibrium that is not weed-choked and supports fishing and boating."
Lake quality also has been helped by a state law that in 2005 banned phosphorus in fertilizers used on most lawns, noted Kehrer. Rain washes fertilizers and grass clippings into gutters and storm sewers that drain into lakes. Alimagnet has about a dozen storm water outfalls, besides the storm-water-fed basins dredged by the two cities, Scheerer said.
In the first few years after the city cleanup began in 2005, Scheerer said he wasn't sure the work would help much. He knew it could take years to remedy the buildup of fertilizer and nutrients that had been accumulating for half a century.
"I wanted us to do something. I didn't want to see the lake continually get worse," he said. "Both cities encouraged us to stay involved."
Jim Adams • 952-746-3283