By mid-summer, Lake Independence is a slimy, gooey mess that grows greener every year, the result of too much fertilizer washing into its waters and jump-starting algae and other aquatic weeds.

Frustrated by a lack of action from officials, lakeshore homeowners recently sued a dairy farmer whose land borders the lake, contending that he has illegally spread manure too close to its waters and contributed to algae growth.

"The water was thick with green blobs all the way down. It's just disgusting," said Barbara Zadeh, a lakeshore owner who is part of the suit.

The farmer, Paul Merz, called parts of the suit inaccurate, but he declined to discuss details.

"We have an awfully big investment here to give this all up for nothing because they think we're polluting the lake," he said.

The lawsuit is the latest example of lakeshore owners across Minnesota banding together to defend their waters, most recently against the onslaught of invasive species and outside boats that spread them.

The condition of Lake Independence is also a major concern for Three Rivers Park District, which is not part of the suit but which has invested millions of dollars in campgrounds, beaches and other amenities in Baker Park Reserve, which borders the lake's southern shoreline and attracts tens of thousands of users.

"We get complaints more from swimmers than from the boaters," said John Barten, natural resources director for Three Rivers. "When the lake gets that green film on top, people find that unpalatable."

Lakeshore owners vs. farmer

The lawsuit was filed earlier this month in Hennepin County District Court by the Lake Independence Citizens Association and 21 individuals who live near the 850-acre lake about 15 miles west of Minneapolis.

It contends that Merz and his son, Jim, who operate a dairy farm and grow crops near the lake, repeatedly violated state laws and polluted the lake with phosphorus in manure and runoff.

"Nobody wants to stop them from farming, but when you farm and the consequences affect thousands of people downstream from you, I don't believe you have the right to do that," said Mike McLaughlin, president of the association.

Merz, 79, said in an interview that he's retired and rents the land to his son Jim. "He has his legal representatives reviewing the inaccuracies of the lawsuit," said Merz, speaking for his son. "Outside of that, we can't get into any details." The family has owned the land since 1965, Merz said, and owns about 135 cows.

Like pea soup

Zadeh, who lives near Merz, typically takes her boat into the lake with her dog and family when they want to swim because her shoreline is bordered by cattails.

As early as mid-June, she said, it was impossible to find a clean place to take a dip.

"There was green slime everywhere," she said. "It's just a sick lake."

John Conlin, another lakeshore owner, said that Independence was clear most of the time when he moved there in 1987 but that now it looks like pea soup all summer.

"I've watched it degrade," he said. "Lake Independence is a gem that is being destroyed right before out eyes and turning into a fetid, smelly, noxious stew of algae and pollution."

Warnings and inspections

The phosphorus fertilizes the algae and aquatic weeds to unhealthy levels, Barten said. Many other lakes also have phosphorus problems, he said, but Lake Independence is one of the worst and is a top priority for Three Rivers. The problem at the lake is familiar to the Minnesota Pollution Control Agency (MPCA), which listed the lake in 2002 as "impaired for aquatic recreation."

Five years later, the MPCA approved a report that detailed the sources and amounts of phosphorus entering the lake and concluded that they needed to be reduced by 45 percent, or about 1,100 pounds per year, to improve water quality.

One pound of phosphorus can produce 500 pounds of algae in a lake, and the report identified the Merz farm as the largest single source, contributing about 166 pounds of phosphorus per year. Manure from the feedlot can wash directly into the lake if spread near field drains or the lakeshore. Even if the manure is incorporated into soil, it can accumulate to levels that saturate the dirt and wash out as soluble phosphorus during rains.

Still polluted, 10 years later

McLaughlin said homeowners and lake users have already waited 10 years since the lake was declared polluted and have done all that they can to improve the lake.

Owners have talked to Merz repeatedly about managing animal waste in ways to avoid polluting the lake, McLaughlin said, but as recently as June 5 neighbors saw his son spreading manure on two separate plots of land near the lake. The family has also spread manure on frozen ground in winter, he said, which washes into the lake with spring rains.

State pollution investigators, responding to citizen complaints, sent Paul Merz a warning letter in April 2011 that its inspectors observed alleged violations of manure applied within 10 feet of a field drain and within 25 feet of a wetland at the lakeshore. Merz responded by letter that the inspectors' statements were false, but gave no other information, other than that he would cooperate and had a vested interest in keeping the lake as clean as possible.

MPCA spokesman Forrest Peterson said inspectors were also at the farm on May 25 of this year and again on July 6 to help Merz complete a manure-management plan, which is now under review.

Merz acknowledged that one time the family applied manure that wasn't supposed to be spread on frozen ground. "Since then they've had the MPCA out here a couple times and we did not receive another warning," he said. "As far as I know, we're doing what we need to do."

A separate approach

Hennepin County's Department of Environmental Services and Three Rivers Park District may negotiate with Merz about a conservation easement -- essentially offering a buyout that would allow him to keep the land but sharply restrict the phosphorus leaving it. The Three Rivers board gave the go-ahead for negotiations at its monthly meeting last Thursday.

Such an arrangement, if reached, would essentially require Merz and his son to move the cows to a different farm, or ship most of their manure to more distant fields. How much that easement would cost, where the money would come from and whether the effort would be successful are all uncertainties that frustrate lakeshore owners.

McLaughlin said action already taken hasn't been enough to turn the lake around. Nearby cities and homeowners have spent a total of about $2 million, he said, much of it from taxpayer funds, to reduce phosphorus from relatively small sources.

They have altered their manure runoff from horses on hobby farms, built rain gardens, restored shoreland to prevent erosion and extended a sewer system to one neighborhood that had septic systems, he said.

"All this expense to reduce a pound of phosphorus here, or five pounds there," McLaughlin said. "All these things are going on, at the same time we've got a guy putting manure right on the shoreline."

Tom Meersman • 612-673-7388