A popular but pollution-plagued west-metro lake will have cleaner water in the future because of a recent out-of-court settlement between a dairy farmer and lakeshore residents.

Every summer, Lake Independence becomes a slimy, gooey mess, in part because too much manure and other fertilizers flow into the body of water, where they fuel the explosive growth of algae and other aquatic plants.

Dairy owners James and Paul Merz agreed to shut down much of the operation and improve manure handling to resolve a lawsuit filed last summer by the Lake Independence Citizens Association and 21 individual homeowners.

The settlement came after court-ordered mediation last month, but attorneys for each side have declined to comment until a joint statement is released.

The changes will benefit YMCA Camp Ihduhapi along the lake’s northeast shore, about 100 shoreline owners, and tens of thousands of boaters, swimmers and campers who visit Baker Park Reserve on the lake’s southern shore, managed by Three Rivers Park District. The kidney-shaped, 851-acre lake is about 15 miles west of Minneapolis.

John Barten, natural resources director for Three Rivers, called the settlement a “good start,” and said Lake Independence is one of dozens of lakes in the metro area and hundreds statewide that receive far too much phosphorus from lawns, leaking septic systems, cropland and livestock.

“Getting a handle on feedlot and manure management on the landscape certainly is something that needs to be done on a larger scale in the state in order to achieve our water quality goals,” he said.

Largest of many sources

Under the terms of the settlement, the Merz family agreed to convert its 135-cow dairy operation to 60 beef cattle by 2015, to stop spreading manure on two fields near the lake, to shelter manure piles from the rain, and to make other changes specified in a manure management plan.

Barten said the dairy is the single largest source of phosphorus to the lake, but that fertilizer also comes from some lawns along the lakeshore and from hobby farms.

The Minnesota Pollution Control Agency listed the lake in 2002 as “impaired for aquatic recreation,” and lake users have complained about its ubiquitous green slime, comparing its summer color to pea soup. A state report in 2007 concluded that the amount of phosphorus needed to be reduced about 45 percent, or about 1,100 pounds per year, to improve water quality.

It also estimated that the Merz farm contributed about 166 pounds of phosphorus per year. One pound of phosphorus can produce 300 to 500 pounds of algae in a lake.

Spring runoff

Manure from feedlots can wash directly into a 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.

The citizens association sued the dairy owners last summer in Hennepin County District Court for allegedly polluting the lake with manure and runoff. Citizens also complained to state pollution officials that the family spread manure on frozen ground in winter and that it washed into the lake in spring.

Mike McLaughlin, the association’s president, said last year that the goal was not to close the farm, but to stop the manure runoff. McLaughlin said last week that he was not at liberty to discuss the settlement until attorneys have agreed on the wording of a statement announcing it.

Paul Merz said in an interview last year that he’s retired and rents the land that he’s owned since 1965 to his son, Jim. He acknowledged that one time the family applied manure on frozen ground, but that since then he and his son have cooperated with state pollution officials.

Warnings and inspections

Pollution inspectors sent Paul Merz a warning letter about alleged manure-spreading violations two years ago, and visited the farm twice last summer to help the family craft a manure-management plan. Agency spokesman Forrest Peterson said the plan was reviewed and approved last fall.

Barten said he hopes the settlement with the citizens group will encourage others to help clean up the lake.

Nearby cities and homeowners have begun to do that by spending a total of about $2 million, much of it tax money, to build rain gardens, restore shore land to prevent erosion, build vegetative buffers, and extend a sewer system to one lakeshore neighborhood that had septic systems.

That’s beginning to make a positive difference, Barten said, but the majority of the problem still comes from livestock in the watershed, especially the many hobby farms. A few horse owners are managing manure better, he said, but many more need to follow suit.

“From a purely scientific perspective, doing watershed and lake management through the court system is probably not the ideal way for this to be done,” he said. “But if we can build on this, I think we’ll see some real dramatic improvements in lake quality.”