Part of boat access on Lake Independence shut down to treat lake for zebra mussels

For the second time in Minnesota, crews will use a chemical on a west metro lake to try to kill off zebra mussels that have infested a part of the lake.

On Wednesday, crews applied potassium chloride, or potash, on Lake Independence near the boat access in Baker Park Reserve — shutting down half the boat launch in time for the unofficial start to the boating season Memorial Day weekend, one of the busiest boating times of the year.

The access at the Maple Plain lake will be partly closed through June 8 as crews curtain off the area of the lake and apply the chemical.

"We're going to try to get the best result we can while keeping access open," said Tom Knisely, spokesman for the Three Rivers Park District, which manages the lake. "We're asking people to be patient … expect longer wait times."

The state Department of Natural Resources asked for emergency approval from the U.S. Environmental Protection Agency last year and got federal and state approval to use potash on Christmas Lake near Lake Minnetonka and Lake Independence. The chemical has been successful in waterways in Texas and Virginia. It kills zebra mussels by cutting off their oxygen, but doesn't affect fish, the DNR says.

Zebra mussels, which have infested hundreds of waterways in Minnesota, quickly proliferate by the millions after entering a lake, often on boats. They clog motors, alter the ecosystem and can be a hazard to swimmers.

On Christmas Lake near Lake Minnetonka, crews used potash and a biological pesticide, Zequanox, last fall and winter, and in April announced the treatments had been a success.

On Lake Independence, crews discovered thousands of mussels last fall that were two times larger. It was too cold for Zequanox to be effective, but copper sulfate was used. Then in April, the boat access was shut down for 10 days so potash could be used, with both treatments killing 70 percent of the zebra mussels.

Now, crews want to ensure that 100 percent of the fingernail-sized pests are gone with the second treatment of potash. It's not clear how much all three treatments will cost, but the expense is being split by the DNR and Three Rivers.

The park district also put $64,000 more in increasing boat inspections on the lake and adding a decontamination unit this summer; between now and Labor Day, inspections will take place on weekends and peak weekday hours.

Kelly Smith • 612-673-4141