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Months after more than 170 people became ill following July 4th festivities on Lake Minnetonka’s Big Island, officials with the lake’s conservation district have approved a stricter ordinance banning sewage discharge in the lake.

The ordinance requires boat owners to remove marine toilet pumps and to lock discharge valves (called Y valves) before entering the water. Anyone who launches a watercraft with a marine toilet that doesn’t meet the requirements will be subject to a petty misdemeanor charge.

Vickie Schleuning, executive director of the Lake Minnetonka Conservation District, said she knows of no other Minnesota lake with the same restrictions.

“But we’re unique because we are a very busy lake with big gatherings,” she said. “Some people think dilution is the solution to pollution, but that’s not really the case when it comes to the spread of illness.”

County officials interviewed more than 200 people who reported illness and confirmed that more than 170 of them — those who were in the Big Island area over the holiday and experienced vomiting, diarrhea or both — were part of the outbreak at Lake Minnetonka.

The source of the contamination hasn’t been identified, but it could have been a boater carelessly pumping out a marine toilet, or even a single person with norovirus defecating or vomiting in the water, public health experts told the Star Tribune in July.

“While the discharge of sewage in the lake was already prohibited by [the conservation district] and state and federal regulations, this new ordinance makes it clearer and takes an additional step to protect the lake and all those who enjoy it,” said Lt. Shane Magnuson of the Hennepin County Sheriff’s Office Water Patrol.

Businesses that provide launching and sewage-pumping services are required to report to the conservation district if they know of a watercraft on the lake that is not in compliance.

Months of collaboration

The new measure was adopted in late October after months of collaboration with Tonka Bay Marina owner Gabriel Jabbour, the Sheriff’s Office Water Patrol unit and other lake service providers, who will help with enforcement.

Even if a boat owner doesn’t intentionally pump sewage into the lake, boats with marine toilet pumps can accidentally release raw sewage, said Gregg Thomas, board chairman for the conservation district.

“That’s not in the best interest of public health,” he said.

Those with watercraft equipped with a toilet and macerator pump, which shreds waste before it’s pumped out of a holding tank, will have to remove the pump if they plan to go out on Lake Minnetonka. It can be replaced for trips to other lakes, Schleuning said.

Over the next several months, conservation district officials will be working to educate people about the change and will consider other solutions to help prevent future outbreaks.

High levels of E. coli also temporarily closed several beaches across the Twin Cities this summer.

Mara Klecker • 612-673-4440