Lake Kohlmier closed without warning Thursday after test results showed high levels of bacteria.
The city of Owatonna notified the public early Thursday afternoon that the lake would be closed until further notice.
“Bacteria levels in a lake fluctuate based on various factors, such as heavy rain or wind, time of day, amount of people visiting the beach, beach wildlife, and physical characteristics of the beach,” the notification read. “At this time, there has been no specific cause for the spike in bacteria identified.”
The beach was closed temporarily earlier this summer due to flooding, but was re-open to the public after only a few days. Parks and Rec staff report they do weekly tests, though that is not required by the Minnesota Department of Health.
According to the Environmental Protection Agency guidelines on beach monitoring, the “geometric mean based on not less than five samples within a 30-day period shall not exceed 126 organisms per 100 milliliters.” The guidelines also state a single water sample should not exceed an E. coli count of 235 organisms per 100 milliliters.
Shortly after the flooding incident earlier this summer, safe-to-swim levels with shallow water contained 32 E. coli per 100 milliliters and deep water containing six E. coli per 100 milliliters.
According to Dani Licht, recreation supervisor for the city, the most recent water tests showed high levels of E. coli, with 387 E. coli per 100 milliliters in deep water and 1,120 E. coli per 100 milliliters in shallow water.
E. coli — or Escherichia coli — is a type of fecal coliform bacteria that is most commonly heard about in raw or undercooked hamburger meat, however it can end up in water from animal or human waste contamination. Rain can also wash fecal matter form beaches, wildlife or pet droppings into water sources, and waterfowl can also directly contaminate the water.
Lake Kohlmier will remain closed until the bacteria levels return to the recommended range according to the MDH. The safety of the community is the top priority. City staff will conduct frequent testing to ensure the lake area is reopened as soon as possible. Some structured programming scheduled at Lake Kohlmier has been cancelled or reformatted.
Other efforts at the lake
The city also treats Lake Kohlmier annually at the beginning of the swimming season to minimize occurrences of swimmer’s itch — a skin rash caused by an allergic reaction to microscopic parasites found in fresh water. The parasite is commonly found on waterfowl and snails.
The city used hydrothol 181 granular to kill weeds, and copper sulfate to kill the snails. This treatment, per Department of Natural Resources guidelines, is done 500 feet along the shore and 150 feet out into the lake where the swimming area is.
In addition, the city cuts up to 30% of the weeds in the lake in compliance with a permit issued by the DNR and renewed annually.
City staff also rakes goose droppings from the beach area daily.
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