For the second time in a week, the threat of bacteria that can sicken swimmers has arisen on popular Twin Cities lakes.
Beaches on Lakes Minnetonka and Calhoun were among several closed Wednesday after tests revealed unsafe levels of E. coli bacteria, which can cause diarrhea, abdominal cramps or, occasionally, more serious problems.
Last week, the state Health Department announced that three swimmers contracted E. coli near Big Island in Lake Minnetonka, leaving one swimmer hospitalized.
The bacteria are the most common reason beaches are closed in the summer, but they are serious enough for officials to post the “No Swimming” signs on the beaches and urge people to stay away.
“We test on a regular basis,” said Brett Altergott, parks and recreation director in Lakeville, where Valley Lake Beach has been closed since last Thursday. “This is all done in public safety.”
E. coli in lakes often comes from runoff after a rainfall, where animal feces are caught up in the stormwater and swept into lakes before the water can be treated. Sometimes an undiapered child is the culprit.
Officials are not sure what has caused the recent spate of beach closings due to E. coli. Other theories range from high water temperatures that could help the bacteria live to an increase in sightings of birds, which sometimes can be carriers of infectious diseases.
“So many factors play into what cause these kinds of things to happen,” said Hennepin County Public Health spokesman Bill Belknap, whose department monitors Excelsior Beach. “It’s hard to predict.”
The other beaches closed Wednesday were at Lake Hiawatha in Minneapolis and Snelling Lake at Fort Snelling State Park.
Lake Hiawatha has a history of closing temporarily and briefly most summers due to spikes in bacteria levels because Minnehaha Creek carries in goose droppings, pet waste and other runoff from Lake Minnetonka, according to Dawn Sommers, spokeswoman for the Minneapolis Park and Recreation Board, which oversees the city’s lakes.
Years ago, the Park Board reconsidered having a beach there but decided to keep it open because it’s so popular, she said.
“Luckily, the community appears to have a growing understanding of the impact the creek has on the lake, and they readily head the short distance down the road to Nokomis to cool off and swim,” she said.
Sommers said it’s rare for one of Lake Calhoun’s three beaches to close. When they do, it’s usually an isolated short-term spike caused perhaps by a flock of geese in the area or storm runoff.
“While the public doesn’t seem to recall what little rain occurred this weekend, it fell on some pretty hard, dry soil, and unfortunately that means it runs into nearby lakes instead of being absorbed,” she said.
Officials are still encouraging people to continue to swim in lakes and urged them not to be alarmed by the closings.
“Typically for us, we may have 1-2 beaches closed,” said Rachael Crabb, a water quality supervisor for the Park Board. “So far this year has been really good to us.”
In reference to the closure of Valley Lake Beach, Lakeville’s website said the water will be retested daily until the E. coli levels are acceptable for public swimming.
The water at all the beaches will be tested this week. Officials in Excelsior believe that its beach could reopen as soon as Thursday afternoon. Sommers said the Park Board will know about Calhoun on Thursday afternoon and Hiawatha next week.