Swimming at these Johnson County beaches is not recommended for unsafe levels of E. coli

Swimming is not recommended at all three Coralville Lake beaches after testing positive for high levels of E. coli.

The U.S. Army Corps of Engineers announced the positive tests on Facebook on Wednesday. They recommend that people avoid swimming at the lake's public West Overlook Day Use Beach and Sugar Bottom Day Use Beach.

The Sugar Bottom Campground Beach, open to registered campers only, also tested positive for "above allowable" levels of E. coli. The engineers recommended keeping pets away from the beaches to keep them from drinking the potentially harmful water.

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What are Iowa's E. coli regulations?

Beaches in Iowa are typically shut down after E. coli levels pass a certain threshold. The Iowa Department of Natural Resources follows the EPA guidelines, which say the bacteria level in the water is "acceptable" if the geometric mean is not greater than 126 colony-forming units per 100 milliliters of water for E. coli bacteria.

The U.S. Army Corps, in a social media post, said the water in the main body of Coralville Lake did not test positive for unsafe levels of E. coli, meaning boaters are still free to use the lake.

The Corps said the beaches can have higher levels of bacteria because the water is often shallow and typically doesn’t produce a current. The beaches also attract waterfowl, which can leave behind unsafe bacteria.

The Army Corps has erected temporary warning signs at the Coralville Lake beaches.

The most recent test Iowa DNR test of the water at Lake Macbride State Park, conducted on Aug. 14, showed the water was "okay for swimming."

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Iowa beaches impacted by E. coli throughout summer

Iowa's beaches saw a rise in positive E. coli tests in July. The Iowa Department of Natural Resources reported that as many as 12 beaches tested positive for the bacteria the weekend of July 19.

The DNR collects weekly samples at 39 state-owned swimming beaches to determine the public's risk of coming in contact with waterborne diseases. Testing begins a week before Memorial Day and runs through Labor Day.

The Army Corps will update the public when swimming is recommended again at the Coralville Lake beaches.

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Ryan Hansen covers local government and crime for the Press-Citizen. He can be reached at [email protected] or on X, formerly known as Twitter, @ryanhansen01.

This article originally appeared on Iowa City Press-Citizen: Coralville Lake beaches record unsafe levels of E. coli