Swimming not recommended at Lake Darling due to high E.coli test

With the warm summer days, Lake Darling State Park's beach has been packed with community member soaking up the summer rays, but now, the Iowa Department of Natural Resources (DNR) has recommended no swimming due to high levels of E. coli.

On June 12 the DNR found high levels of E. coli and placed Lake Darling in 'Swimming is Not Recommended.”

E. coli is an indicator for fecal material that can carry parasites or other pathogens and can be dangerous to swimmers.

The type of E. coli that is tested is not a version that makes people sick, but it is an indication and when the numbers are high it is likely other viruses and other pathogens are potentially high as well, said Dan Kendall, DNR ambient lake monitoring coordinator.

Water tests are conducted five times in a 30-day period to ensure the levels are within the standards safe for swimming.

The most recent sample at Lake Darling by the DNR found 540 colony forming units of E. coli per 100 millimeters of water, or 540 CFU/100ml. The maximum standard on a single sample is 235 CFU/100ml. Because Lake Darling exceeded the standard signs are posted stating 'Swimming is Not Recommended.” Kendall said in the grand scheme it is not a high number but it is safer to err on the side of caution. The standard is based on trying to people that are vulnerable such as little kids and the immunocompromised.

There are many different causes for high E. coli levels in beaches such as septic systems, manure spills, stormwater runoff, pet and wildlife droppings or any animal as all warm-blooded animals produce E. coli.

Kendall said the spike in E. coli may be from the rainstorm before the last test. During the rain, a lot of bacteria that is in the sand is washed into the water.

At Lake Darling, the high numbers are usually within the beach area, and further off shore the numbers drop drastically.

It is unknown when the levels will be low enough for the warning to be removed, but Kendall expects the levels to be lower when the results are in from the most recent test.

'We sample weekly on these systems so the advisory can come and go within a week, were very proactive with our program to protect public health,” Kendall said.

Lake Darling on average only has one or two E. coli events like this to take place each year and most of the time they are early season events, Kendall said.

Kendall recommends individuals watch advisory signs, keep their head above water and wash off after swimming to be safe.

Information signs are posted at monitored beaches with information on indicator bacteria and blue-green algae toxins. Posting occurs between Memorial Day and Labor Day and are generally updated on Fridays of each week.

DNR also has a beach monitoring website that shows the state and local beaches and indicates if they are safe for swimming each week.