Getting your Evanston news from Facebook? Try the Evanston RoundTable’s free daily and weekend email newsletters – sign up now!

Due to high E.coli counts, the City of Evanston’s beaches are closed for swimming on Wednesday, July 25, 2012.

Residents who want to check beach status for Evanston beaches in advance have several options. They can call the lakefront operations recorded message at 847/859-7822 or check the city’s beach status page. Starting this season, beach patrons also are able to sign up for text message or e-mail alerts from that page.

City staff tests the water from the City of Evanston’s five beaches, one dog beach and Northwestern University’s beach on a daily basis. The samples take 18 hours in an incubator to test. When E. coli counts exceed 235 CFU (chloroform forming units), an indicator of bacterial colonies in the water, the Evanston Health Department closes the beach (s). Sample results for today indicated a count of 238 to about 800 CFU for Evanston’s various beaches.

Factors such as natural die-off, wind and wave action, and ultraviolet light from the sun will help to reduce the level of bacteria. The length of time this takes is unpredictable; however, it is usually less than 24 hours.

The water needs to be resampled and the samples from both the shallow and deep areas must be below 235 CFU of E. coli/100 ml. before the beach will be allowed to re-open. It takes 24 hours after receipt of the samples to determine the bacteria levels.

Escherichia coli (E. coli) bacteria live in the digestive systems of humans and other warm blooded animals. Therefore, they are found in sewage and other wastewater. Most strains are not harmful, but some are, and they can indicate the presence of other disease-causing bacteria.

There are a variety of sources that contribute bacteria to surface water: illegal sewer connections to storm sewers or roadside ditches, or direct discharges to the lake; malfunctioning sewage disposal systems; combined and sanitary sewer overflows; storm runoff following a rain; wild and domestic animal waste; agricultural runoff; and swimmer defecation.

E. coli Gastroenteritis type illness is the most common, with symptoms such as diarrhea, nausea, vomiting, abdominal pain, headache and low grade fever. Skin rashes and earaches also may be experienced.