Source Information
Chicago Park District monitors beaches daily from end of May to September 5. When sample results are reported on the County's website, Lake Ontario Waterkeeper updates Swim Guide. Recreational public beaches in Illinois are tested at least once every week, typically from May to September. In popular beach areas such as Chicago, beaches are tested five times per week or even daily.
New to 2017, The Chicago Park District Department of Cultural and Natural Resources (DCNR) will be testing for Enterococci instead of culturing live E. coli bacteria cells. Doing so allows for quicker results: DCNR are able to get water quality results back within 3-4 hours instead of the typical 18-24 hours. DCNR then posts same day results for people to see. If a water sample exceeds 1000 CCE of Enterococci bacteria, the Chicago Park District will issue a swim advisory (indicated with a yellow flag).