Also, Illinois beaches have the highest number of samples exceeding safe bacterial levels in the nation, according to the National Resources Defense Council (NRDC). However, Illinois also monitors its beaches more than some other states in its attempt to protect public health. Mostly in the morning, samples are taken in water that is knee- to waist-deep. The results are generally known within 24 hours.
Because of the waiting period for results, beach managers may close beaches or issue advisories because of rain or other factors.
In 2007, the level of bacteria found in daily water samples exceeded the state's maximum 21-percent of the time. That number is up from the 14-percent found in both 2005 and 2006.
The beaches with the most bacteria:
Lake County had the highest percent exceedance in 2007 (32%) followed by Cook County (21%)
Illinois has 73 public beaches on its 60-miles of shoreline along Lake Michigan. Most of them are tested daily as part of Illinois' attempt to protect public health.
The Chicago Park District monitors 23 beaches in the city limits while the rest of the Cook County beaches are monitored by other municipalities. Each monitoring department is responsible for closing or issuing advisories.
Illinois beaches are open from Labor Day to Memorial Day.