The Laboratory Division Staff sample the water of Lake Michigan at several points along North and Zoo Beaches five days per week during the summer beach season (Memorial Day through Labor Day). This sampling is done in an effort to look for E. coli, an indicator organism useful in determining the presence of other pathogens within the waters of Lake Michigan.
Do you have questions about how, when, and why we test the water at local beaches? See our answers to some Frequently Asked Questions Regarding Swimming at North Beach.
Explanations of the three possible beach conditions are given below:
The green sign is the default sign and will be displayed at the beach at all times. Please read the sign and consider the potential health risks of swimming in untreated water based on your personal health condition. Fresh bodies of water, such as Lake Michigan beaches, unlike swimming pools, are not treated in any way and there is always some risk attached to swimming. When the green sign is displayed without any additional advisory or closure signage it means that water quality for that day has met US EPA standards of acceptable risk for full body exposure, i.e. putting your head under the water. To reduce your risk of illness and the transmission of disease to those around you: shower before you swim, never swim when you are ill, and wash your hands thoroughly before you eat or drink.
A yellow advisory sign will be posted whenever E. coli levels exceed 235 MPN/100 ml in a single sample. A yellow sign indicates a potential increased risk to human health from exposure to recreational water at this time. While swimming is not prohibited, the Health Department strongly encourages people to enjoy the beach but avoid full body contact with water until the advisory is removed. Certain persons should especially avoid contact during these times: very young, elderly, or those with compromised immune systems.
A red closure sign will be posted whenever E. coli levels are equal to or greater than 1000 MPN/100 ml in a single sample. The red stop sign indicates a risk to human health from contact with surface water and swimming is prohibited at this time. While you may enjoy other activities on the beach, you will not be allowed to swim. It is important to obey these recommendations to reduce your risk of waterborne illness.
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