Beach Monitoring

Epidemiological studies of fresh water bathing beaches have established a direct relationship between the density of Escherichia coli (E. coli) in water and the occurrence of swimming-associated gastroenteritis.

District Health Department #10 collects water samples at 21 public beaches on Lake Michigan to determine if the water is safe for swimming for a 10 week period between the Memorial Day and Labor Day holidays. Samples are generally taken one foot below the surface in water that is between three and six feet in depth.

Results are posted on the State of Michigan Beach Guard website: Michigan Beaches

District Health Department #10 collects three samples each time a beach area is monitored. The daily geometric mean calculated from these samples must be below 300 E. coliper 100 milliliters for the water to be considered safe for swimming. After 30 days, a geometric mean is calculated for all the individual samples collected within that time frame. This 30-day geometric mean must be below 130 E. coli per 100 ml for the water to be considered safe for swimming.