Bathing Beaches

District Health Department No.4 staff samples and monitors certain public bathing beaches for levels of Escherichia coli (E. coli) bacteria during the summer season.  Many bathing beaches along the Great Lakes shoreline, and at inland lakes are sampled to determine if E. coli are within safe levels established under Michigan law.  Funding to conduct the bathing beach monitoring program comes from the Michigan Department of Environmental Quality in the form of a grant and contractual arrangements.

What is E. coli?

E. coli is a bacteria that is found in the intestinal tract of warm blooded animals, including cattle, deer, dogs, birds, and humans. It may be present in high levels in recreational surface waters due to wastewater contamination from human activities such as combined sewage overflows , by animal waste that has been deposited in or near a swimming area, or by contaminated storm water runoff from nearby stream.

What are the Health Effects of E. coli?

High levels of E. coli in bathing beach waters have been associated with gastrointestinal and respiratory illness’.

What is the Michigan Standard for E. Coli Levels at Bathing Beaches?

There are two standards for E. coli in Michigan bathing beach waters: one is a single day sampling event and the other is the 30-day average.  A “sampling event” is the geometric average of three (3) samples collected at a bathing beach location.

1) A Daily sampling event consisting of 3 samples collected once per week from a single beach location resulting in no more than   300 E. coli colonies per 100 ml as a geometric average of the 3 collected samples.

2) A 30-day average of at least 5 Daily sampling events (at least 15 individual samples) resulting in no more than 130 E. coli colonies per 100 ml as a calculated as a geometric average of all samples .

What if Bacteria Levels are High?

Typically, E. coli levels are found to be low at both the great lakes and inland lakes beaches in the four counties of District Health Department No.4.  However, sampling experience has shown that specific events may cause high levels of E. coli in bathing beach waters.  Heavy rains may result in runoff water containing fecal material from farming activity, waterfowl, or sewage discharges.  Additionally, on shore winds may concentrate the contaminated storm runoff against the beaches and also create turbidity in which suspended algae and other natural debris may harbor bacteria.

Should water samples indicate that the E. coli standards have been exceeded, District Health Department #4 will then notify the beach operator of the exceedance, issue a health advisory limiting body contact, conduct repeat sampling to ensure low bacteria levels and evaluate the site in order to determine the source of the contamination.

Where to Find Results of Bathing Beach Samples?

All bathing beaches sample results for both great lakes and inland lakes sampling locations, will be posted on the MDEQ Beachguard beach monitoring website.  Advisories due to high levels of E. coli will be posted at this same site. (See the links below).