The State of Michigan and local municipalities have worked closely together to develop programs that help assess the current status and condition of Michigan’s lakes and streams. These assessment efforts determine whether or not water quality standards are being met. County health departments routinely collect water samples to verify that the waters are safe enough for recreational use.
E. coli as an indicator species
Escherichia coli (E. coli) measurements are used as an indicator of the potential harm to human health from both partial and total body contact (e.g., wading, swimming). E. coli bacteria live in the digestive systems of humans and warm-blooded animals. Most strains of E. coli are not dangerous, but they can indicate the presence of more harmful, disease causing bacteria. E. coli are a suitable indicator species because they will consistently be found in fecal waste and overall have similar survival and transport properties as the more harmful pathogens. The downside to using E. coli bacteria as an indicator is that each species of bacteria will respond differently to temperature, sunlight, nutrients and turbidity; and E. coli are not a good indicator of viruses and parasites.
There are many sources of E.coli
State and Federal Regulations
Michigan Water Quality Standards for partial and total body contact recreation were developed with guidance from the U.S. Environmental Protection Agency. These standards were established in order to ensure safe use of recreational waters and meet requirements of the federal Clean Water Act. Michigan’s rivers, streams and lakes frequently exceed these standards, posing risks to human health. Accurately and frequently monitoring our surface waters is essential to address these issues.
E. coli summer season geomeans from 2004-2013 in the Red Cedar River at the Farm Lane Bridge, East Lansing, MI. The red line indicates the total body contact recreation water quality standard for Michigan.Data source: Ingham County Surface Water Sampling Program
Monitoring E. coli
Water quality samples are generally taken one foot below the surface in waters that are three to six feet deep. A minimum of three samples are taken from the water, and the geometric mean of the three samples is calculated in order to exclude outliers from the data.
One sample is taken from the left river bank, one from center of the river, and one from the right river bank. In order for the water to be safe for full body contact, the geometric mean of the three samples must be below 300 E. coli per 100mL. A minimum of five sampling events is required within a thirty day period in order for the results to be an accurate indication of the water quality. After thirty days, the geometric mean is calculated for all samples, and this mean must be below 130 E. coli per 100mL. E. coli testing for the Red Cedar River is conducted by the Ingham County Health Department in cooperation with local communities.