Frequently Asked Questions | No Swimming Advisories | Michigan Department of Environmental Quality
Frequently Asked Questions
What are Sewer Overflows and What Causes Them?
Sewer systems collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. Most of the time, sewer systems transport all of their wastewater to a sewage treatment plant, where it is treated and then discharged to a water body. During periods of heavy rainfall or snowmelt, however, the wastewater volume in a sewer system can exceed the capacity of the sewer system or treatment plant. For this reason, sewer systems were designed to overflow occasionally and discharge excess wastewater directly to nearby streams, rivers, or other water bodies. Historically, overflows are among the major sources for beach closings and other water quality impairments.
Many sewer systems have retention/treatment basins, which are designed to capture the sewage and rain water long enough to provide initial treatment and disinfection. This initial treatment often involves allowing solids to settle, the skimming of floatable materials such as oils; and disinfection of disease causing organisms, often accomplished through the addition of chlorine. This combined rainwater and sewage wastewater, with chlorine disinfection is the typical treated overflow discharge in the state of Michigan; therefore, many sewage releases are considered partially treated sewage. The treatment provided significantly reduces the amount of pollutants discharged and the associated public health risk.
Who Will Let Me Know Whether the Water Is Safe for Swimming, Fishing or Canoeing?
When raw or partially treated sewage is released into a river, lake or stream the responsible city is required to notify the Department of Public Health . The Department of Public Health may sample, or require the responsible municipality to sample, the water-body that received the sewage discharge. If the discharge poses a public health threat, then the Department of Public Health will issue a public health advisory to notify people of the dangers associated with river or lake water contact.
How are Sewage Overflows Addressed?
Sewage overflows are a problem nationwide. Michigan initiated a sewage overflow control program in 1988, and in 1994 the federal government developed a nationwide policy. This policy suggested that states use an enforceable mechanism, preferably the permit program that was initiated by the federal Clean Water Act (called the National Pollutant Discharge Elimination System) to require communities to implement interim measures referred to as nine minimum controls by January 1, 1997, and to develop Long-Term Control Plans (LTCPs). The nine minimum controls basically included interim measures that could be undertaken to improve the quality of the combined wastewater before major sewer system construction activities would be undertaken as part of the LTCP. Once the state and the community reached agreement on the LTCP, the community would then implement the controls as soon as practicable. In Michigan, these LTCPs are contained in various legal documents including state issued NPDES permits, Administrative Consent Orders, Abatement Orders, and other types of court orders. In Michigan, all municipalities have completed the necessary interim control measures and have developed LTCPs.
What is the Main Challenge for Communities to Address in Controlling Sewage Overflows?
Several challenges exist in controlling sewage overflows, but the main challenges are the costs associated with mounting water and wastewater infrastructure improvements and the financial resource-intensive nature of sewage overflows controls. LTCPs typically involve major infrastructure investments that must compete with other community needs.