Combined Sewer Overflow Project

What is Combined Sewer Overflow?

Combined Sewer Overflow (CSO) is the discharge of combined sewage into a water body such as a river, lake or stream. Combined Sewage is a combination of untreated sewage and stormwater.

What Is Its Purpose?

As with all cities with sewer infrastructure built prior to the 1950s, Lansing’s sewage collection system was designed as a “combined sewer system” (i.e., a single pipe system) to collect sewage from residences, commercial properties and industrial facilities and transport it to the Wastewater Treatment Plant (WWTP), but the combined sewer system also collects rain and snow melt, including flow from road drainage, roof drains, yard drains and other drainage structures.

When this large flow volume exceeds the capacity of the sewers and the WWTP, it is diverted through a CSO regulator (underground diversion chamber) directly into the Red Cedar River or the Grand River. Overflows of untreated sewage diminish water quality and threaten public health.

Why CSO Is Important

The CSO Project is an opportunity for the City of Lansing and its residents to have a positive, lasting impact on the water quality of the Grand and Red Cedar rivers for many decades to come. Not only by improving public health and the water quality of the rivers as they flow through the City, but for all downstream communities and four of the five Great Lakes.

The project also offers the City the opportunity to improve other aging infrastructure such as roads, curbs, water mains, natural gas lines and other utilities located within the publicly-owned right of way. By teaming with Lansing Board of Water and Light, many old water mains and services are being replaced in conjunction with the sewer installation. The new pipes should provide long-term service ranging from 50 to 100 years or more.

When Lansing’s CSO Control Program is completed, the City will have:
  • Addressed Federal and State regulatory requirements
  • Eliminated 1.65 billion gallons of raw sewage from entering the Grand River each year of CSO
  • Protected the Grand and Red Cedar Rivers and four of five Great Lakes
  • Revitalized hundreds of miles of sanitary sewers and roads