Combined Sewer Overflows (CSO)


Protecting our natural resources by reducing Combined Sewer Overflows

West Lafayette is committed to protecting our natural resources. The city has recently updated its 20-year,  CSO Long Term Control Plan, which will result in a cleaner Wabash River.

What is a combined sewer overflow?

According to the U.S. Environmental Protection Agency, CSOs are remnants of the country's early infrastructure. In the past, communities built sewer systems to collect both storm water runoff and sanitary sewage in the same pipe. During dry weather, these "combined sewer systems" transport wastewater directly to the sewage treatment plant. In periods of rainfall or snowmelt, however, the wastewater volume in a combined sewer system can exceed the capacity of the sewer system or treatment plant. For this reason, combined sewer systems are designed to overflow occasionally and discharge excess wastewater directly to nearby streams, rivers, lakes, or estuaries.

CSOs contain not only storm water but also untreated human and industrial waste, toxic materials, and debris. This is a major water pollution concern for cities with combined sewer systems. CSOs are among the major sources responsible for beach closings, shellfishing restrictions, and other water body impairments.

While not subject to secondary treatment requirements, CSOs must nevertheless meet water quality-based and technology based standards under National Pollution Discharge Elimination System (NPDES) permits to comply with the Clean Water Act. Based upon U.S. EPA's 1989 CSO strategy and 1994 National CSO Policy, CSO communities are required to implement nine minimum control technologies, and develop a long-term CSO control plan to meet water quality standards. The nine minimum controls are generally met through management of the existing Combined Sewer Systems (CSS), while the long term controls will involve capital improvements such as the retention and treatment, or sewer separation.

More than 100 Hoosier cities and towns have CSOs. There are over 700 cities with combined sewers nationwide. In West Lafayette, there are 3 CSO locations. You can view those locations by clicking here.

What is West Lafayette doing to reduce CSOs?

In 1993 the city began an aggressive 20-year plan to significantly reduce CSOs and comply with federal regulations related to the Clean Water Act. Over the next 10 years, a number of major improvements were made, including:

  • An $18 million upgrade to the wastewater treatment plant that included ammonia removal and de-chlorination
  • Completion of the $2.2 million foundation drain disconnect program in the Barbarry neighborhood (1999)
  • Construction of the $2.3 million North River Road lift station (1999)
  • The $1.9 million rehabilitation of the Happy Hollow interceptor (2001)
  • Construction of the $5.9 million wet weather treatment facility to significantly reduce CSO impacts on the Wabash River (2003)

The city has recently updated its 20-year plan. Click here to download the CSO Long Term Control Plan. The western sanitary interceptor, projected to be a $13 million investment, now takes a portion of sanitary flows out of the combined storm and sanitary system, reducing the number of CSOs and the strength of the wastewater in a CSO overflow event. The project also included the elimination of 3 lift stations.

CSO Relief Interceptor Project

How do I sign up for the city's CSO public notices?

CSO UpdatesThe Wastewater Treatment Utility is committed to reducing CSO impacts to the Wabash River. If you would like to begin receiving CSO e-updates, please sign up for an ENotify account (located under Site Tools at the top of this page) and choose Combined Sewer Overflow Notices.

Combined Sewer Overflow Events

Web Resources

Contact Us

David Henderson, Utility Director
500 S River Rd
West Lafayette, IN 47906

  • Office: (765) 775-5145
  • Office Fax: (765) 775-5149
  • Office Hours:
    8:00 a.m. - 4:00 p.m.

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