What is a CSO and why is it a problem?

CSO stands for Combined Sewer Overflow (CSO). The City of Terre Haute, like many Midwestern cities, contributes to the pollution of the Wabash River through CSO's.

What is a Combined Sewer?

The City of Terre Haute has miles of underground sewer pipes that collect sewage from household and business drains.

Additionally, there are many places where streets and downspouts also drain those same sewers. These are called combined sewers. When a rainfall occurs, stormwater from the streets and downspouts flow into the combined sewer system. The wastewater treatment plant cannot handle the additional flow, so the system automatically overflows to the Wabash River through CSO's.

Every year, millions of gallons of combined sewage, stormwater, and debris overflow to the Wabash River, causing increased E. coli readings and other pollution to the river. The City of Terre Haute is undertaking a plan to reduce the number of overflows to the river. The City submitted a plan called a Long-Term Control Plan (LTCP) in 2001 to the Indiana Department of Environmental Management. Although the Plan has not yet been approved, the City has received approval to move forward with several "Early Action" projects. The City will then have a number of years to complete all the approved projects. While all the overflows will not be completely eliminated, the plan will eliminate most of the instances of overflow.

The goal of the program is to have a cleaner city, resulting in a cleaner river.