Combined Sewer Overflow

In older sewer systems such as Springfield’s, combined sewers were commonly constructed to collect and transport sanitary sewage and stormwater together in one pipe. During heavy rain events, the combined sewer fills up beyond capacity with stormwater runoff and diluted sanitary sewage. To prevent the excessive flow from backing up into basements and spilling onto roadways, discharge relief points were installed so the excess flow would empty into water bodies. Each discharge relief point is known as a combined sewer overflow, or CSO (illustrated below). A CSO is the discharge of wastewater and stormwater from a combined sewer system directly into a river, stream, lake or ocean. CSOs are caused by stormwater runoff during rainfall events. These overflows are called combined sewer overflows (CSOs), they contain not only stormwater but also untreated human and industrial waste. They are a major water pollution concern for Springfield and approximately 772 other cities in the U.S. that have combined sewer systems.

What is the Commission doing to eliminate CSO’s?

Beginning in 1995 the MADEP and USEPA have issued Administrative Orders for CSO specific projects. Since then the Commission has maintained compliance with these orders by completing the following projects:

Mill River CSO 2003-2004 $4,800,000
Watershops Pond 2003-2006 $1,200,000
Washburn CSO Replacement 2006-2007 $7,900,000
Chicopee River CSO 2004-2009 $36,400,000
Phase I Connecticut River CSO 2005-2012 $18,352,000
Washburn CSO Phase II Design 2009-2012 $2,500,000
Washburn CSO Phase II Construction 2012-2014 $20,497,000
Integrated Wastewater Plan 2009-2014 $8,700,000
Total Spent on CSO’s to date $100,349,000

We estimate that work to reduce CSOs will continue for the next 20 years and beyond, and total program costs will likely exceed $200 million.

To learn more about our CSO Program, please see the links below:

CSO Capital Improvement Plan
Springfield CSO Fact Sheet
CSO Long Term Control Plan
Washburn CSO Control Project