Removing and alleviating sewer overflows

Throughout the Metropolitan St. Louis Sewer District’s (MSD) service area, there are hundreds of points where a combination of stormwater and wastewater may discharge into local waterways from the sewer system during moderate to heavy storms. These sewer overflow points act as relief valves when too much stormwater enters the sewer system, and without them, our community could experience thousands of basement backups and/or extensive street flooding. Depending on where sewer overflows are located within MSD’s system, they are classified as constructed separate sewer overflows–or—combined sewer overflows. If an overflow discharges or not is dependent upon a number of factors, including how much rain falls over a given period of time. The result is that not all overflows discharge every time it rains – in fact, some overflows will go months or years without discharging.

The issue of overflows has been a significant focus of MSD’s work for many years. For example, from 1992 to 2012 MSD spent approximately $2.7 billion to eliminate over 38 overflows. Today, our work to address sewer overflows and improve water quality continues in the form of MSD Project Clear, which calls for $4.7 billion in spending over 23-years. MSD Project Clear work began in MSD’s fiscal year 2013 and addresses our community’s wastewater collection and treatment capabilities on a system wide basis. This program is a mammoth undertaking that will benefit St. Louisans-and our environment – for generations to come.

All remaining sewer overflows, indicated with red “dots”, above, will be addressed in the coming years of MSD Project Clear. This page will be updated as additional planning and progress is made.

For more information on sewer overflows and their locations please visit or call (314) 768-6260.