Minneapolis Department of Public Works

Public Works

350 South 5th Street
RM 203 City Hall
Minneapolis, MN  55415-1390

Combined Sewer Overflow -
A Minneapolis Solution

What is a Combined Sewer Overflow (CSO)?

CSOs occur when heavy rain or melting snow causes sanitary sewers to overflow into stormwater drainpipes. This allows sewage to mix with runoff from buildings, parking lots and streets and flow, untreated, into the Mississippi River.

Compared to many other cities, CSOs are relatively rare in Minneapolis. The City has been actively working on sewer separation, a key strategy for preventing CSOs, since the 1960s. Most of the City’s sewer system has been separated.

When a CSO does occur, however, it can cause serious health and environmental problems that affect City residents and all who live, work or play downstream.

The threats posed by CSOs are serious enough that federal and state mandates have been issued that require the City of Minneapolis to stop CSOs into the Mississippi River. Not complying with these mandates could lead to fines and other legal action against the City.

Stopping CSOs

Fixing the remaining problems that can cause CSOs in Minneapolis won't be easy. Here is why:

See History of Combined Sewer Separation in Minneapolis

A Five-Year Plan

The City of Minneapolis has joined forces with the Metropolitan Council Environmental Services (MCES) to eliminate combined sewer overflows. Key components of the plan include:

Passage of an ordinance to prevent the kinds of discharges to the sanitary sewer system from homes and commercial buildings that can contribute to CSOs:

Chapter 56. Prohibited Discharges to Sanitary Sewer System (PDF)

High priority areas have been targeted first. Every parcel and building has been inspected to check for prohibited connections to the sanitary sewer system.

For more information about the ordinance and how you might be affected, see the Rainleader Ordinance Fact Sheet

Commitment to significant investment in capital improvements and maintenance repairs to our sewer systems:

The City has committed to giving higher priority to capital improvement and repair projects that will contribute to eliminating CSOs. Examples of such projects include:

Launching of a community outreach program to educate residents and business owners about CSOs and ways to prevent them

This CSO website is part of this outreach. How-to-disconnect brochures and other instructional pamphlets have been produced and been distributed to residents and business owners directly affected by rainleader ordinance compliance requirements.

Last updated Jun. 5, 2012