An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »


St. Louis Clean Water Act Settlement

(Washington, DC - August 4, 2011) The Metropolitan St. Louis Sewer District (MSD) has agreed to make extensive improvements to its sewer systems and treatment plants, at an estimated cost of $4.7 billion over 23 years, to eliminate illegal overflows of untreated raw sewage, including basement backups, and to reduce pollution levels in urban rivers and streams, the Department of Justice and the U.S Environmental Protection Agency (EPA) announced today. This injunctive relief is historic in its scope and importance to the people of St. Louis.

On this page:

Overview of Company and Facility Locations

The Metropolitan St. Louis Sewer District (MSD) provides sewage treatment and wastewater services to St. Louis, Missouri and 93 surrounding communities.

Top of Page


  • The Complaint alleges violations of the Clean Water Act (CWA) in the form of discharges of untreated sewage from MSD's sewage collection system, including sanitary sewer overflows (SSOs), combined sewer overflows (CSOs), and wastewater treatment plant (WWTP) bypasses to nearby waters.
  • MSD currently discharges approximately 13.4 billion gallons of untreated sewage into urban streams in St. Louis and into the Mississippi River, Missouri River, Meramec River, River Des Peres, and their associated tributaries, and numerous private property backups.
  • Many of these illegal overflows violate water quality standards and other provisions of MSD's National Pollutant Discharge Elimination System (NPDES) permits, as well as Sections 301 and 402 of the CWA. The private property backups likely resulted in exposure of residents to raw sewage, which presents an imminent health threat under Section 504 of the CWA.
  • Finally, the complaint alleges that MSD also failed to submit a Long Term Control Plan (LTCP) to the State of Missouri (State). This last claim was resolved when MSD submitted an LTCP for approval to the State.

Top of Page

Injunctive Relief

Under the proposed settlement, MSD will implement remedial measures intended to eliminate a substantial percentage of CSOs from the District's sewer systems and eliminate the 200 or more constructed SSO outfalls. The Consent Decree requires elimination of the vast majority of constructed SSOs within 12 years, and completion of the construction and full implementation of all CSO remedial and control measures within 23 years. The overall cost of the injunctive relief is approximately $4.7 billion.

Combined Sewer System: MSD will implement its Long Term Control Plan and CSO Control measures that, when combined with existing upgraded controls and work already underway, will reduce CSO discharges from approximately 13 billion gallons per year to approximately 8 billion gallons in a typical year and capture for treatment more than 83 percent of total wet weather flows.

Separate Sanitary System: Remedial measures to be implemented under the Consent Decree will eliminate the approximately 400 million gallons per year of SSO discharges. During the next two years, the Decree requires MSD to spend at least $30 million to reduce "inflow and infiltration" (I&I) in the separate sewer system. This action is targeted in areas with a high concentration of low-income customers experiencing high occurrence of private property backups. The Decree also requires MSD to develop and submit a Sanitary Sewer Overflow Control Master Plan that includes specific remedial measures for removal of I&I, increased capacity throughout the system and at the treatment plants by December 31, 2013.

The Decree also requires MSD to eliminate at least 85 percent of the constructed SSO outfalls and other known SSOs by December 31, 2023. MSD may request EPA to approve an extension of time for the remaining 15 percent, but such an extension would potentially be granted only upon demonstration of technical need.

Top of Page

Green Infrastructure

The Consent Decree also includes a $100 million green infrastructure program to reduce storm water flows through a storm water retrofit program, focused in sewersheds in the City of St. Louis, that drain to the Mississippi River. This is an area impacted by environmental justice concerns. The initial goal is to reduce CSO discharges to the Mississippi River by ten percent.

Top of Page

Pollutant Reductions

Through implementation of the Decree, MSD will eliminate or capture for treatment approximately 5.4 billion gallons of current CSO and SSO discharges. These reductions will substantially lower releases of microbial pathogens, suspended solids, toxics, and nutrients.

  • Total suspended solids (TSS) - 4,504,150 pounds per year
  • Biological oxygen demand (BOD) - 1,545,014 pounds per year
  • Total nitrogen - 426,258 pounds per year

Top of Page

Health and Environmental Effects

Elimination of SSO discharges and elimination or treatment of CSO discharges will substantially reduce releases of the following pollutants:

  • Microbial pathogens
  • Total Suspended Solids (TSS) - TSS indicates the measure of suspended solids in wastewater, effluent or water bodies. High levels of TSS in a water body can diminish the amount of light that penetrates the water column and reduce photosynthesis and the production of oxygen.
  • Toxics
  • Nitrogen
  • Biological oxygen demand (BOD) - BOD is an indirect measure of the biologically degradable material present in organic wastes. High BOD means there is an abundance of biologically degradable material that will consume oxygen from the water during the degradation process. It may take away oxygen that is needed for aquatic organisms to survive.

Top of Page

Supplemental Environmental Projects (SEPs)

MSD will spend at least $1.6 million on a supplemental environmental project (SEP) that includes implementation of a sewer connection and septic tank closure program (Program). Under the Program:

  • MSD will install sewer lines to homes of participating property owners and remove septic tanks from operation for these homes by capping, filling or other means determined and approved by MSD and consistent with local ordinances
  • MSD will also replace, rehabilitate or repair as necessary private lateral connections, thereby reducing I&I that contributes to overflows in the sewer system

The Program is a no cost construction program for eligible low-income property owners who elect to close their septic tank and connect to the adjacent public sewer, or where MSD finds contributions of I&I to the sewer system for a defective private lateral connection. The Program will benefit EJ communities, as it is solely in low-income areas.

For more information on SEPs, see EPA's SEP Web site.

Top of Page

Civil Penalty

MSD will pay a civil penalty totaling $1.2 million to the United States.

Top of Page

State Partners

The state of Missouri joined EPA as a Plaintiff in the complaint filed in 2007 but has declined to sign the Consent Decree. Both the State's claims and MSD's counterclaims regarding CWA §309(e) liability will not be resolved under the Consent Decree.

Top of Page

Comment Period

The proposed settlement, lodged in the U.S. District Court for the Eastern District of Missouri, is subject to a 30-day public comment period and final court approval. Information on submitting comment is available at the Department of Justice website.

Top of Page

For more information, contact:

Joanna Citron Day
Water Enforcement Division
Office of Civil Enforcement
1200 Pennsylvania Ave., NW
Washington DC 20460
(202) 564-5568

Top of Page