Metropolitan St. Louis Sewer District agreed to pay $1.2 million civil penalty and implement a $4.7 billion, 23-year improvement program to eliminate 200+ constructed SSO outfalls, reduce CSO discharges from 13 billion to 8 billion gallons annually, and implement a $100 million green infrastructure program.

Metropolitan St. Louis Sewer District — $4.7 Billion CSO/SSO Consent Decree (2011)

Outcome: MSD agreed to pay $1.2 million civil penalty and implement a $4.7 billion, 23-year comprehensive improvement program addressing 200+ constructed SSO outfalls, reducing combined sewer overflow discharges from 13 billion to 8 billion gallons annually, and funding a $100 million green infrastructure program — one of the largest sewer consent decrees in EPA history.

The Metropolitan St. Louis Sewer District (MSD), the public agency providing sewage collection and treatment services to the greater St. Louis metropolitan area, operated a sewer system with documented violations including sanitary sewer overflows (SSOs) from 200+ constructed overflow structures that discharged untreated sewage to local waterways, combined sewer overflows discharging approximately 13.4 billion gallons of untreated combined sewage annually, and wastewater treatment plant bypasses. These violations affected the Mississippi River, the Missouri River, and numerous tributaries in the St. Louis region.

The settlement, announced August 4, 2011, required MSD to pay $1.2 million in civil penalties and implement a 23-year comprehensive program estimated at $4.7 billion. Key requirements included: elimination of the vast majority of constructed SSO outfalls, with 85% eliminated by December 31, 2023; reduction of annual CSO discharge volume from approximately 13 billion gallons to 8 billion gallons; implementation of a $100 million green infrastructure program incorporating rain gardens, bioswales, permeable pavement, and green rooftops to reduce stormwater inputs to the combined sewer system; and completion of a $1.6 million supplemental environmental project benefiting low-income communities.

The MSD consent decree was notable for its scale, its green infrastructure component, and its 23-year implementation timeline — a recognition that the physical scale of infrastructure replacement required for CSO elimination cannot be compressed without creating public health and financial sustainability risks. The $4.7 billion program represents one of the largest environmental compliance investments ever committed by a single municipal utility.

Primary Source: St. Louis Clean Water Act Settlement | US EPA