Consent Decree

Our Consent Decree (learn more at is a federally enforceable, legally binding agreement that resolves alleged violations of the Clean Water Act for untreated overflows from Louisville’s combined and separate sanitary sewer systems.

Combined Sewer System:  A sewer system in which wastewater and stormwater are carried by the same pipe.

Separate Sewer System:  A sewer system designed to carry wastewater only.

Stormwater System:  A system designed to carry stormwater only.

The earliest sewers in Louisville were built in the 1800s and designed to drain stormwater to the Ohio River or nearby streams. When indoor plumbing became common in Louisville homes, a sanitary sewer became necessary to drain wastewater. Combining wastewater with stormwater in the same pipe was considered the most convenient way to accomplish this.

These combined sewer systems were the industry standard in Kentucky until 1955 when they were banned by the state. MSD had stopped building combined sewers two years earlier, but combined sewers had already been built in Louisville and Jefferson County, particularly in the area inside the Watterson Expressway (I-264).

Combined sewer systems were banned because they released both stormwater and untreated wastewater into local waterways, harming local wildlife and plant-life. They also exposed people to bacteria and pathogens. MSD modified the combined sewers, sending most of the wastewater to its treatment plants. Unfortunately, during heavy rain events, these combined sewer systems may become overloaded by stormwater, allowing it to mix with wastewater. This unsanitary mixture will sometimes overflow into local streams and the Ohio River. These overflows are called Combined Sewer Overflows (CSOs).

If you live in the area outside I-264, you are probably served by separate sewers, which are less likely to overflow. However, stormwater finds ways to enter these often old and leaky pipes. When the pipes fill up, they may overflow—either into a waterway, onto the ground or into a building. These overflows are called Sanitary Sewer Overflows (SSOs).

In 2005, MSD committed to taking steps to control overflows under a federal Consent Decree, a legal document signed by Louisville MSD, the United States Environmental Protection Agency, the Kentucky Department for Environmental Protection and the United States Department of Justice.

To help meet the Consent Decree, MSD prepared a plan to reduce and mitigate the effects of CSOs, and to eliminate SSOs and other unauthorized discharges. This long-term plan will be carried out through 2024, at an estimated cost of $1.15 billion.

In the coming years, you’ll continue to notice infrastructure improvements that will remedy the community’s aging sewer systems. This will reduce sewer overflows and backups, reduce health risks associated with exposure to bacteria and contaminants; and help achieve safe, clean waterways for our community.