Posted inInvestigating Responses

Explainer: What is a sanitary sewer overflow?

Sanitary sewer overflows, SSOs, are a release of untreated or partially treated waste from a city sewer. Sanitary sewer overflows are illegal. But when normal systems become overloaded through heavy rain or a larger load from an increasing population, SSOs occur.

by Janelle O'Dea June 17, 2025June 17, 2025

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Explainer: What is a sanitary sewer overflow?

by Janelle O'Dea, Illinois Answers Project
June 17, 2025

<h1>Explainer: What is a sanitary sewer overflow?</h1>
<p class="byline">by Janelle O'Dea, Illinois Answers Project <br />June 17, 2025</p>
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<p>This <a target="_blank" href="https://illinoisanswers.org/2025/06/17/explainer-what-is-a-sanitary-sewer-overflow/">article</a> first appeared on <a target="_blank" href="https://illinoisanswers.org">Illinois Answers Project</a> and is republished here under a <a target="_blank" href="https://creativecommons.org/licenses/by-nd/4.0/">Creative Commons Attribution-NoDerivatives 4.0 International License</a>.&nbsp;<img src="https://i0.wp.com/illinoisanswers.org/wp-content/uploads/2022/11/cropped-favicon.png?resize=150%2C150&amp;ssl=1" alt="" width="16" height="16" style="width:1em;height:1em;"></p>
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A sign warning of a sewer overflow near a small home — A sign by William McNeal’s house warns that there is a sanitary sewer overflow and warns residents of potential health risks if exposed to the contaminated water. Credit: Kyle Pyatt for Illinois Answers Project

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Tagged: Explainer, sewage, sewer overflows, wastewater, southern illinois, Wasted Waters, sanitary sewer overflow, State Investigations Team

Janelle O'DeaState Investigative Reporter

jodea@bettergov.org

Janelle O’Dea is based in St. Louis as an investigative reporter with the Illinois Answers Project State Investigations Team. Her beat covers Southern Illinois and the Metro East. Before joining the Illinois Answers Project, she worked in Colorado, Florida, at the St. Louis Post-Dispatch and at the Center for Public Integrity. She is a graduate of the University of Illinois Urbana-Champaign and grew up in central Illinois.

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