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Sanitary Sewer Overflows

Explanation of sanitary sewer overflows due to wastewater facility impacts from Hurricane Harvey.

Texas wastewater facilities are prepared for increased inflows during heavy rainfall events. However, the magnitude and the nature of the record-setting flooding from Hurricane Harvey impacted facilities in a way that they could not respond to operationally. Entire wastewater facilities were inundated with floodwater, including many that were underwater for an extended period of time, resulting in record sanitary sewer overflows (SSOs). An SSO is a type of unauthorized discharge of untreated or partially treated wastewater from a collection system or its components (e.g., a manhole, lift station, or cleanout) before it reaches a wastewater treatment facility.

The SSO Tracking Report Adobe Acrobat PDF Document provides all reported SSO information to date, even when the quantity is unknown or a volume could not be calculated. Some discharges originally reported to the TCEQ were later determined to be industrial discharges, rather than an SSO; therefore, the format of the Tracking Report was modified on October 9, 2017 to provide for separate reporting of these two types of discharges.

To put in perspective the 22.5 million gallons of SSOs reported to the TCEQ, as of 10/10, by wastewater facilities in the impacted areas, the SSOs equate to less than one percent (0.00012 percent) in volume of the 19 trillion gallons of rainwater that caused the extreme flooding that impacted these same Texas facilities. The highest total rainfall in U.S. history of 60.58 inches fell near Nederland, Texas due to Hurricane Harvey in just a few days. This compares to the total average rainfall for a full year in the Houston area falling in less than one week. For another comparison, the total rainfall of 19 trillion gallons would raise the entire Great Lakes, the largest freshwater lake system in the world, by almost a foot.