Sewage treatment
Power failure, human error, or mechanical failure may cause similar discharge of untreated or partially treated sewage from a sewage treatment plant; but this is typically regarded as a sewage treatment plant malfunction rather than a sanitary sewer overflow. Sewage treatment plants may be designed to capture overflow from malfunctioning units and discharge it to alternative treatment facilities. Flooding of private or public property is typically avoided by discharging the overflow to an outfall designed for discharge of treated sewage.