RTB stands for Retention Treatment Basin. An RTB is a large underground concrete storage tank and treatment facility used to hold combined sewage (Typically more than 95 percent storm water and rest wastewater) when the sewage disposal system reaches its maximum capacity during wet weather. The combined sewage will either be held until there is adequate capacity in the system, or it will be treated through a settling, screening and disinfection process in the RTB before it is released. Discharges of this nature are authorized by a National Pollution Discharge Elimination System (NPDES) permit that is issued and regulated by the State of Michigan. These four CSO control projects have effectively controlled the discharge of untreated sewage from Oakland County CSO's in the Rouge and Clinton River Watersheds. These basins have been successful in efficient and cost-effective treatment of CSO's:
