The Birmingham Combined Sewer Overflow (CSO) control facilities were constructed as part of an $82 million national demonstration project.   The demonstration project is a three-phase project aimed at eliminating CSOs in the Rouge River watershed.   The Birmingham Retention Treatment Basin (RTB) and Tunnel were constructed under the second phase of the project, which implemented CSO controls.   Phase I included monitoring and optimizing existing combined sewer systems and planning for CSO controls.   Phase III evaluates the results of Phase II CSO controls and initiates further controls (if necessary) to meet water quality standards.

The Birmingham RTB and Tunnel service a 1,185-acre watershed, treating approximately 230 million gallons of CSO annually, of which 50 million gallons are discharged to the Rouge River.   The RTB has a capacity of 5.5 million gallons and is 266' x 147' x 20'.   The facilities are designed to provide 30 minutes detention of the 1-year, 1-hour storm (1.0”).

The RTB receives gravity flow from the 12' x 18' influent sewer.   Two separate cells are sequentially filled, as the facility provides disinfection, settling and skimming. Flow exceeding the storage capacity of the two cells is screened through 3/4” x 3-3/4” openings and overflows via weir troughs to an effluent channel that discharges to the Rouge River.   Retained flow in the RTB is pumped back into the Evergreen Interceptor sewer system for treatment at the Detroit POTW.   After the basin is dewatered, a pivoting trough flushing system is used to flush any remaining sediment from the tank bottom to the interceptor sewer.

Construction of the RTB was substantially completed in December 1997.   Located within the Birmingham Municipal Park, the control building was designed to resemble a gristmill and extensive woodlands landscaping was completed in order to blend with the aesthetics of the site.

The Birmingham RTB instrumentation and controls are relayed into Oakland County's Supervisory Control and Data Acquisition (SCADA) system.   This allows the County to monitor the facility from a remote location and optimally operate the facility.