CSO 012’s watershed covers 1.2 square miles of historic neighborhoods, including the University of Cincinnati, Cincinnati State, and Burnet Woods Park. The watershed’s steep hillsides and heavily developed urban area posed unique challenges, leading Stantec to explore a wide range of potential project elements. Options considered were to separate and daylight streams currently conveyed through historic combined sewers, construct new separate storm sewers and bio-retention cells, disconnect downspouts, and grey water treatment and equalization. The options determined to provide the greatest economic, environmental, and social benefits to the community and the Municipal Sewer District of Greater Cincinnati were green street designs and highly visible bio-retention facilities to provide both CSO reduction benefits and stormwater quality improvements. Phase 1 includes separation of 50 acres of CSO area using 3,000 feet of 12 foot storm box culvert and a bio-retention facility. In future phases, the 12 foot culvert will be extended from the bio-retention facility to the Mill Creek, separating nearly 75 percent of the sewer shed.