From Grey to Green, and Everything In-Between: A CSO Case Study

Metropolitan Sewer District of Greater Cincinnati (MSDGC) has been examining the potential of utilizing green infrastructure techniques within defined watershed areas, to reduce combined sewer overflows (CSO). Potential CSO control techniques are screened and those appropriate for project location and goals are selected for detailed analysis. An Alternatives Comparison Tool (ACT) was developed using these techniques to examine many different combinations which meet MSDGC-s goals. The ACT was then used to determine which combination of techniques accomplishes MSDGC-s goals most effectively.Partial separation of the CSO watershed utilizing stream daylighting in combination with conventional stormsewer construction and bypassing the existing pump station with a new gravity interceptor and CSO regulator presented the greatest overall benefit. This combination of components provides environmental benefits of additional terrestrial and aquatic habitat while improving ground and surface water quality. It also provides the social benefit of beautifying the community while avoiding major private property impacts.