Post Construction Monitoring Analysis: Measuring the Bang for the Buck

The City of Fort Wayne (Indiana) Combined Sewer Overflow (CSO) Long-Term Control Plan (LTCP) uses a combination of open-air storage ponds, satellite storage/treatment units, a parallel interceptor system and sewer separation to capture and control CSO. Prior to the construction of the storage basins and parallel interceptors, the City is conducting studies of individual combined sewer subbasins to identify cost-effective sewer separation project that will remove storm water from the CSO system. These partial separation projects have the potential to reduce the size of the ultimate CSO controls, and continue an ongoing City program that uses sewer separation to mitigate areas with basement flooding issues.As part of this program, the City is interested in defining the benefits achieved by and cost effectiveness of sewer separation projects. While simple in concept, this cost-benefit analysis has proven to be a question with many layers. On a technical basis, there were needs for defining cost effectiveness as a basis for determining whether projects proceed and verifying the approach used to project effectiveness. On a public outreach basis, there was a need report back to the public on progress made on the CSO Long Term Control Plan and the Consent Decree (CD) to support the investments being made.Several different methods were used to collect, analyze and report project costs and post construction monitoring results. This paper presents the different methods and discusses their strengths, limitations and appropriate uses.