Real Time Control Study to Reduce Combined Sewer Overflows in Louisville and Jefferson County

The Louisville and Jefferson County Metropolitan Sewer District (MSD) has shown interest in Real Time Control as a possible alternative to be included in their LTCP. This paper presents the result of a RTC study for the Regions 2 and 3.The RTC Strategy analyzed and optimized in this study is made up of 8 control sites using a total of 72 MG additional inline storage capacity. Performance was compared with simulations of the system behavior under reference conditions. Each scenario has been simulated using 4 reference storms (1-month, 3-month, 6-month and 2-year events) from the MSD reference storm approach.For the four events simulated, an overflow reduction of 70 to 90 MG was found. Global RTC brings to all CSO sites an overall reduction of 64% in average annual overflow. Most interesting, the percentage of capture approaches the 85% goal of the presumptive approach with 83%, 75% and 74% capture for the most important CSO sites.The results from this first study show that a global RTC strategy applied to Regions 2 and 3 could enable a more efficient use of the existing system capacity and reduce the overall cost of the LTCP. Preliminary cost estimations show relatively low cost when compared to alternatives that form part of the actual MSD CSO LTCP. When using unit cost per gallon of avoided annual CSOs, for each solution developed, most of the actual solutions are close to 0.05 or 0.10. In comparison, conceptual cost estimates show that for solutions using RTC and in-system, the average unit cost is 0.006 per gallon of avoided annual CSOs. And in all cases, it is less than 0.013.