An Optimization Planning Framework for Cost-effective Wet-Weather Planning A Case Study From Evansville, Indiana

The Evansville Water and Sewer Utility applied an optimization approach to screen potential alternative technologies for reducing the frequency and volume of combined sewer overflows. The project team defined a range of potential locations and sizing options for technology alternatives deemed technically feasible. The baseline EPA-SWMM hydraulic model was set up to support automated evaluation of these alternatives, and the optimization linkage formulated to convert optimization output into the hydraulic model, calculate life-cycle costs for selected alternatives, and extract results from the hydraulic model to characterize alternative performance. A hybrid optimization approach was applied, using over 100 user-defined specific technology combinations to seed the automated optimization using the Shuffled Frog Leaping Algorithm. The optimization process resulted in identifying a range of best-performing solutions across a range of investment levels, enhanced system understanding, and increased confidence in specific solutions that were subsequently developed further for Evansville's Integrated Overflow Control Plan.