Maximizing Your Budget Impact – Optimized Phasing of Projects to Accelerate the Environmental Benefits of Reduced CSO Volumes

This paper introduces the concept of Affordability Optimization as a key step in planning wastewater collection system capital improvement plans (CIP). Affordability optimization (AO) is critical to ensure the utility is maximizing the impact of its precious capital budget to achieve the greatest possible returns as it proceeds to implement its collectionsystem master plan or long term control plan (LTCP) projects.The paper describes a case study for South Bend, Indiana where Optimized Decision Support (ODS) was used to review and revise the City’s existing CSO LTCP to develop an optimized LTCP. In effect, the South Bend optimization project represented a value-engineering study aimed at improving the hydraulic performance of the LTCP while also reducing itsoverall cost. Once the optimized LTCP was developed the next step was an Affordability Optimization. The AO analysis identified which of the capital and green infrastructure projects in the 20-year optimized LTCP should be completed in each 5-year phase to maximize overflow reduction within the available budget. This analysis was highly rigorous and effective in phasing projects.In 2011 the City of South Bend, Indiana was completing negotiations on its Consent Decree with Federal and State regulators aimed at alleviating the frequency and volume of CSOs into the St. Joseph River. Developed based on extensive trial-and-error alternatives analysis, the City’s EPA-approved CSO LTCP cost of approximately $500 million would burden its rate payers with rising monthly utility bills.To ensure rate payers were receiving the best value-for-money, the City undertook a detailed optimization using the Genetic Algorithm (GA) based software, Optimizer WCS. The optimization technology enabled an exhaustive analysis of conveyance, storage, Real Time Control (RTC) and green infrastructure alternatives. Optimizer WCS was coupled with the City’s combined sewer system hydraulic model and updated capital and O&M cost data for the range of improvement options.Optimizer could automatically evaluate more than one hundred thousand alternative improvement configurations (trial solutions) in a single optimization run to minimize total life cycle cost, and then run multiple times to undertake critical sensitivity analyses.In comparison to the City’s 2011 LTCP, the 2012 optimization project achieved cost savings on the order of 30%(over $100 million), eliminated an additional 30% CSO volume, eliminated an additional three CSO locations, and selected extensive city-wide green infrastructure that contributed to approximately 10% of the total cost savings achieved.