Stakeholder Involvement Improves System Optimization

Optimization techniques using genetic algorithms, simulated annealing, and linear programming can help identify cost effective collection system improvements on a regional scale. Although these techniques will arrive at an optimized set of system improvements, they often lack the ability to incorporate real world knowledge into the objective functions, therefore producing the potential for unrealistic solutions. As a result, an optimized solution set (using linear programming for example) will often be modified in the end to accommodate real world issues such as public opposition, utility conflicts, environmental impacts, and political considerations (i.e., balancing competing needs), to name a few.This paper presents an optimization study developed for the Racine Wastewater Utility (Utility), which incorporates stakeholder involvement in the optimization process to address real world issues as they arose. This process led to an optimized and realistic system-wide solution. This paper will focus on the optimization techniques used, and will describe how stakeholder involvement was critical to the study's successful outcome.In Racine, recent wet weather events have produced system-wide basement backups and bypassing. As a result, the Utility developed a System Optimization Plan to mitigate these issues, which incorporated monthly Technical Advisory Committee (TAC) meetings into the planning process. The TAC, consisting of technical representatives from the ten (10) satellite communities, provided the Utility with input into the process, reviewed the results as they were completed, and provided real world information necessary to develop an optimized and realistic set of solutions.System optimization was achieved by modeling the Utility's interceptor system, using the collection system model MIKE URBAN. This model was extensively calibrated prior to evaluating alternatives, which included using the model's RDII and RTC modules and the Scenario Manager. Eliminating basement backups and system bypassing were defined as the evaluation / optimization criteria, as well as reducing peak wet weather flow at the wastewater treatment plant (WWTP) sufficient to meet a flow threshold of 231 MGD. The optimized solution consisted of a combination of storage and conveyance measures which best met the evaluation criteria: 1) the lowest unit cost for total bypass elimination (*/gallon removed); 2) the lowest unit cost for system-wide surcharge reduction (expressed as a system-wide average surcharge); and 3) the lowest total cost to meet a flow threshold at the WWTP.