Metropolitan Water Reclamation District of Greater Chicago (MWRD) is undertaking an aggressive Phase II Stormwater Management study within a 27 square mile area in the South Side of Chicago that intricately examines urban flooding within a combined sewer system. The study is explicitly modeling the performance of green infrastructure to reduce basement backups, surface flooding, and the volume of water reaching the combined sewer system.
The detailed modeling of the system explores various methods to model and quantify the performance and cost of green infrastructure within the City's existing intricate InfoWorks model. Additionally, a detailed 2-D surface flow model is being developed for target sewersheds to explore the intricacies of overland flow to green infrastructure systems and their subsequent interaction with the combined sewer lines.
A key to the quantitative approach to evaluating the performance of "upscaling" green infrastructure at a broad scale is the integration of optimization software to evaluate over 500,000 potential combinations of both green and gray infrastructure solutions within the 27 square mile study area. Detailed costs and performance metrics are being evaluated and compared. Detailed pareto front curves are being developed for the range of solutions, comparing cost to performance. These intuitive graphs will provide MWRD and the City the breadth of knowledge to make informed capital improvement plans and policy decisions. The focus of the pilot study is to compare the range of performance and costs of a full suite of green and gray solutions, both traditional and innovative public private options. This study represents the first application of a genetic algorithm optimization evaluation on a combined sewer system to explicitly evaluate both green and gray infrastructure solutions.