258 - Optimization of LID in a Chicago Catchment using EPA- SWMM

Combined sewers can overflow during heavy rain and snowmelt events, causing untreated sewage to be discharged into local waterways. To better understand combined sewer overflows in Chicago, we combined an existing Environmental Protection Agency Storm Water Management Model (EPA-SWMM) model with Normalized Difference Vegetation Index (NDVI) derived from LandSat imagery to simulate hydrologic and hydraulic flows associated with different land cover types. The EPA-SWMM model was adapted to incorporate different land impervious fractions and water quality data from the Racine Avenue Pumping Station (RAPS) Service area, based on an existing model of the Tunnel and Reservoir Plan (TARP) system hydraulic flows in Chicago. We vary low impact development (LID) placement in the EPA-SWMM simulation using multi-objective optimization to minimize both water quality impacts and discharge quantities. Total suspended solids (TSS) was analyzed as a water quality metric indicative of nutrients, bacteria, and pesticides in the water. Through this study, we aim to determine efficient placements of LID to improve water quality through a case study of RAPS Service area. Findings from this study can directly be utilized to reduce the frequency and severity of overflows in the Bubbly Creek region of Chicago, and provide methods for optimization of LID design in similar cities with combined sewers.