Supervisor, Hydrologic and Hydraulic Modeling Philadelphia Water Department
A significant component of Philadelphia Water Department’s Green City, Clean Water program is implementation of green stormwater infrastructure (GSI) to help reduce combined sewer overflow and provide pollutant reduction over the duration of the 25-year program and beyond. At each 5-year milestone, PWD must aim for a target cumulative amount of GSI implemented using public and private funding as well as partnerships. While we have rough estimates of the 5-year totals by drainage district and across the city, there is high uncertainty in the actual sewershed location, amount, and type of GSI that will be completed. To address this uncertainty, we’ve paired a previously described and updated hydrograph interpolation tool with an algorithm that randomly places GSI control in select sewersheds. The hydrograph interpolation tool approximates the performance of GSI using existing SWMM simulations and has since been extended to estimate annual CSO volume reduction. We demonstrate the paired tool/algorithm on a large section in the city. This methodology will continue to evolve and help provide insights to PWD regarding their GSI implementation. These insights will be especially useful for the publicly funded program where PWD has more influence over the location of GSI implementation.
