EVALUATION OF INFLATABLE DAMS IN CSO ABATEMENT

As part of its Long Term Combined Sewer Overflow Control Plan (LTCP), the Philadelphia Water Department (PWD) has proposed implementing a number of technology-based capital improvement projects to the City's sewerage to further increase its ability to store and treat combined sewer flow, decrease CSO volumes, and improve receiving water quality. A major component of the proposed capital improvement projects is the installation of an inflatable dam operated under real time control (RTC) in the City of Philadelphia's Southwest Drainage District (SWDD). The RTC structure will provide the PWD with the ability to optimize the use of available in-system storage during wet weather and to minimize overflows to the receiving water.In the planning phase of the project, the U.S. EPA's Storm Water Management Model (SWMM) Extended TRANsport (EXTRAN) module was used to develop a control logic for the inflatable dam to optimize storage utilization and minimize potential flooding impacts of the project. A continuous simulation EXTRAN model was modified to incorporate the inflatable dam, drain-down gate and their associated control logic. In order to characterize the benefit of the inflatable dam project, continuous simulations were performed to quantify the CSO reductions on an average annual basis. A 50 million gallon (70%) reduction in average annual CSO volumes to the Schuylkill River is expected through the implementation of the capital project at this location.The paper documents the control logic development of the inflatable dam to optimize utilization of in-system storage and reduce CSO discharges, the development of the continuous simulation models used to quantify the average annual CSO reductions, and model simulation results.