Abstract
The Mainstream-Des Plaines TARP system is a critical resource for protecting water quality and reducing flooding in Chicago and surrounding communities. Comprised of a network of 66 miles of Deep Tunnels, and the 3.5 BG McCook Reservoir, the TARP system intercepts combined sewer overflows and relieves regional drainage infrastructure for the City of Chicago and 37 suburban communities.
Hydraulic geysers have been a recurring challenge for operating the Mainstream TARP system since its inception in the 1970s. High rates of inflow into the tunnel system combined with rapid pressurization of the large diameter tunnel systems occasionally result in powerful, dynamic geyser events where an air-water mixture is pressurized above grade level, endangering property and human health. Despite numerous past studies of geysering, specific factors contributing to geyser occurrence remain challenging to understand.
This seminar will describe recent modeling analysis of recent geyser events to better understand the factors contributing to geyser occurrence, and to explore mitigation measures to reduce the frequency and/or intensity of geyser occurrence. Confluency and the University of Illinois have worked together with MWRDGC to apply a multi-scale modeling approach to analyze this complex phenomenon. Detailed radar rainfall data processing was performed to load the Illinois Urban Hydrologic Model and Chicago trunk sewer model to simulate system hydrology, and the hydraulic routing of flows through trunk sewers and the tunnel system. Results from this system-scale analysis were loaded to the Illinois Transient Model (ITM), a multi-purpose finite volume model capable of representing pressure wave propagation within the tunnel system at the short timescales necessary for resolving the hydraulic phenomena associated with geysering events. The ability of hydrologic and hydraulic models to replicate the macro-scale system response to widely varying rainfall conditions will be discussed, as well as specific hydraulic factors concurrent with field observations of geysering events. Alternative conditions modeling of alternative operations and/or structural mitigation measures will be explored.
Bio
Mason Throneburg is a hydraulic modeler, project manager, and software developer with a passion for applying advanced data analysis techniques to help understand complex infrastructure operational and planning decisions. He is deeply experienced with the hydraulic modeling of large urban collection systems, and was a key developer of both the Chicago Trunk Sewer model and Chicago All Pipe model, as well as very experienced user of the District’s CS-TARP model. In 2019, he co-founded Confluency, which has developed a cloud-based simulation and analytics platform that enables continuous insight into the performance of ever-changing and evolving water and wastewater networks. In his free time, he enjoys reading, biking, and exploring the Chicago outdoors with his family.