Hydrologic and hydraulic modeling of the Lawrence Avenue Underflow Sewer System

摘要

The Lawrence Avenue Underflow Sewer System is a small deep tunnel system located in the Northwest part of the city of Chicago. This tunnel system connects to the Main Stream Des Plaines Tunnel and Reservoir Plan (TARP) system. This tunnel was constructed to convey and store combine sewage in an effort to prevent combine sewer overflows (CSOs) and alleviate flooding in the city of Chicago, issues that are likely to occur during extreme storm events. The Lawrence Avenue Underflow Sewer System is characterized by unsteady flow conditions along with lack of geometric and spatial information of the pipe sewer network. This study herein focuses on the analysis of the system through the use of hydrological and hydraulic models. Two models, the Illinois Urban Hydrologic Model (IUHM) and the TARP Connecting Structures Model developed at University of Illinois Urbana-Champaign (UIUC) were used in this study in combination with the commercial software Storm Water Management Model (SWMM) $5.0$. In this study, analysis of the hydraulic response of the system to four historical storms and four design storms is used to assess its optimal operation. The storm event analysis highlighted that the Lawrence Avenue underflow sewer system has the capacity to convey and capture flows from each of the modeled storms. Simulations showed significant surcharge throughout the interceptor system for all the storms. Moreover, surcharge conditions existed in the deep tunnel system during the peak time of two of the simulated storms. Furthermore, the real time regulation of the gate showed to be beneficial for the system's operation. Not only allowed for the maximum storage of combined sewer in the tunnels without surcharge. But also the volume of water leaving the system is controlled based on the storage capacity of the tunnels. Lastly, real time operation of the gate, leaded to determine that if the gates needed to be set at a fix position the opening should not be less than $33$%, independently of the conditions presented in the downstream system to which the Lawrence Avenue Tunnel connects. This gate opening showed to prevent surcharge conditions and the subsequent geyser events in the tunnel.