Updated Bulletin 70 Evaluation, Stormwater Storage Design
Team Members Heading link
- Layan Abu Than
- Devonte Evans
- Peter Morris
- Mark Regalado
Advisors: Dr. Christopher B. Burke, PE; Luke Sherry, PE, CFM
Project Description Heading link
Within the past decade, the region of Northeastern Illinois has experienced more frequent severe storm events that have resulted in damages of approximately $1.5 billion. Typically, the rainfall depths and intensities exceeded the design return period values of the Illinois standard for extreme rainfall events, Bulletin 70. In response, an update to Bulletin 70 was developed in 2019 by the Illinois State Water Survey, resulting in increased rainfall depths and updated rainfall distributions. This is the first update to Bulletin 70 since the standard’s original development in 1989, and the updated standard has been adopted by regulatory agencies to go into effect in 2020.
A hydrologic and hydraulic analysis of the McDonald Creek Watershed, which is located in the Northwestern Chicago suburbs, will be evaluated using the updated Bulletin 70 depths. The analysis will evaluate the riverine system, as well as the Lake Arlington Flood Control Reservoir, to determine the effects of the new rainfall depths on the flow rates, flood elevations, and reservoir performance of the watershed.
A hydrologic and hydraulic analysis of the McDonald Creek Watershed was completed in 2010 using the 1989 Bulletin 70 rainfall. That modeling will be updated using the 2019 Bulletin 70 rainfall depths and distributions so that the performance of the system with the new standard can be determined. The US Army Corps of Engineers’ (USACE) HEC-HMS software will be used for hydrologic modeling of the watershed, and the output of the hydrologic model will be used as inputs to the USACE HEC-RAS hydraulic model to determine the stream and storage response. ArcGIS software will be used to map the results of the updated analysis. A design for improved stormwater storage will be produced adhering to the updated standard. Both online and offline storage schemes will be evaluated to determine the most suitable design alternative to accommodate the increase in flow rates and flood elevations. Conceptual construction cost estimates will be developed for those storage alternatives.