Alternatives Analysis and a 12-Month Design-Build Reduce Overflows

The Village of Wilmette is a fully-developed, mature suburb of Chicago and a tributary MWRDGC community. Village officials regularly received reports of basement backups during major rain events and were looking for a way to mitigate these backups. 

The first step in the program was to develop a system-wide hydraulic model to study the system, evaluate capacity under various design storm scenarios, and identify solutions to address capacity issues. The village system was not only undersized due to recent tear-downs but also experiencing backflows from its connection to the MWRDGC interceptor.  After a cost-benefit analysis, wet-weather storage presented the best value alternative. 

Selecting the right site for the storage tank, acquiring MWRDGC permits, and constructing the 5.5 million gallon underground tank within a 12-month timeline posed unique challenges. Design-build proved to be the best solution for the construction of backflow prevention measures at the MWRDGC interceptor connection, the tank, and a pump station designed to divert flows from the collection system based on flow levels and empty the tank automatically when flows slow. 

Since the West Park wet-weather facility went live, reported backups have been negligible. Engineer-led design-build allows the project to be completed within 12 months, allowing community members to fully use the sports fields built on top of the tank.

Project Metrics

• 2016 APWA National Project of the Year award recipient
• The 5.5 MG concrete tank included backup prevention, check valves, pump over lift station, a pump-out lift station, gravity sewers, and water line extension for tank maintenance.
• Design and construction were completed under budget within the required 14-month window.
• West Park was restored and improved to an artificial turf multi-use facility in time for the spring athletic season.