Location: Westmont, IL
Product used: 3′-6″ SingleTrap
Number of pieces: 31
Number of systems: 1
Total water stored: 10,558.40 cf
Market: Commercial – Office/Warehouse
Project Details: The development involves the construction of a parking lot on a 0.5-acre vacant lot that was a gas station over ten years prior. To meet the DuPage County stormwater management requirements and the tenant’s needs to maximize usable area for parking, an underground stormwater detention system was installed.
Challenge: One of the main challenges of the project was that there was minimal headroom for water storage. The system was a retrofit design that needed to work around the existing site constraints, part of which were the existing hydraulic conditions. In addition, the design was limited by the relationship between the existing Normal Water Line and the finished elevation of the parking lot, reaching approximately 4 feet. Another challenge was to meet the county’s Volume Control Best Management Practices (VCBMP). Infiltration could not be used due to soil conditions, and, instead, the VCBMP required that the volume be directed to the ultimate discharge point, a pond located close to the site.
Solution: StormTrap designed a system with an interior baffle wall and an overflow weir. The first 0.5 inches of stormwater fulfill the VCBMP requirements by being stored in the interior baffle before overflowing to the detention area of the StormTrap. The design for the system was sufficiently versatile to meet the site restrictions and fit within the allotted footprint and maximize usable land area.
Thomas McCabe, P.E., Vice President of Spaceco, Inc., stated that the modular StormTrap design was a good solution for the site because of StormTrap’s design flexibility. “Together we were able to design and construct a solution, that could be built off-site, and easily assembled on site with little potential for installation error. The baffle wall system allowed us to provide the VCBMP storage and the detention storage within the same structure, and allowed the VCBMP to be restricted at a rate much lower than the detention system restrictor (i.e. volume control).”