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 0.5 acre parking lot on existing vacant land. In order to meet DuPage County stormwater management requirements and tenant`s requirements to maximize usable area for parking, an underground stormwater detention system was installed on site. Previously, the land was used for a gas station which had been demolished for over 10 years.
Challenge: One of the main challenges of the project was that there was a minimal headroom for water storage. The design was a retrofit and it was necessary to work around the existing site constraints. Part of that was accommodating the existing hydraulic conditions on site. In addition, the design was limited by the relationship between the existing Normal Water Line and the finished elevation of the parking lot, which was roughly 4 feet. Another challenge was to meet the county`s volume control BMP. Infiltration could not be used to meet the county`s Volume Control BMP requirements due to soil conditions. The ordinance required that the VCBMP volume be conveyed to the ultimate discharge point, which in this case was a pond located close to the site.
Solution: The stormwater management solution for this site was to custom built StormTrap with an interior baffle wall with an overflow weir. Water entering the system first fills the VCBMP section. Once the first 0.5 inches has been stored, the VCBMP section overflows to the normal detention area of the StormTrap.
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)” McCabe.