With a mandate to account for total building mass and footprint, and that held stormwater be released within 48 hours, the client required something special: a “blue” roof.

Very near Lake Michigan in Chicago, Northwestern Medical Center faced several challenges in bringing a new campus building to life. Designed by Perkins+Will, the project involves a phased construction where a 14-story base building is presently under construction; a 20-story tower addition is planned for construction in 5 to 10 years. Since the project is built-out to all property lines there are no at-grade landscape areas, which presented a particular challenge given the city’s Dept. of Stormwater Management permit requirement that the project account the total building mass and footprint. Translation: 10,000 cubic ft. of stormwater detention was required. Further, city code required that this volume be released through the flow control drains within 48 hours. This challenge was met with the implementation of a pair of “blue roofs.” A creation of American Hydrotech, the detention system is a composite of materials and products that can hold, and slowly release, large volumes of stormwater. According to Hydrotech’s Richard Hayden, the blue roof lies below layers of pavers and vegetation, with drains that utilize an insert with an orifice to regulate the flow of water out of the drain.