"The new South Air Traffic Control Tower and Base Building serves the new southernmost runway at O'Hare International Airport. The design provides a simple, economical and durable solution to meet the operational needs of the FAA, while addressing the interest of Chicago in creating a sustainable and iconic image. The most striking aspect of the design is the simple extruded shaft - a break from traditional slender-shaft bulb-top towers. The form evolved in response to two primary challenges: first, the City's classification of the tower as a high-rise structure and therefore, the life-safety requirement of two exit stairs (previously only a single stair was required); and secondly, the FAA's need for easy access and simple geometry in routing critical cabling/electrical/mechanical services from the Junction Level into the Cab directly above, with adaptability to change as technologies advance.
The solution inverts conventional tower plans by pushing core elements (elevator/stairs/shaft) to the perimeter, opening the center for direct access underneath the cab from the Junction Level rooms. The Tower's cast-in-place concrete shaft provides an economical, durable and non-combustible structure that facilitated speed in construction and reuse of standard formwork. The concrete edge is expressed as a ribbon that frames the glass-clad stair and visually ties the Tower with the Base Building and ground, all capped by the jewel-like cab.
The Base Building is organized in two parallel bars, one housing "equipment" spaces and the other housing "people" spaces. This strategy minimizes the building volume by providing higher clearances only where necessary, locates "people" spaces to the south to maximize daylight and views, and presents a friendly face to visitors from the entrance. Exterior mechanical equipment is discretely integrated into the design that is captured by the trellised extension of the building roof. The Tower is designed to achieve LEED Gold."