The roof of the Main Post Office in Chicago is covered with a 3.5 acre park that absorbs excess rain water via native plants..
By Lois Kimmelman, LEED AP
Two Roaring Twenties-era structures in the Chicago area are meeting that challenge by collecting and conserving stormwater on a grand scale.
Dominican University
The entry gate to Parmer Hall.
In 2007, while working on the blueprints for a new science building, Parmer Hall, Dominican University in suburban River Forest, Illinois, discovered a perfect source of water for air-conditioning in Parmer Hall: a cistern buried under planks and debris in the basement of the old science building. Out of commission and out of sight for half a century, the huge, 60,000-gallon concrete cistern was originally used to collect rainwater from campus gutters and downspouts, which was then pumped out into the municipal sewer.
Project engineers and architects had a “eureka moment” when they realized that the old cistern, constructed in the 1920s in what is now known as Magnus Arts Center, could be reactivated and expanded to collect and reuse water campuswide. The cistern would not only be a repository for campus rainwater, but its contents could be augmented by a well to supply water even during dry times. And what better use for all this water but to help cool Parmer Hall, as well as keeping the soccer field and lawns green? To this end, a new well was installed at the cistern, and underground piping to connect it to Parmer’s mechanical water system and the university irrigation system.
Today Dominican realizes a savings of up to 6 million gallons of water per year due to this imaginative reuse of an old technology. The cistern, coupled with other water-saving features—for example, a bioswale plus over 200,000 square feet of permeable paving in Dominican's parking lots—prevent rain from escaping off site.
Old Post Office
Against all odds, the old Main Post Office in the heart of downtown Chicago has been brought back to life after sitting idle for over two decades. Filled with antiquated mail-sorting machines and haunted by the ghosts of old postal workers, it was gutted and reopened in 2019 as the home of Walgreens and several other businesses. The historic landmark built in the 1920s is now crowned by a 3.5-acre rooftop park that includes walkways through fields of native perennial plants and grasses.
During construction, over 40,000 individual plants, representing more than 50 species, were placed in a specially formulated, six-inch layer of lightweight soil mix that wouldn’t overload the roof (much of the rooftop material was flown in by helicopter). Like a mega-sponge, these fields absorb moisture and filter out pollutants, while preventing more than 250,000 gallons of stormwater from entering the City’s storm sewer each year.
To add to the building’s green buzz, three colonies of honeybees have set up shop on the rooftop as well; they produce up to 300 pounds of honey annually. The renovated Post Office project achieved LEED Gold certification.
Read more about historic buildings getting a green makeover on Lois Kimmelman’s website/blog, Historecycle. She promotes restoration and renovation, not demolition.