The Chicago Department of Transportation’s “greenest street in America” initiative involves planting 95 drought-tolerant, native plant species in bioswales and infiltration planters to both reduce storm-water runoff and to create a strong sense of place. Chicago Department of Transportation
The Chicago Department of Transportation is upgrading two rundown street sections by rebuilding them with recycled materials, permeable pavers, bioswales, drought-tolerant streetscaping, and sustainable storm-water runoff solutions.
November 13, 2012—Last month Chicago unveiled the first phase of what it is billing as the “greenest street in America”—in reality stretches of two streets on the city’s South Side that are the beneficiaries of an innovative experiment not only in “green” street building but, more importantly, sustainable place making.
“The project was a concept before it was a project,” says Janet Attarian, a project manager for the Chicago Department of Transportation (CDOT). “Starting back in 2004 I really started to look at this idea of, what does it mean to say that you’re going to build a sustainable street. How do you go about that?”
The Washington, D.C.-based U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) program was there, to be sure, but at that point it was only focused on individual buildings—not on larger systems like roadways or infrastructure. (To read a Civil Engineering feature article on a model for a green street rating program, click here.) So Attarian and others at CDOT “picked a bunch of different categories we thought were appropriate … and then we started to think, ‘If you were trying to define platinum, how would you go about that?’”
They were interested in everything from material reuse to storm-water management to energy reduction. But first, they needed the demonstration roads. They found two at the southern edge of the city’s Pilsen neighborhood, a gentrifying, heavily Latino area with enormous cultural character—and industry to match. One street was Cermak between Halsted and Ashland. The other was Blue Island between Ashland and Western.
Chicago’s green streets project may divert up to 80 percent of the
typical average annual rainfall from sewers through bioswales, rain
gardens, and permeable pavements. Chicago Department of
But why these gritty stretches of the city’s Near South Side? “The infrastructure on these two roads was in very poor shape, and nobody had really done anything to make improvements for a very long time,” Attarian says. “We knew we weren’t going to have to force the scope of the project to accommodate what we wanted to accomplish. We knew that the work needed to be done, and it was just a question of how we did it, not whether we did it. It wasn’t like we were trying to put a square peg in a round hole.”
The second reason was that these were heavily trafficked, four-lane truck roads serving industry, schools, parks, and businesses. No dainty and empty side streets here—Cermak and Blue Island would put the viability of sustainable roads to the test. “If you can do it on streets like this you can do it on any street,” Attarian says.
The $14-million project was funded through the city’s Tax Increment Financing system, as well as grants from the Federal Highway Administration, Illinois Environmental Protection Agency, and Midwest Generation, a power company. The streetscaping features a variety of sustainable measures. More than 60 percent of the construction waste was recycled—the sidewalk concrete itself was made with 30 percent recycled concrete, and the asphalt was composed of ground tire rubber, reclaimed pavement, and recycled asphalt shingles.
In addition, the streetscapes feature 95 drought-tolerant, native plant species, and have a sophisticated storm-water drainage system that consists of permeable pavers, bioswales, and infiltration planters. The remediation systems are expected to divert up to 80 percent of the typical annual rainfall. Additionally, pedestrian lights are powered by wind and solar generators, and the streetscapes will feature the first LED light poles in the city.
The demonstration project, which involves portion of two streets on
the city’s south side, includes pedestrian lights powered by wind
and solar energy. Chicago Department of Transportation
But the real innovation is on the ground.
To tackle the heat island effect, engineers sought a concrete light enough in color to reflect light rather than absorb it. They were shooting for a solar reflectance index of 29, which would reduce the heat gain 42 percent from the city’s baseline.
But in a city with extremely rugged weather, the pavers wouldn’t work if they were covered in grime—they needed to stay reflective. But how? Attarian found the answer at a conference: photocatalytic cement.
David Leopold, LEED-AP ND, a project manager for Knight Engineers and Architects, a consultant to CDOT based in Kinley Park, Illinois, explains that photocatalytic cement is “basically an addition of titanium dioxide to the cement that goes into the concrete.” He adds that it was originally developed for architectural applications—specifically Richard Meier’s 2003 Jubilee Church in Rome. Because the Eternal City has serious air pollution, church officials wanted a structure that would stay white over time and clean itself. When catalyzed by sunlight, the tiny particles of titanium dioxide eat up pollution and grime. Not only does it help “self clean” the pavers, it has an additional benefit—it cleans the air up to 8 ft above the ground by absorbing nitrogen oxide, which makes up about 30 percent of tailpipe emissions.
The downside to photocatalytic cement is the cost. A 5 in. thick catalytic paver would have been cost prohibitive. But the CDOT designers achieved nearly the same benefits from a thin half-inch layer of photocatalytic cement at the top of the pavers. While the permeable pavers were not deemed ready for the wear and tear of being on the roads’ through lanes, they were installed on the bike lanes and the parking lanes.
The CDOT has also made clear its commitment not just to clever design and engineering solutions but also to building partnerships. For instance, the CDOT worked with Juarez Community Academy, a high school on Cermak that was embarking on a new addition. “We had a really narrow sidewalk condition,” Attarian says. “We think this should be a place. It shouldn’t just be a street next to a high school or a high school next to a street. But we should really think about how we can make [a] place together.”
So the school and CDOT worked together to fashion a permeable plaza with a zero-depth water feature as well as seating and a wind and solar kiosk. The plaza, school roof, and street will work in combination to remediate storm water. Additionally, the CDOT narrowed sidewalks from 20 to 15 ft—to discourage light commercial trucks from parking on the curb—and built a pedestrian refuge island on Cermak next to the school to make it safer for kids to cross to the bus stop across the street.
City agencies will be monitoring the performance of the streets over the next few years, and the city hopes to apply many of the streetscape lessons into its sustainable urban infrastructure guidelines.
As Attarian notes, making green streets is about more than engineering a better cement mix. Sustainable design, she says, “requires that boundaries be crossed,” meaning city agencies, local businesses, schools, and other community stakeholders all have to be brought on board.
“Sustainability is not just about permeable pavement and bioswales and recycled content,” Attarian says. “It’s also about complete streets, it’s about safety, it’s about mode share and mode hierarchy. It’s about great places and spaces. Real sustainability is when you bring the two together.”