Urban alleyways. Grubby places that only scrappy cats or cop-show perps could love, right? Not in Chicago, where the Department of Transportation is giving them some serious TLC with its recently implemented Green Alley Program. This city-wide renovation initiative will offer some surprising environmental benefits and improve quality of life for residents.
Alleys may seem like a tiny fraction of a city’s infrastructure. But Chicago has more than any other city in the world – 1,900 miles of alleyways that translate to 3,500 acres of paved landscape. And traditional alley designs have been plagued with flooding problems that overwhelm the city’s sewers, plus they can worsen nighttime light pollution and trap heat in the summer months. In response to this, The Chicago Department of Transport has followed the lead of Portland and companies like Aviva and Johnson & Johnson who have introduced impressive green initiatives. The four basic components of Chicago’s Green Alley program are effective stormwater management, minimizing heat absorption, creating designs to reduce light pollution, and maximizing the use of recycled materials wherever possible.
Using permeable pavement along with proper grading for drainage is a key element of managing water runoff. Paving materials that let rainwater infiltrate the soil (instead of entering the sewers) allow groundwater to be recharged, and reduce unnecessary stress on water treatment plants. A variety of pavers are being used, including permeable asphalt and concrete materials as well as open grid-style pavement tiles.
The “heat island” effect that occurs when paved surfaces absorb the sun’s rays can substantially increase ambient temperature (and energy demand) in the summer months. The Green Alley program mandates the use of high-albedo (light-colored) pavements that absorb minimal heat. Benefits include reducing the need for air-conditioning in surrounding structures, and creating a better environment for vegetation growth.
Nighttime light pollution means that in most urban areas, a starry sky is a rarity. The Green Alley program requires the use of directional light fixtures that give street-level illumination for residents without shining upward into the sky. The new fixtures also provide a natural white light instead of the ubiquitous yellow glow seen from older sodium lamps.
Using recycled construction materials is also crucial for the Green Alley program, and creates cost savings while reducing raw material consumption and stress on landfills. Recycled concrete aggregate is being used in both foundation and surface layers, and reclaimed asphalt and ground tire-rubber can be used in pavement. Slag waste from steel production can also be used in the concrete components of the projects.
The Green Alley upgrades are being gradually implemented throughout the city. The Department of Transportation is also working with property owners to encourage their involvement in the Green Alley program, by providing maintenance advice and encouraging projects like rain gardens to complement the new alley designs.
(Via Chicago Department of Transportation)