Chicago's Green Alley program is one of many environmentally friendly initiatives put forth by CDOT.
Green alleys incorporate a variety of characteristics:
- Permeable pavements (asphalt, concrete or pavers) that allow storm water to filter through the pavement and drain into the ground, instead of collecting on hard surfaces or draining into the sewer system. The pavement can be used on the full width of an alley, or simply in a center trench.
- Catch basins connected with perforated pipe and installed in retention trench to capture water and funnel it into the ground
- High-albedo pavement, a lighter-colored surface that reflects sunlight instead of absorbing it, helping reduce the urban heat island effect
- Recycled materials, such as concrete aggregate, slag and recycled tire rubber
Other green alley techniques include using proper grading and pitch to facilitate drainage, and using dark sky-compliant light fixtures to reduce light pollution and provide uniform illumination.
Green Alleys are part of CDOT's "green infrastructure" -- which includes recycled construction materials, permeable pavements and other efforts.
The program began in 2001, and through 2017, more than 300 Green Alleys have been installed.
The handbook below provides an overview of CDOT's Green Alley program.