Worldchanging examines a city-wide program to green the alleyways of Chicago:
In 2006, the City of Chicago’s Department of Transportation instituted a program to reduce damage wreaked by alleyways. Conventional concrete and asphalt are gradually being replaced by a variety of permeable pavers, some made from recycled industrial wastes like slag and tire rubber. The new porous paving allows up to 80 percent of rainwater to infiltrate the subsoil, filtering out pollutants as water returns to the aquifer and, ultimately, the lake.