Model “green” alleyways in Chicago have been re-surfaced with permeable or porous pavement that allows water to seep through asphalt, concrete, stone, or plastic. After filtering through a stone bed, the water can then recharge local water tables, instead of becoming polluted runoff that flows off the road into streams and rivers. The new alley surfaces are made with recycled material and light-colored pavement that reflects heat, keeping them cool on hot days and reducing the “urban heat effect.” The alleys also use energy-saving overhead lighting that directs light downward to minimize light pollution.

The new initiative is one of the most ambitious public street-retrofitting projects in the nation. “The alley is not only functional, but an educational green landscape that is helping a city experiment with design and different ways to handle water,” Michael David Martin of Iowa State University’s Department of Landscape Architecture told the Tribune. Chicago expects to have 46 green alleyways completed by the end of the year. This story was produced by Eye on Earth, a joint project of the Worldwatch Institute and the blue moon fund.