From: Alana Herro, Worldwatch Institute, More from this Affiliate
Published December 3, 2007 09:09 AM

Chicago’s Alleys Turning Green

A new initiative will help make Chicago's 1,900 miles (3,000 kilometers) of alleyways more sustainable. The miniature streets behind homes and buildings, used mainly for garbage collection and parking access, keep main roads cleaner and less congested but are prone to flooding. The city’s innovative Green Alley Program promotes improved construction techniques and materials that can improve drainage, reduce runoff, and relieve strain on the city’s aging sewer system.

Model "green" alleyways in Chicago have been re-surfaced with permeable or porous pavement, a relatively new technology 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.

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Retrofitting the alleys to be more green can cost two to three times as much as the conventional method. But the alternative option—connecting Chicago's alleys to the city’s sewer system—would be equally expensive, with fewer benefits, according to The Chicago Green Alley Handbook. There are indications that permeable paving can be replaced less frequently than the older alleyways and will save residents the costs that come with frequently flooded basements. Chicago has more miles of alleyways than any other city in the world—enough to pave five midsize airports.

Experts say 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. View the complete archive of Eye on Earth stories, or contact Staff Writer Alana Herro at aherro [AT] worldwatch [DOT] org with your questions, comments, and story ideas.

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