Green alleys in Chicago and Montreal are bringing
sustainability to the back door.
By Adam Regn Arvidson, ASLA
The humble alley is perhaps the most utilitarian, most
neglected, and least loved urban space. Home to garbage cans, garage entrances,
and utility poles, these little streets are crucial to the functioning of the
cities that have them. They are not, however, typically seen as places for
sustainable design. Alleys, though, just like any other hard surface,
contribute stormwater to often overburdened municipal sewers, and exactly
because of the utilitarian nature of alleys, the water that runs off them is
This would seem to make the case for considering alleys in
any citywide stormwater management plan, but that, in fact, is rarely done. In
most cities, alleys are simply pitched to the center, allowing water to course
out into the street and the nearest catch basin. Wherever the slopes don’t work
quite right, extra water ends up in basements or adjacent yards. Two North
American cities, however, are reconsidering their alleys. Chicago and Montreal
have been converting these narrow strips of pavement into spaces that
infiltrate water, help mitigate the urban heat island effect, and create more
usable area for residents. Though the two programs are quite different, they
both offer lessons for other cities considering green alleys.
“We have a lot of alleys,” says Janet Attarian, “the
equivalent of five Midway Airports.” Attarian is project director of the
Streetscape and Sustainable Design Program for the Chicago Department of
Transportation (CDOT). She says many of Chicago’s nearly 19,000 miles of alleys
have developed flooding problems and that all of them drain stormwater into an
already overtaxed sewer system. The city, as is well-known, also has an
environmental mandate from the mayor’s office. Thus the green alleys program
was born. The task: to retrofit aging infrastructure in a sustainable way.
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