Source: Google Images
Image: City of Chicago
http://www.cityofchicago.org/dam/city/depts/cdot/Green_Alley_Handbook_2010.pdf
http://www.cityofchicago.org/dam/city/depts/cdot/Green_Alley_Handbook_2010.pdf
Chicago is the alley capital of America with nearly 2,000 miles of small service streets. Experts say Chicago's Green Alley initiative is among the most ambitious street makeover plans in the country. An alley-laden city prone to flooding and with runoff water straining its sewer system, Chicago decided to retrofit its alleys with road-building materials which are environmentally sustainable.
Source: Google Images
Image: City of Chicago
Originally unpaved, most of Chicago's alleys had no drainage structures or connection to the sewer system, leaving rainwater to simply grain through the gravel or cinder surfacing. As alleys were paved over with with concrete or asphalt, Chicago alleys became covered by 3,500 acres of impermeable surface. Flooding became a problem for properties abutting ally right of ways (Fiegel, 2008).
Source: Google Images
Image: City of Chicago
The initial six pilot projects approved by Mayor Daley in 2006 were yet another eco-friendly improvement in storm water management, heat reduction, material recycling, energy conservation and glare reduction on behalf of The City of Chicago's Department of Transportation. Storm water runoff into the storm sewer system was reduced by up to 80%. Flooding of adjacent properties was also reduced, as well as the urban heat island effect. One of the great successes of the Green Alley Program is how quickly it moved from pilot to program. In 2007, 46 alleys were transformed, and every alley that CDOT constructed incorporated some aspect of the program. The city plans to continue this practice well into the future.
Source: Google Images
Image: City of Chicago
In green alleys, water penetrates the soil through the pavement, which is made of permeable concrete or porous asphalt. The water is then filtered through stone beds and recharges the underground water table instead of becoming polluted runoff in rivers, streams and even Lake Michigan.
The four pilot approaches consist of:
1. Green pavement materials with conventional drainage: a properly graded and pitched alley surface directs storm water towards the center of the alley, into the adjacent streets, and finally into the existing sewer system. Optional inlet structures connected to under drain pipes assist the system during heavy rains.
2. Full alley infiltration using permeable pavement: the entire alley surface integrates permeable pavement materials (permeable asphalt, permeable concrete or permeable pavers).
3. Center alley infiltration using permeable pavement: the alleyway is pitched to direct storm water towards permeable pavement materials at the center of the alley. optional inlet structures connected to underdrain pipe assist the system during heavy rain events.
4. Green pavement materials with subsoil filtration systems: the concrete alleyway is pitched to inlet structures with perforated sides, which allow storm water to seep into an infiltration trench.
Source: Flickr
Image: jmogs
Some residents felt the city should have first focused their green efforts on a more comprehensive recycling program. In 2013, Mayor Rahm Emanuel expanded the Blue Cart Residential Recycling Program citywide, adding to a vast array of "green initiatives" which make Chicago one of the most environmentally conscious cities in the country. It is currently ranked at number nine, just ahead of Austin, Texas and quickly on the rise. Other green programs include: an expedited permitting process for builders using green technology, 2.5 million square feet of rooftop gardens, over a half-million new trees, garbage trucks and street sweepers with emission-control devices and more than 200 acres of parks.
The Green Alley Handbook:
