Alleys offer opportunities for green infrastructure by replacing impervious pavement with pervious materials and landscaping. Cities can also swap older lighting with energy efficient fixtures.
Benefits & Problems Addressed
Stormwater management: Instead of creating polluted runoff, alleys can absorb and filter rainwater. With new materials and greening, alleys are also more attractive.
Urban heat island abatement: Replacing heat-absorbing dark pavement with light, porous alternatives, together with landscaping, reduces temperatures.
Noise abatement: landscaping and new materials can reduce noise from alley activity.
Reduced icing in winter: Melting snow seeps into porous pavement rather than icing over at night.
Material recycling: Cities can recycle construction waste and rubber into new paving materials.
Tips & Techniques
Getting started: Begin with a pilot project and willing landowners to determine the best opportunities. Alleys prone to flooding or in need of immediate repaving are good, first candidates. Document existing conditions to perform before-and-after studies. Contact manufacturers who can donate and test the market for pavers & lighting fixtures. Brand the effort to raise support and awareness.
Materials: Replace conventional pavement with newer models (porous asphalt, porous concrete, pavers, recycled pavement or combinations). Where heat islands are a concern, use lighter colored and plant materials. Make sure to plan for activity: heavy vehicles will need structural support and some materials may produce noise. Plan for snow plowing as well as room for plowed snow.
Pre-construction: Working with the city or county, determine who uses the alley and make arrangement (e.g. trash collection). Take skeptics on a walking tour to point out existing conditions like flooding, pollution & noise. Consider a "block party" so neighbors and others interested in green infrastructure learn about the project, its benefits and to document concerns. If a pilot project, invite classes (colleges, High School). Plan for re-routing trash collection, deliveries, access and emergency response.
Landscaping: Small rain & linear gardens can be an option (though choose design and plants that will not become a home to nuisance species of plants and animals). Small trees can also be used as long as they will not impede activity like electric lines & solar collectors.
Construction phase: Clearly mark the re-pavement process and expected time frames for disruption.
Maintenance: Pavers will need on-going maintenance (over time dirt accumulates within the cracks, reducing the infiltrative performance).
Hot Buttons: Disruption during construction, on-going maintenance. Renovated alleys can attract more bike and foot traffic.
Resources
Green Alley Handbook, Chicago IL US
Image: Flickr/cartosmaj