Case Study Source: The Joint U.S.-Brazil Initiative on Urban Sustainability, part of the U.S. Environmental Protection Agency.
Green streets and alleys can help local governments green their transportation network by managing stormwater runoff within transportation rights-of-way.
Communities across the country are realizing the green potential of their streets. Streets and sidewalks can be the largest single category of public impervious cover in urbanized areas. To mitigate the impact of this impervious area, a number of communities, including Portland, Seattle, Chicago, and Philadelphia, have developed green street and alley programs to provide green stormwater management, while maintaining the primary function of the street for vehicles and pedestrians.
Philadelphia's Green Streets program is currently focused on planning, design, and implementation of projects within the combined sewer service area of Philadelphia. The Philadelphia Water Department provides technical assistance to other City agencies undertaking renewal projects within the right-of-way in order to encourage green stormwater infrastructure elements. A green streets manual is being developed, which will set a "green standard" for all streets within the City. To date, green streets have been inserted in 32 blocks of the City. Another 217 blocks of green street projects are currently in design or have complete designs, and will begin construction in 2012 or 2013.
How to Apply this Policy
A community could require that streets and alleys be retrofitted as part of any repair, maintenance, or other disturbance to the road, sidewalk, or transportation right-of-way that would provide an opportunity for street-level stormwater management. For example, green stormwater elements (such as bioswales, planters, rain gardens, and street trees) could be retrofitted into streets when on-street parking is added, sidewalks widened, or medians installed. Such green elements have been found to contribute to decreased crashes and injuries, and contribute to a more comfortable and visually interesting environment for all users. Traffic-calming elements like islands and curb extensions-all popular in creating complete streets-provide site opportunities for green stormwater elements.
Philadelphia Water Department
Fax: +1 (215) 685-6043
Mail: Office of Watersheds
Philadelphia Water Department
1101 Market Street, 4th Floor
Philadelphia, PA 19107
Centrally located in Seattle, the Taylor 28 residential mixed-use project included a zero-discharge streetscape with each planting area serving as a rain garden. Curb extensions are home to some of these rain gardens, and they also help to slow traffic, allowing bicyclists a safer ride. Numerous trees reduce the heat island effect and offset CO2, while widened sidewalks and increased pedestrian features make the street friendlier to those walking by. Such improvements complement Seattle's complete streets policy.