There are many ecological technologies that can make a street green, but the key element is being "flexible, adaptable," said Neil Weinstein, executive director of the Low Impact Development Center, a non-profit organization dedicated to promoting the use of green infrastructure in the built environment, at a session organized by the National Building Museum. Weinstein, who is a licensed engineer and landscape architect, was co-chair of an American Society of Civil Engineer (ASCE) conference on green streets, and through the LID Center, has been a pioneer in green infrastructure, so his take is worth hearing.

Weinstein said there are lots of different technologies both landscape architects and engineers are using to make streets greener, including deeper street tree pits; compost-amended soils; permeable sidewalks, bikelanes, parking lots, and streets; and bioretention systems, including bioswales. These systems create not only "complete streets" that offer equal access for pedestrians, bicyclists, and cars, but are also ecological systems that manage stormwater.

More than a decade ago, Weinstein was involved in creating the first green street in Washington, D.C. on 8th street, which features a "permeable structured swale" along the sidewalk. Since then, the green street movement has grown, with some even looking at "green highways" that can offer conservation and ecosystem protections, include recycled or reused materials, and provide "watershed-driven" stormwater management. 

Perhaps one sign of the growing demand for green streets is that there are more 25 rating systems offering points or credits to enable these systems, said Weinstein. In fact, Envision, a new one created by the Institute for Sustainable Infrastructure (ISI) in collaboration with the Zofnass program for sustainable infrastructure at the Harvard University Graduate School of Design, was just released. Envision, which was largely designed by a consortium of engineering organizations and is primarily aimed at engineers, seeks to provide a "a holistic framework for evaluating and rating the community, environmental, and economic benefits of all types and sizes of infrastructure projects." ISI says that the Envision can also be used by landscape architects and architects, planners, community groups, regulators, and policymakers for "roads and bridges, airports and waste treatment facilities, ports and refineries, high rise buildings and electricity grids." 

With or without rating systems, the LID Center has had some recent success designing and implementing green streets. In the D.C. area, the Edmonston green street has gotten lots of attention. Financed in part by E.P.A. stormwater management grants, the project is increasingly viewed as an easily-replicable model. Weinstein said the project involved putting this community's main street on a "road diet," narrowing the space for cars in favor of new bioswales, permeable sidewalks, and bicycle lanes that "better tie into natural systems." He said this project and others demonstrate how useful it is for local government to move from a "prescriptive" approach that dictates what needs to go where to a "performance-based" approach that asks what is needed to solve environmental issues.

Still, there's more work to be done to make green streets mainstream. Within national standards organizations, there should be a move towards "concurrence (not consensus) about new approaches and materials." Local demonstration projects "that ask the right questions" are still needed to show how national models can be applied to the unique conditions of local communities. Communities need to see and understand how these green street systems actually work.

Image credit: Edmonston Mayor Robert Kerns demonstrates permeable pavement / Greg Dohler. The Gazette