By Steven Peck, GRP, Honorary ASLA
Water is a crucial aspect of the urban ecosystem and one that is gaining attention in cities around the world.
Green roofs and walls are key components in restoring vital water resources in urban environments, and improving the health and well-being of communities. Local and state governments throughout North America are beginning to realize the value of improving urban water through green infrastructure. The City of Philadelphia and Pennsylvania Horticultural Society, co-hosts of the CitiesAlive Green Roof and Wall Conference, have developed a multi-billion dollar plan to develop an integrated water management system that will include green roofs and walls, and other forms of green infrastructure. They plan to invest more than $2 billion over the next 25 years to produce more than 9,000 “green acres” to manage their stormwater.
The United States Environmental Protection Agency (EPA) is also connecting citizens across the country through its Urban Waters Movement, by empowering communities to learn about their local waterways, share ideas and solutions, and act to clean up and improve access to those waters with tools like green roofs and walls. In April, the EPA launched an initiative to promote green infrastructure, partnering with 10 cities throughout the country.
CitiesAlive will explore the full potential of living green infrastructure through expert panel discussions and meetings with experts highlighting the latest science on green roof and wall performance research. It will also feature an industry trade show, tours of extraordinary green roof and wall projects, and award-winning green roof designs. Highlights of award-winning green roof and wall projects for 2011 include Brooklyn Grange, and a living wall in Phoenix.
Photo courtesy of Brooklyn GrangeBrooklyn Grange is a pioneer in the emerging niche of rooftop agriculture. The 40,000 square foot commercial farm is located on the rooftop of a six-story building in the dense urban environment of Queens, N.Y. The project integrates traditional intensive green roof design with organic agriculture and permaculture principles to create a commercially viable urban farm. In its first abbreviated growing season the farm raised 13,000 pounds of produce, a number that will be topped in 2011. In its second season (year) of full production, the farm is producing dozens of varieties of vegetables and herbs, and is selling the output to local restaurants and direct to the public through farmers markets and community supported agriculture (CSA) shares. This local distribution lowers the fossil fuel consumption by transportation. The farm participates in community outreach programs by providing tours and volunteer opportunities to local residents, schools, community groups and other community members who otherwise would not have an opportunity to experience an organic farm.
The green roof uses a 6- to 18-inch media depth depending on the location, using organic soil media by Rooflite mixed with compost. The roof is designed to use minimal resources. Food scraps, fallen leaves, wood shavings, and other biodegradables are collected from the local community for Brooklyn Grange’s compost program, and this further reduces the amount of inputs needed to maintain the growing medium. As well, the green roof system holds up to 1 inch of water in reserve, reducing the burden on New York City’s stormwater management system, and allowing for less frequent crop irrigation. The farm covers all the available space on the roof to maximize growing area and stormwater management capacity.
There is little doubt that projects like this will continue to multiply in cities across North America. Brooklyn Grange not only grows high-quality produce, but it has, in the words of its pioneer Ben Flanner, “become a critical community resource, bringing many people together to share in the labor and many benefits of rooftop agriculture.”
Phoenix living wall
Photo by Bill TimmermanIn a quest to make the desert city of Phoenix more comfortable, sustainable, and more in harmony with its natural environment, the leaders of this project created a habitat garden that thrives on the urban structure that embraces it. The living wall was inspired by the sheltered canyon habitats of the Sonoran Desert and the settlement of Hohokam Indians that lived on this site. It was proposed that the water the building produces — condensate from the air conditioning system — be used to support and allow nature to thrive within the urban desert context.
At its peak flow, the building generates more than 800 gallons of condensate water per day from 15 of its air-handling units. Typically, this water would be directed into the sanitary sewer system. Instead, it is collected, stored, and used for irrigating the garden. Condensate is harvested and stored in two collection tanks. One of the tanks is located on the second floor of the Convention Center, where a window to Building Condensate Collection Point is a visual display to conventioneers of the condensate collection point before its entry into the habitat garden. The condensate generation is directly correlated with seasonal irrigation demands of the garden.
The harvested condensate is UV-treated for purification, then pumped outside. In celebration of water’s movement, the purified condensate descends through three stainless-steel discs, trickling down an Arizona rain chain before its journey through a steel angle channel to nourish the living wall. The overstructure living wall is constructed of steel columns, wire mesh, lightweight soil, filter fabric, volcanic rock and then planted with a native seed mix and seedlings such as Octopus Agave, Yucca, Chuparosa, and Brittlebush. All water runoff from the wall is then diverted via runnels to the adjacent sunken water-harvesting garden. The gardens and architecture do more than just exist together; they each make it possible for the other to thrive. The building supplies the desert gardens with condensate water and the landscape provides comfortable outdoor gathering spaces.
You can also read more about these and other Award Winning projects by visiting [ital>www.greenroofs.orgwww.citiesalive.org<ITAL].
Steven Peck is founder and president of Green Roofs for Healthy Cities (GRHC), a membership-based industry association developing the green (vegetative) roof and wall industry in North America. GRHC’s mission is to increase the awareness of the economic, social and environmental benefits of green roofs and green walls, and other forms of living architecture through education, advocacy, professional development and celebrations of excellence. For more information, visit www.greenroofs.org