City Is Cultivating a Greener Future
Thursday, January 10, 2008
Two billion. That's the number of gallons of sewage and polluted rainwater that overflow from the District's antiquated sewer system into the Anacostia River each year.
It is, coincidentally, also the number of dollars it would cost to fix the problem in the long run, with the construction of underground storage tanks to hold the overflow water for treatment, says Jim Connolly, executive director of the Anacostia Watershed Society, a nonprofit environmental group.
But until that plan becomes a reality, the District is taking other, smaller measures to protect the Anacostia, the most recent being the installation of two green roofs on city government office buildings.
"A green roof is a series of layers that allow for plant life to grow directly on the roof," said Criston Mize, a designer at DC Greenworks, a nonprofit company that installed the District's two green roofs, at One Judiciary Square and at the Franklin D. Reeves Center on 14th Street NW.
It starts with the waterproofing membrane that is standard on most regular roofs, Mize said. On top are several inches of soil and plants, a garden of sorts that helps to capture and absorb rainwater, preventing it from carrying pollution into nearby rivers and streams. In between are other layers to protect the roof from the plants' roots.
"Historically, architects have designed buildings to get the water off of the roofs," said Barbara Deutsch, a green infrastructure consultant who has worked on and studied the District's "green" efforts for years. "But now, we're trying to figure out ways to store water on the roof to sustain the plants we have up there" and to keep the water from draining into the sewer.
In 2006, the green roof industry organization Green Roofs for Healthy Cities found the District to be second only to Chicago in terms of green roof square footage, reporting more than 300,000 square feet at the time. It has continued to grow.
But even though the city has seen green roofs sprout on several private residences, businesses and federal office buildings, including a 68,000-square-foot green roof on the federal Department of Transportation building, the ones at One Judiciary Square and the Reeves Center are the first green roofs to be installed on city government buildings.
"Green roofs have taken up a lot of interest in the last five years," said Robin Snyder, the associate director of environmental initiatives in the District Office of Property Management. "But there was always a lot of talking and no real action. Then, in his 100-day plan for the city, [Mayor Adrian M.] Fenty required a green roof demonstration project before the end of the year."
The result was a 4,000-square-foot green roof at the Reeves Center and an 8,000-square-foot green roof at One Judiciary Square, completed in September and November, respectively. Snyder said the city hopes to continue to add green roofs wherever it is feasible, on buildings that are still under construction and on existing buildings that may need roof repairs or replacements.
Susan Riley-Laudadio, the District's green program manager, said the city utilized two green roofing systems in their projects. The first, at One Judiciary Square, used a method in which plugs were planted directly into a thick layer of soil covering the roof. The system used at the Reeves Center involved laying out pre-planted trays of greenery into a puzzlelike patchwork on the roof surface. Riley-Laudadio playfully called it the "instant green roof" method.
Both projects used sedums, cactus-related plants with leaves that hold water for a long time before slowly releasing it, said Sarah Murphy, DC Greenworks' program coordinator. Sedums are hearty plants that can last for 80 to 90 days without water, so there isn't much maintenance needed.