By Lindsay Minnema
Washington, DC (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 ReevesCenter 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, atOne Judiciary Square, used a method in which plugs were planted directly into a thick layer of soil covering the roof. The system used at theReeves 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.
Green roofs have numerous private benefits. They help to insulate the building, protect the roof from UV rays and extend its life by as many as 15 years, Murphy said. But a green roof’s biggest impact is environmental: slowing the flow of storm water into area rivers. “Storm-water runoff brings with it toxic pollution, such as oil and grease from cars,” Connolly said. “The rain is literally like a broom that sweeps everything into the storm drain and into the river. “If we do not control and capture and infiltrate storm water, we’re not going to clean up the Anacostia,” he said.
At the heart of the District’s storm-water runoff problem, Connolly said, is its century-old sewer system, which dumps raw sewage and storm water runoff into the Anacostia whenever the city receives more than a half-inch of rain. The billions of gallons of polluted water have serious consequences for the Anacostia’s plant and animal wildlife. To help remedy the problem, the DC Water and Sewer Authority is working to repair all the broken pumps, clogged pipes and malfunctioning dams in its system, a project that Connolly said will reduce the combined sewer overflow into the Anacostia by about 40 percent. It should be completed in the fall.
But taking care of the remaining 60 percent requires the construction of $2 billion storage tanks that will hold storm-water overflow until it can be treated, Connolly said. So far, the project doesn’t have the necessary funding. Until it does, green roofs make a big difference.
In a report released in May 2007, local environmental advocacy group Casey Trees, working with environmental engineers from Limno-Tech, estimated that greening efforts could stop as much as 311 million to 1.2 billion gallons of storm water from entering area rivers. “The idea with a watershed is that it’s the land from where all the problems are coming,” Connolly said. “We need to reestablish the cycle where the water sinks down into the soil. With roofs and pavements, we’ve taken away that step where it filters in, and instead it just rolls down a hill and into a stream.”
“It’s all about reducing what they call the ‘footprint’ of the building, or the impact it makes on the environment,” Murphy said. “InSwitzerland, when they’re building a new building, they sometimes scoop up the dirt that was there and just put it on the roof. The U.S. is not quite at that stage,” but it seems to be on its way.
Snyder said she thinks the District will continue to be on the forefront of the green efforts. “I see D.C. becoming an environmental leader in the nation,” she said. “We became a leader in the nation [when] we established mandatory green standards not only for our own buildings, but for private sector development. The point now is for us to follow through and to continue to push the edge.”
Getting Into Greenroofs