The National Park Service's parent agency, the U. S. Department of the Interior, recently completed a project with both literal and symbolic "green" benefits. Earlier this week, Secretary of the Interior Dirk Kempthorne announced completion of a "green roof" on the 3rd wing of the Main Interior Building in Washington, D.C.
Green roof technology has been growing rapidly, especially in other parts of the world. An estimated 10% of all flat roofs in Germany are now "green," and the technique is catching on in the U.S. In case you aren't familiar with this approach, it involves a lot more than the color of the roof.
There are different types of green roofs, but all involve these basic elements: a waterproof membrane, soil (or another growing medium) and a variety of living plants that grow in the soil on top of the roof.
"What more suitable place for a green roof than the headquarters of America's conservation department in Washington, D.C.?" Secretary Kempthorne asked. With more than half of Washington, D.C. covered with paved or constructed surfaces that do not allow water to infiltrate the ground, 75 percent of rainfall becomes runoff." The vegetation and soil on the green roof will absorb rainwater and curb runoff.
Washington, D.C. has a huge problem from storm runoff and sewer overflows. Each year in Washington, approximately 1–2 billion gallons of raw sewage are discharged into the Potomac River, Anacostia River and Rock Creek—all tributaries to the fragile Chesapeake Bay Watershed.
The green roof at the Main Interior Building will help alleviate this problem and provide other benefits as well:
• Improve water quality by neutralizing acid rain effects and filtering pollution from rainwater.
• Hold up to .7 inches of rain to reduce stormwater runoff entering the sewage system and reduce streambank erosion.
• Shield the roof from the sun's direct rays, which extends the roof's life span, insulates the building during the summer and saves energy as well as mitigates urban "heat island" effects.
• Improve air quality by filtering the air that moves across the plants and, through photosynthesis, convert carbon dioxide into oxygen.
• Provide habitat for songbirds and pollinators.
• Reduce noise transfer from the outdoors.
• Provide a visually attractive sight for employees and visitors.
Are these benefits just feel-good hype? Not according to several studies, including one by the American Society of Landscape Architects. That group put a green roof on their headquarters in the nation's capital in 2006, and decided to gather some hard data over a year's time. Among their findings: the roof retained nearly 75 percent of all precipitation that fell on it, lowered the air temperature by as much as 32 degrees and saved about 10 percent on energy costs.
The project at the Interior Building started more than seven years ago when Mike Cyr, National Business Center's Chief of the Division of Facilities Management Services, read an article on the benefits of green roofs in Europe. Although such roofs were not commonplace at the time, Cyr's group decided to explore possibilities for installing a green roof on the Main Interior Building.
Other agencies in the Washington, D.C. have also adopted the concept, including 68,000 square feet of planted roof at the Department of Transportation's new headquarters and a 104,000 square-foot green roof on the Census Bureau's headquarters complex in Suitland, Md.
Even the Bureau of Alcohol, Tobacco, Firearms and Explosives—not an agency that immediately leaps to mind if you're looking for environmentalists—has gotten on board at its headquarters.
Will some criticize this project as a fad and waste of tax dollars? You can count on it, but it's appropriate for Interior and other agencies charged with good environmental stewardship to set the example in energy conservation, clean water and similar issues. This project at Interior's headquarters in Washington confirms that there are dedicated employees in the agency who are willing to break out of the "business as usual" rut and try new approaches to solving long-standing problems.
This is a small step in the right direction.