PHILADELPHIA — Federal and local officials celebrated the completion of the third largest green roof in the District of Columbia — a $1.1 million project funded in part by the U.S. Environmental Protection Agency (EPA) through the American Recovery and Reinvestment Act (ARRA). Sitting atop the World Wildlife Fund headquarters in Northwest D.C., the 27,750 square feet of green roof will help reduce stormwater runoff to nearby Rock Creek and bring additional benefits to the urban environment.
“EPA is proud to have awarded the District Department of Environment (DDOE) and D.C. Water more than $40 million in Recovery Act funds for rebuilding portions of the district’s drinking water, and wastewater infrastructure and controlling stormwater runoff,” said EPA regional administrator Shawn M. Garvin. “The district used $14 million of these funds to fund 22 ‘green projects,’ to improve local and regional water quality, helping the district to become a national leader in sustainable infrastructure and growing the green economy.”
In the Mid-Atlantic region, stormwater is responsible for more than 4,000 miles of impaired streams, including the Potomac River and Chesapeake Bay. As stormwater flows over land, it picks up heavy metals, bacteria, pesticides, suspended solids, nutrients, and floating materials. In the United States, stormwater runoff is responsible for 45 percent of impaired estuaries and 21 percent of impaired lakes.
“In the past, water and wastewater utilities have specialized in concrete and steel solutions to environmental issues,” said Christopher J. Carew, District of Columbia Water and Sewer Authority (DC Water) chief of staff. “But we’re excited to partner with other government agencies to explore green infrastructure opportunities for the future.”
The impacts from stormwater are caused not only by the pollutants in the runoff, but also by volume of the water flow. As the water flows over land, it can erode soil and then redeposit that as sediment in streams, causing murky water and degrading aquatic habitats.
Green roofs — rooftop gardens or a vegetative layer grown on a rooftop — provide shade and remove heat from the air, reducing temperatures of the roof surface and the surrounding air. On hot summer days, the surface temperature of a green roof can be cooler than the air temperature, whereas the surface of a conventional rooftop can be much warmer.
Other benefits of green roofs include:
• Reduced energy use: Green roofs absorb heat and act as insulators for buildings, reducing energy needed to provide cooling and heating.
• Reduced air pollution and greenhouse gas emissions: By lowering air conditioning demand, green roofs can decrease the production of associated air pollution and greenhouse gas emissions. Vegetation can also remove air pollutants and greenhouse gas emissions through dry deposition and carbon sequestration and storage.
• Improved human health and comfort: Green roofs, by reducing heat transfer through the building roof, can improve indoor comfort and lower heat stress associated with heat waves.
• Improved quality of life: Green roofs can provide aesthetic value and habitat for many species.