When precipitation events hit urban areas the resulting runoff into local sewer systems and waterways is far from clean. Instead, the rainwater carries with it trash and chemical pollutants from building roofs, parking lots, streets and other impervious surfaces. Without proper natural filters in place, the polluted runoff enters city sewer systems and local water ways unfiltered. To combat the pollution problem associated with urban stormwater runoff, the US Environmental Protection Agency announced Wednesday that Washington, DC will serve as a test case for ambitious efforts to stop pollution from flowing off of urban surfaces into rivers when it rains. The agency put forth requirements that new and redeveloped buildings in the District must install green roofs, rain barrels and other measures to trap runoff. The proposed permit requires developers in the District to trap 90 percent of the water that falls on their plot during a storm. Under the permit, water would be filtered naturally through plants and dirt, or it would be caught in rain barrels for use on the building’s premises for watering plants. If the plan is put into place, it would make the District’s rules on stormwater among the strictest in the nation. For more information, read today’s Washington Post story on the proposed permit.