WASHINGTON — The U.S. Environmental Protection Agency announced plans Wednesday to require "green roofs," rain barrels and other measures that trap runoff at new and redeveloped buildings in the District of Columbia, making the city a test case for an ambitious effort to stop pollution from flowing into rivers along with the rain.
The EPA's plan, contained in a proposed permit for the District's storm-sewer system, would require developers to trap 90 percent of the water that falls on a plot during a storm.
Water usually hits roofs and parking lots and runs into sewers, carrying trash and chemical pollutants. Under the permit, that water would be filtered naturally, through plants and dirt, or be caught in a receptacle and used for watering plants.
If developers cannot make the changes, the EPA proposed, they would be required to pay for projects elsewhere.
The EPA will seek public comment on the plan, which would last five years. If approved, it would mean a major shift in thinking for a city covered in glass, concrete and shingles. EPA officials estimated that some buildings currently might trap 30 percent of rainwater with gardens or landscaping. At sites where the buildings are surrounded only by concrete, the number could be zero.
In the EPA's plan, "you're using water on site as an asset, rather than a waste product," said Jon Capacasa, director of the water protection division of the EPA's mid-Atlantic regional office. He said the changes were part of a larger effort, begun with a presidential order last year, to improve the Chesapeake Bay and its tributaries. "The local water bodies need these levels of (storm water) control to be healthy," he said.
Rainwater is an unlikely sounding, but important, source of pollution for the Chesapeake, bringing down more than 10 percent of the two pollutants that cause "dead zones" downstream.