Nation's Capital Plans Stormwater Protection for Two Rivers

In modifications to a Clean Water Act permit, the district has agreed to undertake innovative measures to stem stormwater flow and pollution, using natural systems such as trees, green roofs, and vegetated buffers.

"This is the most advanced set of green infrastructure controls for urban stormwater that we have seen in the Mid-Atlantic Region," said EPA Regional Administrator Donald Welsh. "The District's commitment to employ sustainable, and measurable solutions for wet weather pollution demonstrates leadership for the Chesapeake Bay watershed."

The enhancements to the stormwater controls and management practices were outlined by the DC government in a letter to the federal environmental agency on November 27. The improvements are being incorporated into a municipal stormwater permit that the EPA is renewing for the city.

Although the eight mile long Anacostia River is surrounded by parkland, it is contaminated by all the pollutants stormwater carries - sediment, nutrients, pathogens, toxics and trash. The Anacostia is flat and moves slowly, it is particularly vulnerable to stormwater pollution.

In November, the nonprofit Potomac Conservancy graded the health of the Potomac river watershed a D+, saying "polluted runoff from our parking lots, roads, and roofs," soil erosion, unhealthy stormwater, and river pollution are overwhelming and degrading the Potomac River system."

To address these problems, the District intends to plant and maintain at least 13,500 additional trees to absorb stormwater and keep it from running off into the Potomac and Anacostia rivers, carrying oil, grease, pet waste and other pollutants with it.

A low impact development plan will be created which will include converting paved areas such as median strips and large sidewalks into green space.

On October 21, the Interstate Commission on the Potomac River Basin and Pepco installed a new rain garden at Pepco's Benning Service Center, adjacent to the Anacostia River. These Eastern High School students helped with the installation. (Photo courtesy ARBC)

The District will write a tax incentive plan for the installation of green roofs covered with plants. Green roofs can reduce sewage system loads by absorbing large amounts of rainwater.

During rainstorms, a green roof acts as a sponge, absorbing much of the water that would otherwise run off. Researchers estimate that three to five inches of soil or growing medium absorbs 75 percent of rains that are one-half inch or less, according to the U.S. EPA.

The District proposes to require all new District-owned buildings and, where feasible, all major renovations of District-owned buildings to include green roofs.

In addition, the District's plan includes the installation of 125 rain barrels installed directly below drainspouts and 50 rain gardens.

A rain garden is basically a shallow depression in the earth, landscaped with permeable soil and hardy water-loving grasses, shrubs, or trees and covered by a thin layer of mulch.

Rain gardens collect the stormwater runoff from impervious surfaces, such as roofs and pavement, and allow it to percolate into the ground instead of draining into sewers or waterways.

Rain gardens have become increasingly popular in the United States in the past two decades, after a 1987 amendment to the Clean Water Act led the EPA to establish stormwater discharge standards for industries, new construction sites, and municipal sewer systems.

The DC Water and Sewer Authority is responsible for the design, construction and maintenance of public facilities that convey stormwater runoff to the Anacostia and Potomac Rivers and other receiving streams.

The stormwater system includes 600 miles of storm sewer pipes, catch basins, inlets, special structures, pumping stations, and related facilities. But some components are over 100 years old, so the green improvements are intended to take pressure off the aging stormwater system.

"The Potomac River is a national treasure, and part of the lifeblood of the Chesapeake Bay," said H. Hedrick Belin, president of Potomac Conservancy. "Decision makers must take immediate action to protect and preserve the river so it is available for all people to enjoy."

Copyright Environment News Service (ENS) 2007. All rights reserved.