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Winter 2009 Vol. 8 Number 3

Table of Contents

From Sidewalks to Streams

Improving Stormwater Management

©Paul Simcock/Stone/Getty Images

Large cities are often described as concrete jungles -- dense areas of manmade materials with little green space. The majority of the U.S. population now lives in cities, with the numbers expected to rise and the areas anticipated to grow. With urban expansion, however, come significant environmental impacts, especially on the nation's waterways.










After rain or snow in urban areas, large quantities of water flow over impervious surfaces -- such as streets, parking lots, and rooftops -- picking up various pollutants like garbage, asphalt sealants, motor fuels, and other chemicals. This polluted stormwater is then collected by natural channels and artificial drainage systems and ultimately routed to nearby streams and other bodies of water -- impacting the quality of those waters.

Although urban stormwater's role in degrading water quality has been recognized for decades, reducing the role has been difficult. As a step toward improvement, in 1987 Congress brought stormwater control under the supervision of the U.S. Environmental Protection Agency, which oversees stormwater discharged by cities, industries, and construction sites. However, the current regulatory framework was originally designed to address sewage and industrial wastes, and has suffered from poor accountability and uncertainty about its effectiveness.

In light of these challenges, EPA asked the National Research Council to examine its stormwater permitting program. ©Matthew Rambo/iStockphotoThe resulting report finds that radical changes are needed. EPA's current approach is not likely to produce an accurate picture of the extent of the problem, nor is it likely to control stormwater's contribution to impairing water quality. Moreover, increased water volume and pollutants from stormwater have degraded water quality and habitats in virtually every urban stream system.

"EPA's stormwater program needs a significant overhaul," said Claire Welty, chair of the committee that wrote the report and director of the Center for Urban Environmental Research and Education at University of Maryland, Baltimore County. "The changes we recommend in the report are aimed to help reverse degradation of fresh water resources and ensure progress toward the Clean Water Act's goal of 'fishable and swimmable' waters."

The committee recommended that all stormwater and other wastewater discharge permits be based on watershed boundaries instead of political boundaries in order to provide meaningful regulation. Currently, stormwater and wastewater regulations require separate permits; within stormwater regulations, different types of permits exist for municipalities, industries, and construction sites. The committee suggested that EPA adopt a watershed-based permitting system that would encompass all discharges that could impact waterways in a particular drainage basin, rather than requiring individual permits. Responsibility and authority for implementing watershed-based permits should be centralized with a lead municipality that would work in partnership with other municipalities within the watershed.

The report also says that stormwater management will be ineffective without integrating stormwater management and land management practices, as the area being appropriated for urban land use is growing faster than the population. Future land development and its potential to increase stormwater problems must be considered and addressed in EPA's program.

Additionally, it should focus less on the chemical pollutants in the stormwater and more on the increased flow of water, as the volume of discharges is generally not regulated by EPA. In urban areas, stormwater flows rapidly across surfaces and arrives at streams in short, concentrated bursts, which in turn increase streambank erosion and sediment pollution of surface water. Many urban streams are degraded as a result of this increased volume of water, but show no measurable changes on water quality.

Lastly, EPA could implement additional stormwater controls in urban areas, including conserving natural areas, reducing hard surface cover such as roads and parking lots that channel stormwater into waterways, and retrofitting urban areas with features that hold and treat stormwater.   -- Jennifer Walsh

Urban Stormwater Management in the United States. Committee on Reducing Stormwater Discharge Contributions to Water Pollution, Water Science and Technology Board, Division on Earth and Life Studies (2008, approx. 624 pp.; ISBN 0-309-12539-1; available from the National Academies Press, tel. 1-800-624-6242; $53.00 plus $4.50 shipping for single copies).

The committee was chaired by Claire Welty, director of the Center for Urban Environmental Research and Education and professor of civil and environmental engineering at University of Maryland, Baltimore County. The study was funded by the U.S. Environmental Protection Agency.

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Copyright 2009 by the National Academy of Sciences