Out of the Gutter
Reducing Polluted Runoff in the District of Columbia
Urbanization has dramatically altered the earth's natural hydrology, and this has resulted in serious problems with stormwater whenever it rains or snows. The process of urbanization begins with construction, which eliminates trees, vegetation, and topsoil -- key components of the natural hydrologic system that otherwise controls the overflow of precipitation (stormwater runoff). After construction, problems continue. Development usually replaces native meadows, forested areas, and other natural landscape features with lawns, pavement, and rooftops -- and these largely impervious surfaces generate substantial quantities of surface runoff.
Engineers traditionally design drainage systems to move rainwater as quickly as possible by directing it over the ground toward curbs, gutters, streets, and sewers. But these conventional drainage systems prevent water from flowing into the ground and filtering through soil before being released into surface and ground waters. Instead, they create more surface runoff, and this results in increased flooding, erosion, and pollution. Today, there is more stormwater runoff -- and more pollution in the runoff -- than ever before. 1 As a result, the health of our water bodies, and the people and wildlife that rely upon them, is in jeopardy.
Stormwater Runoff in the Nation's Capital
As in other cities, the hydrologic impacts of development have contaminated waters in the District of Columbia (District). Approximately 65 percent of the District's natural groundcover has been replaced with impervious surfaces, such as roads, buildings, and parking areas. 2 These impervious surfaces dominate the landscape and generate large volumes of surface runoff when it rains and are exacerbated by significant urban forest canopy losses.
Stormwater runoff frequently overwhelms the urban infrastructure, causing local flooding and neighborhood sewer backups, which create public nuisances and health hazards.
The District's current stormwater management system adversely impacts not only public health and the environment, but also the economy: the increase in the magnitude and frequency of sewer backups and flooding in city streets, polluted rivers, loss of aquatic habitat and recreational opportunities after storm events creates a nuisance and costs citizens and the District money. 5 To maintain and improve the environmental, economic, and social conditions of the District, officials must address both contaminated stormwater and combined sewer overflows.
The Solution: Low-Impact Development
Low-Impact Development (LID) -- a new way of thinking about stormwater management -- is a highly effective strategy for controlling contaminated urban runoff. LID employs lot-level techniques that reduce the impact of development through the use of multiple systems that retain, detain, filter, treat, use, and reduce stormwater runoff. LID is grounded in a core set of principles based on a new paradigm: first, that stormwater management should not be seen as stormwater disposal; second, that numerous opportunities exist within the developed landscape to control stormwater runoff close to the source. 6 The primary goals of LID design are: first, to reduce runoff volume through infiltration, retention, and evaporation; and second, to find beneficial uses for water rather than exporting it as a waste product down storm sewers. Ultra-urban environments afflicted with stormwater ailments -- such as the District of Columbia -- are ideal settings in which to put LID methods to work to benefit the environment, water quality, and public health.
LID practices can be applied to all elements of the urban environment, turning parking lot islands, street medians, planter boxes, and landscaped areas near buildings into specialized stormwater treatment systems. 7 Innovative designs for urban areas may also include roof gardens, methods for capturing and using rainwater, and use of permeable pavement in low-traffic areas, parking areas, and walking paths. 8 Furthermore, LID strategies can help beautify the urban environment and create desirable public open space.
The adoption of LID practices requires a basic paradigm shift involving and educating many interested parties on these new principles, and removing regulatory barriers that stand in the way of progress. Unfortunately, designers, developers, and contractors are often unfamiliar with LID practices and benefits. And even if they do understand the principles, quite often there are legal, institutional, and political obstacles that reinforce status quo stormwater or sewage management practices and behavior -- and even prohibit the use of certain LID practices.
Putting LID to Work in the District of Columbia
In this report, we assess how LID strategies can mitigate runoff problems in the District of Columbia, and we scrutinize development regulations that pose potential impediments to the voluntary application of LID strategies, policies, and programs. To do so, NRDC developed the attached checklist (Appendix A, Legal Review Checklist: Impediments to Voluntary Low-Impact Development in the District of Columbia) for use by the District of Columbia -- as well as communities across the country -- to identify and address these potential legal obstacles to voluntary LID. We then used the checklist to evaluate existing District of Columbia development regulations, identify sections of those regulations that pose impediments to the voluntary use of LID techniques, and suggest ways in which the regulations could be modified to encourage LID practices, which will ultimately produce myriad benefits for the environment and the public.
Lastly, NRDC explored several major areas of policy-making, planning, and management that affect stormwater management; these deserve renewed attention in developing an LID strategy for the District. NRDC recommended a number of changes that will facilitate consideration and implementation of LID in strategic planning, redevelopment, provision of municipal services, and environmental management decisions in the District. These changes include four general areas of recommendations.
1. Leadership by Example
Stormwater management in the District of Columbia is a responsibility shared jointly among four District agencies: the Department of Health (DOH), the Water and Sewer Authority (WASA), the Department of Public Works (DPW), and the District Division of Transportation (DDOT). District of Columbia interagency and interdepartmental cooperation is crucial to the successful promotion and implementation of LID in the District. The other D.C. agencies involved in land-use planning and development need to understand the multiple benefits of LID and take active roles in its promotion.
Forested buffers in riparian areas are an important part of the urban forest and protect rivers and streams from adjacent runoff and erosion.
- issuing state-of-the-art technical guidelines for LID
- promoting high-visibility LID demonstration projects
- developing a large-scale "sewershed" LID application as part of a long-term control plan for combined sewer overflows
- creating commercial incentives to reverse the trend of unsustainable construction activities
- fostering coordination between District agencies and utility companies (including water, gas, electricity, etc.) to accomplish the goals of stormwater management and improve our urban green infrastructure.
Strategic grading and use of pervious pavement as shown here in the Washington Navy Yard can be used effectively to treat and infiltrate parking lot runoff.
The most logical starting point for creating economic incentives lies within the existing stormwater utility fee collected by WASA. Once the stormwater fee is revised to take into account impervious area, economic incentives -- such as those that encourage and credit land conservation and reforestation efforts, low-impact development, and other site-specific stormwater management techniques -- can easily be incorporated. Appendix B is an overview of stormwater rates from across the country.
3. Conservation and Management of Existing Open Space
Much of the remaining open space in the District of Columbia is either National Park Service property or D.C. Department of Parks and Recreation property; it is confined to areas of sensitive environmental significance, including riverfront and riparian areas, wetlands, and areas of extremely steep slopes. Future development and redevelopment efforts must be conducted very carefully; they must be sensitive to the context of the remaining surrounding natural areas and cognizant of ongoing stewardship efforts. Sound strategic planning and decisionmaking must be coordinated with environmental management efforts across the numerous District and federal agencies and jurisdictions. These efforts must focus on the restoration of the urban forest and street tree canopy; the protection of riparian corridors and steep slopes to control erosion; and optimization of city parks and public spaces for stormwater management.
Rain barrels and cisterns are simple and inexpensive techniques to trap, store, and reuse stormwater for efficient landscape irrigation.
There are many water conservation opportunities to be gained in the District of Columbia that warrant investigation and policy analysis; these include opportunities in building plumbing and maintenance, appliances, irrigation practices, and stormwater management.
Water reuse techniques (such as rain barrels and cisterns) represent simple and inexpensive ways we can trap, store, and reuse stormwater; they also provide a measurable level of storage during storm event peak flows, use water more efficiently for landscape maintenance and irrigation, and save consumers money. Low-flow shower heads, horizontal-axis clothes washers, and on-demand hot-water systems represent untapped opportunities to significantly impact dry-weather river flows, reduce ratepayers' water bills, and make strides toward the District's inter-municipal water allocation and consumption goals. These techniques need to be implemented broadly throughout the District.
Low-impact development is emerging as a highly effective approach to managing polluted stormwater runoff. It is particularly effective in ultra-urban settings and should be included as part of a new paradigm for managing stormwater runoff generated from development and redevelopment. LID should be integrated into the broad context of economic redevelopment and stormwater management to help restore the District of Columbia's urban green infrastructure and its valuable waterfront resources, including the Anacostia River. The District and federal governments have significant roles to play in developing broad-based institutional support for LID. They must lead by example in their own projects and management activities; by providing effective technical guidance, education, outreach, and economic incentives, they can prompt and guide residential and commercial entities to follow suit. LID is a valuable and complementary watershed management tool that should be used in conjunction with ongoing land conservation, urban forest management, riparian and wetlands restoration, and water conservation efforts.
Photos: James Woodworth
1. Lehner, P., Aponte Clarke, G., Cameron, D., and Frank, A., Stormwater Strategies: CommunityResponses to Runoff Pollution, Natural Resources Defense Council, New York, May 1999.
2. District of Columbia, Department of Health, Storm Water Guidebook, p. 1.3, May 2001
3. U.S. EPA, 1998 Section 303(d) List Fact Sheet for D.C., www.epa.gov.owow/tmdl/states/dcfact.html
4. District of Columbia Water and Sewer Authority, Combined Sewer System Long Term Control Plan, Draft Report, June 2001.
5. District of Columbia, Department of Health, Storm Water Guidebook, p. 12, May 2001.
6. Prince George's County, Maryland Department of Environmental Resources Programs and Planning Division, Low-Impact Development Design Strategies: An Integrated Design Approach, June 1999; Shaver, E., Low Impact Design Manual for the Auckland Regional Council, Auckland Regional Council, New Zealand, April, 2000; Weinstein, N., Feasibility Study Assessing Low Impact Development Lot Level Controls in Urban Areas with Combined Sewer Systems, Low Impact Development Center, unpublished draft, Beltsville, MD, 2001.
7. U.S. Environmental Protection Agency, Office of Water and Low Impact Development Center, Low Impact Development (LID); A Literature Review, EPA-841-B-00-005, Washington, DC, October 2000.
8. U.S. Environmental Protection Agency, Office of Water and Low Impact Development Center, Low Impact Development (LID); A Literature Review, EPA-841-B-00-005, Washington, D.C. p. 3, October 2000.
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