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Stormwater Strategies
Community Responses to Runoff Pollution

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The next time it rains, look at a street gutter or roadside ditch and think how different what you see is from what runs off in a more natural setting. The rain, rather than seeping into the soil, flows quickly off roads and roofs. It picks up oil, grease, heavy metals, and trash from roads, sediment from construction sites, and pesticides and fertilizers from lawns. It rushes through storm drains and, when discharged to a stream, erodes the natural system. What started as a friendly rain is now a serious polluter.

Urban Stormwater Pollution

Urban and suburban development, with the creation of buildings and roads, and the innumerable related activities, turns the rain and snow into unwitting agents of damage to our nation's waterways. This urban and suburban runoff, legally known as stormwater, is -- with agricultural runoff -- one of the most significant water pollution problems in the United States.

A variety of created surfaces now cover much of our metropolitan land: factories, offices and homes, highways and roads, parking lots. Many of these surfaces are impervious and therefore prevent rainwater and snowmelt from following their natural course into the soil. Roofs and pavement prevent infiltration completely while even suburban lawns absorb far less than natural areas. By decreasing the amount of precipitation absorbed by the soil, these impervious surfaces increase the volume and velocity of water flowing over and off the land to receiving waters. Increased imperviousness causes larger and more frequent floods and it increases erosion of stream beds and banks. The higher flows have other significant impacts on receiving waters such as increasing their temperature, changing habitat, and decreasing stream flow stability.

In addition, our daily activities often cover these impervious surfaces with a coating of unpleasant and often hazardous materials: sediments, toxic metal particles, pesticides and fertilizers, oil, gasoline and grease, harmful viruses and bacteria, excess nutrients, and dust, wastepaper, and trash. Indeed, much of the country's air pollution falls onto these surfaces as tiny particles. As rainfall and snowmelt move rapidly across this transformed landscape, these substances contaminate the flowing water. Eventually these polluted flows degrade the waters we use for drinking, bathing, swimming, fishing, or otherwise enjoy.

The degradation caused by urban stormwater pollution is serious. Even a partial accounting shows that hundreds of millions of dollars are lost each year through added government expenditures, illness, or loss in economic output due to urban stormwater pollution.1 The ecological damage is at least as significant. A full analysis would surely show the annual impacts over a billion dollars. The seriousness of the stormwater pollution problem would seem to be matched, however, by its apparent intractability. Rain and snow fall over large areas, and the resulting runoff flows indiscriminately over those same vast expanses, leaving little obvious hope of control. Until recently, stormwater management primarily addressed flood control, trying to avoid the most severe water quantity and velocity problems. Getting rid of runoff as quickly as possible without causing damage was where many local programs began -- and ended.

Stormwater Strategies

In recent years, however, communities across the nation have begun to take on the challenge of stormwater pollution -- and are succeeding. More and more local officials have demonstrated that strategies to prevent and control urban and suburban stormwater pollution are effective, can be economically advantageous, and can provide collateral benefits to the community. This report documents, with almost 100 case studies, that success.

One example from Staten Island, New York helps to demonstrate this point. In a part of New York City, more akin to most American cities and suburbs than Manhattan, the city has recently completed negotiations for acquisition of the final parcels of land in the Staten Island Bluebelt, a large swath of undeveloped land containing streams and wetlands. By preserving this land that conveys stormwater out of developed areas to prevent flooding, the city can forego construction of a traditional subsurface storm sewer system for the area. The initial net savings is greater than $50 million. Furthermore, use of nonstructural methods naturally cleans the runoff, preventing discharge of tons of harmful pollutants. It also reduces or avoids significant operation and maintenance costs. In addition to the cost savings and runoff reduction improvements, the Bluebelt provides significant recreational opportunities and a wildlife refuge for area residents, and the natural amenity increases property values for residents.2 Many other localities have similarly found that strategic land use planning and protection can both prevent pollution and create vitally needed public amenities at a relatively low cost.

Not all stormwater control projects rely on land preservation. Others educate the public on how to prevent pollution themselves. Some address municipal operations such as maintenance of vehicle fleets, parks, or roads. Still others create wetlands or ponds, infiltration systems at parking lots, or new incentives for compliance. Many are able to achieve multiple goals, creating a win-win situation, such as the constructed wetlands and outdoor classroom at Oberon Middle School near Denver, Colorado. Students there obtained outside funding to create, out of a vacant school parking lot, a stormwater treatment wetland that recycles water for irrigation and provides hands-on learning opportunities for students and surrounding neighborhoods. Despite the variability of these programs, a basic theme remains constant across the case studies collected in this report: implementing stormwater control measures can reduce water pollution in an economically advantageous manner and enhance life in the community.

Many fine handbooks provide theoretical, technical guidance concerning the design and implementation of effective stormwater pollution measures.3 This report takes a different approach. The stormwater case studies collected in this report describe and evaluate actually implemented stormwater control projects and programs from across the United States. All the case studies are, in at least some major way, successful. They show on a practical level that stormwater management works -- that municipalities in all regions of our country have implemented environmentally effective, economically advantageous, and politically feasible stormwater pollution measures. Not a how-to manual, this report is intended to take the mystery and misunderstanding out of stormwater runoff. In a sense also, it is a tribute to those local governments that have developed strong programs and are inspirations for all other local governments.

Criteria For Selecting Case Studies

In selecting the case studies included in this report, the Natural Resources Defense Council (NRDC) has focused on three broad areas of success:

  • environmental gains
  • economic advantages
  • collateral benefits

Stormwater Terminology

The terminology in this area is often confusing. Colloquially, we think of any-thing that runs off the land after wet weather as runoff or perhaps stormwater. Legally, stormwater refers to runoff that gets collected or channelized in a pipe or ditch, and may come from urban areas, industrial sites, or agricultural activities. This report will usually use the term stormwater to refer to urban runoff, but also use "runoff" in its colloquial sense.

Similarly, the term "urban" has many meanings, from the ultra-urban of dense city centers to the growing areas with single family houses on large lots. When discussing stormwater, "urban" is generally use to distinguish it from industrial or agricultural stormwater (or runoff). This report will use the term in that sense, with most case studies, and most discussion, focusing on the more suburban and less dense urban areas, rather than ultra-urban city centers.

NRDC assessed environmental gains by looking at biological, hydrological (flow), or chemical improvements. Biological indicators gauge the success of a given practice by monitoring increases in the abundance of particular fish, insect, and plant species known to be sensitive to degraded water quality, or increases in the number and richness of species found in the relevant body of water. Hydrologic (flow) criteria evaluate how well a given practice mimics natural patterns of rainwater and snowmelt flow and thus avoids or mitigates the damaging effects of the increased volume and velocity of runoff caused by increased impervious cover, including reduced flooding. Chemical water quality monitoring is used to gauge the effectiveness of a control measure at removing or reducing pollutants. In some cases, however, we found innovative programs that did not fit into this set of criteria, but deserved inclusion.

Several different types of economic advantage characterize the stories gathered in this report. Often a particular project provided a cost saving to a municipality or real estate developer. Some practices cost very little in absolute terms, had significantly lower costs than less environmentally sensitive alternatives, provided a key stormwater service within the confines of a very small budget, or have an anticipated long-term cost avoidance. In other cases, implementation of a stormwater pollution prevention measure resulted in property value increases and corresponding tax revenue increases. In still other cases, stormwater pollution prevention practices have brought about other, less easily measured, types of economic enhancement.

In addition to environmental gains and economic advantages, the stormwater pollution control projects and programs described in this report often provide important, less quantifiable benefits to the community. Buffer zones and open areas that remove pollutants from runoff before they reach lakes and streams also provide land for outdoor recreation such as hiking and for wildlife habitat. Innovative approaches to stormwater pollution prevention such as creating a stormwater utility or collaborating with neighboring communities, may make administrative hurdles easier to overcome. Residents of an area with well-designed stormwater pollution prevention measures may voice greater satisfaction with their neighborhood.

The case studies include a description of the project and its marks of effectiveness and, where available, a reference to a measurable goal. A measurable goal is an observable, preferably numerical, viable target or objective selected by the municipality or other project manager that guides -- and measures the success of -- the selection, design, operation or maintenance of the stormwater pollution management measure(s). Typical measurable goals might include a requirement that a municipality send to each household educational information at least once per year, that sediment discharges be reduced 80 percent, that flow regimes mimic pre-development flows, that the number of aquatic species increases, or that developers leave undeveloped a 100-foot buffer of land around streams or wetlands. NRDC believes that measurable goals are critical elements of municipal stormwater pollution programs because, while offering municipalities the flexibility to select targets suitable to local conditions, needs, and resources, they provide a standard by which citizens and the municipality itself can judge municipal efforts. Clear standards are essential to maintaining accountability.

All the case studies presented demonstrate some element of success instrumental as an example for others. We note that this report includes some case studies because they represent regional leadership, such as notable movement in the direction of protection and prevention or the use of innovative strategies to overcome challenges due to local climatic conditions, political issues, or resource constraints. In these cases, there may not have been a clear measure of success. Accordingly, case studies are to be viewed as exemplary within their regional context, recognizing that there may still be room for improvement or that their effectiveness is not yet fully determined. In fact, it is highly likely that adjustments can be made to all the programs. Effective stormwater management will almost certainly be an iterative process, with a continually repeating cycle of program development and implementation, monitoring and analysis of results, and determination of where further progress is necessary. These case studies are points along a trajectory, not a final destination.

Organization of This Report

Scope and Limitations

NRDC has intentionally limited the scope of the case studies included in this report to particular projects and specific components of broader stormwater programs. Inclusion of a case study in this report describing one particular component of a government or private entity's program does not imply NRDC's approval or disapproval of other activities undertaken by the same entity.

Inclusion of a case study in this report does not imply any opinion as to whether or not the practices described in the case study meet federal, state, local or other regulatory requirements

Across the nation, many innovative communities are taking action to control and prevent urban runoff pollution demonstrating that addressing stormwater issues is achievable and desirable. This overall theme guides the content and structure of this report.

Chapter 1 presents the findings of the study describing the major themes distilled from the case studies and the ensuing recommendations for local action.

Chapters 2 and 3 explain the causes and consequences of urban stormwater pollution. These chapters are to be viewed as a source of general information on urban runoff, recognizing that many resources exist that discuss the issue in greater depth.

Chapter 4 discusses strategies for establishing a dedicated and equitable funding source for stormwater programs, and thereby increasing public and political support. This chapter focuses particularly on the steps and issues involved in establishing stormwater utilities or management districts -- independent, or quasi-independent agencies that can charge fees for stormwater management services. With an estimated 500 already in existence, many municipalities have found these utilities to be a good way to provide a steady, non-political source of funding, allowing for better planning and budgeting. The chapter briefly outlines the law governing local development and implementation of stormwater pollution prevention programs.

Chapter 5 presents the more detailed findings of the case studies breaking them out into five broad categories of stormwater strategies. It summarizes the types of strategies used and approaches taken by communities across the country, presents data and practical information from the studies, and identifies what experience suggests are the critical elements of success.

Chapters 6 through 11 present more than 100 case studies of existing effective stormwater programs and projects. The case studies include data on costs and measures of success, as well as contact information for project leaders.

For the purposes of this report, NRDC has divided the United States into six regions based in large part on general rainfall patterns. Division largely follows rainfall zones found in federal environmental regulations4 and was adopted after discussions with EPA and other scientists. The allocation of states is as follows:

Northeast: Connecticut, Delaware, District of Columbia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, West Virginia

Southeast: Alabama, Arkansas, Florida, Georgia, Hawaii, Louisiana, Mississippi, North Carolina, Puerto Rico, South Carolina, Tennessee, U.S. Virgin Islands, U.S. Pacific Islands, and Virginia

Central Southwest: Colorado, New Mexico, Oklahoma, Texas

Northern Rockies and Pacific Southwest: Arizona, California, Idaho, Montana, Nevada, Utah, Wyoming

Pacific Northwest: Alaska, Oregon, Washington

Midwest: Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin

Obviously, rainfall patterns are not similar across any one state. This is especially true for larger states such as California or Texas. While it may have been possible to draw lines within states, this would have unduly complicated the report. NRDC believes, however, that programs formed in virtually any area of the country can be instructive for any locality. Most, if not all, urban stormwater strategies function effectively in any part of the country. Regional differences in weather patterns, type of soil, topography, type of vegetation and other factors, however, may influence stormwater flows and thus the selection and operation of optimal urban stormwater pollutant control measures. NRDC intends the organization of case studies by region to be viewed not as a limitation, but rather as an aid for readers to find examples of particular relevance to their community.

Within each of the regional chapters, case studies are further subdivided into the following five categories of stormwater strategies:

  • Addressing stormwater in new development and redevelopment
  • Promoting public education and participation
  • Controlling construction runoff
  • Detecting and eliminating improper or illegal connections and discharges
  • Implementing pollution prevention for municipal operations

These five categories parallel the categories of measures that large municipalities currently need to address under new federal regulations5 and small municipalities will need to address under pending federal regulations.6 It should also be noted that many case studies represent multiple management measures while others do not fit perfectly into any of the five categories. For example, the report includes urban retro-fit programs, often with structural controls, in the first category of strategies, although they are not a pre-construction measure to address post-construction runoff. After presentation of the detailed case studies, the report provides a list of additional projects or programs which may also serve as good examples; data and space limitations prevented full descriptions.

How to Use This Report

This report is designed as a non-technical source book for municipal officials, policy advocates, and local citizens interested in reducing the harmful effects of stormwater runoff and learning about the good work that is being done to control and prevent urban runoff pollution. At the core of the report are more than 100 case studies on existing programs that have demonstrated some elements of success. The case studies are more than just evidence of effective stormwater management. They provide ideas, information, and strategies that can help other communities address stormwater pollution effectively.

The case studies provide a detailed look at specific projects or programs. In general the case studies provide background on how and why the program evolved; a description of the program and its goals (measurable when available); the key elements that make it a good example; the documented or anecdotal effectiveness of the program; the cost and/or documented cost effectiveness; and insight from program directors and personnel as well as other interested persons. Many of the strategies presented complement essential stormwater management themes such as acting early and planning ahead, interagency cooperation, accountability, or watershed planning.

The case studies can be used as either a general reference for designing a comprehensive stormwater management program, or a guide for solving specific stormwater problems. Therefore, before reading the case studies it may be helpful to review your community's goals and needs. For some communities, all the case studies may be helpful. However, it may be easier to focus on case studies that most closely match your community's situation. This could mean looking at all the programs in one of the five management categories or looking at all the case studies in one rainfall region. The report also provides useful contacts and references throughout the document. Appendix B cross references all programs by project type. Most important, however, these case studies should be a source of inspiration for future stormwater projects and programs.


1. The United States Environmental Protection Agency has estimated the value of reduction of stormwater pollution arising from the proposed Phase II municipal stormwater rule as ranging from $106 million to $574 million. 63 Fed. Reg. 1601 (1998). This range of estimates does not include a measure of the benefits from the already existing Phase I stormwater rule or a measure of the losses that would exist even after full implementation of the Phase I and proposed Phase II rules.

2. For the full case study of the Staten Island Bluebelt, see Chapter 6.

3. Alameda Countywide Clean Water Program, California Industrial/Commercial Stormwater Inspection Program Handbook for Municipal Agencies, March 1996; Schueler, T. R., P. A. Kumble, and M. A. Heraty, A Current Assessment of Urban Best Management Practices: Techniques for Reducing Non-Point Source Pollution in the Coastal Zone, Metropolitan Washington Council of Governments, March 1992; Schueler, T. R., Site Planning for Urban Stream Protection, Center for Watershed Protection & Metropolitan Washington Council of Governments, December 1995; Camp, Dresser & McKee, et al., California Storm Water Best Management Practice Handbook, California State Stormwater Quality Task Force, 1993.

4. 40 CFR 122 Appendix F.

5. 40 CFR part 122.26 for dischargers and part 123.25 for states.

6. Federal Register Vol. 63, No. 6, Friday, January 9, 1998, Part II 40 CFR parts 122 and 123, National Pollutant Discharge Elimination System -- Proposed Regulations for Revision of the Water Pollution Control Program Addressing Storm Water Discharges; Proposed Rule, pp. 15361643.

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