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Stormwater Strategies
Community Responses to Runoff Pollution

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After it rains, the streets look cleaner -- and that's a problem. Stormwater rushing over paved surfaces picks up everything from oil to pesticides and then flows, either directly or via a storm sewer, into our nation's lakes, rivers, and streams.

The United States Environmental Protection Agency (EPA) now considers pollution from all diffuse sources, including urban stormwater pollution, to be the most important source of contamination in the nation's waters. EPA ranks urban runoff and storm sewer discharges together as the second most prevalent source of water quality impairment in the nation's estuaries, after industrial discharges, and the fourth most prevalent source of impairment in lakes after agriculture, unspecified nonpoint sources, and atmospheric deposition of pollutants. Uncontrolled urban runoff also contributes to hydrologic and habitat modification, two important sources of river impairment identified by the EPA.

Most of the U.S. population lives in urban and coastal areas where the water resources are highly vulnerable to and are often severely degraded by urban runoff. 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. The ecological damage is at least as significant.

Unlike industrial or municipal wastewater treatment plant discharges, most stormwater pollution is derived from more diffuse sources that are closely related to everyday municipal and personal activities. While these characteristics pose some challenges, they also provide the opportunity for many approaches to address the problem. This report highlights a broad set of some of the most effective and cost-effective strategies to address stormwater runoff pollution currently in practice around the county.

The Causes and Consequences of Stormwater Runoff

The problem of polluted stormwater runoff has two main components: the increased volume and rate of runoff from impervious surfaces and the concentration of pollutants in the runoff. Both components are highly related to development in urban and urbanizing areas. When impervious cover (roads, highways, parking lots, and rooftops) reaches between 10 and 20 percent of the area of a watershed, ecological stress becomes clearly apparent. Everyday activities, including driving and maintaining vehicles, maintaining lawns and parks, disposing of waste, and even walking pets, often cover these impervious surfaces with a coating of various harmful materials. Construction sites, power plants, failed septic systems, illegal discharges, and improper sewer connections also contribute substantial amounts of pollutants to runoff. Sediments, toxic metal particles, pesticides and fertilizers, oil and grease, pathogens, excess nutrients, and trash are common stormwater pollutants. Many of these constituents end up on roads and parking lots during dry weather only to be washed into waterbodies when it rains or when snow melts.

Together, these pollutants and the increased velocity and volume of runoff cause dramatic changes in hydrology and water quality that result in a variety of problems. These include increased flooding, stream channel degradation, habitat loss, changes in water temperature, contamination of water resources, and increased erosion and sedimentation. These changes affect ecosystem functions, biological diversity, public health, recreation, economic activity, and general community well-being. Urban stormwater is not alone in causing these impacts. Industrial and agricultural runoff are equal or greater contributors. But the environmental, aesthetic, and public health impacts of diffuse pollution will not be eliminated until urban stormwater pollution is controlled.


Increasingly, communities around the United States are recognizing the consequences of uncontrolled urban and suburban runoff. These communities are implementing strategies to prevent, control, or treat stormwater and observing substantial environmental improvements, realizing economic advantages, and enjoying numerous associated quality-of-life benefits. In many cases, these communities are implementing programs without any mandate. Others are overcoming significant institutional barriers to do so.

While many communities are moving in the right direction, there remain substantial concerns about urban runoff as well as a growing interest in new federal stormwater regulations. Comprehensive stormwater regulation is required under Section 402(p) of the Clean Water Act (CWA). Since 1992, cities with a population greater than 100,000, certain industries, and construction sites over 5 acres have had to develop and implement stormwater plans under Phase I of the National Pollutant Discharge Elimination System (NPDES) stormwater regulations. Despite these efforts, stormwater from significant portions of the nation's populated areas is not being addressed.

On December 8, 1999, EPA promulgated a new rule requiring smaller municipalities with populations of fewer than 100,000 people located in urbanized areas (where population density is greater than 1,000 persons per square mile) to develop stormwater plans. Municipalities not in urbanized areas that have more than 10,000 residents and a population density greater than 1,000 persons per square mile will also have to develop stormwater plans if the state so designates. Under this so-called "Phase II" rule developed in consultation with key stakeholders, the EPA and the states will develop "tool boxes" from which the smaller local governments can choose particular stormwater strategies, including strategies similar to those presented in our study, to develop their stormwater plans.

Study Design

The issues presented above prompted the Natural Resources Defense Council (NRDC) to document some of the most effective existing stormwater strategies from around the country. The information collected serves as a guide for local decisionmakers, municipal officials and agency staff, and environmental activists; it is also a resource for citizens concerned about the quality of their local environment and the quality of life in their community.

NRDC compiled and evaluated over 100 case studies highlighting effective pollution prevention, administrative, and financing measures for addressing stormwater runoff. These case studies demonstrate that while many day-to-day activities impact stormwater runoff, there are control strategies that work. By presenting these strategies, NRDC aims to encourage municipal action and build community capacity to address this critical issue.

NRDC gathered information for this study by examining existing programs (several now under Phase I requirements as well as many that started earlier), reviewing literature, contacting regional and local stormwater management experts and researchers, and interviewing representatives from stormwater management or other local government agencies. The case studies represent communities of all sizes, types, and regions.

In conducting this research, NRDC was impressed by a number of existing effective programs as well as the effort and dedication that many municipal agency staff have committed to preventing stormwater pollution and enhancing their communities. NRDC learned a great deal from the communities highlighted in this report, and is pleased to be sharing the information gathered with other communities as they address this important issue.

NRDC selected the final case studies based on three general but fundamental elements of success: environmental gains, economic advantages, and community benefits. NRDC assessed environmental gains by looking at available biological, hydrological, or chemical improvements. Economic advantages used to assess the case studies included cost savings to the municipality or developer, or increases in property values related to the pollution prevention measure. Community benefits can include aesthetic or recreational enhancement, overcoming administrative hurdles or institutional barriers, or improved community relations.

NRDC organized the case studies first by region, dividing the United States into six regions based in large part on general rainfall patterns. Within each of the regions, case studies are further subdivided into the following five categories of stormwater measures:

  • Addressing stormwater in new development and redevelopment
  • Promoting public education and participation
  • Controlling construction site 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 federal regulations (40 CFR parts 122.26 and 123.25) and small municipalities will need to address under pending federal regulations.

The Foundation of Success

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 ancillary benefits to the community. The case studies in this report provide convincing evidence that urban runoff pollution can be prevented and that the most effective responses come from preventative, enforceable efforts that integrate all levels of government, design professionals from multiple disciplines, private organizations, and local citizens.

Each case study included in the report documents a specific strategy or set of strategies that a municipality, community organization, state agency, or developer found to protect the natural environment and benefit the community. Individually, the case studies are excellent examples for communities to consider when designing, implementing, and evaluating stormwater programs.

Collectively, the case studies present a clear model for success. NRDC distilled the common elements among the highlighted programs into a set of broad themes. Since they are based on actual programs, these themes serve as excellent guidance for communities beginning to address urban runoff issues as well as those looking to improve existing programs. NRDC found that when followed, these themes formed a solid foundation for successful programs.

Preventing Pollution is Highly Effective and Saves Money

The case studies demonstrate that the range of measures known as "pollution prevention" dramatically and cost-effectively reduce the quantity and concentration of pollutants winding up in stormwater. In highly urbanized areas, however, such measures may not be possible. In such cases, several communities have found treatment of runoff with structural measures to be an effective alternative.

Preserving and Utilizing Natural Features and Processes Have Many Benefits

Many communities and developers found management measures that rely on natural processes to be highly effective and efficient. Undeveloped landscapes absorb large quantities of rainfall and snowmelt; vegetation helps to filter out pollutants from stormwater. Buffer zones, conservation-designed development, sensitive area protection, or encouragement of infill development all try to enhance natural processes and are among the most effective stormwater programs highlighted.

Strong Incentives, Routine Monitoring, and Consistent Enforcement Establish Accountability

The case studies demonstrate that enforcement, or more broadly accountability, is a key element to improving water quality. Programs with high accountability often reduce pollutant loadings by 50 percent or greater.

Establishing a Dedicated Source of Funding Ensures Long-Term Viability of Programs and Public Support

The case studies found that effective stormwater programs are financially viable and affordable. Dedicated funding sources, such as stormwater utilities or dedicated environmental fees, help ensure that stormwater programs are stable over time and help gain public support.

Strong Leadership is Often a Catalyst For Success

Many times, success, at least at first, requires an individual to champion the project and make it happen.

Effective Administration is Critical

Regardless of which strategies the case-study communities chose, those with clear goals and objectives were most successful. Effective administration allows implementation of broad-based, multi-faceted programs, which these studies suggest are often the most effective at controlling the diffuse problem of stormwater pollution.

Recommendations For Local Action

Through this research, NRDC extracted several critical elements that underlie the effectiveness of these programs. Together these key actions build a strong framework for effective, efficient, and successful stormwater management over the long term. NRDC recommends that these actions, which appear throughout the case studies, be considered in all phases and components of stormwater programs. Following these actions will ensure further successful stormwater programs.

  • Plan in advance and set clear goals.
  • Encourage and facilitate broad participation.
  • Work to prevent pollution first; rely on structural treatment only when necessary.
  • Establish and maintain accountability.
  • Create a dedicated funding source.
  • Tailor strategies to the region and setting.
  • Build broad-based programs.
  • Evaluate and allow for evolution of programs.
  • Recognize the importance of associated community benefits.

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