National Pollutant Discharge Elimination System (NPDES)

Stormwater Discharges from Transportation Sources


Streets, roads, and highways are the primary mode for moving goods, people, and services but also can carry stormwater runoff pollutants from the adjacent land and from cars, trucks, and buses, including heavy metals from tires, brakes, and engine wear, and hydrocarbons from lubricating fluids. If the pollutants are not properly controlled, they can impair waters causing them to no longer support the water's designated uses and biotic communities.

Similar to traditional stormwater management authorities (cities and counties), transportation authorities are also responsible for managing the stormwater runoff that discharges to our nation's waters via regulated municipal separate storm sewer systems (MS4s) along streets, roads, and highways, but there are some key differences:

Transportation MS4s versus Traditional MS4s


(NonTraditional) Transportation MS4

(Traditional) City/County MS4


State transportation agencies often own streets and highways that can stretch for many miles, and cross numerous waterways, watersheds, and jurisdictions

Local governments are typically responsible for streets they own, which are usually in a limited geographical area

Population served by MS4

State transportation agencies often serve a transient population of drivers and passengers

Local governments often serve residents and businesses in their community boundaries


State transportation agencies have little to no enforcement authority to implement ordinances and must use other mechanisms  

Local government can develop and implement ordinances that they then enforce in their community boundaries

An integrated approach is needed to address these challenges and strengthen stormwater management programs (SWMPs). This site provides access to transportation-specific stormwater information primarily for state transportation agencies, but county and local transportation authorities will also find it useful.

Top of Page

Regulations, Permits, and Programs

The NPDES program requires operators of regulated transportation MS4s to reduce the discharge of pollutants from their MS4 to the maximum extent practicable. They must each establish a comprehensive SWMP under their NPDES permit. Most states are authorized to administer their own stormwater permitting programs. EPA remains the permitting authority in New Hampshire, Massachusetts, New Mexico, Idaho, territories, and on most Indian Country lands.

  • Municipal MS4s —Find information on the municipal stormwater program in guides and fact sheets.
  • Authorization Status— Determine your permitting authority for construction and industrial stormwater discharges.
  • Stormwater and TMDLs —Learn about how TMDLs are developed and read case studies.

A permitted Phase II MS4’s SWMP must at least cover:

  • Public education/outreach,
  • Public involvement,
  • Pollution prevention/good housekeeping,
  • Construction,
  • Post-construction, and
  • Illicit discharge detection and elimination.

Top of Page

State Department of Transportation (DOT) Information

Many state departments of transportation (DOTs) maintain a stormwater website where they post their NPDES permit, program-related information, and specific actions they are taking to reduce stormwater pollution.

Visit the following non-EPA websites to learn more about how state DOTs are managing stormwater runoff The following links exit the site Exit.

Other Federal Websites

State DOT Stormwater Websites

Top of Page

Innovative Materials and Good Practices

A stormwater manual should provide helpful methods and techniques in support of an effective and comprehensive stormwater management program (SWMP). Some manuals focus on a particular aspect of stormwater management, such as one of the minimum control measures:
  • public education,
  • public involvement,
  • construction,
  • post-construction,
  • illicit discharge detection and elimination, and
  • good housekeeping.

Other manuals are specific to a particular region, but they still might provide innovative tools from which all transportation authorities can benefit.

Federal Innovation

  • Copper-free Brake Initiative —EPA, the Environmental Council of the States (ECOS), and eight automotive industry groups, signed an agreement to reduce the use of copper and other materials in motor vehicle brake pads. This initiative will decrease runoff of those materials from roads into the nation’s streams, rivers, and lakes and is a national example of pollution prevention/source control.
  • Green Streets, Green Jobs, Green Towns InitiativeExit— This partnership aims to stimulate the green jobs market and enable families to work where they live and play. Small-to-mid-sized communities can boost their local economies and protect water resources through the use of watershed planning, and design and construction of stormwater best management practices (BMPs).
  • Greening America’s Capitals— This EPA program helps state capitals develop an implementable vision of environmentally friendly neighborhoods that incorporate innovative green infrastructure strategies. Through the Partnership for Sustainable Communities, EPA provides design assistance to sustainable communities that protect the environment, economy, and public health and to inspire state leaders to expand the program.


Active Construction

Top of Page

Illicit Discharge Detection and Elimination

Top of Page

Maintenance of BMPs

Top of Page

Pollution Prevention and Good Housekeeping

Top of Page


EPA Resources

  • Green Infrastructure – Learn more about green infrastructure techniques that uses vegetation, soils, and natural processes to manage water and create healthier urban environments.
  • Nonpoint Source Program— Learn about nonpoint source pollution programs in your area and what you can do to protect and conserve valuable ecosystems.
  • OWOW Green Street Page —Green Streets are a sustainable stormwater management strategy that contributes to community redevelopment. Many cities have replaced traditional street rehabilitation with green street strategies to address stormwater, transportation, and neighborhood stabilization goals. By combining transportation choice with environmental strategies, a green street product can support redevelopment efforts from multiple stakeholder perspectives.
  • Stormwater to Street Trees: Engineering Urban Forests for Stormwater Management —This guide can help engineers, planners, developers, architects, arborists, and public officials understand how trees perform and interact in a stormwater management system, and the new technologies that are being used to increase the stormwater utility function of the urban forest, even in the densest urban environments.

State Manuals

The following links exit the site Exit

Fact Sheets


Top of Page

Public Education and Public Participation


Television Advertisement and Radio

Top of Page

Monitoring Strategies

Top of Page

Research, Tools, and Webcasts

Research is an important component in stormwater management. Research can update us on the most recent technologies, improved strategies, cost-effective data, or emerging issues that need to be addressed. Many of the resource listed on this page are specific to stormwater and transportation.

Long-Term Stormwater Planning

  • Community Solutions for Stormwater Management: A Guide for Voluntary Long-Term Planning - Guide to assist states and local governments in developing and implementing effective long-term stormwater plans. This document describes how to develop a comprehensive long-term community stormwater plan that integrates stormwater management with communities' broader plans for economic development, infrastructure investment and environmental compliance.


  • Joint EPA-Federal Highway Administration (FHWA) Webcasts (Coming Soon) —This page provides links to webinars cohosted by EPA and FHWA that feature techniques that state and local transportation departments have implemented in their SWMPs to reduce the discharge of stormwater pollutants.
  • Research—Information on EPA developments and related resources for those who want to know more about stormwater-related green infrastructure practices.
  • Experimental Permeable Pavement Parking Lot and Rain Garden for Stormwater Management—Information on EPA’s green infrastructure research on long-term porous pavement to address stormwater management issues.
  • National Cooperative Highway Research Program Exit —This program under the Transportation Research Board addresses issues state transportation departments suggest to find solutions. The research conducted also can provide useful information to local transportation departments and others.

Top of Page

Regional Planning

  • Eco-Logical Approach Exit —This approach organizes current methods to identify natural resources and avoid, minimize, and mitigate impacts in a systematic, stepwise process. It was developed by a steering team consisting of representatives of federal agencies.
  • Green Highways Partnership (GHP) Exit —The GHP is a voluntary public-private partnership that advances environmental stewardship in transportation planning, design, construction, operations, and maintenance.
  • Watershed Resources Registry Exit—This interactive mapping tool can provide a framework and be tailored to characterize and prioritize natural resource management opportunities using a watershed approach. Preserving and/or restoring natural hydrology for stormwater is one element along with restoration and/or preservation of riparian zones, wetlands, and uplands.
  • Stochastic Empirical Loading and Dilution Model (SELDM) Exit — SELDM is a stormwater-quality runoff model for highways and other land uses that estimates stormwater flows, pollutant loads, and concentrations from roads and upstream watersheds. The USGS developed SELDM in cooperation with the FHWA.

Top of Page


  • Green Infrastructure — This page provides links to EPA and non-EPA Web pages that can provide information on how green infrastructure can be used to help mitigate climate change impacts.
  • Context Sensitive Solutions -- Context Sensitive Solutions (CSS) is a collaborative, interdisciplinary approach that involves all stakeholders and leads to preserving and enhancing environmental resources along with other resources, while improving or maintaining safety, mobility, and infrastructure conditions. 
  • Context Sensitive Solutions in Designing Major Urban Thoroughfares for Walkable Communities —The report by the Institute for Transportation Engineers (ITE) can be used as a guide for roadway improvement projects.

Top of Page


Top of Page

Selecting Best Management Practices

Top of Page

Specific Pollutants

Top of Page

Case Studies and Projects

With the challenges of climate change, impaired waters, and population and development growth, transportation entities are thinking beyond the right-of-way and approaching stormwater on a broader, watershed scale. New development and redevelopment projects are not only altering or creating new conveyance systems, but also incorporating effective stormwater BMPs—including green infrastructure and green street techniques—to reduce stormwater flow. Creating pervious biking/walking paths and curbside vegetation (e.g., bioretention areas) are just two of the many ways to incorporate these techniques.


Top of Page

Local Roads and Streets

Top of Page


  • The Chicago Green Alley Handbook —The Chicago Department of Transportation is working on a green streets pilot project to construct and measure the performance of a complete street/green street infrastructure.

Top of Page

Shared Use Paths

Top of Page

Outfall Specific

  • Coastal Stormwater BMPs Exit —North Carolina Department of Transportation works with Kure Beach to reduce stormwater using a dune infiltration system.
  • Stormwater Curb Extension —The Portland Bureau of Transportation retrofitted a residential collector into a vegetative curb extension. This project incorporates a ramp for pedestrian use and captures, treats, and infiltrates runoff.
  • Stormwater Planters —As part of Portland Green Street projects, a series of stormwater planters are structured so that intense storm events can be captured while maintaining pedestrian circulation and street parking.

Top of Page