EPA’s Storm Water Program: National Pollutant Discharge Elimination System (NPDES)

Problems with Stormwater Pollution

The following information is sourced directly from the Environmental Protection Agency (EPA) website and is intended for educational purposes. It provides an overview of the National Pollutant Discharge Elimination System (NPDES) Stormwater Program, including its scope, importance, and the problems associated with stormwater pollution.

Stormwater runoff is generated from rain and snowmelt events that flow over land or impervious surfaces, such as paved streets, parking lots, and building rooftops and does not soak into the ground. The runoff picks up pollutants like trash, chemicals, oils, and dirt/sediment that can harm our rivers, streams, lakes, and coastal waters. To protect these resources, communities, construction companies, industries, and others use stormwater controls, known as best management practices (BMPs). These BMPs filter out pollutants and/or prevent pollution by controlling it at its source.

The NPDES stormwater program regulates some stormwater discharges from three potential sources: municipal separate storm sewer systems (MS4s), construction activities, and industrial activities. Operators of these sources might be required to obtain an NPDES permit before they can discharge stormwater. This permitting mechanism is designed to prevent stormwater runoff from washing harmful pollutants into local surface waters.

• Authorization Status for EPA’s Stormwater Construction and Industrial Programs – Most states are authorized to implement the stormwater NPDES permitting program. EPA remains the permitting authority in a few states, territories, and on most land in Indian Country.

Population growth and the development of urban/urbanized areas are major contributors to the amount of pollutants in the runoff as well as the volume and rate of runoff from impervious surfaces. Together, they can cause changes in hydrology and water quality that result in habitat modification and loss, increased flooding, decreased aquatic biological diversity, and increased sedimentation and erosion. The benefits of effective stormwater runoff management can include:

• protection of wetlands and aquatic ecosystems,
• improved quality of receiving waterbodies,
• conservation of water resources,
• protection of public health, and
• flood control.

Traditional stormwater management approaches that rely on peak flow storage have generally not targeted pollutant reduction and can exacerbate problems associated with changes in hydrology and hydraulics.

More Information on the Stormwater Program

• Stormwater Centers of Excellence Grants
• Stormwater Planning
• Stormwater Rules and Notices
• Stormwater Best Management Practices Fact Sheets
• Stormwater Webcasts

NPDES stormwater program areas:

• Stormwater Pollutants of Emerging Concern
• Stormwater Discharges from Construction Activities
• Stormwater Discharges from Industrial Activities
• Stormwater Discharges from Municipal Sources
• Stormwater Discharges from Transportation Sources
• Oil and Gas Stormwater Permitting
• EPA’s Residual Designation Authority
• Stormwater Maintenance
• Stormwater Planning

See the following for additional information:

• National Research Council Report on Urban Stormwater
• National Water Quality Inventory Report to Congress (305(b) report)
• Impaired Waters on the 303(d) List
• Chapter 4 (Environmental Assessment) from EPA’s Preliminary Data Summary of Urban Stormwater Best Management Practices (1999)