National Pollutant Discharge Elimination System (NPDES) Stormwater Program

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 pollution is one of the most widespread water quality challenges facing the United States today. When rain falls on streets, parking lots, construction sites, and industrial areas, it picks up contaminants and carries them directly into rivers, lakes, wetlands, and coastal waters. Unlike sewage, this runoff receives little or no treatment before reaching natural water bodies. The consequences affect drinking water sources, aquatic ecosystems, and public health across every region of the country.

To address this problem, the EPA administers the NPDES Stormwater Program under authority granted by the Clean Water Act. The program requires municipalities, construction site operators, and industrial facilities to obtain permits that control what enters stormwater systems and, ultimately, the nation’s waters.

NPDES permitting authority rests with the EPA at the federal level, but 46 states and one territory have received authorization to administer their own NPDES programs. In those locations, the state environmental agency issues and enforces permits in place of the EPA. In states without authorization, including Massachusetts, New Hampshire, New Mexico, Idaho, and the District of Columbia, the EPA regional office manages the permitting process directly.

Each of the EPA’s ten regional offices oversees compliance and enforcement within its geographic area, working alongside state agencies where state programs exist. This structure means permit requirements, deadlines, and enforcement priorities reflect both federal standards and regional conditions. A facility operating in multiple states faces different permit administrators depending on location.

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 National Pollutant Discharge Elimination System (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 may be required to obtain an NPDES permit before discharging 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.