NPDES: National Pollutant Discharge Elimination System

From Beachapedia



Historically, many surface water bodies (rivers, lakes) in the U.S. have been polluted from industrial point source (point sources are discrete conveyances such as pipes or man-made ditches) discharges from industrial facilities and municipal wastewater treatment plants. In response, the Federal Water Pollution Control Act, also referred to as the Clean Water Act (CWA), was amended in 1972 to provide that the discharge of pollutants to waters of the United States from any point source is unlawful, unless the discharge is in compliance with a permit. The National Pollutant Discharge Elimination System (NPDES) permits that are required by the CWA for point sources have helped to dramatically improve water quality in many water bodies in the U.S.

Attention is now increasingly being turned to "non-point sources" or "urban runoff" (water draining off of urban areas during both dry weather and wet weather), because this has been shown to be a leading cause of water pollution in receiving waters (rivers, streams, and the ocean) and is a frequent cause of health warning sign postings and beach closures. In response to this problem, the CWA was amended in 1987 to require medium and large municipalities to obtain National Pollutant Discharge Elimination System (NPDES) permits for stormwater discharges from their municipal separate storm sewer systems (MS4s).

Polluted storm water and non-storm water urban runoff is a leading cause of impairment to the nearly 40 percent of surveyed U.S. water bodies which do not meet water quality standards. Over land or via storm sewer systems, polluted runoff is discharged, often untreated, directly into local water bodies. When left uncontrolled, this water pollution can result in the destruction of fish, wildlife, and aquatic life habitats; a loss in aesthetic value; and threats to public health due to contaminated food, drinking water supplies, and recreational waterways.

What is an NPDES permit?

NPDES permits typically specify waste discharge requirements (for example, maximum flow rate, pollutant concentration limits, allowable pH range, maximum temperature) . NPDES permits also have the following characteristics: they are issued for up to five years; they provide for inspection and monitoring; they require notice to the public, the EPA and the state, they provide for the protection of navigation (if applicable), and they may mandate a pre-treatment program. Municipal storm water NPDES permits may also require inventories and inspections of industrial, commercial, and construction sites. A point source discharger is given a permit from the regional EPA or state agency that lists the levels of pollutants that are allowed to be discharged into a river, lake or the ocean. The permit also requires the dischargers to implement a monitoring and reporting program to ensure that the discharge does not adversely impact water quality, human health, or the environment. It is the responsibility of the discharger to monitor the water quality to insure that the limits of the permit are not exceeded. The data is typically sent to local water quality agencies and/or the EPA. These agencies are often understaffed, so it is difficult for them to enforce every permit. It is primarily a "correct your own homework" honor system, at least until water quality problems in the receiving water body become apparent.

Non-point source dischargers (cities, counties) now also must have an NPDES permit to control the discharge of pollutants to the storm drain system. This is a more difficult problem to solve than point source pollution since non-point source pollution (urban runoff) comes from not only industrial and commercial activity, but also from municipalities, construction sites, and residences. Common activities such as car washing, watering your lawn, and hosing down your driveway contribute to urban runoff.

The municipal NPDES permits were first issued in about 1990, but these first permits were lacking in "teeth" and depended largely on voluntary efforts by the cities and counties to develop and implement their own plans to reduce urban runoff pollution.

By the mid to late 1990s it became clear that the problem of urban runoff and the associated water quality degradation, beach closures, human health impacts, and environmental impairment were not getting better. Since the municipal NPDES permits (also called municipal storm water permits or municipal MS4 permits) must be renewed every 5 years, the local water quality agencies issuing the permits (in California, the Regional Water Quality Control Boards) have strengthened the permits to require specific measures to address the problem.

Who needs an NPDES permit?

If you discharge from a point source into the waters of the United States, you need an NPDES permit. Industrial, commercial, or other operations which discharge wastes directly into municipal, or other publicly owned wastewater collection and treatment systems, are not required to obtain a NPDES permit from the local public entity that operates the collection system, but must comply with waste discharge requirements issued by that entity.

If you discharge pollutants into a municipal storm sewer system or if you operate a municipal storm sewer system, in most cases a permit is required.

Individual homes that are connected to a municipal system, use a septic system, or do not have a surface discharge do not need an NPDES permit; however, industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters. In most cases, the NPDES permit program is administered by authorized states. Non-municipal waste discharges typically regulated by NPDES permits include discharges from the following types of facilities:

  • Oil refineries
  • Chemical manufacturing plants
  • Metal plating shops
  • Semiconductor manufacturing facilities
  • Food processing plant
  • Canneries
  • Fish hatcheries
  • Wineries
  • Groundwater cleanup projects
  • Hardboard manufacturing plants
  • Pulp mills
  • Sawmills
  • Gravel Operations
  • General manufacturing

How are the conditions in NPDES permits enforced by EPA and the states?

EPA Logo

There are various methods used to monitor NPDES permit conditions. The permit will require the facility to sample its discharges and notify EPA and the state regulatory agency of these results. In addition, the permit will require the facility to notify EPA and the state regulatory agency when the facility determines it is not in compliance with the requirements of a permit. EPA and state regulatory agencies also will send inspectors to companies and municipalities in order to determine if they are in compliance with the conditions imposed under their permits. EPA and state regulatory agencies may issue administrative orders, which require facilities or municipalities to correct violations and that assess monetary penalties. The laws also allow EPA and state agencies to pursue civil and criminal actions that may include mandatory injunctions or penalties, as well as jail sentences for persons found willfully violating requirements and endangering the health and welfare of the public or environment.

The state regulatory agency may also take enforcement action in response to significant or chronic permit violations under the authority of the Federal Clean Water Act and Amendments, and state water quality laws, such as California's Porter-Cologne Water Quality Control Act (California Water Code). Enforcement action can range from Notices of Violation issued by agency staff; to Cleanup and Abatement Orders or Administrative Civil Liability Complaints issued by the agency's Executive Officer; to Cease and Desist Orders, Administrative Civil Liability Orders (including civil monetary penalties), or Referrals to the State Attorney General's Office for criminal enforcement.

Equally important is how the general public can enforce permit conditions. The facility or municipality monitoring reports are public documents, and the general public can review them. If any member of the general public finds that a facility or municipality is violating its NPDES permit, that person can independently start a legal action, unless EPA or the state regulatory agency has already taken an enforcement action.

How do NPDES permits protect water?

An NPDES permit will generally specify an acceptable level of a pollutant or pollutant parameter in a discharge (for example, a certain concentration of suspended solids, metals, or biological oxygen demand (BOD)). The permittee may choose which technologies to use to achieve that concentration. Some permits, however, do specify the use of certain generic Best Management Practices (BMPs), such as installing a screen over the pipe to keep debris out of the waterway or Best Available Control Technologies (BACT). NPDES permits are intended to make sure that a state's mandatory standards for clean water and the federal minimums are being met.


California State Water Resources Control Board

EPA, Office of Wastewater Management (OWM)

This article is part of a series on Clean Water which looks at various threats to the water quality of our oceans, and the negative impacts polluted waters can have on the environment and human health.

For information about laws, policies, programs and conditions impacting water quality in a specific state, please visit Surfrider's State of the Beach report to find the State Report for that state, and click on the "Water Quality" indicator link.