National Pollutant Discharge Elimination System (NPDES)

The National Pollutant Discharge Elimination System (NPDES) is a program established by the Federal Clean Water Act and the Pennsylvania Clean Streams Law. It is a permitting system that regulates point sources of water pollution, with the goal of improving water quality.

Both Federal and Pennsylvania laws require wastewater dischargers to receive a permit that establishes their maximum allowable pollution limits, as well as specifies monitoring and reporting requirements for future permitting benchmarks and recordkeeping. The NPDES permit regulates household and industrial wastes that are collected in sewers and treated at municipal wastewater treatment plants. Specifically regulated pollutants include those found in household, commercial and industrial sanitary waste, fecal coliform, oil and grease, toxic pollutants (as listed on the EPA website and other pollutants that according to EPA are "not conventional or toxic that may require regulation," including nutrients like nitrogen and phosphorous.

Pollution also comes from "point" sources, which are discrete conveyances such as pipes or man-made ditches. 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. The permits also regulate industrial point sources and concentrated animal feeding operations (CAFO) that discharge into other wastewater collection systems, or that discharge directly into receiving waterways. Permits regulate these discharges with the goals of protecting public health and aquatic life, and ensuring that every facility treats wastewater. To achieve the goals of the program, permits usually include site-specific discharge limits, as well as compliance monitoring and reporting requirements and enforcement actions if regulated facilities fail to comply with their permits.

Phase I of this program, issued in 1990, required medium and large cities or certain counties with populations of 100,000 or more to obtain NPDES permits for their stormwater discharges. Phase II, issued in 1999, requires regulated small "Municipal Separate Storm Sewer Systems" (MS4s) in urbanized areas, as well as small MS4s outside the urbanized areas that are designated by the permitting authority, to obtain NPDES permit coverage for their stormwater discharges.

The NPDES permit is generally valid for a period of five years. Applications for renewal of NPDES permits must be submitted at least 180 days prior to the expiration of the current facility permit. Applications for NPDES permits can be obtained from DEP regional offices or on the DEP website.


npdesImplementation of NPDES permitting provides the following advantages:


The following challenges are associated with stormwater management BMPs:

How to Address the Implementation of NPDES

npdesThere are a variety of ways to implement the NPDES program at the municipal level. Implementation through public education and outreach, illicit discharge detection and elimination, construction site runoff controls, and post-construction runoff controls can all help municipalities meet the requirements of the NPDES and MS4 programs. Municipal, agricultural, industrial and wastewater treatment plant efforts to design programs and infrastructure systems can ultimately reduce the discharge of pollutants into waterways, and water quality is ultimately improved and meeting the requirements of the Clean Water Act as well as the requirements of the DEP-issued NPDES permits can be achieved.

Permit holders can coordinate and work with the Conservation District, local watershed associations, the Chester County Water Resources Authority and Planning Commission to help navigate the regulatory framework of DEP and the EPA permitting processes.


Watersheds, An Integrated Water Resources Plan for Chester County and Its Watersheds, was adopted in 2002 as the water resources component of Landscapes. The County-wide Act 167 Stormwater Management Plan, which is in the adoption process (as of March 2013), is comprised of the Watersheds Plan with an Act 167 Addendum. The Addendum includes a Model Ordinance as well as a Standards Matrix for stormwater management related to land disturbance, Christina Basin MS4 Total Maximum Daily Load Implementation Strategy, Act 167 Plan consistency requirements for state financed projects, and additional documentation required to fulfill the Act 167 plan requirements. This Plan was written with the intent of assisting municipalities in meeting their NPDES Phase 2/MS4 requirements through the adoption of the standards and criteria set forth in the Model Ordinance and Standards.

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