NPDES Phase II Regulations

What are the NPDES program and Phase II communities?

The NPDES (National Pollutant Discharge Elimination System) program established a comprehensive two-phase approach to managing stormwater discharges. Phase I of the program required permits for municipal separate storm sewers (MS4s) serving populations greater than 100,000 people and for stormwater discharges associated with industrial activities.

Phase II requirements of the NPDES program applied to all non-point source discharges of stormwater from small MS4s with populations less than 100,000. Implementation of the NPDES phase I and II permitting program was delegated to the NC Department of Environment & Natural Resources (NCDENR), which designated that Hendersonville be brought into the program as an owner of an MS4.


Municipal Separate Storm Sewer System (MS4) Program Documents | Braintree,  MA

What are the NPDES Phase II Stormwater Regulations?

  • In 1969 the Cuyahoga River in Cleveland, Ohio became so polluted and full of oily trash and residue that it caught on fire. The fire brought attention to other environmental problems across the country and helped lead to the passage of the Clean Water Act (CWA) in 1972. The CWA established the objective to restore and maintain the chemical, physical, and biological integrity of the nation's waters.
  • Phase I of the US EPA stormwater program was promulgated in 1990 under the CWA. Phase I relies on National Pollutant Discharge Elimination System (NPDES) permit coverage to address storm water runoff from:
    • Municipal separate storm sewer systems (MS4s) generally serving populations of 100,000 or greater
    • Construction activity disturbing 5 acres of land or greater
    • Ten categories of industrial activity.
  • The Stormwater Phase II Final Rule (1999) was the next step in US EPA's effort to help protect the Nation's water resources from polluted stormwater runoff.
    • Expands the Phase I program by requiring additional operators of MS4s in urbanized areas and operators of small construction sites (greater than 1 acre), through the use of NPDES permits, to implement stormwater programs.
    • Permit coverage is obtained from the North Carolina Department of Environment and Natural Resources (NCDENR).

NPDES Phase II goal:

  • A regulated small MS4 operator must develop, implement, and enforce a stormwater management program designed to reduce the discharge of pollutants from their MS4 to the "maximum extent practicable," to protect water quality, and to satisfy the appropriate water quality requirements of the CWA. The rule requires the implementation of best management practices (BMPs) to protect water quality.

NPDES Phase II requirements:

  • The stormwater management program must include the following six (6) minimum control measures:
    • Public education and outreach
    • Public participation/involvement
    • Illicit discharge detection and elimination
    • Construction site runoff control
    • Post-construction runoff control
    • Pollution prevention/good housekeeping


  • The small MS4 operator must identify its selection of BMPs and measurable goals for each minimum measure in the permit application. Must evaluate and assess the chosen BMPs and measurable goals in periodic reports to NCDENR.

 What is Nonpoint source Pollution?

This is another term for polluted runoff and other sources of water pollution that are hard to pinpoint. The term "nonpoint source pollution" comes from the federal Clean Water Act of 1987. There, it is used as a catch-all for all kinds of water pollution that are not well-defined discharges (point sources) from wastewater plants or industries.

Many state agencies have nonpoint source (NPS) management programs that address polluted runoff. North Carolina's NPS program is part of DEQ's Division of Water Quality. It serves as the central coordinating agency for the many NPS-related programs operated by various agencies.

 How are stormwater and runoff "managed"?

"Best management practices" is a term used to describe different ways to keep pollutants out of runoff and to slow down high volumes of runoff.

Preventing pollution from entering water is much more affordable than cleaning polluted water! Educating state residents about how to prevent pollution from entering waterways is one best management practice. Laws that require people and businesses involved in earth disturbing activities --like construction and agriculture -- to take steps to prevent erosion are another way to prevent stormwater pollution. There are also laws about litter, cleaning up after pets and dumping oil or other substances into storm drains.

Education and laws are just two best management practice examples. Some BMPs are constructed to protect a certain area. Some BMPS slow down stormwater, others help reduce the pollutants already in it – there are also BMPs that do both of these things.

Detention ponds fill up quickly after a rainstorm and allow solids like sediment and litter to settle at the pond bottom. Then, they release the water slowly. These ponds are one constructed BMP example. Green roofs, storm drain grates, filter strips, sediment fences and permeable paving are other examples.