Stormwater Basic Information*
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NYDES)
What is the NPDES Stormwater Program?
The National Pollutant Discharge Elimination System (NPDES) Stormwater Program regulates stormwater discharges from three potential sources: municipal separate storm sewer systems (MS4s), construction activities, and industrial activities. Most stormwater discharges are considered point sources, and operators of these sources may be required to receive an NPDES permit before they can discharge. This permitting mechanism is designed to prevent stormwater runoff from washing harmful pollutants into local surface waters such as streams, rivers, lakes or coastal waters.
Most states are authorized to implement the NPDES Stormwater Program and administer their own stormwater permitting programs. EPA remains the permitting authority in a few states, territories and on most tribal lands. For these areas, EPA provides oversight and issues stormwater permits.
STORMWATER DISCHARGES FROM MUNICIPAL SEPARATE STORM SEWER SYSTEMS (MS4s)
Overview
Polluted stormwater runoff is commonly transported through Municipal Separate Storm Sewer Systems (MS4s), from which it is often discharged untreated into local waterbodies. To prevent harmful pollutants from being washed or dumped into an MS4, operators must obtain a NPDES permit and develop a stormwater management program.
Generally, Phase I MS4s are covered by individual permits and Phase II MS4s are covered by a general permit. Each regulated MS4 is required to develop and implement a stormwater management program (SWMP) to reduce the contamination of stormwater runoff and prohibit illicit discharges.
WHAT IS AN MS4?
An MS4 is a conveyance or system of conveyances that is:
* Information taken from the EPA website. For more information, click here.
For more information click here for an educational brochure.
