Stormwater Regulations

Making Sense of Stormwater Regulations
(Ref. EPA 40CFR122.26, National Pollutant Discharge Elimination System (NPDES))

NPDES requires implementation of “Best Management Practices” (BMP’s). A BMP is literally a course of action which, through its implementation helps “to manage the quantity and improve the quality of stormwater runoff” and meets or exceeds the “Minimum Control Measures” performance objectives of the federal NPDES regulation for limiting the discharge of pollutants to surface water supplies via stormwater runoff.

NPDES requires Minimum Control Measures to be put into place by activities in affected Urbanized Areas (UA). There are 405 Urbanized Areas in the US listed in Appendix 6 of the 2000 US Census. Urbanized Areas are not necessarily just cities, but also include suburbs and other nearby areas. Appendix 6 contains detailed maps of each Urbanized Area and can be accessed on-line through the US EPA Office of Wastewater Management (OWM) website @ to determine if a particular place is in an affected UA.

There are a variety of Best Management Practices available for managing stormwater runoff. Regardless of the type, stormwater BMP’s are part of a comprehensive management action program. In general, BMP’s are either “Non-Structural” or “Structural”. There is no one BMP which can address all possible stormwater problems.

Non-Structural BMP’s include a range of practices which are designed to reduce the process of converting rainfall to runoff and which help prevent pollutants from getting into the runoff in the first place. These non-structural BMP’s include education, management, and Pollution Prevention practices including housekeeping, among others.

Structural BMP’s, as the name implies, include engineered and/or constructed systems which are used to directly affect stormwater runoff at the point of generation, or the point of discharge. Structural BMP’s include Proprietary/Miscellaneous Systems like catch basin inserts, as well as other Infiltration, Detention, and Wetland Systems to name just a few.

The applicable regulations require affected activities (see “Summary of Affected Activities Requiring the NPDES Stormwater Permit”) to develop a program to manage stormwater discharges from their facilities. This management program includes, among others, the development and implementation of a Stormwater Pollution Prevention Plan (SWPPP) including BMP’s. The SWPPP identifies:

1) Potential Sources of Pollution and Exposed Materials, including a History of Past Spills & Leaks
2) BMP’s
3) Non-Structural controls such as Good Housekeeping Practices and Spill Prevention & Response
4) And Structural controls such as Containment including Pollution Incident Prevention Plans (PIPP) and Spill Prevention, Control, and Countermeasures (SPCC) plans.

ENPAC products help users comply with the requirements of the NPDES and Stormwater regulations