Storm Water Discharge regulations are found in 40 CFR Parts 122, 123, and 124 and the Arkansas Water and Air Pollution Control Act as defined in Arkansas Regulation 6 "Regulations for State Administration of the National Pollutant Discharge Elimination System (NPDES), effective April 16, 2004".

A permit is required for each point source discharge of storm water associated with industrial activity, municipal separate storm sewer systems (MS4s), and construction activity discharging into water of the United States. Storm Water means storm water runoff, snowmelt runoff, surface runoff and drainage.

"Storm Water associated with Industrial Activity" concerns the discharge from any conveyance, which is used for collecting and conveying storm water and which is directly related to manufacturing, processing, or raw materials storage areas at an industrial plant. Storm Water permits are issued for industry sectors utilizing Standard Industrial Classification (SIC) codes as a bases for defining analytical monitoring requirements. Individual permits are issued to facilities with special operational considerations or requirements.

"Storm Water runoff from Construction Activities" can have significant impact on water quality, contributing sediment and other pollutants at construction sites. The NPDES Storm Water Program requires operators of both large and small construction sites to obtain authorization to discharge storm water under an NPDES construction Storm Water Permit.

The EPA's NPDES storm water permitting program labels municipal separate storm sewer systems (MS4s) as either "small," "medium," or "large" for the purpose of regulation and means a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drain).