MS4
MS4 stands for Municipal Separate Storm Sewer System, which is a publicly owned system of infrastructure, like ditches, curbs, catch basins, and underground pipes, designed to collect and convey stormwater. MS4s are regulated by the EPA’s National Pollutant Discharge Elimination System (NPDES) permit program to control the discharge of pollutants in stormwater runoff to protect water quality. Operators of these systems are required to develop and implement Stormwater Management Programs (SWMPs) that include measures for pollution prevention, public education, and monitoring to reduce the pollution entering local water bodies.
What an MS4 includes: Ditches and man-made channels, Curbs and gutters, Catch basins and storm drains, Underground pipes, and Municipal roads and drainage systems.
Why MS4s are regulated:
- Stormwater runoff collects various pollutants, such as pesticides, litter, oil, grease, and sediment, from urban and developed areas.
- These polluted discharges directly enter local streams, rivers, and other water bodies, harming water quality and impacting recreational use.
- Operators of MS4s are required to obtain an NPDES permit to manage stormwater discharges.
- These permits mandate the development of a comprehensive Stormwater Management Program (SWMP).
- An SWMP includes measures such as:
- Pollution prevention: Strategies to stop pollutants from entering the storm sewer system.
- Public education: Informing the public about the impacts of stormwater pollution and their role in preventing it.
- Treatment or removal of pollutants: Implementing best management practices (BMPs) to reduce the amount of pollutants in runoff.
- Monitoring and reporting: Tracking the effectiveness of stormwater management activities and reporting to regulatory agencies like the EPA.
- Pollution prevention: Strategies to stop pollutants from entering the storm sewer system.