MS4 Operators

12/04/25

“Who is responsible for managing MS4 systems?”

MS4 systems are a wonder of modern technology. In the U.S., whoever owns and operates these systems, whether it’s a city, county, or some other entity, are designated as an MS4 Operator. MS4 operators are legally required to develop and maintain a stormwater management program and to review stormwater pollution prevention plan applications.