Municipal Separate Storm Sewer Systems (MS4s)

By definition an MS4 is a system of conveyances that include, but are not limited to, catch basins, curbs, gutters, ditches, man-made channels, pipes, tunnels, and/or storm drains that discharge into Waters of the State. For these conveyances or system of conveyances to be recognized as an MS4, a state, city, town, village, or other public entity must own them. These conveyances must also not be part of a Publicly Owned Treatment Works and may not operate as a combined sewer.

Operators of large, medium and regulated small Municipal Separate Storm Sewer Systems are required to obtain NPDES permit coverage in order to discharge pollutants into Waters of the State. These designations (large, medium, and small) are based on urbanized areas as determined by the latest census.

South Carolina has one (1) large MS4 - the South Carolina Department of Transportation and three (3) medium MS4s - City of Columbia, Greenville County, and Richland County. These MS4s receive individual NPDES permits for their discharges.

There are also over 70 regulated small MS4s in South Carolina. The operators of these may choose to receive coverage under a general permit or obtain individual permit coverage.

Construction Activities

Technical Documents

Download all MS4 related documents including the general permit, worksheets and checklists.

Design Guidance

Stormwater Contacts

Need to get in touch with an MS4 representative? Check out the MS4 Contact Page for recent regulator information.

Regulated MS4s

Stormwater Links

All internal and external links related to the MS4 Community.

Municipal Separate Storm Sewer Systems (MS4s)

Large and Medium MS4s must prepare and submit a permit application to address each of the following elements:

  • Structural control maintenance
  • Areas of significant development or redevelopment
  • Roadway runoff management
  • Flood control related to water quality issues
  • Municipal owned operations such as landfills, wastewater treatment plants, etc
  • Hazardous waste treatment, storage or disposal sites, etc
  • Application of pesticides, herbicides, and fertilizers
  • Illicit discharge detection and elimination
  • Regulation of sites as classified as associated with industrial activity
  • Construction and post-construction site runoff control
  • Public education and outreach.

Regulated Small MS4s must develop a program to cover each of the following minimum control measures:

  • Public education and outreach
  • Public participation/ involvement
  • Illicit discharge detection and elimination
  • Construction site runoff control
  • Post-construction site runoff control
  • Pollution prevention/ good housekeeping.


Environment Stormwater