Water

MS4 – Municipal Separate Storm Sewer System

Operators of large, medium and regulated small municipal separate storm sewer sytems or MS4s 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.

Large and Medium MS4s | Small MS4s | General Permit & QLPs
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Large and Medium 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.

South Carolina has one (1) large MS4 – the South Carolina Department of Transportion and four (4) medium MS4s – City of Columbia, Greenville County, Lexington County, and Richland County.
These MS4s receive individual NPDES permits for their discharges.

Regulated Small MS4s

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

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

South Carolina has 70 regulated small MS4s. The operators of these may choose to receive coverage under a general permit or obtain individual permit coverage.