A municipal separate storm sewer system, or MS4, is a conveyance or system of conveyances (roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, storm drains, etc.) that is also:

  • Owned or operated by a public entity (which can include cities, townships, counties, military bases, hospitals, prison complexes, highway departments, universities, etc.) having jurisdiction over disposal of sewage, industrial wastes, stormwater or other wastes. This includes special districts under state law, such as a sewer district; flood control district, drainage districts or similar entity; an Indian tribe or an authorized Indian tribal organization; or a designated and approved management agency under section 208 of the Clean Water Act that discharges to waters of the United States.
  • Designed or used for collecting or conveying stormwater
  • Not a combined sewer
  • Not part of a publicly-owned treatment works

The following document is a list containing Missouri Regulated MS4s.

Urbanized Areas

Urbanized areas are a densely settled core of census tracts and/or census blocks that meet minimum population density requirements. These urbanized areas are determined by the U.S. Census Bureau as having a population of 50,000 or more people.

Census Information

Missouri's Nine Urbanized Area Reference Maps 2010 - U.S. Census Bureau


Minimum Control Measures (MCMs) are required focus areas in MS4 permits. These are individual areas, however they can overlap or work together to make a successful Stormwater Management Program.

Six MCMs required for Phase II regulated communities

Resources to help in the development of MCMs


Facility Name Sort descending Permit # County
Arnold MO-R040043 Jefferson
Ballwin 1 MO-R040005 St. Louis
Battlefield MO-R040042 Greene
Bel-Nor, Village of 1 MO-R040005 St. Louis
Bel-Ridge, Village of 1 MO-R040005 St. Louis
Bellefontaine Neighbors 1 MO-R040005 St. Louis
Belton MO-R040018 Cass
Berkeley 1 MO-R040005 St. Louis
Black Jack 1 MO-R040005 St. Louis
Blue Springs MO-R040022 Jackson
Bolivar MO-R040113 Polk
Boone County 3 MO-R040113 Boone
Branson MO-R040111 Taney
Breckenridge Hills 1 MO-R040005 St. Louis
Brentwood 1 MO-R040005 St. Louis


Certification Programs for Managers


In response to the 1987 Amendments to the Clean Water Act, the Environmental Protection Agency (EPA) developed Phase 1 - Overview of the Storm Program of the National Pollutant Discharge Elimination System (NPDES). Phase I Stormwater regulations address runoff in medium and large communities determined by population size in 1990, identified 11 industrial categories required to obtain permits (with some exemptions), and addressed statewide land disturbance on five acres or greater. Missouri MS4s regulated under Phase I are Kansas City, Independence and Springfield.

EPA published the national Stormwater Phase II Final Rule Fact Sheet Series in the Federal Register Dec. 8, 1999. Phase II regulations expanded the program to include communities as determined by population size in 1999 (and subsequent decennial census counts) and land disturbance on one acre or greater. 

  • Certain Communities were exempt under the Phase I Stormwater regulations in 1990 and became subject to Phase II regulations. Regulated MS4s were required to obtain a NPDES permit by March 10, 2003, and to have their stormwater management program (SWMP) in place within five years from date of initial permit issuance. The program must address six specific minimum control measures. 
    • Approximately 156 MS4s are designated and currently regulated under the Master General Permit for Phase II MS4s.
  • Industrial Classifications Modified There are still 11 categories of industrial classifications covering 30 sectors of industrial activity that are required to obtain stormwater discharge permits. However, the North American Industry Classification System classifies establishments by their primary type of activity. In addition, there is now an option for industrial no exposure certifications in lieu of an operating permit.  Municipally operated industries exempted by the Intermodal Surface Transportation Efficiency Act of 1991, are no longer exempt under Phase II. Visit Stormwater Permits for more information.
  • Land Disturbance Permits are now required for disturbance of one acre or greater. Permits must be in place before land disturbance begins at the construction site. This requirement applies statewide. Visit Construction Land Disturbance Permits for detailed information.