What is MS-4?
MS-4 is an abbreviation for Municipal Separate Storm Sewer System. The “Municipal” part pertains to being in municipal or urbanized areas, as defined by the U.S. federal census bureau. Every ten years, the census bureau publishes the location of urbanized areas of the United States. The city of Manassas falls within one of these urbanized areas.

The four “S”s pertain to those urbanized area that have their sewer treatment systems separate from their stormwater infrastructure. There are separate regulations overseeing how sewer systems are maintained and operated, while the MS-4 permit regulates how these dedicated stormwater management systems are operated and maintained.

MS-4 in the City of Manassas

  • There are 5,320 storm drains that connect to 23 public and approximately 34 private stormwater facilities in the city.
  • Surface water in the city flows into either Broad Run or Bull Run. Both of these watersheds drain into the Occoquan River, which in turn, empties into the Chesapeake Bay.
City stormwater staff are pleased to answer questions and accept comments on the following stormwater program plans and reports at anytime. Please submit your questions via e-mail to or contact Susie Orndorff, Stormwater Administrator. Thank you for your input!

get notified Stay up-to-date on what is happening by. . . .