Municipal Separate Storm Sewer System (MS4) Program

What goes here flows here.
In 2014, the City of San Marcos became a Phase II Small MS4 based on the population from the urbanized area. An MS4 is a system of conveyances (roads with curb and gutter, inlets, channels, ditches, storm pipe, etc...) that are owned and operated by a municipality. This conveyance system is meant to allow stormwater to travel quickly and safely to the nearest outfall (a waterbody). The Texas Commission on Environmental Quality (TCEQ) requires that MS4 permit holders must create a Stormwater Management Program (SWMP) to protect water quality at the discharge points. The SWMP contains five Minimum Control Measures (see list below), each of which contain goals that the city must meet each permit year. For more information on what the MS4 program entails, please see related documents on this page or contact 

City of San Marcos SWMP and Annual Reports

Phase II MS4 Permit Minimum Control Measures and their examples

  1. Public Education, Outreach and Involvement 
  2. Illicit Discharge Detection and Elimination
  3. Construction Site Stormwater Runoff Control
  4. Post Construction Stormwater Management in New Development and Redevelopment
  5. Pollution Prevention and Good Housekeeping for Municipal Operations

MS4 Maps