Municipal Separate Storm Sewer System (MS4) Discharges: Am I Regulated?
Municipal Separate Storm Sewer System (MS4) permit requirements were implemented in two phases: Phase I for large and medium MS4s and Phase II for regulated small MS4s.
Phase I MS4 Requirements
If you operate an MS4 which serves or is located in an incorporated place or county with a population of 100,000 or greater (based on the 1990 U.S. Census), then you operate a regulated Phase I MS4 and you must apply for an individual permit*.
*Please note that all Phase I MS4s are already permitted and there are no new Phase I designations.
Phase II MS4 Requirements
If you operate a small MS4:
located in an urbanized area (UA), as defined by the Bureau of the Census (note that MS4s may be regulated based on the 2010 Census UAs), or
located outside of a UA and are brought into the program on a case-by-case basis (i.e., “designated”) by the TCEQ,
To determine if you are located in a UA, you can visit the Environmental Protection Agency's (EPA's) Urbanized Area Map Web page and find maps of urbanized areas in a city near you.
Contact us if you have any questions about this general permit.