Municipal Separate Storm Sewer System (MS4)

Polluted stormwater runoff is commonly transported through municipal separate storm sewer systems (MS4s), and then often discharged, untreated, into local water bodies.

An MS4 is a conveyance or system of conveyances that is:

• owned by a state, city, town, village, or other public entity that discharges to waters of the U.S.,
• designed or used to collect or convey stormwater (e.g., storm drains, pipes, ditches),
• not a combined sewer, and
• not part of a sewage treatment plant, or publicly owned treatment works (POTW).

To prevent harmful pollutants from being washed or dumped into MS4s, certain operators are required to obtain National Pollutant Discharge Elimination System permits and develop stormwater management programs (SWMPs). The SWMP describes the stormwater control practices that will be implemented consistent with permit requirements to minimize the discharge of pollutants from the sewer system.

Annual Reports

As part of our permit requirements, each year we submit an annual report to the Texas Commission on Environmental Quality. The annual report covers each minimum control measure in the Stormwater Management Program. The annual report is a way to measure that we completed all the requirements set by the Stormwater Management Program.