MS4 Introduction

In 1972, Congress amended the Federal Water Pollution Control Act (known as the Clean Water Act (CWA) to prohibit the discharge of any pollutant to waters of theUnited Statesfrom a point source unless the discharge is authorized by a National Pollutant Discharge Elimination System ("NPDES") permit. The NPDES program is designed to track point sources and require the implementation of the necessary controls to minimize the discharge of pollutants.


In 1987, Congress amended the CWA to require implementation, in two phases, of a comprehensive national program for addressing stormwater discharges. The first phase of the program, "Phase I," was promulgated by EPA on November 16, 1990 (Federal Register, Volume 55, Page 47,990 [55 FR 47990]). Phase I requires NPDES permits for stormwater discharge from a large number of priority sources, that include municipal separate storm sewer systems ("MS4's") that serve populations of 100,000 or more and several categories of industrial activity, which include construction sites that disturb five or more acres of land.


On December 8, 1999, EPA promulgated the second phase of the stormwater regulatory program, "Phase II," (64 FR 68722). The complete Federal Register announcement can be accessed on the EPA website as listed in the References Section of this document. Phase II regulations address stormwater discharges from certain MS4's that serve populations of less than 100,000 (identified as "small MS4's"). In summary, the regulations require that all small MS4 operators located in Urbanized Areas (as defined by the latestU.S.census) must "develop, implement and enforce a Stormwater Management Program (“SWMP”) designed to reduce the discharge of pollutants from the MS4 to the maximum extent practicable, to protect water quality…" This information may be found in Title 40, Part 122 of the Code of Federal Regulations (40 CFR 122).


InTexas, authority to issue MS4 stormwater discharge permits has been delegated by EPA to the State ofTexas. Under the authority of the Texas Water Code and the CWA, the Texas Commission on Environmental Quality ("TCEQ") will issue a Texas Discharge Elimination System ("TPDES") general permit to discharge waste from small MS4 systems to waters of the state (TPDES General Permit No. TXR040000). The current draft text of the permit can be viewed on the TCEQ website as listed in the References Section of this document.