KPDES sMS4 Permit


In 1987, Congress amended the Clean Water Act to require the implementation of a comprehensive national program for addressing stormwater discharges to combat pollution caused by population growth and the development of urban/urbanized areas. The Water Quality Act of 1987 required this program to be implemented in two phases. The Phase I Rule, published in 1990, required medium and large cities or certain counties with populations of 100,000 or more to obtain permit coverage for discharges from their stormwater conveyance systems. The Phase II Rule, published in 1999, required small urbanized areas (as defined by the US Census Bureau), or areas designated by the permitting authority, with a population of between 10,000 and 100,000 to obtain permit coverage for their stormwater discharges. This included non-traditional conveyance system owners such as Universities, departments of transportation, hospitals, military bases, and prisons. The stormwater conveyance systems operated by Phase I and II entities are referred to as Municipal Separate Storm Sewer Systems or MS4’s.


The Permit

The EPA has delegated MS4 permitting authority to the Kentucky Division of Water (KDOW). As such, all discharges to waters of the Commonwealth must be permitted through the Kentucky Pollutant Discharge Elimination System (KPDES). Kentucky’s Phase II Stormwater Program began in 2003 and the University obtained coverage under the KPDES Small Municipal Separate Storm Sewer System (sMS4) General Permit beginning in 2010.

As a permittee, the University is authorized to discharge stormwater through its MS4 to waters of the Commonwealth. The University’s system is comprised of over 150 Best Management Practice (BMP) controls such as detention basins, hydrodynamic separators, green roofs, and rain gardens that help reduce and filter onsite runoff before it enters miles of underground piping that discharge via outfalls directly into streams or into the city of Lexington’s stormwater system. The goal of the MS4 permit and the primary objective of the University is to ensure that stormwater runoff does not adversely impact water quality. To accomplish this the permit has established six categories of Minimum Control Measures (MCMs) that the University is required to implement. They include:

  1. Public Education and Outreach
  2. Public Involvement and Participation
  3. Illicit Discharge Detection and Elimination
  4. Construction Site Stormwater Runoff Control
  5. Post-Construction Stormwater Management in New Development and Redevelopment
  6. Pollution Prevention/Good Housekeeping

To learn more about each of the MCMs see The Six Minimum Control Measures.

The permit also authorizes the University to discharge certain non-stormwater sources, prohibits discharges from spills, and requires the University to develop, implement, enforce, and update a Stormwater Quality Management Plan (SWQMP) that details how the required six minimum control measures will be implemented to the Maximum Extent Practicable (MEP).




KPDES sMS4 Permit

MS4 Permit Fact Sheet

Permit Requirement Summary