EPA's 1999 stormwater Phase II regulations established small municipal separate storm sewer systems (MS4s) in urbanized areas, as well as small MS4s outside the urbanized areas that are designated by the permitting authority, to obtain NPDES permit coverage for their stormwater discharges.
Region 2 issued the first Small MS4 General Permit (Small MS4 GP) for those public entities in 2006 for the Commonwealth of Puerto Rico. The current Small MS4 GP and Small MS4 GP Fact Sheet went into effect on July 1, 2016.
The issued general permit requires MS4s to continue implementing and updating their existing Stormwater Management Program. EPA developed a Storm Water Management Program template that is designed to assist MS4s in selecting and incorporating section(s) that provide guidance with the six minimum control measures of the Small MS4 GP. There is a Stormwater Management Program (English Version) and a Stormwater Management Program (Spanish Version).