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Phase I MS4s

Phase I large and medium MS4s were previously designated by EPA, based on the total population within the geo-political boundaries of the municipalities.

  • A large MS4 is any MS4 that is located in an incorporated place or county with a population of 250,000 or greater.
  • A medium MS4 is any MS4 that is located in an incorporated place or county with a population between 100,000 and 249,999.

Other MS4s located in areas with populations below 100,000 were also designated into the program as Phase I MS4s by EPA. DEP assumed responsibility for all Phase I MS4 permits when it became the NPDES Storwmater permitting authority in October 2000.

Permit Requirements

Florida's rules for medium and large MS4s can be found at Chapter 62-624, F.A.C. and 40 CFR 122.26. The following provides a summary of the permit application requirements and program requirements.

Original Applications for Individual Permits

Phase I large and medium MS4s were subject to the two-part permit application requirements found at 40 CFR 122.26(d). The fundamental portion of the application was the development of a proposed stormwater management program (SWMP) that would meet the standard of "reducing pollutants to the Maximum Extent Practicable (MEP)." Upon approval, the NPDES permitting authority (EPA Region 4) incorporated the SWMP into an individual permit which was then issued to the MS4 operator. 

SWMPs for Phase I MS4s include measures to:

  • Identify major outfalls and pollutant loadings.
  • Detect and eliminate non-stormwater discharges to the system.
  • Reduce pollutants in runoff from industrial, commercial and residential areas.
  • Control stormwater discharges from new development and redevelopment areas.
  • Implement a monitoring/assessment program.
  • Address Total Maximum Daily Loads (TMDLs) for regulated MS4s that discharge into TMDL water bodies..


The MS4 individual permits expire after a term of five years. Permittees must re-apply for coverage prior to expiration of each permit term (Rule 62-624.420 F.A.C.).

An MS4 permittee may re-apply for permit coverage concurrently with a timely filing of the Year 4 annual report, or, as an alternative, permittees may re-apply by submitting an application 180 days prior to the expiration of the permit. The required contents of a reapplication are specified in Rule 62-624.440, F.A.C. There is no application form. 

NPDES Stormwater Program
2600 Blair Stone Road, MS 3585
Tallahassee, FL 32399-2400
866-336-6312 (toll-free)
Last Modified:
June 19, 2023 - 10:59am

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