A municipal separate storm sewer system (MS4) is a publicly-owned conveyance or system of conveyances (i.e., ditches, curbs, catch basins, underground pipes, etc.) designed or used for collecting or conveying stormwater and that discharges to surface waters of the state. Examples of MS4 operators include, but are not limited to, municipalities, counties, community development districts, universities, military bases or federal correctional facilities.

Operators of large, medium and regulated small MS4s are required to obtain NPDES permit coverage to discharge to waters of the state.

Get a list of MS4 permits and contacts in Florida.

Phase I MS4s

Provides the regulatory definitions of Phase I large and medium MS4s, outlines the stormwater management program requirements and the permit re-application requirements.

Regulated Phase II MS4s

Explains which Phase II MS4s are regulated under the program, including automatic designation and designation by the permitting authority. Outlines stormwater management program requirements and details on how to obtain coverage under the Generic Permit.

Reporting

Phase I MS4 permittees are required to submit reports annually, using an annual report form provided during permit coverage. Forms are located in the DEP Public Files. Annual reports should be submitted to NPDES-MS4@floridadep.gov.

Annual Reports are due within six months of the anniversary of the date of permit coverage. 

Phase II MS4 permittees are required to submit reports using the 2003 or 2021 annual report form annually during the first cycle of permit coverage, and in years 2 and 4 thereafter, unless the Department requires more frequent submissions, through the acknowledgement letter or other notification. 

Permitting Process

NPDES-MS4@FloridaDEP.gov

Last Modified: Tuesday, Oct 13, 2026 - 10:56am