The goal of the Municipal Separate Storm Sewer System (MS4) program is to reduce the discharge of pollutants to surface waters of the State.  An MS4 is a system of drainage (including roads, storm drains, pipes, and ditches, etc.) that is not a combined sewer or part of a sewage treatment plant.  During wet weather, pollutants are transported through MS4s to local water bodies.

Permits

Stormwater discharges from a regulated MS4 to a surface water of the State in an urbanized area are subject to regulation under the National Pollutant Discharge Elimination System.  MS4 permittees generally include the following municipal entities: cities, townships, villages, county agencies, universities, and school districts.  The Department completed maps to identify MS4s located in an urbanized area that may require coverage under an MS4 permit.

Who may be regulated: Urbanized Area Maps

How to view permits on public notice: MiEnviro Public Notice

Application Information

The following documents are available to assist with completing the abbreviated MS4 application form for permit reissuance in the MiEnviro Portal.

• Total Maximum Daily Loads Applicable to Existing FY26 MS4 Permittees
• Total Maximum Daily Loads Applicable to New MS4 Permittees
• Total Maximum Daily Loads Applicable to Existing FY25 MS4 Permittees
• Total Maximum Daily Loads Applicable to FY24 MS4 Permittees
• Creating KML Files for MS4 Outfalls and Points of Discharge

What to Expect During an Evaluation

• What to Expect During an MS4 Evaluation - YouTube playlist

Compliance Assistance Documents

The following documents are available to assist with developing and implementing a StormWater Management Program (SWMP) as part of the MS4 program.

SWMP Templates

• Enforcement Response Procedure (ERP)
  • Enforcement Action documentation form
• Public Participation Program (PPP)
• Public Education Program (PEP)
• Illicit Discharge Elimination Program
  • Illicit Discharge Elimination Evaluation Form
• Construction Stormwater Runoff Control Program
• Post-Construction Stormwater Runoff Program - pending
• Pollution Prevention and Good Housekeeping Program
• Total Maximum Daily Load (TMDL) Implementation Plan
• Standard Operating Procedure

Public Education

• Public Education Program (PEP) Guidance

Illicit Discharge Elimination

• Illicit Discharge Elimination Program Compliance Assistance Document
• Dry-Weather Screening: A Guide for Permittees

Pollution Prevention and Good Housekeeping

• Maintenance of Common Stormwater Best Management Practices
• Winter Road Maintenance
• Wastewater Discharge from Mobile Power Washing
• MS4 Catch Basin/Street Sweeping BMP
• Catch Basin Materials Management Guide
• Vehicle and Equipment Washing
• Snow Relocation Guidance

Post Construction Stormwater Runoff Controls

• Post-Construction Stormwater Runoff Controls Programs
• Municipal Separate Storm Sewer System (MS4) Program Calculator (xlsx)
• Municipal Separate Storm Sewer System (MS4) Program Calculator Manual

Total Maximum Daily Loads

• E. coli Total Maximum Daily Loads for MS4s in Impaired Watersheds

Stormwater Resources

• EPA's National Stormwater Calculator
• EPA's Stormwater Capture and Use (SCU) Infographics
• EGLE Best Management Practices Manual (Updated)
• Low Impact Development Manual for Michigan
• Information and Education Publications, Including Be Stormwater Savvy
• Part 5 Rules - Spillage of Oil and Polluting Materials
• National Menu of Stormwater Best Management Practices
• Stormwater Management Ordinances
• NOAA Atlas 14 Precipitation Frequency Estimates
• 90-Percent Annual Non-Exceedance Storms
• EPA's Stormwater Smart Outreach Tools