MS4 - Municipal Separate Stormwater Sewer System

The City of Chicago is continuing its efforts to effectively manage stormwater runoff and protect the quality of area waters including Lake Michigan, the Chicago River, and the Calumet River, pursuant to its IEPA General NPDES Permit ILR40.  As part of compliance with this permit, the City’s stormwater management program manages the Municipal Separate Stormwater Sewer System (MS4) to limit the amount of pollutants that are discharged into area waters. The stormwater management program, as outlined in the City’s Notice of Intent (NOI), includes best management practices in the following 6 areas:

  1. Public Education and Outreach

  2. Public Involvement and Participation

  3. Illicit Discharge Detection and Elimination

  4. Construction Site Runoff Control

  5. Post-Construction Runoff Control

  6. Pollution Prevention and Good Housekeeping

Please see the links below to view the City’s MS4 best management practices and goals, and the latest Annual Report providing status and compliance with the City’s MS4 goals.




If a discharge from an outfall during dry weather is observed, please call 311.

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