Baltimore’s MS4 Permit

Baltimore City’s storm drain system is regulated by the federal Clean Water Act, specifically, a National Pollutant Discharge Elimination System Municipal Separate Storm Sewer, also known as the (MS4) permit. The latest MS4 permit was issued to the City on November 5, 2021. This MS4 permit was developed based on Maryland’s Bay TMDL Phase III Watershed Implementation Plan and the local TMDLs (Total Maximum Daily Loads) associated with waterways in the City. This is the 5th generation of the MS4 permit issued to the City of Baltimore. Specific new conditions are as follows:

• Street sweeping and inlet cleaning operations initiated under the previous permit must be continued at a level equivalent to 5,170 acres of impervious area restoration,
• Additional stormwater best management practices (BMPs) must be implemented for an equivalent of 3,696 acres of impervious area restoration by the end of the permit term. A milestone schedule was also established to ensure progress throughout the permit.
• At least 300 tons of litter and debris must be removed from the City’s storm drain system each year.
• At least 15 public outreach efforts/year must be conducted related to stormwater pollution and flooding.
• Monitoring resources may be leveraged by the City by participating in a pooled monitoring program.
• A comprehensive plan for long-term watershed monitoring and trend monitoring and a Polychlorinated biphenyl source tracking plan must be developed and implemented.
• Good housekeeping and pollution prevention plans must be developed for City-owned properties.
• Winter management of de-icing and anti-icing materials must be improved to further reduce chlorides, a pollutant of emerging concern.

The following are documents related to the City’s MS4 Permit:

• Baltimore City MS4 Permit
• MS4 Accounting Guidance
• MS4 Fact Sheet
• To access the State's list of local TMDLs, please visit the TMDL Web page.
• Chesapeake Bay Program

Each year, Baltimore City is required to submit an MS4 Annual Report charting its progress in meeting the terms of the permit

• MS4 Annual Reports
  • FY2022 Annual Report
  • FY2021 Annual Report
  • FY2021 Watershed Protection and Restoration Program Annual Report
  • FY2020 Annual Report
  • FY2019 Annual Report
  • FY2018 Annual Report
  • FY2017 Annual Report
  • FY2016, Annual Report
  • FY2015, Annual Report
  • FY2014, Part I
  • FY2014, Part II

A Financial Assurance Plan (FAP), which demonstrates the City’s financial ability to meet the current and proposed MS4 permit impervious surface area restoration requirements, is required to be submitted every two years.

• 2022 Financial Assurance Plan
• 2020 Financial Assurance Plan
• 2018 Financial Assurance Plan

As part of the MS4 Permit, the EPA approved a "Trash TMDL" for the Middle Branch and Northwest Portions of the Patapsco River, roughly from Harbor Hospital in the south to Ferry Bar Park (Middle Branch) and Tide Point to Canton Waterfront Park (Northwest Portion).

• Trash TMDL Implementation Plan
• Trash TMDL document

Watershed Assessments

To restore a watershed, there must be a Watershed Plan. The MS4 Permit requires that, by the end of the permit term, Baltimore City shall complete detailed watershed assessments for the entire City. The following is a list of the previous assessments (those noted with an * are too large to upload):