Moving closer to creating a fishable and swimmable harbor: Baltimore’s MS4 Permit

The primary cause of water pollution in Baltimore is contaminated stormwater runoff (the only major source of pollution that is growing in the Chesapeake Bay). This is caused by:

  • 45% of Baltimore is impervious surfaces
  • Much of the stormdrain infrastructure is 100+ years old
  • Trash, litter, and pet waste problems
  • Also, Baltimore has a municipal separate storm sewer system (MS4), which means that stormwater runoff is discharged directly into local streams and the harbor. Because of this, the Maryland Department of the Environment requires that Baltimore have an MS4 permit.

On December 27, 2013, The Maryland Department of the Environment (MDE) reissued a National Pollutant Discharge Elimination System (NPDES) stormwater permit to the City of Baltimore. This MS4 permit lasts for 5 years and covers stormwater discharges from the municipal separate storm sewer system owned or operated by Baltimore City.

In order to reduce contaminated stormwater runoff and improve water quality, Baltimore’s MS4 permit requires that the City develop a watershed implementation plan (WIP) by the end of 2014 to restore 20% of the City’s impervious surface area. Twenty percent restoration represents 4291 acres – the equivalent of 3,000 footballs fields or 1,900 rowhouse blocks.

Meeting the MS4 restoration goal will also help us meet Baltimore’s pollution and trash TMDLs (Total Maximum Daily Loads) – these are the targets for reducing nitrogen, phosphorus, sediment, bacteria, and other substances that are polluting our streams and harbor.

How do we do this?
Reducing polluted runoff, and meeting the MS4 and TMDL goals, will be accomplished through a comprehensive approach that includes:

  • Restoring streams
  • Installing “green” stormwater management facilities like bio-retention and rain gardens
  • Planting trees
  • Removing impervious surfaces and replacing with these with green spaces
  • Inspecting and eliminating illicit discharges into the storm sewer system
  • Increasing plans review and permits
  • Upgrading and replacing pipes and conduits
  • Reducing trash and litter with street sweeping, debris interceptors and other collection methods
  • Practicing proper lawn care and vehicle maintenance
  • Educating the public about what they can do to reduce polluted runoff

In 2014 the Department of Public Works (DPW)  prepared an MS4 Watershed Implementation Plan(WIP) for implementing the various methods listed above, including costs, funding, timeline, and locations. The restoration plan was developed in an open process with multiple stakeholders. Four public meetings were held in the summer of 2014, as well as meetings with individual stakeholders and partner organizations.
Click here for Comment Response Document
Who will be involved?
While the Environmental Compliance and Laboratory Services Division of DPW is the lead in developing the MS4 restoration plan, city agencies, environmental non-profits, businesses, and community members all play a role in reducing polluted stormwater.

The following are potential projects and programs that will help us reach our restoration goal:

Planting trees that create greener and cooler neighborhoods.
Sweeping streets at least once a week to create cleaner neighborhoods and less trash.
Creating stormwater ponds and wetlands that become new community amenities and redevelopment opportunities.
Installing rain gardens and bio-retention planters that create greener and more beautiful streets, parks, businesses, and homes.
Replacing pavement with green spaces at schools, resulting in new play areas for students and teachers.
Restoring local streams to reduce flooding and erosion and improve water quality and habitat.
Creating new community green spaces from previously vacant lots.
Installing hundreds of storm drain inlet screens and debris collectors to stop trash from entering into streams and the harbor.


Click here for MS4 Meetings, Information and Annual Reports

For additional information, questions, or comments, please contact: – subject “MS4 Plan”
or call 410-396-0732