MS4 Permit, TMDLs, and Annual Reports


  • MS4 Permit
  • MS4 and TMDL Watershed Implementation Plan (WIP)
  • MS4 Annual Reports

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 permit lasts for 5 years and covers stormwater discharges from the municipal separate storm sewer system (MS4) owned or operated by Baltimore City. The expiration of the Permit is December 26, 2018.

As stipulated in the Permit, the City must manage, implement, and enforce a stormwater management program in accordance with the Clean Water Act and corresponding stormwater NPDES regulations to meet the following requirements:

  1. Effectively prohibit pollutants in stormwater discharges or other unauthorized discharges into the MS4 as necessary to comply with Maryland’s receiving water quality standards;
  2. Attain applicable wasteload allocations (WLAs) for each established or approved Total Maximum Daily Load (TMDL) for each receiving water body, consistent with Title 33 of the U.S. Code (USC) §1342(p)(3)(B)(iii); 40 CFR §122.44(k)(2) and (3); and
  3. Comply with all other provisions and requirements contained in this permit, and in plans and schedules developed in fulfillment of this permit.

The City's MS4 Permit encompasses land within the legal City boundary; the City's properties associated with Back River Wastewater Treatment Plant; and the drinking water reservoirs at Loch Raven, Pretty Boy, and Liberty. For MS4 Permit restoration and TMDL compliance, the WIP focused solely on property within City boundaries, which includes five watersheds:

  1. Back River
  2. Baltimore Harbor
  3. Jones Falls
  4. Gwynns Falls
  5. Lower North Branch of the Patapsco River (LN Branch Patapsco)

The entire City is a part of the Chesapeake Bay watershed and therefore subject to the Chesapeake Bay TMDL, which mandates a significant reduction in nutrients and sediment by 2025. Each of the City watersheds are listed as impaired for nutrients, sediment, bacteria, chlordane and/ or PCBs and have been issued TMDLs associated with the pollutant.

To read the entire MS4 Permit, Click HERE.

To access the State's list of local TMDLs, Click HERE.

MS4 and TMDL Watershed Implementation Plan

The issuance of the MS4 Permit initiating the development of the Baltimore City MS4 and TMDL Watershed Implementation Plan (WIP). As required by the Permit, the WIP presents strategies to meet the 20% impervious restoration requirement and Total Maximum Daily Load (TMDL) waste load allocations for each receiving water body. Specifically, the WIP provides the City basis to:

  1. Provide Best Management Practices (BMPs) to restore an equivalent 20% of the existing impervious area where stormwater runoff is currently not managed to the maximum extent practicable (MEP);
  2. Meet TMDL Waste load Allocations (WLAs) approved by the Environmental Protection Agency (EPA);
  3. Educate and involve residents, businesses, and stakeholder groups in achieving measurable water quality improvements;
  4. Establish a reporting framework that will be used for annual reporting as required in the City’s National Pollutant Discharge Elimination System (NPDES) MS4 Permit; and
  5. Identify necessary maintenance, adaptive management, staffing, and financial strategies to implement the WIP.

To meet the 20% restoration goal, the City will restore over 4,291 acres of impervious surface area by the end of the current permit period, using a diverse approach throughout the City, including installing stormwater management projects, such as traditional/structural Best management Practices (BMPs), environmental site design (ESD) practices, and alternative BMPs selected; employing a variety of operational programs, such as mechanical street sweeping preventive inlet cleaning, and illicit discharge detection and elimination (IDDE); and fostering partnerships to encourage stormwater implementation on private lands, coupled with an increase in environmental stewardship within the communities.

The City’s proposed approach for meeting the 20% restoration requirements will also account for significant reductions of nitrogen, sediment and phosphorus, in compliance with the state’s Phase II WIP for the Bay TMDL.

Various MS4 and TMDL WIP documents can be found below:

Baltimore City Trash TMDL Implementation Plan

On January 5, 2015, the EPA approved a "Trash TMDL" for Baltimore. A Total Maximum Daily Load (TMDL) is a regulatory term in the U.S. Clean Water Act, describing the maximum amount of a pollutant that a body of water can receive while still meeting water quality standards. In this case the pollutant is trash. The TMDL is 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). This is what is considered the impaired area. The TMDL recognizes that trash comes from upstream, so portions of the Baltimore Harbor, Jones Falls, and Gwynns Falls watersheds are included. This comprises approximately 60% of the City. The TMDL requires that the City remove 100 percent of the baseline load, which is 228,371 pounds per year.

To meet the Trash TMDL goals an Implementation Plan was finalized in January 2016, and employs a two-part strategy. The first part will use projects and programs to capture trash as a stopgap measure, and will occur over a 10-year period (with another 10 years of operations and data collection to validate trash loading rates). The second part of the plan will be concurrent with the first, utilizing partnerships as a sustainable method for compliance with the trash TMDL. The initial 5-year phase will initiate education and outreach pilots, while creating and testing anti-litter campaigns. The pilot programs will be expanded over the next 5 years. After 10 years, the education and outreach programs will be modified based on data collected from monitoring, surveys and collection data.



MS4 Annual Reports

Baltimore City is required to submit an Annual Report documenting progress toward meeting the MS4 Permit. Since 2013 these reports are on a fiscal year fiscal year (July 1 - June 30) in order to align with the City's financial reporting. A list of recent Annual Reports can be found on the left side of the page.

Click HERE to view the City's most recent Annual Report for Fiscal Year 2015 (July 1, 2014 - June 30, 2015).

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