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Total Maximum Daily Load (TMDL) is a tool to help protect and improve water quality. Since the Clean Water Act was passed in 1972, each state is required to set standards for water quality and periodically analyze the water to see if the particular stream, river, reservoir or inlet meets the standard. If it falls short of the standard, it is said to be impaired.

A TMDL is like a diet for a waterway. If a person has high cholesterol, for example, their doctor might recommend a restricted diet. The patient would be evaluated to determine how high their cholesterol is and their current consumption might be examined to see what foods should be eliminated. A plan is put in place for the patient to help reduce their cholesterol level to a healthy standard.

The TMDL works the same way. A water body is determined to have too high of a level of a particular pollutant. The TMDL describes the watershed, identifies likely sources for the pollutant, and identifies opportunities to reduce the amount of pollutant to meet the accepted standard. Each pollutant requires a separate TMDL.

Measuring Impairments

In order to better evaluate, monitor, and manage waterways, the state has segmented these waterways into drainage areas. Baltimore County has 2,145 miles of stream and 219 miles of tidal shoreline in 14 watersheds. Each of the 14 watersheds that are in or are connected to Baltimore County is impacted by pollutants and requires TMDLs.

Let's use the Back River as an example. In the Back River, the level of Total Phosphorus (TP) exceeds the standards. Phosphorus is a nutrient and may enter the waterway from sewage treatment plants, industry, fertilizers and other sources. In order for Back River to be considered healthy the TP load from all sources must be reduced to 99,991 pounds per year. The Back River Waste Water Treatment plant has already made recent investments to reduce phosphorus and is considered to have lowered its contribution as low as current technology allows. Therefore, the TMDL for Back River focuses on reducing TP entering the waterway from urban runoff by 15 percent.

Trash TMDL

Baltimore County is one of just six jurisdictions in the United States under Total Maximum Daily Load (TMDL) federal mandates, which stem from the federal Clean Water Act and aim to reduce trash in specific waterways. Our Trash TMDL states that each year, 159,626 pounds of trash needs to be stopped from entering the Gwynns Falls and Jones Falls watersheds, both of which originate in the County and flow into the Baltimore Harbor.

The County is currently implementing Phase One of both our Trash TMDL Implementation Plan and our 2014 Trash Reduction Strategy, which involves continuing existing removal efforts, applying additional source reduction efforts and monitoring. If this approach does not reach the goal, the County will need to move to Phase Two, which involves very expensive structural changes, such as installing trash-trapping devices, which require ongoing routine maintenance and do not get to the root of the litter problem.

TMDL Implementation Plans

TMDL Implementation Plans guide the restoration or cleanup to reach the target pollutant load. Calculations based on scientific studies are made to determine the amount and types of restoration practices to be completed. The Department of Environmental Protection and Sustainability (EPS) developed TMDL Implementation Plans for all of its existing TMDLs in 2014, per its Municipal Separate Storm Sewer System (MS4) permit requirements. In response to comments by the Maryland Department of the Environment (MDE), Baltimore County revised and resubmitted the plans in 2016. Implementation Plans for any new TMDLs will be developed within one year of final TMDL approval; this timeframe includes a 30-day public comment period.

Annual updates and progress toward the Implementation Plans will be reported in Section 10 of Baltimore County’s annual National Pollutant Discharge Elimination System (NPDES)—Municipal Stormwater Discharge Report.

The Implementation Plans developed by Baltimore County are linked below, organized by impaired watershed. Select the pollutant name beneath the watershed name to view the respective plan.

Public Comments

Periodically, the plans will be reviewed and revised. Public comment on existing Implementation Plans will be accepted at any time and will be addressed upon the subsequent revision. If you wish to comment or have questions about the Implementation Plans, please email Include the name of document, section and page numbers along with your comments. Email is preferred, and comments will also be accepted in hard copy, either through the mail or delivered to:

Attention: Watershed Management
111 West Chesapeake Avenue, Room 305
Towson, Maryland 2120

More Information

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Watershed Management and Monitoring

County Office Building
111 West Chesapeake Avenue
Room 305
Towson, Maryland 21204





Horacio Tablada