What is a TMDL?
A Total Maximum Daily Load (TMDL) is a written, quantitative assessment of water quality problems in a water body and contributing sources of pollution. A TMDL specifies the maximum amount of pollutant a water body can receive and still meet water quality standards, and allocates pollutant load reductions. TMDLs are sometimes referred to as a pollution “diet” or “budget” for a water body. A TMDL budget incorporates loads from point sources, non-point sources, natural background sources, and includes a margin of safety. pollutant load reductions. TMDLs are sometimes referred to as a pollution “diet” or “budget” for a water body. A TMDL budget incorporates loads from point sources, non-point sources, natural background sources, and includes a margin of safety.
What is the Purpose of a TMDL?
TMDLs is a tool that helps to restore polluted rivers and streams.
How does DOEE Decide When to Create a TMDL?
Every two years, DOEE prepares a report on the quality of the District’s waters to the Environmental Protection Agency and Congress called the Integrated Report. In the Integrated Report, DOEE lists water bodies that aren’t meeting water quality standards. Those water bodies are placed on the District’s 303(d) list and TMDLs are prepared for those water bodies and pollutant pairs..
What kinds of TMDLs does the District have?
The District has over 350 TMDLs for various water quality issues such as bacteria, organic toxics, metals, PCBs, nutrients, oil and grease, excess sediments, low oxygen, and trash. The District is within the Chesapeake Bay watershed and is an active partner working toward restoration of the Bay. The District has also collaborated with regional partners to develop watershed-scale TMDLs for PCBs (2007), total suspended solids (2007), nutrients/biochemical oxygen demand (2008), and trash. The chart below summarizes District TMDLs grouped by pollutant type.
Please see TMDLs for the District's Water Bodies for specific TMDL documents.
District TMDLs by Pollutant Group
- Toxic organics (chlordane, DDE, DDD, DDT, Dieldrin, heptachlor epoxide, PAHs, Total PCBs) 58%
- Trash 1%
- Nutrients 4%
- Bacteria 6%
- Low oxygen 2%
- Metals (arsenic, copper, lead, zinc) 16%
- Oil and grease 1%
- PCB 8%
- Sediment 4%
For more information, call 202-535-2600.