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Maryland State Government Maryland Department of the Environment

The Chesapeake Bay TMDL, Maryland's Watershed Implementation Plan and Maryland's Two-Year Milestone Goals 

The Chesapeake Bay TMDL: A Pollution Diet for the Chesapeake Watershed

The Chesapeake Bay is a national treasure constituting the largest estuary in the United States and one of the largest and most biologically productive estuaries in the world.  Despite significant efforts by federal, state, and local governments and other interested parties, pollution in the Chesapeake Bay prevents the attainment of existing water quality standards.  The pollutants that are largely responsible for impairment of the Bay are nutrients, in the form of nitrogen and phosphorus, and sediment.

The United States Environmental Protection Agency (EPA), in coordination with the Bay watershed jurisdictions of Maryland, Virginia, Pennsylvania, Delaware, West Virginia, New York, and the District of Columbia (DC), developed and, on December 29, 2010, established a nutrient and sediment pollution diet for the Bay, consistent with Clean Water Act requirements, to guide and assist Chesapeake Bay restoration efforts.  This pollution diet is known as the Chesapeake Bay Total Maximum Daily Load (TMDL), or Bay TMDL.

MDE took part in an ongoing, high-level decision-making process to create the essential framework for this complex, multi-jurisdictional TMDL that will address nutrient and sediment impairments throughout the entire 64,000 square mile Chesapeake Bay watershed. 

MDE participated in numerous inter-jurisdictional and inter-agency workgroups and committees over the last three years to provide technical expertise and guidance for developing the Bay TMDL in a manner consistent with the State’s water quality goals and responsibilities. In particular, MDE worked to ensure that the Bay TMDL addressed the nutrient and sediment impairments in all of Maryland’s tidal waters listed as impaired by those pollutants on the State’s Integrated Report of Surface Water Quality

MDE took the lead on developing an allocation process that will enable the State to meet a key requirement for the Bay TMDL and Maryland’s Watershed Implementation Plan:  the sub-allocation of major basin loading caps of nutrient and sediment to each of 58 “segment-sheds” in Maryland – the land areas that drain to each impaired Bay water quality segment – and to each pollutant source sector in those areas.

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Maryland’s Watershed Implementation Plan for the Bay TMDL

Concurrent with the development of the Bay TMDL, EPA charged the Bay watershed states and DC with developing watershed implementation plans in order to provide adequate “reasonable assurance” that the jurisdictions can and will achieve the nutrient and sediment reductions necessary to implement the TMDL within their respective boundaries.

Maryland’s Phase I Plan provides a series of proposed strategies that will collectively meet the 2017 target (70% of the total nutrient and sediment reductions needed to meet final 2020 goals). After more than a year of cooperative work, MDE and the Departments of Natural Resources, Agriculture, and Planning released a Draft Phase I Plan for public review in October 2010 and, following extensive consideration of hundreds of public comments, submitted Maryland’s Final Phase I Watershed Implementation Plan to EPA on December 3, 2010.

Maryland’s Phase II Plan provides a series of proposed strategies that will collectively meet the 2017 target (60% of the total nutrient and sediment reductions needed to meet final 2025 goals). This was changed from Phase I due to concerns that the implementation was not achievable with that timeframe. Maryland worked many partners in local jurisdictions to develop Phase II Watershed Implementation Plans with more detailed reduction targets and specific strategies to further ensure that the water quality goals of the Bay TMDL will be met. See Maryland's Development Support for the Chesapeake Bay Phase II WIP webpage.

MDE is continuing to work with its partners in local jurisdictions to implement the Phase II WIP. See the Implementing Maryland’s WIP: Making Progress toward Bay Restoration Goals webpage.

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Contact Info

Please direct questions or comments concerning this project to Tom Thornton with Maryland's TMDL Program at (410) 537-3656 or email at


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