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The Clean Water Act: What Are TMDLs And Why Do They Exist?

Updated: Jul 16, 2020

By Ashley Ellixson

Lake surrounded by forest (Photo by Edwin Remsberg).

If you live in Maryland, or even the neighboring states, you are familiar with the Chesapeake Bay. Not only is it the largest estuary in North America but it is also the body of water constantly under scrutiny for concerns over pollution and runoff. Have you ever wondered how the Chesapeake Bay came under environmental regulation or why environmental regulation exists as it pertains to the Bay? Today I am going to walk you through some history of how regulations of the Bay came to be, clear up or answer questions, and just shed some light on this beautiful body of water which seems to be a hot topic of conversation everywhere you go.

In order to understand why the regulatory schemes cover the Bay, it is imperative to know exactly what the Bay is. The Bay’s watershed includes seven states: Virginia, West Virginia, Maryland, Delaware, Pennsylvania, New York, and Washington, D.C. The watershed covers 64,000 square miles, and contains thousands of lakes, streams, rivers, and creeks. The Bay itself has a surface area of 4,500 square miles and a shore line of 11, 684 miles which is longer than the coastline from San Diego, CA to Seattle, WA. Currently there are approximately 17 million people living in the watershed with an expected 20 million by 2030.

As many of you already know, not only does the Bay sustain a growing human population but it is also home to many commercial industries such as fishing, shipping, farming, and tourism. All these activities obviously contribute to pollutants in the Bay. It is because of these factors and the opportunities for growth in the Bay area, as well as many other bodies of water throughout the United States, that the Clean Water Act (CWA) legislation was passed in 1972.

Broken bridge on a lake (Photo by Edwin Remsberg).

Under the CWA, the Environmental Protection Agency (EPA) and the states are to participate cooperatively to clean U.S. waters. Today, we are discussing the provision in the CWA act which establishes “total maximum daily load” (TMDL) requirements of pollutants for certain waters. The TMDL is not defined in the CWA, but EPA has interpreted the meaning to be “required publication of a comprehensive framework for pollution reduction in a given body of water.” This basically means that whatever the TMDL is, it needs to help reduce pollutants entering into the body of water. The CWA says that the states will set the TMDL and then EPA will approve or disapprove it. If EPA disapproves, EPA must set the TMDL itself.

The states and EPA made commitments to reducing pollution in the watershed under the Chesapeake Bay Agreement in 2000. This agreement led to the states’ submission to the EPA of “Phase I Watershed Improvements.” This draft proposed target pollutant limitations and how the states would achieve them. EPA developed TMDLs with reliance on this agreement. After many revisions and a “Phase II Watershed Improvement Plan” released by the states in the Bay watershed, EPA promulgated its final Chesapeake Bay TMDL. In 2010, the EPA published the TMDLs for nitrogen, phosphorus, and sediment which can safely be released into the Chesapeake Bay in order to comply with the Clean Water Act.

Now we are current and up to date. If you read last Friday’s post, you already know that the Third Circuit Court of Appeals upheld the Bay TMDL earlier this month after a lawsuit between the American Farm Bureau Federation and EPA a few years ago based on the 2010 TMDLs. For a full review of the decision check out the overview post here.

Hopefully this help clears up questions or concerns in your understanding of why and how the Chesapeake Bay is regulated under the CWA and the role TMDLs play in the regulatory scheme. Let me know if you have any questions and I will be happy to address them

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