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Total Maximum Daily Load Program

What is a TMDL?
Who is developing TMDLs?
How important is local input to the development of a TMDL?
Task Force on Bacteria TMDLs
Where are TMDLs being developed?
What TMDLs are approved?
How will TMDLs Be Carried Out?
For More Information

What is a TMDL?

The federal Clean Water Act (CWA) requires Texas to identify lakes, rivers, streams and estuaries failing to meet or not expected to meet water quality standards and not supporting their designated uses (swimming, drinking, aquatic life, etc.). This list of impaired waterbodies is known as the Texas 303(d) List and must be submitted to the U.S. Environmental Protection Agency (EPA) for review and approval every two years.

The State must then establish a Total Maximum Daily Load (TMDL) for waterbodies identified on the 303(d) List. A TMDL defines the maximum amount of a pollutant that a waterbody can assimilate on a daily basis and still meet water quality standards. The pollution reduction goal set by the TMDL is necessary to restore attainment of the designated use of the impaired waterbody. The maximum amount of pollutant is determined by conducting a detailed water quality assessment that provides the information for a TMDL to allocate pollutant loads between point sources and nonpoint sources. It also takes into account a margin of safety, which reflects uncertainty and future growth. The effects of seasonal variation are also included.

Based on the environmental target of the TMDL, an Implementation Plan (I-Plan) is then developed that prescribes the measures necessary to mitigate anthropogenic (human-caused) sources of that pollutant in that waterbody. The I-Plan specifies limits for point source dischargers and recommends best managment practices for nonpoint sources. It also lays out a schedule for implementation. Together, the TMDL and the I-Plan serve as the mechanism to reduce the pollutant, restore the full use of the waterbody and remove it from the 303(d) List. EPA must approve the TMDL, but the I-Plan only requires State approval.

Who is developing TMDLs?

Responsibility to develop and implement TMDLs is shard between two State agences: the TSSWCB and the Texas Commission on Environmental Quality (TCEQ).

The TCEQ has general jurisdiction and primary responsibility over Texas' water quality program including water quality management planning, the issuance of permits for point source discharges, abatement of nonpoint source pollution other than from agricultural and silvicultural sources, and enforcement of water quality rules, standards, orders, and permits. The TCEQ is responsible for establishing the level of quality to be maintained in, and controlling the quality of, water in the state.

With authority as the lead agency in Texas for planning, implementing, and managing programs and practices for preventing and abating agricultural and silvicultural nonpoint source pollution, TSSWCB is a fundamental partner with TCEQ in the Texas TMDL Program. TSSWCB is committed to funding and collaborating with TCEQ on TMDL projects encompassing monitoring, assessment, modeling, planning, education and implementation. TSSWCB TMDL projects are funded through CWA §319(h) NPS Grants to various entities.

On September 27, 2006, at a joint work session, the TSSWCB and the TCEQ approved a revised Memorandum of Agreement on Total Maximum Daily Loads, Implementation Plans, and Watershed Protection Plans (PDF, 431 kB). This framework for collaboration between the two agencies describes the programmatic mechanisms the agencies employ to develop and implement TMDLs.

If the State fails to meet its obligations and develop a TMDL for an impaired waterbody within 13 years of when it was placed on the 303(d) List, the CWA requires EPA to establish TMDLs for the State.

There are certain aspects of developing a TMDL or I-Plan that may be contracted out by TSSWCB or TCEQ to certain research institutions or private consultant firms. However, TSSWCB and TCEQ hold the responsibility for the funding, leadership and reporting of all TMDL activities in Texas. As a result, any organization considering undertaking a TMDL project for an impaired waterbody in Texas must coordinate efforts with the TCEQ, and with the TSSWCB where agricultural or silvicultural nonpoint sources are involved.

Developing Total Maximum Daily Load Projects in Texas: A Guide for Lead Organizations (PDF, 1.32 MB) serves as a "how to" guide for consultants, universities, governmental agencies, river authorities, industries, communities, and others to use in conducting TMDL projects. This publication describes the process for completing a TMDL project in Texas and, although lead organizations are the principal audience, any stakeholder who participates in a TMDL project will find this publication useful. TCEQ has additional resources for developing TMDLs.

How important is local input to the development of a TMDL?

Commitment by the citizens who live and work in a watershed is essential to success in reducing the pollutant loads and improving water quality as prescribed by a TMDL and its I-Plan. To achieve collaboration with and among stakeholders, it is critical they share in the decision making for the project. Stakeholders provide direct advice and innovation in planning a TMDL project, collecting data, setting the water quality target, allocating pollutant loads, developing an I-Plan and putting that plan into action.

A successful stakeholder process will:

  • improve the quality and quantity of contributions to TMDL projects
  • promote government accountability
  • ensure that state government considers the local perspective in its decisions
  • lead to consensus-based solutions
  • help stakeholders gain insight into the nature of water quality problems and alternative solutions
  • educate stakeholders about pollution prevention techniques
  • encourage open dialogue on water quality issues
  • increase a stakeholder's understanding of the views of other interest groups
  • reduce the probability that a particular advocacy group will dominate the process
  • improve the probability of successful implementation of TMDL load allocations
  • lead to voluntary individual actions to curb pollution

Task Force on Bacteria TMDLs

The TSSWCB and the TCEQ established a joint technical Task Force on Bacteria TMDLs to make recommendations on effective bacteria TMDL development methodologies, including modeling and bacterial source tracking (BST) and on a science roadmap to reduce uncertainty in what we know about how bacteria behave under water conditions in Texas. The work of the Task Force is being faciltiated by the Texas Water Resources Institute.

Where are TMDLs being developed?

The TSSWCB is engaged in the development of TMDLs for waterbodies impaired due to known or suspected agricultural or silvicultural nonpoint sources. Watersheds and pollutants of concern include:

TMDLs with TSSWCB Involvement

Visit the TCEQ website for a complete list of all TMDL projects in Texas.

What TMDLs Are Approved?

The TSSWCB has been actively involed in the development of TMDLs for waterbodies impaired by agricultural or silvicultural nonpoint source pollution. Approved TMDLs addressing agricultural or silvicultural nonpoint source pollution include:

Visit the TCEQ website for a complete list of all approved TMDLs in Texas.

How will TMDLs Be Carried Out?

Through its CWA §319(h) NPS Grant Program, the TSSWCB funds implementation activities that support approved I-Plans addressing agricultural or silvicultural nonpoint source pollution:

Visit the TCEQ website for a complete list of all approved I-Plans in Texas.

On November 2, 2006, TCEQ released a new status report on the progress of implementing TMDLs in Texas (PDF, 926 kB). The report highlights the TMDL Program's activities to restore impaired surface waters in Texas through August 2005. The report includes environmental results, program managment, summaries of restoration projects being implemented and discusses TSSWCB activities associated with the Aquilla Reservoir TMDL for atrazine, the E.V. Spence Reservoir TMDLs for salinity, and the North Bosque River TMDLs for nutrients.

For More Information, contact:

For additional information or questions, contact TJ Helton at 254-773-2250, ext. 234, or by e-mail at thelton [at]

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