Total Maximum Daily Loads (TMDLs)

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Introduction
TMDL FAQ's
TMDL Flow Chart
Contacts
Useful Links

Introduction

Welcome! On this page you will find information on TMDLs or Total Maximum Daily Loads. TMDLs create the framework for limiting pollutant discharges into an impaired water body, with the goal to improve overall water quality and achieving its goals set by water quality standards. A TMDL includes calculations of the maximum amount of a pollutant allowed to enter a water body also known as the loading capacity. When the loading capacity is not exceeded, the water body will meet its water quality standards and its designated use(s). The EPA Region 8 TMDL Program reviews and approves, or disapproves, the states' 303(d) lists, and reviews and approves, or disapproves, state-submitted TMDLs. EPA Region 8 can also develop TMDLs for impaired waters as needed.

Click on a Region 8 State below to be directed to the corresponding state TMDL web site. Here you can search for state specific TMDL information.

TMDL FAQs

1) What is a TMDL? Fact vs Fiction.

"A TMDL is a plan" FICTION. A TMDL is a measurement. TMDLs are calculations of the maximum amount of a pollutant that a given water body can receive and still meet water quality standards, as well as an allocation of that amount to the pollutant's sources. However, a TMDL provides valuable information necessary for developing plans to manage pollutant loads to a water body. While plans to meet the loading allocations that TMDLs prescribe are not a required component of the TMDL itself. EPA does encourage TMDL developers to include as much additional information as possible on how the loads may be met in the TMDL document itself.

"A TMDL corrects impaired waters independent of other Clean Water Act components" FICTION. A TMDL provides critical information needed to properly manage the maximum load of a pollutant that can be allowed to enter a water body without causing the water body to fail to meet its water quality goals. However, TMDLs do not contain any direct regulatory authority. It is the task of other clean water programs to ensure the maximum pollutant load called for by the TMDL is met. TMDLs assign waster load allocations (WLAs) to point sources of a pollutant. WLAs provide the information needed by pollutant discharge permit writers to ensure the permitted discharge of a pollutant does not cause or contribute to a water quality standards violation (as part of the National Pollutant Discharge Elimination System (NPDES) Permit Program). The load allocations assigned to non-point sources of a pollutant in a TMDL help guide other clean water programs when determining the pollutant management practices needed to protect the water body.

"A TMDL requires an implementation component" FICTION. A TMDL may consist of nothing more than a determination of the maximum load of a pollutant that a water body can safely assimilate and an allocation of that load to the respective sources. However, during the course of determining this information, the TMDL practitioner will often develop a better understanding of the water body and its contributing watershed. This knowledge may put them in a good position to make recommendations that will aid other clean water programs when attempting to meet the load allocations prescribed by the TMDL report. Therefore, EPA strongly recommends that those who develop TMDL reports, also include a section with recommendations on how the load allocations might be met.

"A TMDL can only be developed by a state". FICTION. States typically set the water quality standards that the TMDL must use as its goal. States are also generally much more acquainted with the nature of the impaired water body and the stakeholder community. Therefore, EPA prefers that states develop the TMDL to meet the water quality standards, and incorporate the local stakeholder community in its processes. The vast majority of TMDLs are indeed developed by states; however EPA can develop TMDLs on an as-needed basis.

"Public participation in the TMDL process is required by law". FACT. The Clean Water Act requires public involvement in the TMDL development process, and the level of citizen involvement can vary by state. When a draft TMDL is written, a variety of opportunities are provided to the public to ensure their viewpoints are received (public meetings, provide written comments, etc). TMDLs do not contain any regulatory authority that requires the load allocation to be met. Therefore, an involved stakeholder community, which helps to establish and then advocates for the goals of the TMDL, can make a major difference in the successful restoration of the water body.

2) Understanding impaired waters and State 303(d) lists. The term "303(d) list" is short for the list of impaired and threatened waters (stream/river segments, lakes) that the Clean Water Act (in section 303(d)) requires all states to submit for EPA approval. States' list water bodies as impaired when monitoring indicates they are not meeting their water quality standards. If the state believes that a water body may not meet its water quality standards in the future, the state may also choose to add the water body to the 303(d) list as threatened. If evidence indicates that the water body is impaired or threatened due to the excess loading of a pollutant, then the Clean Water Act requires the state to develop a TMDL for the water body, specific to that pollutant. Regulations say states must evaluate "all existing and readily available information" in developing their 303(d) lists.

3) What role does a TMDL play in advancing Water Quality? A goal of the Clean Water Act is to ensure that water bodies are properly managed so as to meet the uses for which they have been designated. Water quality standards are established to ensure that these uses will be protected. A TMDL is developed to determine the maximum amount of a pollutant that a water body can assimilate without causing the water body to fail to meet the standards established to protect it. Through the pollutant load allocations established by the TMDL, critical information is provided that is used by other programs when establishing point source discharge permits and determining the scope and type of managed practices needed to reduce non-point sources of pollution to acceptable levels.

Water-Quality Flow Chart

Flow chart depicting several Clean Water Act activities and how they relate to the 303(d) Program to provide a water quality-based approach. Graphic begins with adopting water quality standards, then monitoring and assessing waters, listing impaired and threatened waters, developing TMDLs for those waters, and the implementation of control sources for managing nonpoint and point source pollution