Portions of hundreds of lakes, rivers and streams in the Bay watershed fail to meet their water quality standards. Under the Clean Water Act, the states are required to write detailed cleanup plans, known as TMDLs, for each of those impaired waterways.

In addition, the Bay itself is considered impaired, and will need an enforceable TMDL unless it is “cleaned up” before 2011. Here — adapted from EPA fact sheets — is an overview of the TMDL program, and proposed revisions to the program in question and answer form.

What Is a TMDL?

A TMDL — or total maximum daily load — is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. In other words, it is the sum of the allowable loads of a single pollutant from all contributing sources, and includes a margin of safety and consideration of seasonal variations. In addition, a TMDL calculates the reductions needed to meet water quality standards and allocates those reductions among pollution sources in the watershed.

Who Is Responsible for Establishing and Implementing TMDLs?

States are responsible. If they fail to establish the TMDLs, the EPA must do it.

When Do TMDLs Need to Be Established?

The EPA is proposing that TDMLs should be established over a 15 year time frame, with TMDLs for high-priority waters to be completed first. Priorities are based on the severity of the pollution and uses of the waterbody. The proposed changes would also give high-priority status to impaired waters that are drinking water sources or have endangered species.

How are 303(d) lists established and who is responsible for establishing them?

Under current regulations, states identify their impaired or threatened waters and submit a list of these waters to the EPA every two years. This is known as the 303(d), or “dirty waters” list. The EPA has 30 days in which to approve the lists or add waters to a state’s lists, if it determines the state’s list is not complete. TMDLs are required for waterbodies on the 303(d) list. In its proposed regulation, the EPA is asking for comment as to whether the two-year time frame for 303(d) list submittal should be changed.

What Are the Major Causes of Impairments in Our Waterbodies Nationwide?

Both the 1996 and 1998 section 303(d) lists reflect similar patterns with sediments, nutrients, and pathogens being the top three causes of impairment. Other causes include: dissolved oxygen, habitat and flow alterations, pH, metals, mercury (including fish advisories) and pesticides.

TMDLs Need to Be Established Within 15 Years, But When Will the Individual Waters Actually Be Cleaned Up?

It is very difficult to estimate a specific time frame. The amount of time that is required for a waterbody to reach water quality standards can vary considerably, depending upon the complexity of the pollutants, the uses of the land surrounding the waterbody and the commitment of the community or upstream dischargers to reducing pollutants.

What Is the Relationship of TMDLs to the Watershed Approach?

Lasting solutions to water quality problems are best achieved by looking at all activities in a watershed. TMDLs are an important part of translating water quality standards into any point (end-of-pipe discharge) and nonpoint (runoff) source load reductions needed to achieve healthy watersheds. The EPA encourages watershed approaches in establishing TMDLs so that the cumulative and synergistic effects may be considered. TMDLs will be less expensive and more effective when bundled together to clean up an entire watershed. At the watershed level, TMDLs can structure innovative solutions, e.g., nutrient trading among wastewater dischargers and nonpoint sources; or the development of new point or nonpoint source technologies.

What Are the Major Changes Being Proposed?

The proposed revisions in the TMDL rules would require states, territories and authorized tribes to:

  • Set out schedules for establishing TMDLs over a 15-year period, starting with the highest priority waterbodies;

  • Provide more specific and consistent listing methodologies to the EPA and make them subject to public review;

  • List waterbodies until water quality standards have been achieved;

  • Include an allowance for reasonably foreseeable increases in pollutant loadings to encourage “Smart Growth”; and

  • Include an implementation plan in the TMDL, with on-the-ground actions — for example discharge permit conditions, best management practices, etc.— to ensure that water quality standards are achieved in the time frame.

How Will Further Progress Toward Attaining Water Quality Standards Be Achieved in Impaired Waterbodies Until a TMDL Is Developed?

The EPA has proposed that large, new or significantly expanded dischargers will be permitted to discharge to impaired waterbodies provided they offset their discharge by obtaining pollutant load reductions from an existing source(s) of the same pollutant in the waterbody.

What Is an Offset?

An offset is a form of effluent trading. It involves an increased discharge of a particular pollutant to a waterbody in exchange for a decreased discharge of that same pollutant to the waterbody. The end result would be a net environmental improvement in the water quality of an impaired waterbody.

From What Source(s) Can an Offset Be Obtained and for How Long Must It Be Maintained?

An offset could be obtained from one or more existing point or nonpoint sources in the same waterbody. The offset must be maintained either until the TMDL has been established and is reflected in the discharger's permit or until the discharger stops discharging.

How Will the Changes to the Discharge Permit Program Help to Assure that TMDLs, Once Established, Will Be Implemented?

States, when establishing a TMDL, must provide reasonable assurance that all affected sources will be able to meet their allocated load reductions. There may be instances where the EPA, in approving a TMDL, will find that the state did not provide reasonable assurance that a particular nonpoint source will meet its allocated load reduction. In such a case, the EPA will work with the state to provide that reasonable assurance. Where working with the state has failed and reasonable assurance was not provided, the EPA would disapprove the TMDL and establish it itself.

Changes to the permit program will give the EPA, in establishing a TMDL, the discretion to designate certain dischargers causing significant water quality impairment as point sources requiring a discharge permit. Dischargers that may be designated include selected animal feeding operations, aquatic animal production facilities and forestry operations.

In states authorized to administer the permit program, the EPA will also have the discretion to object to and reissue expired permits which contain limits that are inconsistent with an established TMDL where the state has failed to do so.