Section 303(d) of the 1972 Clean Water Act (CWA) requires all states to develop a list of their state’s impaired water bodies (rivers, lakes, estuaries). The 303(d) list consists of those water bodies that do not meet state regulatory water quality standards. The CWA also requires all states to establish priority rankings for waters on the 303(d) list. States must develop Total Maximum Daily Loads (TMDLs) for these waters based on their individual priority ranking.
A TMDL is a pollution budget for a specific water body. It is the maximum amount of a pollutant that can be released into a water body without causing it to become impaired and/or violate state water quality standards. The maximum allowable amount is the sum of pollutant loads from point, nonpoint, and natural sources. A TMDL must also include a margin of safety to allow for any uncertainties in the scientific methods used to derive the load allocation, such as water quality monitoring assumptions.
TMDL = Wasteload Allocation (point sources) + Load Allocation (nonpoint sources and natural background sources) + Margin of Safety
History of TMDLs
TMDLs were first required by the CWA of 1972. Initially, states and the Environmental Protection Agency (EPA) focused on the point source part of the TMDL, called the wasteload allocation. Some TMDLs were developed but, until recently, very little national emphasis or resources were placed on developing the scientific tools necessary to produce TMDLs for complex problems. It is also important to note that prior to the development of TMDLs, some level of technology and water quality based controls had been required from point sources under the CWA.
The absence of TMDLs does not mean that no discharge controls are in place on state water bodies. Many times controls of point sources are adequate to protect water uses without a TMDL.
Several years ago, however, citizen organizations began bringing legal actions against the EPA, seeking the complete listing of impaired waters and development of TMDLs as required by the CWA. To date, there have been about 40 legal actions in 38 states, including Texas. However, since Texas began doing TMDLs in 1996, the EPA has not been sued regarding the state’s 303(d) list or TMDL development. The EPA is under a court order or consent decree in many other states to ensure that TMDLs are established. The CWA authorizes the states to develop TMDLs, but if the states do not develop the TMDLs, then the EPA must develop them.
One approach EPA used to address the large numbers of lawsuits was to revise the current TMDL regulations. Those draft regulations were issued in 1999. After the Agency’s review and consideration of more than 34,000 comments, the TMDL rule was finalized on July 13, 2000. The EPA temporarily suspended the 2000 TMDL regulations before they could take effect, and repealed them completely in March 2003. Therefore, the regulations adopted by the EPA in 1992 remain in effect today.
The 1992 rule mandates that states list impaired water bodies, as required under Section 303(d) of the CWA, and develop TMDLs for those water bodies. By law, the EPA must approve or disapprove state 303(d) lists and TMDLs. If a state submission is disapproved, the EPA must establish a new 303(d) list and/or develop new TMDLs.
TMDL Action
In Texas, TMDLs are developed through a cooperative process involving the people and organizations who will have a stake in implementing them. After the final draft of a TMDL document is completed by TCEQ staff or contractors, it goes through the adoption process. The Commission, made up of three officials appointed by the governor, plays a big role in TMDL approval. First, the TMDL Program seeks permission from the Commission to publish the TMDL for public comment for a period of 30 days. If permission is given, the public comment period is advertised on TCEQ’s Web site, in the Texas Register, and in area newspapers. The TCEQ also holds a public meeting to receive comments from citizens, organizations, and interest groups, in addition to accepting written comment.
After the public comment period is complete, the TCEQ and any partner agencies review the comments, make changes to the TMDL document as needed, and publish a response to public comment.
When the final TMDL document is complete, the TMDL Program presents it to the Commission for adoption at a public meeting. Notice of this meeting is given in the Texas Register and on the TCEQ Web site. If the Commission adopts the TMDL, it is submitted to the EPA for approval.
In cases where another agency is the co-author of a TMDL document, that agency may also take the document before its governing commission or board for approval or adoption. This is not required, however.
As soon as the TMDL is adopted by the Commission, the TMDL Program begins work on developing an Implementation Plan (IP). An IP puts the TMDL into action by outlining the steps necessary to reduce pollutant loads through regulatory and voluntary activities. IPs describe the actions that local, regional and state organizations must take to reduce pollutant loads to levels established in TMDLs.
The IP goes through a stakeholder process and public comment period almost identical to that of the TMDL. The final IP is submitted to the Commission for approval at a public meeting. The IP is not subject to approval by the EPA.
After a TMDL is approved by the EPA, the impairment is removed from the 303(d) List. The impairment is downgraded to Category 4 of the Water Quality Inventory, which includes waters that do not meet standards, but for which a TMDL is complete or a TMDL is not needed. It is usually a long while before implementation is completed and water quality is restored.
Recognizing that it is difficult to predict improvements in water quality with so many different variables in play, IPs are often written to put activities into practice in phases. Checkpoints are set up along the way to determine whether water quality is improving as implementation moves forward. If sufficient progress is not being made toward meeting the load allocation when one of these checkpoints is reached, the IP may be revised, or a new, more stringent phase may be automatically triggered. This adaptive approach ensures that adjustments are made as needed to reach the goal of restoring the impaired uses of the water body.
A TMDL remains in effect until it is revised or updated, which would only occur if conditions in the watershed changed substantially.
