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 management 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 shared between two State agencies: 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.
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