For each waterbody or segment, states are required to set a total maximum daily load (TMDL) of pollutants at a level that ensures that applicable water quality standards can be attained and maintained. A TMDL is both a planning process for attaining water quality standards and a quantitative assessment of problems, pollution sources, and pollutant reductions needed to restore and protect a river, stream, or lake. Environmentalists see implementation of Section 303(d) as important both to achieving the overall goals and objectives of the act and to pressuring EPA and states to address nonpoint and other sources that are responsible for many water quality impairments nationwide but have not been well controlled. The final rule built on the existing regulatory program and added details, specific requirements, and deadlines requiring states to implement plans to clean up polluted waters. Developing even these relatively straightforward TMDLs presented substantial technical and scientific challenges, but the national program has by now become a core element of overall efforts to protect and restore water quality. At the same time, the 303(d) program has evolved, and especially during the last decade, EPA and states have addressed more complex issues, including TMDLs for less-traditional causes of impairment, TMDLs involving both point and nonpoint sources, and multi-jurisdictional TMDLs. Under Section 303(d)(2) of the CWA, upon disapproval of a TMDL, EPA must establish a new TMDL to implement applicable water quality standards, and EPA has begun a new phosphorus TMDL for the impaired Vermont segments in Lake Champlain. A central feature of the overall strategy is EPA's establishment of a TMDL for Chesapeake Bay, which was necessitated because the Bay states' previous restoration efforts were insufficient to attain water quality standards. It addresses all segments of the Bay and its tidal tributaries that are impaired from discharges of nitrogen, phosphorus, and sediment, with a goal of having TMDL implementation measures in place by 2025. Detailed plans identifying specific reductions are to be developed by the seven jurisdictions located in the Chesapeake Bay watershed in Watershed Implementation Plans (WIPs). The Chesapeake Bay TMDL has a number of novel elements. EPA's TMDL and the overall federal Bay restoration strategy under the executive order are controversial with a number of groups that are concerned about the likely mandatory nature of many of EPA's and states' upcoming actions. That said, when a TMDL is developed, implementation is a huge gap in the program for several reasons. First, as noted previously, CWA Section 303(d) requires development of a TMDL for impaired waters but does not require implementation. States' strategies for implementation vary widely. Second, a number of barriers to TMDL implementation can be identified. The most prominent hindrance is funding. At the same time, several factors that seem to aid effective implementation also can be identified. The TMDL program is in a period of transition. Many states are emerging from earlier consent decree mandates and are increasingly addressing new challenges—for example, more complex and resource-intensive TMDLs, larger scale impairments, and nonpoint sources. Other than recent oversight hearings on the Chesapeake Bay TMDL, Congress has not shown active interest in the TMDL program for more than a decade. Some stakeholders, especially states, believe that several issues present Congress with an opportunity to examine the TMDL provisions of the CWA.
Section 303(d) of the Clean Water Act (CWA) requires states to identify waters that are impaired by pollution, even after application of pollution controls. For those waters, states must establish a total maximum daily load (TMDL) of pollutants to ensure that water quality standards can be attained. A TMDL is both a quantitative assessment of pollution sources and pollutant reductions needed to restore and protect U.S. waters and a planning process for attaining water quality standards. Implementation of Section 303(d) was dormant until states and the Environmental Protection Agency (EPA) were prodded by lawsuits. The program has been controversial, in part because of requirements and costs faced by states, as well as industries, cities, farmers, and others who may be required to use new pollution controls to meet TMDL requirements.
Despite controversies, the TMDL program has become a core element of overall efforts to protect and restore water quality. States and EPA develop several thousand TMDLs annually, but many more need to be completed. The most recent information indicates that over 41,000 waterbodies do not meet water quality standards and need a TMDL to initiate corrective measures. The 303(d) program has evolved, and especially during the last decade, EPA and states have addressed more complex issues, including TMDLs involving both point (direct discharges) and nonpoint sources (diffuse discharges) such as stormwater; TMDLs for less-traditional causes of impairment such as climate change; TMDLs for pollutants such as mercury that involve coordination among water, air, and other environmental programs; and multi-jurisdictional TMDLs.
The largest multi-jurisdictional TMDL, for the Chesapeake Bay watershed, has drawn considerable attention. It was developed by EPA and was necessitated because previous largely voluntary restoration efforts by the Bay jurisdictions were insufficient to attain water quality standards. It addresses all segments of the Bay and its tidal tributaries that are impaired from discharges of nitrogen, phosphorus, and sediment, with a goal of having TMDL implementation measures in place by 2025. The Chesapeake Bay TMDL has a number of novel elements, including Watershed Implementation Plans in which the jurisdictions identify specific measures to achieve needed pollutant reductions, and biennial reports to the public on progress in implementation. The Bay TMDL has been controversial with a number of groups concerned about the costs of implementation and the likely mandatory nature of many of EPA's and states' actions. EPA's authority to develop the TMDL was upheld, after a legal challenge.
When a TMDL is developed, implementation is a major uncertainty. First, Section 303(d) does not require implementation, and states' strategies for implementation vary widely. Only a few have laws requiring implementation plans, while many others rely on less structured policies. Second, a number of barriers to implementation can be identified. The most prominent is insufficient funding, but technical impediments such as insufficient scientific data also are a challenge. At the same time, factors that may aid effective implementation include active involvement of stakeholders and governments, and adequate resources.
The TMDL program is in a period of transition and increasingly is addressing new challenges—more complex TMDLs, larger scale impairments, and nonpoint sources. Other than oversight hearings on the Chesapeake Bay TMDL, Congress has not shown active interest in the TMDL program for more than a decade. Some stakeholders, especially states, believe that several issues present Congress with an opportunity to examine the TMDL provisions of the CWA.