Impaired Waters and TMDLs: Statute and Regulations
Section 303(d) of the Clean Water Act
The Clean Water Act (CWA) is the primary law regulating pollution of the nation’s waterways. Originally enacted in 1948, it was amended in 1972 to add programs for water quality improvements that remain in place today. The objective of the Act is the restoration and maintenance of the chemical, physical and biological integrity of the country’s water. One of the goals is to achieve water quality that is both "fishable" and "swimmable" by the mid-1980s. While the date has passed, the goal remains and efforts to attain it continue.
Section 303(d) of the CWA, requires states to identify waters where current pollution control technologies alone cannot meet the water quality standards set for that waterbody. Every two years, states are required to submit a list of impaired waters plus any that may soon become impaired to EPA for approval. The impaired waters are prioritized based on the severity of the pollution and the designated use of the waterbody (e.g., fish propagation or human recreation). States must establish the total maximum daily load(s) of the pollutant(s) in the waterbody for impaired waters on their list.
The following both contain the text of CWA section 303(d) only in slightly different formats. The first is the section as it appears in Title 33 of the U.S. code. The second is the text from the Act itself.
Water Quality Standards and Implementation Plans:
Part 130.7 of Title 40 of the Code of Federal Regulations
Regulations governing impaired waters and TMDLs are in Part 130.7 in the Code of Federal Regulations (CFR). Issued in 1992, the regulations stipulate that states are to continue to identify waters that require TMDLs and ascertain the pollutants causing or expected to cause the impairment based on readily available data and information. States are to include in their impaired waters report a description of the method used to develop the list, the data and information used and the decision rationale. States establish a priority ranking to put in place plans for establishing a total pollutant load and parse out the load from point (the wasteload allocation) and nonpoint sources (the load allocation) with a margin of safety.
- 40 CFR section 130.7 – Total maximum daily loads (TMDL) and individual water quality-based effluent limitations (PDF)(3 pp, 189 K, About PDF)