Clean Water Act and Pollutant Total Maximum Daily Loads (TMDLs) [September 21, 2012] [open pdf - 291KB]
"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 to implement this 40-year-old provision of the law, 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 ocean acidification and climate change; TMDLs for pollutants such as mercury that involve coordination among water, air, and other environmental programs; and multi-jurisdictional TMDLs."
CRS Report for Congress, R42752