Section 303(d) of the Clean Water Act requires the identification of water bodies that do not meet, or are not expected to meet, water quality standards or are considered impaired. The affected water body, and associated pollutant or stressor, is then prioritized in the 303(d) list. The act further requires the development of a
total-maximum-daily-load for each listing.
The requirement to develop TMDLs has been in the Clean Water Act since 1972. In the 1970s, point-source pollution was considered the most significant problem affecting water quality in rivers and streams. The innovations in the Clean Water Act established extensive programs to address point sources, and nearly all Federal dollars went to implement point-source controls. State funding priorities mirrored the Federal effort. During the 25 years after the enactment of the Clean Water Act, the technology-based effort received the highest priority and the most funding (Houck, 2002).
