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Impaired Segments
303(d) Lists & 305(b) Reports
Under Section 303(d) of the Clean Water Act, states are required to develop a list of Impaired Segments (i.e., stream segments and lakes) in that state. The waterbodies are determined to be impaired if they do not meet the state water quality standards, even after pollution controls required by law have been implemented. The law requires that the states place these Impaired Segments on a list called the 303(d) list and develop TMDLs for the waterbodies on that list. States must use "all existing and readily available water quality-related information" when developing their 303(d) lists.
The waterbodies on the list are ranked, taking into account the designated uses of the water and the severity of the pollution problem. The states must also identify the waterbodies targeted for TMDL development in the next two years. States must submit their list of impaired waters to EPA on April 1 in every even-numbered year and EPA is responsible for either approving or disapproving the list. Section 305(b) of the Federal Clean Water Act requires each state to also deliver a Watershed Assessment Report, known as the 305(b) report, to EPA on April 1 of every even-numbered year. The states use information from a wide variety of sources for evaluation and inclusion in the 305(b) report. The state 305(b) reports are considered to be a primary source of information used to compile the states' 303(d) lists.
The 305(b) reports are based on water quality information on streams, stream segments, and lakes. The reports must include a description of the water quality of all waterbodies in the state and an analysis of the extent that they are meeting their water quality standards. The report must also recommend any additional action necessary to achieve the water quality standards and for which waters that action is necessary. An estimate of the environmental impact, as well as the economic and social impacts, necessary to achieve the water quality standards in each particular state must be included.
