4(d) Rule
April 11, 2022
The term is short for a state’s list of impaired and threatened waters (e.g. stream/river segments, lakes). States are required to submit their list for EPA approval every two years. For each water on the list, the state identifies the pollutant causing the impairment, when known. States often submit an “integrated report” that includes section 305(b) water quality reports for all state waters.
