in-20200129-IR-318200006ONA: Basic Purpose and Background The IDEM Office of Water Quality (OWQ) is preparing to update its 303(d) List of Impaired Waters, as required by Section 303(d) of the federal Clean Water Act (CWA) and the Water Quality Planning and Management regulation contained in the Code of Federal Regulations (CFR) at 40 CFR Part 130. Under the CWA, each state is required to assemble all existing and readily available water quality-related data and information for use in assessing its waters for compliance with the state's water quality standards (WQS). States may adopt national water quality criteria or develop state-specific criteria, or do both, to protect the uses described in their WQS. In Indiana, these uses include recreational uses, aquatic life use, and the use of some waters as a drinking water resource. States are required to prepare and make public a list of waters that do not meet the WQS and the methodology used to evaluate the data and determine impairment status. The 303(d) List of Impaired Waters will identify the following: • The reach or reaches of the stream or river waterbody that is impaired or the lake that is impaired (lakes are evaluated as a single waterbody). • The pollutant or pollutants that do not meet the WQS, thereby causing the impairment. • A schedule for development of a Total Maximum Daily Load (TMDL). A TMDL evaluation is a process that quantifies the amount of a specific pollutant that a waterbody can assimilate and still meet WQS. A description of what constitutes a pollutant is provided in Section 502(6) of the CWA and includes materials such as sewage, chemical wastes, biological materials, and wastes from industrial, municipal, and agricultural operations. The definition also encompasses drinking water contaminants that are regulated under Section 1412 of the Safe Drinking Water Act (SDWA). A TMDL is a written, quantitative assessment that accomplishes the following: • Identifies how much of the pollutant is coming from point sources and nonpoint sources. • Specifies the amount of pollutant reduction necessary from each source in order to meet the WQS set for that pollutant. • Lays the groundwork for developing and implementing a plan to reduce the amount of the pollutant coming from each source. As part of IDEM's TMDL process, the public is invited to participate in the plan to develop and implement the TMDL.