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Section 303(d) List of Impaired Waters

Every two years, IDEM Office of Water Quality (OWQ) develops Indiana's 303(d) List of Impaired Waters as part of the state's Integrated Water Monitoring and Assessment Report (IR), which is submitted to the U.S. EPA in accordance with Sections 305(b) and 303(d) of the Clean Water Act (CWA).

CWA Section 305(b) requires states to make water quality assessments and provide water quality reports to the U.S. EPA, and CWA Section 303(d) requires states to identify waters through their Section 305(b) water quality assessments, that do not or are not expected to meet applicable state water quality standards with federal technology based standards alone. Under CWA Section 303(d), states are also required to develop a priority ranking for these waters taking into account the severity of the pollution and the designated uses of the waters. Once this listing and ranking of impaired waters is completed, states are required to develop Total Maximum Daily Loads (TMDLs) for these waters in order to achieve compliance with the water quality standards.

These requirements were met for the 2012, 2014, 2016, and 2018 cycles by IDEM’s submittal of its 303(d) lists for each of these cycles in their corresponding Integrated Reports. U.S. EPA issued a consolidated approval of all four 303(d) lists on May 9, 2019.

Indiana’s 2020 303(d) List of Impaired Waters

On January 29, 2020, IDEM published Indiana’s draft 2020 303(d) list and the Consolidated Assessment and Listing Methodology (CALM) in the Indiana Register for a 90-day public comment period, which ended on April 28, 2020. IDEM received no comments from the public during this time.

IDEM presented the 2020 303(d) List of Impaired Waters to the Indiana Environmental Rules Board in a virtual public meeting on May July 8, 2020.

On June 25, 2020, IDEM uploaded its 2020 Integrated Report, including its finalized 2020 303(d) List of Impaired Waters to U.S. EPA’s Assessment and Total Maximum Daily Load Tracking and Implementation System (ATTAINS) online.

U.S. EPA reviewed Indiana’s 2020 303(d) list of Impaired Waters and issued a partial approval on February 19, 2021. In its partial approval, U.S. EPA concluded that IDEM has met the requirements of Section 303(d) of the federal Clean Water Act and all applicable requirements in the Code of Federal Regulations for all waters submitted on its 303(d) lists to date. However, U.S. EPA has determined that IDEM’s 303(d) list is not fully consistent with the requirements of Section 303(d) of the CWA and EPA’s implementing regulations based on IDEM’s decision to not list a number of waterbodies for certain metal pollutants.

U.S. EPA issued a Public Notice for the waters it added to Indiana’s 2020 List of Impaired Waters and accepted public comments on this issue through April 14, 2021. More information regarding U.S. EPA’s decision and is available on the U.S. EPA website:

A complete set of documents comprising U.S. EPA’s partial approval of Indiana’s 303(d) List of Impaired Waters is provided in the links at the bottom of this page.

Appendix L of the 2020 Integrated Water Monitoring and Assessment Report includes the 303(d) List (Category 5 of Indiana’s Consolidated List) and Category 4 waters, which are those that are impaired but do not require a Total Maximum Daily Load. Combined, these categories include all known impairments to Indiana waters:

U.S. EPA’s Partial Approval of Indiana’s 2020 303(d) List of Impaired Waters

General information on the 303(d) list is available on the Section 303(d) List Frequently Asked Questions page. You may also contact the Integrated Report Coordinator with any questions you have regarding the 303(d) list or to obtain files for previous listing cycles.