The 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, which is submitted to the U.S. EPA every two years 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 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 considering 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.
Indiana’s 2024 303(d) List of Impaired Waters
On February 1, 2024, IDEM published Indiana’s draft 2024 303(d) list and the Consolidated Assessment and Listing Methodology (CALM) on the IDEM Integrated Water Monitoring and Assessment Report and Section 303(d) List web pages for a 45-day public comment period, which ended on March 18, 2024. A notice directing the public to the draft 2024 303(d) list and CALM was posted in the Indiana Register on February 14, 2024. IDEM received several comments from the public and U.S. EPA during this time.
On March 29, 2024, IDEM uploaded its 2024 Integrated Report, including its finalized 2024 303(d) List of Impaired Waters to U.S. EPA’s Assessment and Total Maximum Daily Load Tracking and Implementation System (ATTAINS) online database. The 2024 303(d) List of Impaired Waters was presented to the Indiana Environmental Rules Board in a public meeting on April 10, 2024.
U.S. EPA reviewed Indiana’s 2024 303(d) list of Impaired Waters and issued a partial approval on May 17, 2024. In its partial approval, U.S. EPA concluded that IDEM’s 303(d) list is not fully consistent with the requirements of Section 303(d) of the Clean Water Act and EPA’s implementing regulations based on IDEM’s decision to not list several waterbodies for certain metal pollutants.
U.S. EPA is accepting public comments on the partial approval of the 2024 303(d) list of Impaired Waters from June 16, 2024 to July 16, 2024. A complete set of documents comprising U.S. EPA’s partial approval of Indiana’s 2024 303(d) List of Impaired Waters is provided at the EPA’s Additions to Indiana’s 2024 Impaired Waters List web page and in the links at the bottom of this page.
IDEM’s 2024 303(d) List of Impaired Waters Submittal
Appendix L of the 2024 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:
The Listing Tables include the following information:
- Category 5 of Indiana’s Consolidated Listing of All Waters (the 303(d) List)
- Category 4 of Indiana’s Consolidated Listing of All Waters, which includes impaired waters that do not require a Total Maximum Daily Load (TMDL) under Section 303(d) of the Clean Water Act
- A TMDL Key for the impairments identified in Category 4A
- A change file for Categories 4 and 5, which describes all the modifications made to these lists since IDEM’s 2022 303(d) list was approved by U.S. EPA.
U.S. EPA’s Partial Approval of Indiana’s 2024 303(d) List of Impaired Waters
- U.S. EPA Letter Indicating Partial Approval of Indiana’s 2024 303(d) List [PDF]
- Enclosure 1: Review of Indiana’s 2024 Section 303(d) List of Impaired Waters [PDF]
- Enclosure 2: Analysis of Indiana’s Section 303(d) List and the State’s Integrated Report (IR) Submittal for 2024 [PDF]
- Enclosure 3: Tables in Support of EPA’s 2024 Action on Indiana’s 2024 303(d) List of Impaired Waters [XLSX], [PDF]
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.