Section 305(b) of the Clean Water Act (CWA) requires the Indiana Department of Environmental Management (IDEM) to assess and report on whether state waters support the beneficial uses designated in Indiana’s water quality standards. IDEM’s CWA Section 305(b) assessments are made by comparing existing and readily available water quality data to applicable water quality criteria, following guidance in IDEM’s Consolidated Assessment and Listing Methodology (CALM).
Most of the data IDEM uses in its 305(b) assessments are collected by IDEM staff using a rotating basin approach. IDEM has divided Indiana into nine major water management basins and monitors one major basin each year. IDEM staff assess the data collected in each basin the following year.
| Basins | Water Quality Data Collected in the Basin | Water Quality Data Assessed for the Basin | Results Published in Indiana's Integrated Report and 303(d) List | Indiana’s Major River Basins |
|---|---|---|---|---|
| Ohio River Tributaries | 2019 | 2020 | 2022 |  Click to Enlarge |
| White River, West Fork Basin | 2020 | 2021 | ||
| Patoka River Basin | 2021 | 2022 | 2024 | |
| White River, East Fork Basin | 2022 | 2023 | ||
| Great Miami River Basin (Whitewater River) | 2023 | 2024 | 2026 | |
| Upper Wabash River Basin | 2024 | 2025 | ||
| Lower Wabash River Basin | 2025 | 2026 | 2028 | |
| Upper Illinois River Basin | 2026 | 2027 | ||
| Great Lakes Basin | 2027 | 2028 | 2030 |
In addition to agency-collected data, IDEM solicits data through its External Data Framework from external organizations and agencies, including the United States Geological Survey, Indiana University’s School of Public and Environmental Affairs, and the Indiana State Department of Health. IDEM also solicits water quality data from other colleges, universities, and local organizations, such as county health departments, watershed management groups and cities and towns. OWQ’s Integrated Reporting Program solicits data for its 305(b) assessment and 303(d) listing processes every two years.
Water quality data collected by IDEM’s water monitoring programs and through the External Data Framework are assessed and results are reported to the United States Environmental Protection Agency (U.S. EPA) every two years through the Indiana Integrated Water Monitoring and Assessment Report (IR), which describes the condition of Indiana’s lakes, streams, ground water and its Lake Michigan shoreline.
Indiana’s 2024 Integrated Water Monitoring and Assessment Report
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 webpages 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.
IDEM uploaded its 2024 Integrated Report, including the finalized 2024 303(d) List of Impaired Waters to U.S. EPA’s online Assessment and Total Maximum Daily Load Tracking and Implementation System (ATTAINS) database on March 29, 2024.
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 webpage and in the links at the bottom of this page.
IDEM’s 2024 Integrated Water Monitoring and Assessment Report Submittal, Including the 2024 303(d) List of Impaired Waters
- Indiana's 2024 Integrated Water Monitoring and Assessment Report to the U.S. EPA [PDF]
- Appendix A: Integrated Report Tables [PDF]
- Appendix B: Integrated Report Figures [PDF]
- Appendix C: Metadata and Definitions [PDF]
- Appendix D: Status of Category 4 Waters [PDF]
- Appendix E: IDEM’s Priority Ranking and 2024-2026 Schedule for Total Maximum Daily Load Development [PDF]
- Appendix F: IDEM’s 305(b)/303(d) Monitoring, Assessment, Reporting, and Listing Schedule [PDF]
- Appendix G: IDEM’s 2024 Consolidated Assessment and Listing Methodology [PDF]
- Appendix H: Comprehensive Aquatic Life Use and Recreational Use Assessments [PDF]
- Appendix I: Trend and Trophic Status of Indiana’s Lakes
- Appendix J: IDEM’s Notice of Comment Period for the 2024 Draft 303(d) List [PDF]
- Appendix K: IDEM’s Responses to Comments on the Indiana Draft 2024 303(d) List of Impaired Waterbodies and Consolidated Assessment and Listing Methodology (CALM) [PDF]
- Appendix L: Listing Tables Including Indiana’s Finalized 303(d) List of Impaired Waters (Category 5) for 2024 [XLS]
- Appendix M: Indiana’s 2024 Consolidated List (Categories 1-5) [XLS]
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 regarding the 303(d) list or to obtain files for previous listing cycles.