2024 Integrated Report: Draft 303(d) Methodology and Guidance

States are required under the Clean Water Act (CWA) Section 303(d) to compile a list of waters that do not support their designated beneficial uses and submit the list in a biennial Integrated Report to the Environmental Protection Agency (EPA) for approval. Beneficial uses include drinking water, recreation, aquatic life, and agriculture.The 303(d) list identifies the pollutant(s) causing the impairment and prioritizes the development of Total Maximum Daily Loads (TMDLs) to meet state water quality standards and support beneficial uses.

The Draft 303(d) Assessment Methods describe Utah’s proposed process for determining whether waterbodies are/are not supporting their designated beneficial uses in the 2024 Integrated Report cycle. The document complies with federal regulations that require states to evaluate all existing and readily available data against both narrative and numeric criteria when developing their 303(d) lists.

The Draft 2024 Integrated Report 303(d) Assessment Methods were available for public review and comment October 24 to December 8, 2022. DWQ is currently compiling, reviewing, and responding to comments and will publish its responses and a new version of the assessment methods in 2023.

Note: This will be the only opportunity to provide comments on the 303(d) Assessment Methods until the next IR reporting cycle. Any comments on assessment methods received after the close of the current comment period will be considered out of scope for the 2024 Integrated Report.

Summary of Methods Changes

Final 2024 303(d) Assessment Methods – Changes from previous version and draft

SectionSubsectionPage RangeTiming of ChangeNature of Change
IntroductionAssessed Parameters14Draft 303(d) MethodsChanged Assessed and Priority Parameters Section to Assessed Parameters. Removed reference to former Appendix 1, which contained a list of priority parameters. The purpose of this list was unclear, so removed.
Assessment Process and Time FramesPublic Review of the 303(d) List19Draft 303(d) MethodsChanged timeframe over which TMDLs are completed and reviewed by the Water Quality Board.
Scope of the AssessmentAssessment Units21, 23Draft 303(d) MethodsAdded that river and stream assessment units are reported using perennial stream miles, rather than intermittent and perennial.
Data QualityComponents of Credible Data25Draft 303(d) MethodsShortened Example SOPs language.
Data QualityCredible Data Matrices27-31Draft 303(d) MethodsAdded waterbody type to the essential metadata needed as outlined in the credible data matrices.
Data Submission ProcessPeriod of Record32Draft 303(d) MethodsChanged period of record for the 2024 IR.
Assessments Specific to Rivers, Streams, and CanalsConventional Parameter Assessments34Draft 303(d) MethodsRemoved term “instantaneous” from DO conventional parameter assessment notes.
Assessments Specific to Rivers, Streams, and CanalsConventional Parameter Assessments35Draft 303(d) MethodsAdded clarifying sentence about multiple beneficial use assessments.
Assessments Specific to Rivers, Streams, and CanalsNarrative Standards: Biological Assessments45-47Draft 303(d) MethodsRewrote and shortened Biological Assessments section.
Toxic Parameter Assessments for all WatersEquation-Based Toxic Parameters57Draft 303(d) MethodsCorrected ammonia criteria equations, which were missing terms from the standards outlined in R317-2.
Escherichia coli Assessment for All WatersAssessment Process62Draft 303(d) MethodsCorrected E. coli language to reflect the process outlined in the flow diagram, which was updated in the 2022 IR.
Narrative Standards for All WatersHarmful Algal Blooms (HAB)66-67Draft 303(d) MethodsUpdated harmful algal bloom section.
Narrative Standards for All WatersFish Tissue Assessments and Consumption Health Advisories67Draft 303(d) MethodsClarified the definition of a p-value in the fish tissue mercury section.
Determinations of Impairment: All Assessment UnitsAggregation of Site-Specific Assessments to Assessment Unit Categories70Draft 303(d) MethodsUpdated flow diagram used to show how DWQ aggregates from site-specific parameter assessments to an AU-level assessment category.
AppendicesAppendix 182Draft 303(d) MethodsRemoved appendix containing a list of priority parameters. The list covered most parameters in R317-2, and it was unclear the purpose of the list. Removed to improve methods conciseness and clarity.
Appendix 3Summarizing Assessments From site to Assessment Unit Level90-93Draft 303(d) MethodsRewrote Appendix 3 demonstrating how DWQ summarizes sites to AU-level assessments.
Appendix 5Delisting Guidelines96Draft 303(d) MethodsRewrote Appendix 5 delisting guidelines.


Elise Hinman (ehinman@utah.gov)
Integrated Report Coordinator
(385) 602-7277

Jodi Gardberg (jgardberg@utah.gov)
Watershed Protection Section Manager
(801) 536-4372