What is a TMDL?
A TMDL is a calculation that identifies the amount of a pollutant (in this case, heat) that a river or other waterbody can receive and still meet specific standards developed by a state or tribe to protect water quality.
If the waterbody does not meet these standards for certain pollutants, it is considered impaired for those pollutants and a TMDL must be developed.
The EPA assists states, territories, and authorized tribes in submitting lists of impaired waters and developing TMDLs. Learn more about TMDLs.
On May 18, 2020, EPA issued for public review and comment the Total Maximum Daily Load (TMDL) for temperature on the Columbia and Lower Snake Rivers (see "Documents" below).
The TMDL addresses portions of the Columbia and lower Snake Rivers that have been identified by the states of Washington and Oregon as impaired due to temperatures that exceed those states' water quality standards.
See "Documents" below to view all comments received by EPA during the public comment period from May 21 through August 20, 2020 (extended from July 21).
After considering comments, EPA may make modifications, as appropriate, and then transmit the TMDL to Oregon and Washington for incorporation into their current water quality management plans.
Questions? Contact Mary Lou Soscia (soscia.marylou@epa.gov), 503-326-5873, or Jill Nogi (nogi.jill@epa.gov), 206-553-1841.
Documents
You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.-
Public Comments on TMDL for Temperature in the Columbia and Lower Snake Rivers (PDF)(657 pp, 69 MB,
September 3, 2020)
Compilation of all comments received by EPA during the public comment period from May 21 through August 20, 2020. Please note large file size may take several minutes to download.
- Total Maximum Daily Load for Temperature in the Columbia and Lower Snake Rivers (PDF)(85 pp, 5 MB, May 18, 2020)
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Appendix A: Temperature Water Quality Standards for the Columbia and Lower Snake Rivers (PDF)(31 pp, 2 MB,
April 15, 2020)
Existing temperature water quality standards for the Columbia and Lower Snake Rivers within the geographic scope of the TMDL.
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Appendix B: Temperature Data Compilation, Quality Assurance and Analysis (PDF)(63 pp, 6 MB,
April 15, 2020)
Existing conditions and water quality criteria exceedances for temperature.
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Appendix C: RBM10 Model Development Report (PDF)(225 pp, 21 MB,
September 2019)
Update of the RBM10 Temperature Model of the Columbia and Snake Rivers.
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Appendix D: RBM10 Model Scenario Report (PDF)(97 pp, 4 MB,
March 2020)
Assessment of impacts to Columbia and Snake River temperatures using the RBM10 Model.
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Appendix E: Tributary Assessment Methods and Results (PDF)(12 pp, 3 MB)
Temperature analysis for tributaries discharging into the Columbia River.
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Appendix F: ORD Technical Memorandum on Tributary Restoration (PDF)(32 pp, 7 MB,
November 20, 2018)
Stream temperature predictions under varying shade and climate scenarios in the Columbia River Basin.
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Appendix G: Climate Change (PDF)(35 pp, 2 MB,
March 2020)
Assessment and synthesis of the literature on climate change impacts on temperatures of the Columbia and Snake Rivers.
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Appendix H: Temperature Metric Analysis (PDF)(6 pp, 399 K,
November 20, 2018)
Comparing Daily Maximum, Daily Average and 7-Day Average of the daily maximum temperature averaging periods on the Columbia and Snake Rivers.
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Appendix I: Temperature Heat Loads (PDF)(5 pp, 314 K)
Calculated head loads for loading capacity and allocations.