TMDL Title: Temperature TMDLs for the Lower Columbia-Sandy Subbasin
Water Quality Limited Parameters: Temperature
Pollutants: Heat
Approved: The Lower Columbia-Sandy Subbasin TMDL for temperature was adopted by the Environmental Quality Commission into rule on Aug. 6, 2024.
Lower Columbia-Sandy Subbasin Temperature TMDL. Please note that the hyperlinks for this item go to zip files that contain the staff report, attachments and appendices for each TMDL.
EPA approved the TMDL on Sept. 12, 2024.
Project summary
In 2013, the United States Environmental Protection Agency disapproved the Natural Conditions Criterion contained in Oregon's water quality standard for temperature due to the 2012 U.S. District Court decision for NWEA v. EPA, 855 F. Supp. 2d 1199 (D. Or., 2012). This portion of the temperature water quality standard was used in most temperature TMDLs issued from 2003 through 2012. On October 4, 2019, the U.S. District Court issued a judgment for NWEA v. EPA, No. 3:12-cv-01751-HZ (D. Or., Oct. 4, 2019) and required DEQ and USEPA to replace 15 Oregon temperature TMDLs that were based on the Natural Conditions Criterion and to reissue the temperature TMDLs based on the remaining elements of the temperature water quality standard.
A Total Maximum Daily Load is a water quality restoration plan and the calculation of the maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards for that particular pollutant. The maximum amount of loading a waterbody can receive is called the loading capacity. Loading from all pollutant sources must not exceed the loading capacity (TMDL) of a waterbody, including an appropriate margin of safety.
Quality Assurance Project Plans: Sandy Subbasin
A Quality Assurance Project Plan is developed prior to writing the TMDL and does the following:
- Define the issue and objectives of the TMDL, including the spatial and temporal extents of the water quality impairments.
- Provide a high-level description of the key processes and variables for temperature
- Outlines the overarching technical approach for the TMDL, including the appropriate modeling and analytical tools to be used.
- Provides the data sources for defining and creating inputs to the models, including data that were used in the modeling for the original TMDLs, if an original exists. Examples of these inputs can include meteorological data, stream flow and temperature, point sources and vegetation characteristics
- Describes how the analysis and modeling will be evaluated for acceptability
- Describes potential scenarios for evaluating management strategies for reducing anthropogenic thermal loads
- Provides various aspects for managing the TMDL development project, including documentation, the project team, data, and records management
Lower Columbia-Sandy Subbasin Quality Assurance Project Plan and interactive project mapThis Quality Assurance Project Plan summarizes the modeling approach to be used for the temperature TMDL replacement project applicable within the Lower Columbia-Sandy Subbasin (17080001).