Temperature TMDL Replacement: Lower Columbia-Sandy Subbasin

TMDL Title: TMDLs for the Lower Columbia-Sandy Subbasin
Water Quality Limited Parameters: Temperature
Pollutants: Heat
Status: Approved. The temperature TMDLs for the Lower Columbia-Sandy Subbasin were adopted by the Environmental Quality Commission into rule on Aug. 6, 2024. 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 map

This 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).

Contact

Andrea Matzke
Basin Coordinator

Steve Mrazik
Watershed Management Manager

Rulemaking

TMDL development and implementation is a public process. DEQ will develop this TMDL by rule per Oregon Administrative Rule Chapter 340 Division 42. During a rulemaking process, DEQ seeks public involvement by holding public hearings, establishing rule advisory committee meetings for technical and policy input, and for feedback regarding potential fiscal impacts related to the rule.

Lower Columbia-Sandy Subbasin TMDL rulemaking

Please visit the rulemaking web page for rule advisory committee meeting information, draft project documents including the TMDL, Water Quality Management Plan, Technical Support Document, and Fiscal Impact Statement.