Proposed rule
Rulemaking contact:
Smita Mehta, 541-797-1790
The Oregon Department of Environmental Quality is developing a water quality restoration plan, called a Total Maximum Daily Load, for temperature in the Middle Columbia-Hood (Miles Creeks) Subbasin. This restoration plan addresses temperature listings. The exact area of the restoration plan is described in the Quality Assurance Projects Plan listed on the Temperature TMDL Replacement Middle Columbia-Hood (Miles Creeks) Subbasin project page.
The purpose of this restoration plan is to calculate the maximum amount of a pollutant a waterbody can take while still meeting water quality standards. Temperature is considered a pollutant, because too much of it can make a waterbody exceed water quality standards. The maximum amount of a pollutant a waterbody can take while still supporting the most sensitive use is called the loading capacity. The loading capacity plus a small amount of additional load known as the “human use allowance" is the water quality standard for temperature.
Background
In 2013, the U.S. Environmental Protection Agency disapproved the Natural Conditions Criterion contained in Oregon's water quality standard for temperature due to a court ruling (2012 U.S. District Court decision for NWEA v. EPA, 855 F. Supp. 2d 1199).
DEQ used the Natural Conditions Criterion in most temperature TMDLs issued from 2003 through 2012. In 2019, the U.S. District Court issued a judgment for the case and required DEQ and EPA to replace 15 Oregon temperature TMDLs that were based on the Natural Conditions Criterion. The agencies were required to reissue the temperature TMDLs based on the remaining elements of the temperature water quality standard. The order in which these temperature TMDLs are being reissued is based on the extent of the water quality models being used to support the TMDLs, court order requirements, and DEQ's available resources.