Temperature TMDL Replacement: Middle Columbia-Hood (Miles Creeks) Subbasin

Project Area: The project will include all surface waters that flow to the Columbia River within the central portion of the Middle Columbia-Hood Subbasin, also sometimes known as the Miles Creeks area. The specific watersheds include Eightmile Creek Watershed, Fifteenmile Creek Watershed, Mill Creek-Columbia River Watershed, and four subwatersheds within the Mosier Creek-Columbia River Watershed. These subwatersheds include Upper Mosier Creek Subwatershed, Lower Mosier Creek Subwatershed, Rock Creek Subwatershed, and Rowena Creek-Columbia River Subwatershed. The Columbia River and waters in the State of Washington are not included in the project area. 

Project Area Map

• Project area map

Project summary

Monitoring data show temperatures for multiple streams in the project area watersheds are too warm for sensitive fish and do not meet Oregon's EPA approved temperature standards. As a result, the waters not meeting standards have been placed on a national list of impaired waters. The federal Clean Water Act requires states or EPA to develop a Total Maximum Daily Load, or TMDL, for each water listed as impaired. Once approved, the updated TMDL will replace the Middle Columbia-Hood (Miles Creeks) Subbasin temperature TMDL issued by DEQ in 2008 and approved by the United States Environmental Protection Agency on February 5, 2009.

DEQ is replacing the existing TMDL following the outcome from two court cases and related EPA actions. In response to a 2012 court decision, EPA disapproved Oregon's Natural Conditions Criterion for temperature in 2013, which had been used in most temperature TMDLs from 2003 through 2012. A 2019 court ruling then required DEQ and EPA to replace 15 TMDLs using the remaining approved parts of Oregon's temperature water quality standard.

Sign up for email updates on the TMDL Replacement Project web page. 

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 of a waterbody, including an appropriate margin of safety.

Quality Assurance Project Plan

A Quality Assurance Project Plan is required prior to writing the TMDL. The plan outlines the framework for developing a temperature TMDL, including defining the problem scope, key temperature-related processes and technical modeling approach. It also details the data sources, evaluation methods, potential management scenarios and project management components such as documentation and team coordination. 

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.

DEQ will hold two rule advisory committee meetings and a public hearing. DEQ will present the draft TMDL and Water Quality Management Plan to the Environmental Quality Commission, DEQ's formal policy and rulemaking body, for adoption before submitting the TMDL to EPA for approval or disapproval.

DEQ will have a rulemaking webpage for rule advisory committee meeting dates and information, draft project documents including the TMDL, Water Quality Management Plan, Technical Support Document, and Fiscal Impact Statement, and to sign up for email updates.

Contact

Michele Martin, Project manager

Smita Mehta, Basin Coordinator

Steve Mrazik, Watershed Management Manager