Webinar - Jan. 31, 2023
DEQ provided an informational webinar about the Temperature Total Maximum Daily Load Replacements for the Lower Columbia-Sandy Subbasin and the Willamette Subbasins on Jan. 31, 2023. The webinar provided information about the rulemakings and the technical approach to revising the TMDLs and the Water Quality Management Plans.
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 (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 Plans and interactive project maps
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).
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
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 in November 2023 before submitting the TMDL to EPA for approval or disapproval.
Please visit the rulemaking web page 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.