Announcing adoption of updates to Natural Conditions Provisions (WAC 173-201A)

The Washington State Department of Ecology revised chapter 173-201A WAC, Water Quality Standards for Surface Waters of the State of Washington. We adopted revisions to natural conditions provisions in our surface water quality standards to provide water quality protection for aquatic life and to establish methods for deriving those protective values.  

We adopted the following changes as part of this rulemaking: 

• Added a definition for a “performance-based approach” method for calculating natural conditions criteria. 
• Added a definition for “local and regional sources of human-caused pollution”.  
• Updated minimal allowances for local and regional human impacts to fresh and marine waters for dissolved oxygen and temperature when the natural conditions represent the water quality criteria. 
• Updated the natural conditions criteria language to limit use to aquatic life criteria and describing methods for determining natural conditions criteria values. 
• Updated how site-specific analyses must be conducted and other minor changes to the site-specific criteria section to reflect the latest version of referenced documents. 
• Adding a new section to describe and reference a method called a “performance-based approach” to determine natural conditions criteria values. This method is detailed in a separate document. 

We are not including a final Performance-based Approach document with this rule adoption. We will continue to revise the performance-based approach document based on public comment. Our goal is to share our progress early next year and go back out for public comment on that document in Spring 2025. We will carefully consider comments received and publish a final version of the publication alongside our response to comments on the document by Summer 2025. After we finalize the Performance-Based Approach document next year, we will send the document to EPA for review and approval.  

Our priority for the performance-based approach document is to establish methods to develop natural conditions criteria for marine dissolved oxygen (DO). The rule language allows us to write a performance-based approach for any of the five parameters listed (marine and freshwater DO, marine and freshwater temperature, or freshwater pH). To finalize the first chapter of the performance-based approach document next year, we will focus on one method for marine DO – later we will consider updates for the other parameters. Freshwater temperature would likely be prioritized after marine DO.  

Any future updates to the performance-based approach document will include an opportunity for public and Tribal review. Because this document governs how Ecology will use the performance-based approach for site-specific criteria development, it must meet federal Clean Water Act requirements, which includes a public review process and EPA review and approval before use in federal Clean Water Act actions. 

Until we publish a final version of the Performance-based Approach document and receive EPA approval following their review, we will not be able to use the performance-based approach for natural conditions site-specific criteria under the Clean Water Act. If you have questions about Ecology’s plan to finalize the performance-based approach, please reach out to Kalman Bugica, at kalman.bugica@ecy.wa.gov.  

What does chapter 173-201A WAC do? 

The state’s water quality standards, Chapter 173-201A WAC, set limits on pollution in our lakes, rivers, and marine water in order to protect beneficial uses, such as swimming and fishing. The water quality standards are implemented through discharge permits and other regulatory mechanisms under the federal Clean Water Act. They are also used to identify polluted waterbodies and set levels for water cleanup. 

Rule adoption and effective dates 

We adopted this rule on Nov. 14, 2024. The adopted changes to this rule become effective Dec. 15, 2024. The rule goes into effect for Clean Water Act purposes, such as for the Water Quality Assessment and water quality permits, after it has been approved by the Environmental Protection Agency (EPA).  

Following the rule adoption, the next step is to submit the final rule to EPA for review and approval. After we submit the final rule to EPA they have 60 days to approve or 90 days to disapprove the updated water quality standards. EPA must also consult with the US Fish and Wildlife Service and National Marine Fisheries Service to determine if the rule adequately protects endangered species. 

After we finalize the Performance-Based Approach document next year, the Office of the Attorney General will certify that the document is legally binding, then we will send the performance-based approach document to EPA for review and approval. 

View the final rule documents 

The rule language, and other supporting documents, are available on the rulemaking webpage. 

Documents include: 

• Final Rule Language 
• CR-103 Form
• Concise Explanatory Statement
• Rule Implementation Plan
• Final Regulatory Analyses
• Technical Support Document 

Response to Public Comments 

We held a public comment period from May 10, 2024, to July 26, 2024. We held virtual public hearings on June 27 and July 2, 2024.  

Ecology's response to comments received during the public comment period is now available, which you can read in the Concise Explanatory Statement. You can view the comments we received on our online comment page. 

What changed from the proposed rule to the adopted rule? 

We changed some rule language from the proposed rule based on public comments. We provided a detailed summary of changes in the Concise Explanatory Statement. 

We included a draft performance-based approach document with the rule proposal. We plan to publish a final version of this document in 2025 after we make additional revisions and provide another opportunity for public comment on the revised draft. 

How can I get technical help once WAC 173-201A is effective?  

For more information on compliance and implementation, please contact Marla Koberstein at marla.koberstein@ecy.wa.gov or 360-628-6376. 

Can I appeal the adoption of this chapter? 

You may appeal this adoption under procedures described in the Administrative Procedure Act (RCW 34.05), including those found in RCW 34.05.330.  

• For supporting information on this rulemaking, browse the rulemaking webpage 
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