The department of ecology (ecology) is accepting comments on the revised draft of a methods document that provides the information and process we must follow to calculate natural conditions criteria. This document is called "A Performance-Based Approach for Developing Site-Specific Natural Conditions Criteria for Aquatic Life in Washington."

This document details the process ecology will use to develop natural conditions site-specific criteria. It is not rule language; it supports the natural conditions provisions in the surface water quality standards in chapter 173-201A WAC. While this document is not rule language, the Environmental Protection Agency (EPA) requires that we hold a comment period and public hearing whenever we make changes to it.

This methods document will cover marine dissolved oxygen natural conditions first. We anticipate future chapters to address other waters and other conventional pollutants.

What is the performance-based approach? A performance-based approach is like a recipe that guides what data to collect and how rigorous a scientific model must be to determine the natural state of the water body. This is a tool ecology can use to develop site-specific water quality criteria for aquatic life based on the natural conditions of a site.

The benefit of such a tool is that, when properly designed and approved by the EPA, it can be used to develop site-specific water quality criteria without needing additional formal rule making. A properly designed performance-based approach includes enough detail and suitable safeguards to ensure predictable, repeatable outcomes. Therefore, it can be less time consuming than developing site-specific criteria on a rule by rule basis for different locations. However, we are committed to holding a public review whenever we use the performance-based approach to develop natural conditions criteria. This will most commonly be through the public review process for water clean-up plans.

What has changed from the last draft? We provided a draft performance-based approach methods document for public comment during the natural conditions rule making in 2024. The first draft originally included methods to calculate natural conditions criteria for all five parameters that our rule allows this method to apply to: Marine and freshwater dissolved oxygen, marine and freshwater temperature, and freshwater pH. Based on feedback received during the comment period and guidance from the EPA, we have revised the document and are focusing only on a method for marine dissolved oxygen at this time.

Document for review: You can view the draft performance-based approach document at https://apps.ecology.wa.gov/publications/summarypages/2510022.html.

Public hearing: May 13 [15] at 2:00 p.m. Register for the hearing at https://waecy-wa-gov.zoom.us/meeting/register/uCPCedBERkqGbh8stiuUkg. After registering, you will receive a confirmation email containing information about joining the meeting, including joining by phone only.

The hearing will begin with a brief presentation on the draft performance-based approach document and time for questions, followed by an opportunity to provide formal comments. The hearing will end once everyone who wants to provide comments has the opportunity to do so. Written comments will receive the same consideration as oral testimony.

Next steps: After the close of comment period, we will publish our response to comments received and the final performance-based approach document. Then, the office of the attorney general will certify that the document is legally binding, and we will send the performance-based approach document to the EPA for review and approval.

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.

If the EPA approves the performance-based approach for marine dissolved oxygen, we will consider updating the document again for the other parameters, such as for freshwater temperature.