Chapter 173-201A WAC (Natural Conditions)

Ecology is proposing revisions to Chapter 173-201A WAC, Water Quality Standards for Surface Waters of the State of Washington.

We are proposing revisions to the parts of the surface water quality standards that address natural conditions. We have natural conditions provisions because conditions in some water bodies naturally do not meet water quality criteria. For example, a naturally low-flowing stream in a natural prairie without any human alteration may have seasonally higher temperatures than the limit set to protect fish. Water bodies may not meet the limits set to protect aquatic life because of natural processes or seasonal conditions. 

We are proposing a new method to calculate natural conditions criteria, called a performance-based approach. We've proposed a definition for this method and a new section to describe it. Also, we are providing a draft rule document with details about how to calculate natural conditions criteria using the performance-based approach. 

In addition, we are proposing the following changes:

  • Updating 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. We are also adding a definition for "local and regional sources of human-caused pollution."
  • Updating the natural conditions criteria language to limit use to aquatic life criteria and describing methods for determining natural conditions criteria values.
  • Updating how site-specific analyses must be conducted and other minor changes to the site-specific criteria section to reflect the latest guidance.

Rulemaking timeline


Announcement phase (CR-101)

Filing date:
Sept. 27, 2022

Announcement documents

Rule development phase

Sept. 27, 2022 - early 2024

Public input & involvement

April 23, 2024 – Preliminary Rule Webinar

During this workshop, we presented draft rule language and share our plan to include a method to calculate natural conditions criteria. We then opened it up for questions and informal feedback. We welcome feedback on our preliminary changes as we prepare a draft rule proposal for public comment later this spring.

View presentation slides (pdf)

March 1 and 2, 2023 – Public Informational Webinars

We hosted an informational webinar for the rulemaking to update our natural conditions provisions in the surface water quality standards, chapter 173-201A WAC. During this webinar, we provided an overview of:

  • Natural conditions provisions – what they are and what they protect
  • Importance of natural conditions in Washington
  • Options and scope of the rulemaking
  • Timelines and opportunities for public participation

View presentation slides (pdf)

Workshops offered via webinar allow individuals to view the presentation and ask questions via computer or mobile device.

Rule proposal phase (CR-102)

Filing date:
May 10, 2024

Rule proposal documents:

Comment period

Comments due July 12, 2024

Ecology will review all comments received and plans to make a decision on rule adoption July 2024. See above for documents related to the Proposal Phase of the rulemaking.

You can submit comments through one of the following ways:

  • Mail to
       For standard US Mail:
         Marla Koberstein
         Department of Ecology
         Water Quality Program
         PO Box 47696
         Olympia, WA 98504-7696

       For Parcel Service:
         Deparment of Ecology
         Water Quality Program
         Marla Koberstein
         300 Desmond Dr SE
         Lacey, WA 98503

Public hearings

The hearings will be begin with a short presentation and question and answer session, followed by the opportunity to provide testimony. The hearing will conclude once everyone who wants to provide testimony has had the opportunity to do so. Written comments will receive the same consideration as oral testimony.

Webinars are an online meeting forum that you can attend from any computer using internet access.

Any information (e.g., personal or contact) you provide may be publicly disclosed and posted on the Internet.

To request ADA accommodations, contact Ecology’s ADA Coordinator by April 1, 2024, at:

Additional languages

Español (Spanish) 中文 (Chinese) Tiếng Việt (Vietnamese) 한국어 (Korean)


To request ADA accommodation for disabilities, or printed materials in a format for the visually impaired, contact Ecology's ADA Coordinator by email at, or call 360-407-6831. People with impaired hearing may call Washington Relay Service at 711. People with speech disability may call TTY at 877-833-6341.