WSR 25-23-113

PREPROPOSAL STATEMENT OF INQUIRY

DEPARTMENT OF ECOLOGY

[Order 25-09—Filed November 19, 2025, 8:40 a.m.]

Subject of Possible Rule Making: The department of ecology (ecology) is considering amendments to chapter 173-423 WAC, Washington's clean vehicles program, rule. Washington law (RCW 70A.30.010) requires ecology to adopt certain California regulations to maintain consistency with California's emissions standards for new motor vehicles and engines. To date, ecology has delivered on this statutory requirement by adopting regulations consistent with the following California programs: Advanced clean cars, advanced clean cars II, advanced clean trucks, and heavy-duty low NOx omnibus standards. These regulations ensure that new motor vehicles sold in Washington pollute less, and they are an essential policy tool for addressing climate change and improving air quality, particularly in communities overburdened by vehicle emissions.

In this rule making, ecology is considering amendments to Washington regulations that will track amendments to the following California regulations: Advanced clean cars, advanced clean cars II, advanced clean trucks, and heavy-duty low NOx omnibus standards.

Additionally, ecology is considering adopting components of California's 2010 medium- and heavy-duty vehicle in-use standards to maintain consistency with RCW 70A.30.010, particularly in light of ongoing federal attempts to revoke California's waivers for the current medium- and heavy-duty low-emission vehicle standards (i.e., heavy-duty low NOx omnibus). Although ecology holds these recent federal waiver actions as unlawful, this rule making will ensure the cleanest available standards are implemented in Washington.

The relevant sections that ecology is considering adopting by reference from the California code of regulations are listed below.

Revising Existing Sections:

New Sections:

Furthermore, amendments under consideration include any changes to components of these regulations in chapter 173-423 WAC that are needed to address Washington-specific vehicle market conditions. These changes must be limited to aspects that do not create a "third vehicle" for regulatory purposes outside of those created for the California and federal markets, as is required by the federal Clean Air Act. Ecology is also evaluating additional fleet reporting requirements, beyond the one-time report required in 2023, to authorize additional data collection. These amendments are important to streamline program implementation, provide additional compliance flexibility and clarity, maintain consistency with other states and the federal government, and work toward meeting Washington's requirements for greenhouse gas emissions.

Statutes Authorizing the Agency to Adopt Rules on this Subject: Chapter 70A.30 RCW, Motor vehicle emission standards.

Reasons Why Rules on this Subject may be Needed and What They Might Accomplish: In accordance with chapter 70A.30 RCW, ecology is exploring amending these rules to maintain consistency with and implement California's motor vehicle emission standards. Amendments to both the heavy-duty low-NOx omnibus regulation and the advanced clean trucks regulation from California, as well as potential additional California motor vehicle emissions standards, are crucial to achieving Washington's greenhouse gas emissions reduction mandates in RCW 70A.45.020.

Other Federal and State Agencies that Regulate this Subject and the Process Coordinating the Rule with These Agencies: 42 U.S.C. Section 7507 (also known as Section 177 of the Clean Air Act) allows states to adopt and enforce California's vehicle emission standards, for which the United States Environmental Protection Agency (EPA) has issued a waiver, instead of the federal ones if the state standards are identical to the California standards. EPA regulates the subject at the federal level. At the state level, ecology will be coordinating with the department of licensing to discuss implementation of the rule.

Process for Developing New Rule: Ecology will follow the standard process for the adoption of rules under the Administrative Procedure Act (chapter 34.05 RCW).

Interested parties can participate in the decision to adopt the new rule and formulation of the proposed rule before publication by contacting Gopika Patwa, Department of Ecology, Climate Pollution Reduction Program, P.O. Box 47600, Olympia, WA 98504-7600, phone 360-338-2419, Washington relay service or TTY call 711 or 877-833-6341, email Gopika.patwa@ecy.wa.gov, website https://ecology.wa.gov/regulations-permits/laws-rules-rulemaking/rulemaking/wac-173-423-clean-vehicles-program. Sign up for rule updates at https://public.govdelivery.com/accounts/WAECY/subscriber/new?topic_id=WAECY_233.

Additional comments: Interested parties can stay informed about the rule making and public involvement opportunities as described above. Ecology will extend an offer for government-to-government consultation with tribal governments during each phase of rule development.

Ecology will conduct an environmental justice assessment in accordance with RCW 70A.02.060 as a part of this rule making.

November 19, 2025

Joel Creswell, Manager

Climate Pollution Reduction Program