SEPA laws and regulations: current & historical revisions

Ecology is responsible for overseeing state rules that put the State Environmental Policy Act (SEPA) in place.

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2025 legislative session: Ecology SEPA bills

During the 2025 session of the Washington Legislature, several bills were enacted related to the State Environmental Policy Act. The following information identifies these bills, including the changes they make to the law.

Transit Oriented Development (HB 1491), effective July 27, 2025

Third Substitute House Bill 1491 prioritizes increasing transit-oriented development within Washington cities. The addition to the State Environmental Policy Act (SEPA), RCW 43.21C.229, adds a new categorical exemption for residential and mixed-use density around transit station areas within cities managing their growth and development under the state Growth Management Act (GMA). The new exemption affects locations meeting the definition of a “station area” added to RCW 36.70A.030(51). Generally, these areas are located within one-half mile walking distance of a rail station area or within a quarter mile of a bus rapid transit stop. The categorical exemption is limited to the construction of multi-family residential buildings or mixed-use buildings containing a residential portion located within a zone that allows mixed-use development.

This new categorical exemption is subject to the following exceptions to the exemptions identified in WAC 197-11-800(1)(a); or in other words, if any of the following criteria apply to a commercial or residential construction project in a service area, the proposal it is not SEPA exempt:

The proposal includes other components that are not exempt from SEPA , see WAC 197-11-305(1)(b).
The project is located wholly or partially on lands covered by water defined in WAC 197-11-756. These lands are surface water bodies in Washington, including wetlands, lakes, rivers and streams and saltwater bodies, and artificial water bodies like reservoirs, impoundments and channelized streams.

The project requires an air emission permit not exempt under RCW 43.21C.0381;
The project requires a water discharge permit not exempt under RCW 43.21C.0383. This includes a project that disturbs five or more acres of land, or another water discharge permit issued by the state Department of Ecology.
The project requires a rezone that triggers a comprehensive plan amendment identified in WAC 197-11-800(6)(c).

The bill also adds several planning and regulatory requirements for GMA fully-planning cities for the exempted station areas. More information about these requirements can be found on the state Department of Commerce website. The bill incentivizes these planning requirements by providing a safe harbor clause for cities by exempting SEPA appeals for local non-project actions approved by Commerce by June 30, 2026. The SEPA appeal exemption is limited to city’s adoption of a plan or implementing regulations for a specific station area taken by cities for the compliance with the bill.

Also, although not included as an amendment to SEPA, the bill also adds a new section to the Growth Management Act (RCW 36.70A) prohibiting cities from issuing a SEPA determination of significance (DS) based solely for project applications proposing no off-street parking within station areas.

Designation of historic landmarks (HB 1576), effective July 27, 2025:

Substitute House Bill 1576 creates new processes and criteria for nominating and establishing property to be put on the historic register in Washington under the state Growth Management Act. The changes to SEPA add an appeal safe haven for cities and counties adopting ordinances, development regulations and other nonproject actions under the new law. The bill’s new language adds RCW 43.21C.495 identifying nonproject actions taken by cities and counties for consistency with sections 1 and 2 of the bill. These are not subject to SEPA administrative or judicial appeals.

Energy Transformation Act (SB 5445), effective July 27, 2025:

Engrossed Substitute Senate Bill 5445 encourages the development of distributed energy resources to support clean energy goals under the Clean Energy Transformation Act. The bill adds a new section to SEPA creating categorical exemptions for solar energy projects. Three types of projects are now categorically exempt:

Small-scale projects on previously disturbed or developed lands
Projects located over existing parking lots
Solar energy projects located on landfills and reclaimed surface mines

Read the details below for specific criteria for each of the three new exemptions.

Projects less than 1,000 square feet on previously disturbed or developed lands include projects to place arrays of solar energy panels, associated equipment or the construction of structures that support solar panel arrays and associated equipment. All of the following criteria must be met for the exemption to apply:

Structures and arrays must have a footprint of less than 1,000 square feet;
The proposed project must not be located on:
- Lands covered by water as defined in WAC 197-11-756; or
- Lands considered open space, agricultural or timberlands eligible for current use valuation under RCW 84.34.020; and,
The project must be located on previously disturbed or developed lands including but not limited to driveways, lawns, patios and walkways.

Projects located over parking lots include the construction of structures that support solar energy panels and associated equipment located completely over parking lots. Projects located wholly or partially on lands covered by water are excluded from being exempt under this new provision.

Solar energy projects located on closed landfills and reclaimed surface mine lands include solar energy generation, accompanying energy storage and electricity transmission and distribution facilities when the project is located wholly on closed or capped portions of landfills or surface mine lands that are reclaimed or no longer active. To be exempt under this new provision the project must be served by and accessible to emergency fire response services, as determined by the lead agency; And must not:

Be located on lands covered by water defined in WAC 197-11-756; nor,
Involve the penetration of an asphalt or soil cap on a landfill;

Lands covered by water, defined in WAC 197-11-756, include all surface water bodies in Washington, including: wetlands, lakes, rivers and streams and saltwater bodies, including artificial water bodies manipulated by humans like reservoirs, impoundments and channelized streams.

Lands covered by water do not include the protective buffer associated to a water body. And the definition does not include water bodies created on upland sites for the purpose of water quality utilities such as drainage ditches, swales, catchment basins, farm ponds and wastewater treatment facilities.

Note: the SEPA Rules also contain an exemption for the installation of solar generation equipment on existing structures in WAC 197-11-800(2)(l).

Growth Management Act – Housing Element (SB 5471), effective July 27, 2025:

Third Engrossed Senate Bill 5471 authorizes counties fully planning under the Growth Management Act (GMA) to allow for middle housing in unincorporated urban growth areas.

Changes to SEPA include a new subsection to RCW 43.21C.495 providing an appeal safe haven to counties adopting non-project action implementing section 1 of the bill. The new language blocks all administrative and judicial appeals under SEPA for any locally adopted ordinance, resolution, development regulation or other non-project action taken by a GMA-fully-planning-county to incorporate the middle housing allowances into their planning and regulatory scheme.

Growth Management Act- Comprehensive Plan Housing Element, (SB 5148), effective July 27, 2025

Engrossed Second Substitute Senate Bill 5148 establishes a new approval process with the state Department of Commerce for the housing element of comprehensive plans and associated housing development regulations for cities and counties fully planning under the Growth Management Act (GMA).

The bill adds a new subsection to RCW 43.21C.495 identifying a SEPA appeal safe haven for cities and counties adopting nonproject actions implementing the housing element requirements in RCW 36.70A.070(2). The new section blocks all administrative and judicial appeals under SEPA for adoption of ordinances, development regulations, amendments to development regulations for compliance with the housing element under GMA.

The bill also identifies compliance with SEPA as criteria for approval by Commerce for the housing element and associated housing regulations.

State Transportation System (SB 5801), effective July 27, 2027:

Engrossed Substitute Senate Bill 5801 enacts comprehensive changes to several laws for ongoing development and maintenance of the state transportation system.

Section 605 of the bill adds a new section to the State Environmental Policy Act (SEPA) that applies to transit projects when a “detailed statement” or Final Environmental Impact Statement (Final EIS) has been prepared by a transit agency. The new section identifies two different scenarios for compliance with SEPA when a transit agency prepares a Final EIS: One for a SEPA Final EIS and one for a Final EIS under the National Environmental Policy Act..

Engrossed Substitute House Bill 5165 updates planning and permitting requirements for high-voltage electric transmission line projects. The updates attempt to help the state’s electricity transmission systems:

improve long-term efficiency
increase capacity to match renewable electricity generation and electricity demand
promote resilience against climate change impacts

The first new section requires EFSEC to prepare nonproject EIS’s for electrical transmission facilities with a nominal voltage of 230 kV or greater. Like other EIS’s, the bill requires disclosure and evaluation of probable environmental impacts and identification of mitigation measures. It also lists a handful of specific impacts that EIS’s must consider and requires each EIS to include a map showing probable significant adverse impacts in relation to the area evaluated.

The second section added to SEPA authorizes lead agencies conducting project-level environmental reviews of electrical transmission facilities of 230 kV or greater to consider nonproject EIS’s prepared under HB 5165 Sec. 6. The bill requires any project-level review of a proposed facility begin with a review of the applicable nonproject EIS to determine if any potential impacts will occur that the nonproject EIS does not consider. If the nonproject EIS recommendations address all significant adverse impacts, project-level impacts are considered mitigated. If additional significant adverse impacts would occur, the lead agency must complete an addendum or supplemental EIS to disclose and analyze these impacts, as well as identify mitigation measures to address the impacts.

Implementation notes: No rulemaking at Ecology will result from these changes.

2024 Legislature : Ecology SEPA bills

No changes were made to the State Environmental Policy Act during the 2024 legislative session.

Average time to complete an environmental impact statement

Every two years, Ecology is required to submit a report to the legislature documenting the average time it takes to complete a final environmental impact statement under SEPA. The report is required under 43.21C.0311(2). You can find these reports on our publications page.

State Environmental Policy Act case law summary:

The following summaries are a collection of court decisions affecting Chapter 43.21C RCW. This is not a complete list of all applicable opinions on SEPA. To find the complete written opinions related to these summaries, we recommend searching Washington State Courts

Contact information

SEPA Help
sepahelp@ecy.wa.gov
360-407-6922