SEPA laws and regulations: current & historical revisions

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

Find full text of SEPA and state rules:

2024 Legislature : Ecology SEPA bills

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

Questions? Contact Sarah Cassal,, 360-407-6922.

2023 Legislature: Ecology SEPA bills

During the 2023 Legislative session, several bills were enacted related to the State Environmental Policy Act (SEPA). The following information identifies these bills and briefly explain the changes they make. Questions? Contact Fran Sant, (360) 529-6375. 

Climate Change and Land Use Planning (HB 1181)

Engrossed Second Substitute House Bill 1181 adds a climate change mitigation and resiliency goal to the Growth Management Act (GMA) for cities and counties to implement. The bill adds a new section to SEPA RCW 43.21C.497 making nonproject actions related to implementing new GMA requirements immune from administrative and judicial appeals. 

SEPA Categorical Exemption for Infill Housing (SB 5412)

Second Substitute Senate Bill 5412 amends SEPA RCW 43.21A.229 to allow proposed housing within urban growth boundaries to rely on environmental reviews completed at the comprehensive planning level rather than  the individual project level. Provided certain criteria are met the bill creates a new SEPA categorical exemption for residential housing projects within cities and “middle housing” projects in unincorporated urban growth areas. To be eligible a housing project must be consistent with all development regulations adopted under the GMA. 

Middle Housing, Accessory Dwelling Units and Existing Buildings (HB 1110)

Engrossed Second Substitute House Bill 1110 amends both GMA and SEPA. It requires Commerce to develop model middle housing ordinances, a process cities use to seek state approval of required local actions. Commerce will also create guidance to assist cities on what to include in a parking study as well as general technical assistance. The bill includes several provisions amending SEPA, including a “safe harbor” clause for local governments that eliminate SEPA appeals for nonproject actions by local governments. The bill also creates a SEPA categorical exemption for amending development regulations to remove parking requirements from development proposed to fill in a UGA (RCW 43.21C.450).

Implementation Notes: Local governments will implement the bill.

Clean Energy Siting, and Transmission Planning (HB 1216)

Engrossed Second Substitute House Bill 1216 adds a new section to SEPA 43.21C.535 Clean energy projects—Nonproject environmental impact statements. This addition supports timely and effective siting and permitting for new clean energy projects while protecting the environment, overburdened communities, and Tribal rights and cultural resources. The bill establishes an Interagency Clean Energy Siting Coordinating Council, co-led by Ecology and Commerce, to consider and implement actions to improve permitting clean energy projects and provide an annual legislative report with recommendations. 

Light Pollution (HB 1173)

Engrossed Substitute House Bill 1173 requires utility-scale wind energy facilities to install light mitigation systems that turn off aviation hazard lights when there are no planes nearby. The bill adds a new exemption to SEPA for projects to implement light mitigation projects in RCW 43.21C.540.

Electrical Transmission Facility Siting (HB 5165)

Engrossed Substitute House Bill 5165 updates planning and permitting requirements for high-voltage electric transmission line projects and adds two new sections to SEPA in RCW 43.21C.405 and RCW 43.21C.408. One directs EFSEC to prepare a non-project EIS for transmission facilities and the other requires lead agencies to incorporate the EFSEC nonproject EIS in their environmental review. 

Additional Housing Units in Existing Buildings (HB 1042)

Engrossed Substitute House Bill 1042 includes one amendment to SEPA in RCW 43.21C.450. The attempts to increase housing units in existing buildings by streamlining permitting and planning requirements for those types of development. The only change to SEPA amends nonproject actions under RCW 43.21C.450 to categorically exempt amendments to numerous types of local development regulations that govern development of existing buildings. Examples of these types of regulations include but are not limited to those that provide increased protections for critical areas and vegetation retention on shorelines, as well as protections against increased impervious surface area. In addition, the bill categorically exempts amendments to local building, energy, electrical, and other technical codes that ensure consistency with minimum state standards. 

Implementation notes: Implementation will take place at the local government level. No rulemaking at Ecology will result from these changes.

Accessory Dwelling Unit Construction (HB 1337)

Engrossed Substitute House Bill 1337 attempts to expand housing options by streamlining the planning and permitting process for construction of accessory dwelling units. The only change to SEPA is an amendment to RCW 43.21C.495 adding a subsection that prohibits judicial or administrative appeals under SEPA of nonproject actions that are consistent with the accessory dwelling unit requirements in Sections 3 and 4 of HB 1337. These nonproject actions can include adoption of ordinances and development regulations, as well as amendments to comprehensive plans or subarea plans. 

Implementation notes: Implementation will take place at the local government level. No rulemaking at Ecology will result from these changes.