Transmission programmatic environmental impact statement (PEIS)

In 2023, the Legislature asked us to study the environmental effects of building, upgrading, and operating transmission facilities in Washington.

Study background

We followed the requirements under the Washington State Environmental Policy Act (SEPA) in preparing the Programmatic Environmental Impact Statement (PEIS) examining electrical transmission facilities with a voltage of 230 kilovolts (kV) or more.

Released on March 31, 2025, the Draft Transmission PEIS analyzes potential direct, indirect, and cumulative impacts of the building, operating, maintaining, upgrading, and modifying transmission facilities in Washington. It includes an analysis of the potential impacts on the natural and built environments mentioned in RCW 43.21C.405(3), WAC 197-11-444, and WAC 463-60-535. We expect to finalize the draft after considering all comments by the Autumn of 2025.

This Programmatic EIS differs from most other SEPA EISs. The Legislature's direction to us under RCW 43.21C.405 required us analyze additional topics when preparing the document. Also, under RCW 43.21C.408, SEPA lead agencies must consider this document during environmental reviews for transmission facilities that this Programmatic EIS covers. When a specific proposal uses recommendations (mitigation measures) from this Programmatic EIS, those proposals “are considered to have mitigated the probable significant adverse project-specific environmental impacts under this chapter for which recommendations were specifically developed.”

Report findings

This Programmatic EIS analyzes the environmental effects of large electrical transmission facilities but doesn't review any specific facility. Specific proposed transmission facilities will need their own SEPA environmental reviews.  

Our goals for this Programmatic EIS are to:

  • Broadly assess environmental impacts
  • Help simplify planning
  • Support informed decision-making
  • Identify strategies to reduce negative effects
  • Initiate public and stakeholder engagement

Areas we studied

The geographic scope, or study area, of this Programmatic EIS includes areas throughout Washington where developers are likely to build transmission facilities. Tribal lands and undersea cables aren't part of the study area. For details, see Section 1.5.1 Geographic Scope.

Requirements for environmental review

This Programmatic EIS includes three categories of requirements for project-level environmental review:

  • General conditions
  • Avoidance criteria
  • Mitigation measures

For details, see Sections 3.1.3.1 General Conditions, 3.1.3.2 Avoidance Criteria, and 3.1.3.3 Mitigation Measures.

Project-specific applications would include details about the precise location and site-specific conditions. For most environmental details, the Draft Programmatic EIS provides a GoldSET suitability map (see Section 3.1.6 Suitability Map). Using this map can make environmental planning more informative and efficient.  

Participants

We directed the preparation of this Programmatic EIS with the support of WSP USA Inc. and contributions from the following state and federal agencies:

  • Department of Ecology
  • Department of Fish and Wildlife
  • Department of Natural Resources
  • Department of Archaeology and Historic Preservation
  • Department of Transportation
  • Utilities and Transportation Commission
  • U.S. Department of Defense

The Department of Ecology is also creating separate Programmatic EISs for wind, solar, and green hydrogen facilities.