Overview of Washington State Environmental Policy Act (SEPA)

The Washington Legislature enacted the State Environmental Policy Act in 1971. Commonly called SEPA, the law helps state and local agencies identify environmental impacts likely result from projects and decisions such as: 

  • Issuing permits for private projects such as an office building, grocery store, or apartment complex.
  • Constructing public facilities like a new school, highway, or water pipeline.
  • Adopting regulations, policies, or plans such as a county or city comprehensive plan, critical area ordinance, or state water quality regulation.

Every day, state and local agencies use SEPA to evaluate proposed decisions. Information learned through the review process can be used to:

  • Change a proposal to reduce likely impacts.
  • Apply conditions to or deny a proposal when adverse environmental impacts are identified.

SEPA: Legal overview

The State Environmental Policy Act may be Washington's most powerful legal tool for protecting the environment. Among other things, the law requires all state and local governments to:

  • "Utilize a systematic, interdisciplinary approach which will insure the integrated use of the natural and social sciences and the environmental design arts in planning and in decision making which may have an impact on man's environment." 
  • Ensure that "environmental amenities and values will be given appropriate consideration in decision making along with economic and technical considerations...." (RCW 43.21C.030)

SEPA policies and goals supplement existing authorizations for Washington's executive, legislative and judicial branches including state agencies, counties, cities, districts, and public corporations. Any governmental action may be conditioned or denied pursuant to SEPA.

Purpose and intent

SEPA is intended to ensure that environmental values are considered during decision-making by state and local agencies. When SEPA was adopted, the state lawmakers identified four primary purposes:

  1. To declare a state policy which will encourage productive and enjoyable harmony between people and their environment.
  2. To promote efforts which will prevent or eliminate damage to the environment and biosphere.
  3. Stimulate public health and welfare.
  4. Enrich the understanding of the ecological systems and natural resources important to Washington and the nation.

To meet these purposes, state SEPA rules direct state and local agencies to:

  • Consider environmental information (impacts, alternatives, and mitigation) before committing to a particular course of action.
  • Identify and evaluate probable impacts, alternatives and mitigation measures, emphasizing important environmental impacts and alternatives (including cumulative, short-term, long-term, direct and indirect impacts).
  • Encourage public involvement in decisions.
  • Prepare environmental documents that are concise, clear, and to the point.
  • Integrate SEPA with existing agency planning and licensing procedures so procedures run concurrently rather than consecutively.
  • Integrate SEPA with agency activities at the earliest possible time to ensure planning and decisions reflect environmental values, avoid delays later in the process, and seek to resolve potential problems.

The environmental review process

The environmental review process in SEPA is designed to work with other regulations to provide a comprehensive review of a proposal. While most regulations focus on particular aspects of a proposal, SEPA requires the identification and evaluation of probable impacts on all elements of the environment.

Combining the review processes of SEPA and other laws reduces duplication and delay by combining study needs, combining comment periods and public notices, and allowing agencies, applicants, and the public to consider all aspects of a proposal at the same time.

SEPA can address project proposals such as:

  • New construction
  • Demolition
  • Landfills
  • Exchanges of natural resources

Or non-project proposals such as:

  • Comprehensive plans
  • Zoning
  • Development regulations

SEPA also gives agencies the authority to condition or deny a proposal based on the agency's adopted SEPA policies and the environmental impacts identified in a SEPA document.


First adopted in 1971, the State Environmental Policy Act (SEPA) provided Washington's basic environmental charter. Prior to its adoption, the public had voiced concern that government decisions did not reflect environmental considerations. State and local agencies responded there was no regulatory framework enabling them to address environmental issues. SEPA, modeled after the National Environmental Policy Act (1969), was created to fill this need.

It gives agencies the tools to allow them to consider and mitigate for the environmental impacts of proposals. Provisions were also included to involve the public, tribal governments, and interested agencies in most review processes prior to a final decision being made.