Environmentally Critical Areas Update - Background

Enviornmentally Critical Area Updates


In 1978, in response to the State Environmental Policy Act (SEPA), the City produced a map designating areas thought to be environmentally sensitive. The designated areas included steep slopes, landslide-prone areas, floodplains, landfills, and certain water bodies. The purpose of those designations was to help ensure that the impact of new development on those areas could be assessed and mitigated as part of the required environmental review of new development. Until 1990, these maps and the SEPA review process were the only way jurisdictions could control the unintended consequences of new development in sensitive areas.

In 1990, the Washington State Legislature adopted the Growth Management Act. The GMA required Seattle and other local governments to adopt comprehensive plan policies and development regulations that protect ECAs, instead of assuming that only development subject to SEPA affected critical or sensitive environmental areas. Seattle adopted interim environmentally critical areas regulations to regulate development while permanent policies and regulations were developed. In 1992, Seattle adopted the first permanent ECA policies and code. Amendments have been made over time to our critical areas policies and code in 1995, 1997, 2006, 2014, and 2017.

In Seattle, environmentally critical areas include five areas and ecosystems:

  • Wetlands
  • Fish and wildlife habitat conservation areas (including riparian corridors, shorelines (regulated under the Shoreline Master Program), and other priority habitat and species areas)
  • Geologic hazard areas (including landslide-prone, steep-slope and liquefaction-prone areas; steep slopes are also protected for erosion control to protect water-quality)
  • Flood-prone areas
  • Abandoned landfills

Policies and regulations designating and protecting ECAs are required by, RCW 36.70A.060(2), RCW 36.70A.170, and RCW 36.70A.172(1)

For additional information, see SDCI’s Environmentally Critical Areas (ECA) Code webpage.