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Environmentally Critical Areas (ECA) Code

What Is It?

Our Environmentally Critical Areas (ECA) Code governs areas of Seattle that provide critical environmental functions. For example, wetlands can protect water quality and provide fish and wildlife habitat. Our ECA code also addresses areas that represent particular challenges for development due to geologic or other natural conditions. The goal of our ECA regulations, (Seattle Municipal Code (SMC) chapter 25.09) is to effectively protect these areas and to protect public safety, while allowing reasonable development in our growing city.

Designated environmentally critical areas are defined in SMC 25.09.020 and are generally described as:

  • Geologic hazard areas including:
    • Landslide-prone areas (including steep slope areas, potential landslide areas, and  known landslide areas)
    • Liquefaction-prone areas (sites with loose, saturated soil  that lose the strength needed to support a building during earthquakes)
    • Peat-settlement-prone areas (sites containing peat and organic soils that may settle when the area is developed or the water table is lowered)
    • Seismic hazard areas
    • Volcanic hazard areas
  • Flood-prone areas
  • Wetlands
  • Fish and Wildlife Habitat Conservation Areas including:
    • Riparian watercourses (all streams and Haller and Bitter Lakes)
    • Riparian Management Areas (the land within 100 feet of riparian watercourse)
    • Areas designated by Washington State Department of Fish and Wildlife as priority habitats and species areas
    • Areas designated by our Director as habitat for species of local importance
    • Corridors connecting priority habitats and species areas or habitat areas for species of local importance, when certain criteria are met
    • Shoreline Habitat, which is all Type 1 waters in Seattle, including Puget Sound, Duwamish River, Ship Canal, Lake Union, Portage Bay, Union Bay, Lake Washington, and Green Lake
  • Abandoned landfills

You can use our online map tool to see if your property has any mapped ECAs. Most of these maps are advisory; they help us identify potential ECAs on your property.  We will use detailed property information, such as a topographic survey or wetland report, to confirm if an ECA is present. There are some types of ECAs that we are required to identify based on the maps; for example, priority habitat areas identified by the Washington Department of Fish and Wildlife and peat-settlement prone areas. Your property may also have ECAs that are not shown on our maps.

If your property contains an ECA or a buffer for an ECA, we have specific regulations, based on the type of ECA, for how you can develop your property or disturb any land, including altering vegetation or adding impervious surface.  We suggest that you visit our Applicant Services Center for more information.

Read the Code

If you have an ECA on your property, you will need to comply with the rules that apply to that ECA.You can find detailed definitions of each ECA in Regulations for Environmentally Critical Areas (SMC 25.09). 

Proposed Changes

None

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