Critical Areas Ordinance and Shoreline Master Program Update

Logo for the Critical Areas Ordinance and Shoreline Master Program Update



In 2018-2019, the City of Mercer Island will be updating its Critical Areas code and Shoreline Master Program. The Critical Areas code is the portion of the City's code that sets standards and requirements for areas like wetlands, landslide hazard areas, watercourses. The Shoreline Master Program contains regulations pertaining to parts of Mercer Island within 200 feet of Lake Washington.



In 2018-2019, the City of Mercer Island will be updating its Critical Areas code and Shoreline Master Program. The Critical Areas code is the portion of the City's code that sets standards and requirements for areas like wetlands, landslide hazard areas, watercourses. The Shoreline Master Program contains regulations pertaining to parts of Mercer Island within 200 feet of Lake Washington.

  • What are Critical Areas? Watch the Video!

    about 1 month ago

    The City has created a brief 6-minute video to inform the community about the Critical Areas and Shoreline Master Program update. Watch the video to learn more about critical areas and shorelines and why the city is updating the regulations.

    Watch it here!

    The City has created a brief 6-minute video to inform the community about the Critical Areas and Shoreline Master Program update. Watch the video to learn more about critical areas and shorelines and why the city is updating the regulations.

    Watch it here!

  • Best Available Science

    26 days ago
    Critical areas

    The Growth Management Act (RCW 36.70A) requires Washington’s counties and cities to review, evaluate, and update comprehensive land use plans, as well as updating development regulations using Best Available Science (BAS) to identify, designate and protect critical areas.

    Mercer Island last updated its Critical Area regulations in 2005, and an update is due by summer, 2019. The City hired a consultant, ESA, to conduct an analysis of the Best Available Science as it pertains to the critical areas located in Mercer Island. ESA's findings are available in two reports here and here.

    Mercer Island is home to 5 types of critical areas:

    1. Wetlands
    2. Watercourses
    3. Fish and wildlife habitat conservation areas
    4. Geologically hazardous areas
    5. Critical aquifer recharge areas
    ESA analyzed scientific research pertaining to the protection of these 5 types of critical areas and performed a gap analysis of the BAS findings and Mercer Island's current critical area regulations. At a high level, the BAS shows that the City should expand buffers around critical areas (buffers are a setback area around the critical area where development activities are restricted). The Planning Commission has been briefed on these findings and is considering the BAS as they develop draft code language.


    The Growth Management Act (RCW 36.70A) requires Washington’s counties and cities to review, evaluate, and update comprehensive land use plans, as well as updating development regulations using Best Available Science (BAS) to identify, designate and protect critical areas.

    Mercer Island last updated its Critical Area regulations in 2005, and an update is due by summer, 2019. The City hired a consultant, ESA, to conduct an analysis of the Best Available Science as it pertains to the critical areas located in Mercer Island. ESA's findings are available in two reports here and here.

    Mercer Island is home to 5 types of critical areas:

    1. Wetlands
    2. Watercourses
    3. Fish and wildlife habitat conservation areas
    4. Geologically hazardous areas
    5. Critical aquifer recharge areas
    ESA analyzed scientific research pertaining to the protection of these 5 types of critical areas and performed a gap analysis of the BAS findings and Mercer Island's current critical area regulations. At a high level, the BAS shows that the City should expand buffers around critical areas (buffers are a setback area around the critical area where development activities are restricted). The Planning Commission has been briefed on these findings and is considering the BAS as they develop draft code language.


  • Why are we updating critical areas and shorelines regulations?

    4 months ago

    The City is required by state law to periodically update its Critical Areas Ordinance (CAO) and Shoreline Master Program (SMP). In addition to being a legal requirement, the periodic update provides an opportunity for the community to ensure its critical areas and shoreline codes are up to date with the latest science and in line with the City's current land use policies.

    The process began with the City Council setting a scope of work, providing a framework for what will be covered over the course of this project. The City's Planning Commission has started on that scope of work, first reviewing the state laws pertaining to CAO and SMP updates, and next by reviewing the latest science on managing development in and around critical areas. Through review of scientific information, the City's comprehensive plan and public input, the Planning Commission will draft new code language for review and approval by the City Council.

    The City is required by state law to periodically update its Critical Areas Ordinance (CAO) and Shoreline Master Program (SMP). In addition to being a legal requirement, the periodic update provides an opportunity for the community to ensure its critical areas and shoreline codes are up to date with the latest science and in line with the City's current land use policies.

    The process began with the City Council setting a scope of work, providing a framework for what will be covered over the course of this project. The City's Planning Commission has started on that scope of work, first reviewing the state laws pertaining to CAO and SMP updates, and next by reviewing the latest science on managing development in and around critical areas. Through review of scientific information, the City's comprehensive plan and public input, the Planning Commission will draft new code language for review and approval by the City Council.