Critical Areas - Overview and related permits

Critical Areas Ordinance Update 2026

Applications Vesting Information

Vesting depends on whether a CAD is effective when the permit is deemed complete. Under KCC 21A.24.500(E), a CAD is effective if it is within 5 years of issuance, with no site changes and no updated state or federal maps.

• New CAD applications and all other permit applications without an effective CAD:
  • Where permit applications are submitted on or after February 18 → new CAO applies. 
  • Where permit applications are submitted before February 18:
    • If the application is deemed complete within 28-day triage → prior CAO applies.
    • If the application is deemed incomplete during triage and later deemed complete on or after February 18 → new CAO applies.
• Permit applications with an effective CAD (within the 5-year effectiveness period, no change in site conditions, and no updated state/federal maps determined under KCC21A.24.500(E)):
  • If the CAD letter was dated before August 2023, the language of the CAD vested the existence, location, and classification of critical areas and critical area buffer widths to the prior CAO.
  • If the CAD letter was dated after August 2023, the language of the CAD clarified in more detail what information was included in the determination. The existence, location, and classification of on-site critical areas is vested, but all regulations including buffers must comply with the new CAO.
  • *Important Note: An effective CAD is a decision regarding critical areas on a site and does not automatically vest a project to all local ordinances.

CAO Documents and Guidance 2026

Critical Areas Ordinance 2026 Update Guidance, Applications, and Information

Affidavit Concerning Critical Areas Compliance

Consultant Guidance Ecological Information

Critical Areas Restoration and Enhancement

Critical Areas Designation Guidance

Critical Areas Mitigation Guidelines

Critical Areas Alteration Exception Instructions Information

Critical Areas Alteration Exception Application Public Agency

Critical Area Alteration Exception Application for Private Development

Ecological Critical Area Report Criteria

Geological Critical Areas Report Guidance

Landslide Hazard Area Guidance

Land Use Application

Reasonable Use Exception Instructions Information

Reasonable Use Exception Application

Steep Slope Hazard Areas Guidance

What are critical areas?

Critical areas are lands with natural hazards or lands that support certain unique, fragile or valuable resource areas.

Wetlands, streams and other aquatic areas, riparian areas, fish and wildlife habitat conservation areas, frequently flooded areas, and groundwater critical aquifer recharge areas are all examples of critical areas. Geologically hazardous areas also fall under this definition, including landslide, erosion, coal mine, and seismic hazard areas, among others.

The King County Code protects critical areas as well as their buffers to protect public health and safety, and to promote environmental health in the region. Buffers are areas adjacent to certain critical areas that are also restricted from specific building and development activities.

When a development proposal occurs near wetlands, streams, lakes, steep slopes, or other critical areas, an applicant will usually be asked to provide additional information, such as a critical area report, with the permit application to enable the Department of Local Services, Permitting Division (Permitting) staff to better assess potential impacts the development might have on these critical areas. If you are not sure whether critical areas are on or near your property, in most cases you will need to hire a private environmental consultant to take a look at your property. King County iMap can be a useful source of preliminary information, especially for geologic hazards, but is not a complete picture. The wetland and stream layers, for example, include data collected at a regional scale, and are not a complete source of information for a specific site.

Development restrictions vary between different types of critical areas, and King County Code (KCC) Chapter 21A.24 lays out what is allowed and under what conditions. In all cases, development proposals must make every effort to avoid critical area impacts and minimize and mitigate any impacts that cannot be avoided. Each critical area has development standards which must always be followed. For some critical areas, only the development activities or alterations listed in a table in KCC 21A.24.045 are allowable if specific conditions are met in addition to the avoidance of critical areas impacts and the overall development standards.

If certain critical areas or buffers on a property would prohibit a proposed alteration, a critical area alteration exception may allow for relief, within limits.

A reasonable use exception is used only when all reasonable uses of a site, as allowed by adopted zoning, are denied as result of critical areas. Both critical area alteration exceptions and reasonable use exceptions are only options if no feasible alternative for the site with less impacts to critical areas exists.

Critical area reports

The purpose of a critical area report is to show the location, extent, type, and important characteristics of critical areas and their buffers on a given site. If a development proposal includes any modifications or impacts to a critical area or buffer, additional information will also be required, such as an assessment of the proposed impacts and a plan to provide mitigation to compensate for impacts and/or restore areas to their prior conditions. Mitigation plans are also used when there has been unpermitted activity, such as clearing and grading, in a critical area or buffer to help get the property owner back into compliance with code and the critical area better protected. Critical area reports should be prepared by, or under the supervision of, a qualified professional. 

The following report guidelines are available to assist in preparing these reports:

• Ecological Critical Area Report Criteria - An ecological critical area report conveys objective information about wetlands, aquatic areas, riparian areas, and wildlife habitat on a development site, and may also include an impact assessment and mitigation plan when applicable.
• Critical Areas Restoration and Enhancement - This document is intended to assist property owners in the restoration or enhancement of critical areas and their buffers, typically for the purpose of mitigating impacts. It includes instructions on how to determine the number and types of plants to use, how to prepare a basic planting plan, and how to monitor and maintain the project.
• Geological Critical Area Report Criteria - A geological critical area report conveys objective information about geological hazard areas on a development site, such as steep slopes, landslide hazards, alluvial fans, channel migration zones, coal mine hazards, and seismic hazard areas. It may also include recommendations to apply specific buffer widths or descriptions of what measures will be used to reduce or eliminate the safety risks posed by certain geological hazards.

Critical Areas Designation

A Critical Areas Designation (CAD) is a pre-development application that allows a property owner to request that King County Permitting determine the existence, location, and classification of critical areas on their project site before submitting an application for a development or land use permit. Permitting typically requires an ecological critical area report from the applicant to have enough site-specific information to make their determination.
A CAD is required before submitting an application to Seattle-King County Public Health for a septic system design or well site approval for residential projects. However, a CAD can also be useful for projects that do not require septic or well approval, as it can help inform property owners about how critical areas may affect a proposed project early in the design phase before beginning the permitting process.

Learn more on the Critical Area Designation Handout

Advantages of a Critical Areas Designation

• Offers customers consistency and predictability in decision-making as applied to critical areas and provides preliminary information about associated buffers and regulations that may apply.
• Puts critical area review at the beginning of the permit review process. This means that customers will know where they can and cannot build on their property. In the case of wells, septic tanks and drain fields, customers will know prior to hiring an engineer or critical areas consultant where these systems can be located.
• Can save time and money associated with plan changes or redesigns that might occur in the middle of the permit review process, if critical area issues have not been addressed prior to submitting and application.
• Allows customers who wish to sell property an opportunity to identify critical areas and their buffers on site. The designation helps identify buildable areas and offers the associated predictability and reliability for 5 years after the determination.

Cost

Check our current fee schedule

Timeline

• A Critical Areas Designation is subject to timelines set forth in KCC Chapter 20.20 for applications that do not require public notice. See “Application review process” for a helpful outline. 
• A Critical Areas Designation is valid for 5 years from the date of the completed CAD letter, unless one of the following occurs: 
  • The site conditions change;
  • A state, federal, or county agency adopts new critical area maps that conflict with the determination; or
  • New information becomes available that invalidates information that formed the basis of Permitting’s determination, such as discovery of an unpermitted alteration or adoption of revised methodologies for critical area classification.

Application

The Critical Areas Designation application is available online through MyBuildingPermit.com.  

Critical area alteration exception

A critical area alteration exception is a process that allows an applicant to propose an alteration that would otherwise be prohibited by critical area regulations in KCC 21A.24. A proposal that directly impacts wetlands, aquatic areas, or wildlife habitat conservation areas typically requires a reasonable use exception instead. The application must meet all applicable conditions in KCC 21A.24.070 as well as the criteria for approval in KCC 21A.44.030, as it a type of variance. One of the key review criteria is that the proposed impacts must be the minimum necessary to accommodate the proposed use of the property. Note that relief cannot be granted from development standards or restrictions that apply to flood hazard areas, severe channel migration hazard areas, or alluvial fan hazard areas.

Cost

Check our current fee schedule

Note that additional costs for mitigation or restoration, such as financial guarantees or mitigation credit purchases, may be required under the subsequent development permit.

Timeline

• A pre-application meeting is not required before submitting an application, but is highly recommended, as these types of projects can be complex.
• A critical area alteration exception or reasonable use exception is subject to timelines set forth in KCC Chapter 20.20 for applications that require public notice. See “Application review process” for a helpful outline.
• After Permitting staff determines that the application is complete, a Notice of Application is issued. The minimum public comment period is 14 days.
• Once a decision is issued, there is a 24-day appeal period whereby an aggrieved person can file an appeal together with an appeal filing fee to the King County Hearing Examiner.
• After the appeal period has ended for an approved exception, a development permit application can be submitted. The exception is valid for 4 years from issuance, with the option to extend one additional year.

Application

The applications for critical area alteration exceptions and reasonable use exceptions are not currently on MyBuildingPermit.com. Refer to guidance and forms on the Permitting webpage.

Flood Hazards and Floodplain Development

Flood Hazard Certification

Information

Worksheet

Floodplain Development Permit

Information

Floodplain, FEMA Elevation Certificate

Form & Instructions

Important Note: After clicking the link above, you may see an error message page starting with "Please wait..." Please ignore this message. Proceed to save the PDF to your computer using the top-left floppy disk icon. Then, reopen the file from the saved location to view the full document. You can navigate between instructions and form view by clicking the "Form Instructions" button at the top of page three when you first open the file. This document is a duplicate from FEMA's website here.