Critical Areas - Overview and related permits

The CAO is a set of King County regulations that govern how critical areas must be protected in unincorporated King County. Critical areas include both environmentally sensitive areas and hazard areas. The purpose of critical areas regulations is to protect public health or safety and the environment.

Critical areas are defined in state law as:

1. Wetlands;
2. Areas with a critical recharging effect on aquifers used for potable water, known as Critical Aquifer Recharge Areas or CARAs;
3. Fish and wildlife habitat conservation areas, such as riparian areas, aquatic areas, and species of local importance;
4. Frequently flooded areas; and
5. Geologically hazardous areas, such as landslide hazard areas, erosion hazard areas, and seismic hazard areas.

For some critical areas, adopted maps show where the areas are located and are used as the basis for applying regulations. This is the case for Critical Aquifer Recharge Areas or CARAs, wildlife habitat networks, erosion hazard areas, channel migration zones, tsunami hazard areas, and some flood hazard areas.

For all other critical areas, location, extent, and classification are determined by King County based on information presented in a site-specific critical area report conducted by an ecological or geological professional. The critical area report is based on definitions and standards in the King County Code. The county's online mapping system, iMap, provides information about the general location of some critical areas, but it is not suitable for determining the exact location and classification of the critical area. Permit applicants are responsible for locating and disclosing the presence of critical areas and any associated buffers on the development proposal site.

The update to the CAO clarifies critical areas identification and analysis requirements. The Department of Local Services, Permitting Division (Permitting) will provide bulletins in 2026 to support customers in understanding the requirements.

The Critical Areas Ordinance (CAO) update expands buffers around certain critical areas in unincorporated King County to protect public health and safety, and to promote environmental health in the region. Certain building and development activities are restricted within buffer areas around critical areas.

When a development proposal occurs near a critical area (such as a wetland, stream, or steep slope), an applicant may be asked to provide additional information with the permit application so Department of Local Services, Permitting Division (Permitting) staff can assess how the proposed development might impact these critical areas. If you have questions, please contact Permitting's Customer Service.

Depending on the activity you wish to pursue on your property, and whether that activity or construction is allowable, you may have to complete additional steps and/or a different process and pay additional fees to obtain a permit compared to properties not near a critical area.

Permit fees can be found here: Permit fees - Building and land use - King County, Washington

In general, anyone who is conducting permitted or legally established ongoing activities, such as commercial agriculture, on their property prior to these changes can continue to do so. However, if your operations change or you’d like to perform any construction that requires a permit, then you would likely be affected. (Please see below for additional FAQs related to agriculture and Farm Management Plans).

When a development proposal occurs near a wetland, lake, wildlife habitat or stream, an applicant may be required to provide additional information with the permit application to enable Permitting staff to better assess potential impacts the development might have on these critical areas. Information that may be required in a critical area report commonly includes wetland delineation and rating, stream delineation and type, wildlife habitat assessment, and/or geological hazard risk assessment, which must be completed by a qualified professional. Based on the critical area report, Permitting staff verify the limits of critical areas and their buffers as they apply to the proposal. Critical areas can also be determined through a Critical Areas Designation (CAD) prior to applying for a development permit. The extents and classifications of critical areas determined by a CAD are valid for five years from the approval date.

In addition, development proposals that encroach into a stream, wetland, or buffer will require a Critical Area Mitigation Plan. Small projects, such as those involving less than 1,000 square feet of buffer impact, can typically apply the Restoration and Enhancement Guidelines to develop a plan. These mitigation and enhancement 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. In some cases, when onsite mitigation opportunity is limited, offsite mitigation through a mitigation bank or in-lieu fee program may be necessary. 

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 five 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:
  • Permit application submitted on or after February 18 → new CAO applies.
  • Permit application 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 five-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 for applications submitted on or after February 18.

*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.

There are two types of approvals that provide flexibility for development in critical areas and associated buffers. A critical area alteration exception may allow for certain limited development that would otherwise be prohibited, while a reasonable use exception may be applied if all reasonable use of a site, as allowed by adopted zoning, would be denied as result of critical areas.

If your long-term plans for your property include voluntary protection or restoration of portions of your property near wetlands, streams, and wildlife corridors, or conservation of agriculture and forestland, you may qualify for tax incentives through the County’s Current Use Taxation Program or Public Benefit Rating System. More information can be found here: Current use taxation programs - King County, Washington.

No. The CAO includes provisions that recognize and support commercial agriculture engaging in agricultural activities in continuous operation by the property owner or farm operator. This means that legally established commercial agriculture activities can continue, and cropland doesn’t need to be taken out of production. At the same time, to ensure that riparian areas and wetlands with native vegetation are not being lost to clearing over time, the proposed CAO would prohibit new clearing to expand the footprint into established native vegetation in riparian areas, wetlands, and wetland buffers.

Yes, if an established crop farm introduces livestock after the updated regulations go into effect, and the property was not already in compliance with the Livestock Management Ordinance (LMO) (e.g., hadn’t excluded livestock from streams), then the updated livestock ordinance and grazing area buffers will apply.

No, ADAP provisions have not changed with this CAO update. Maintenance of agricultural waterways remains an allowable activity under subsection C and condition D.58 of K.C.C. 21A.24.045.C.7 (previously code condition 69 of K.C.C. 21A.24.045.C). This condition allows maintenance in aquatic areas and riparian areas (previously referred to as aquatic area buffers), wetlands, wetland buffers, and alluvial fan hazard areas. ADAP continues to require minimizing disturbance to existing native vegetation to allow for maintenance to occur and replacing cleared vegetation after maintenance is complete.

Yes. Developing and implementing a Farm Management Plan (typically created by the King Conservation District) is a condition for certain provisions of code that offer more flexible application of critical areas standards to agriculture and livestock. King County is updating the Farm Management Plan Public Rule to reflect CAO updates to clarify when a Farm Management Plan is required, how plans are reviewed and approved, and how they are monitored over time. If you would like more information or want to comment on the Farm Management Plan Public Rule, please contact Richard.Martin@kingcounty.gov.