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Critical Areas - Land use permit process

The critical areas designation and alteration exception processes.
Aerial view of wetland

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

Lands designated by King County as critical include areas at high risk for erosion, landslides, earthquakes or flooding; coal mines; or wetlands or lands adjoining streams, rivers and other water bodies.

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

When a development proposal occurs near wetlands, lakes, wildlife habitat or streams, an applicant may be asked to provide additional information with the permit application in order to enable the Department of Local Services, Permitting Division (Permitting) staff to better assess potential impacts the development might have on these critical areas.

A reasonable use exception is used only when all reasonable uses of a site, as allowed by adopted zoning, is denied as result of critical areas.

Critical area reports

When a development proposal occurs near wetlands, lakes, wildlife habitat or streams, an applicant may be asked to provide additional information with the permit application in order to enable Permitting Department staff to better assess potential impacts the development might have on these critical areas. Reports commonly requested are a Wetland Delineation Report and/or a Stream Survey Report.

In addition, some development proposals may encroach into the stream or wetland or buffer. If this occurs, a Critical Area Mitigation Plan will be required. For small projects, typically on single-family residential lots involving less than 1,000 square feet of buffer enhancement, a Basic Restoration and Enhancement Plan may be required. 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.

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

  • Critical Areas, Wetland Delineation Report Criteria (191KB) The purpose of a wetland delineation report is to convey an objective, factual picture of the extent and location of wetlands at a given site.
  • Critical Areas Restoration and Enhancement (614KB) This document is intended to assist property owners in the restoration or enhancement of critical areas and their buffers. They include 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.
  • Stream Survey Report Criteria -- This document is not currently available in electronic format. It can be obtained by contacting Customer Service at 206-296-6600 or by email at These guidelines address the appropriate scope and methods of stream and fisheries studies, and recommend 3 progressive levels of detail based on stream system classification and fish utilization.

Critical areas designation

A Critical Areas Designation is a process that allows a property owner to define the limits of critical areas on or near the project site, establish buffers and other required mitigation measures and, when coupled with the Consolidated Review option, address all related site issues such as access and drainage control.

Learn more on the Critical Area Designation Handout (215KB)

A Critical Areas Designation is required before submitting an application to Seattle-King County Public Health for a septic system or well approval for residential projects. As of January 1, 2007, customers are required to complete the Critical Areas Designation (CAD) process prior to filing an application for a new subdivision.

Advantages of a Critical Areas Designation

A Critical Area Designation offers:

  • Customers consistency and predictability in decision-making as applied to critical areas and associated buffers.
  • 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 Seattle - King County Public Health Department review.
  • 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.
  • Allows for critical areas issues beyond location and classification to be addressed. For example, wetland buffer widths or a mitigation plan for driveway crossing impacts could be included within the designation.


Check our current fee schedule

Under some circumstances, performance and maintenance financial guarantees may be required for restoration and mitigation activities. See the Permitting Customer Information Bulletin #40, Financial Guarantees, for more information.


  • We will determine a Critical Areas Designation within 120 days after the application for a Critical Areas Designation is complete. 
  • A Critical Areas Designation is valid for 5 years from the date of the completed CAD letter. 


The Critical Areas Designation application is available online through  

Critical area alteration exception

This application process allows adjustments in the application of zoning code standards related to critical area buffers to a particular property.

Check Type 1-4 Applicant Designation and criteria for approval in 21A.44.030 of the King County Code (KCC).


Check our current fee schedule


  • Permitting staff will schedule a pre-application meeting within 30 days from the date of the request.
  • Permitting staff has 28 days from the date the application is filed to determine whether the application is complete. After Permitting staff determines that the application is complete, a Notice of Application is issued.
  • The minimum public comment period is 21 days.
  • The process to make a final decision on a critical area alteration exception generally takes 120 days provided no appeals are filed or substantial additional information is required.


A pre-application meeting is required before filing a critical area alteration exception application.

Check our online permits page to see if you can submit these forms through MyBuildingPermit

Flood Hazards

Flood Hazard Certification

Information (187KB)

Worksheet (147KB)

Floodplain Development Permit

Information (210KB)

Worksheet (303KB)

Application (1.23MB)

Floodplain, FEMA Elevation Certificate

Form (4.06MB)