This project is a periodic review of Burien’s Critical Area Ordinance (CAO), in accordance with Revised Code of Washington (RCW) 36.70A.130 and is a part of implementing the recently adopted 2044 Comprehensive Plan. The City is working closely with Facet, an environmental and engineering consulting firm, in order to align these updates with the Best Available Science.
Critical Areas are complex natural ecosystems that need to be protected for resiliency and for public safety. Below you will find a list of frequently asked questions around critical areas and the 2025 CAO update.
What is the Critical Area Ordinance (CAO)?
The Critical Area Ordinance (CAO) is a collection of development regulations that are in place to protect and conserve the functions of environmentally sensitive areas, and to protect the community from hazards (such as floods, landslides, etc.). This is a key component of the Burien Municipal Code (BMC) and directly impacts site planning for developments that are located within or near a critical area. The Growth Management Act (GMA) and Washington state law requires cities to protect these 5 types of critical areas:
- Wetlands
- Frequently Flooded Areas (FFAs)
- Fish and Wildlife Habitat Conservation Areas (FWHCA)
- Critical Aquifer Recharge Areas (CARAs)
- Geologically Hazardous Areas
How do I know if my property is within a Critical Area?
Use the Burien Critical Areas interactive map to determine if your property is within a mapped critical area.
While critical areas are dependent on site-specific characteristics and may change over time, the Burien Critical Areas map showcases what is currently mapped. This means that if there is already a critical area or its buffer on your property, this update will impact your property. If you home is located near a critical area, it is likely this update will also affect your property.
What changes can we anticipate with this update?
The recently published Gap Analysis, prepared by Facet, details high-level topics that are currently not addressed adequately in the existing regulations and will need to be updated to integrate the Best Available Science (BAS) to comply with state law. Below lists a high-level summary of the major changes considered in the CAO updated and excludes any administrative and code clarification updates.
- Consideration of the Department of Ecology’s recommended habitat corridors in the context of wetland buffers – this would change the way we look at wetland buffers, giving wetlands and streams with a specific habitat score the ability to reduce buffers when located near another wetland or stream with a specific habitat score. This would create a large increase in buffer widths for wetlands.
- Use of a water typing system with associated buffer widths based on type (current) OR establish 202-ft Riparian Management Zone for all streams or consider something in between. Again, increasing buffer widths for streams.
- Incorporate programmatic mitigation approaches and advanced mitigation.
You can access the comprehensive Gap Analysis Report here.
How will the City address concerns about increased density while also protecting critical areas?
The City is required by state law to do both: protect critical areas and allow for housing growth. Sometimes these goals overlap, and it is the City’s role is to balance them. Balancing the goals of density, while also ensuring the protection of critical areas can be a tricky planning challenge since these often collide.
Not every parcel is the right fit for large development projects, especially when there are natural hazards and sensitive areas located on or near the site. The recent periodic update to the Comprehensive Plan informed the Housing Code and Zoning Map Amendments project (Ordinance No. 868), resulting in new residential zoning regulations increasing the number of units and type of housing allowed across the city. The CAO continues to apply to all properties regardless of the new zoning. The means:
- Critical areas must be protected through buffer standards, mitigation requirements, and habitat conservation provisions (per WAC 365-190).
- Projects must ensure “no net loss” of ecological function.
- Development is only allowed if it meets the CAO standards in BMC 19.40.
Why does the Best Available Science Report for the CAO, not include a review of the Shoreline (Puget Sound, Lake Burien and other Shorelines of the State)?
The Shoreline Master Program (SMP) and Critical Areas Ordinance (CAO) are adopted through separate processes under state law. The SMP can be amended only through a locally initiated amendment or a periodic update process per WAC 173-26-090 and WAC 173-26-104 and requires review and approval by the Washington State Department of Ecology.
The SMP will continue to use the CAO adopted under Ordinance 623 on June 15, 2015, for regulating critical areas in shoreline jurisdiction until a locally initiated amendment or the scheduled 2029 SMP periodic review occurs.
While the existing SMP’s appendices contain some useful background data, such materials are outside the scope of the current CAO update and are not a part of this project in any way apart from background information. However, relevant information may inform future planning efforts or be reviewed during a future SMP update, anticipated in 2029.
You can access the comprehensive Best Available Science Report here.
Does the CAO also regulate shoreline properties such as those on Lake Burien or near Puget Sound?
Critical Areas are an overlay of regulations, where there can be multiple regulations and standards that could apply depending on site characteristics. While the ecological importance of Lake Burien and the Shorelines are acknowledged, these areas are subject to the provisions of the Shoreline Master Program (SMP) and Ordinance 623, which governs critical areas within shoreline jurisdiction pursuant to RCW 36.70A.480(3)(b). This means that with this update, changes to the wetland and stream buffers will not change until the Shoreline Master Program update in 2029.
The Department of Ecology has started the rulemaking process to amend Chapters 173-18, -20, -22, -26, and -27 under the Shoreline Management Act. If you are interested in learning more, or would like to see the draft language, you can do so on the Department of Ecology’s website here.
What is no net loss, and how is it measured?
No net loss is a principal for critical areas and refers to the regulatory objective: to ensure development or other impacts do not degrade the functions and values of the ecosystem. The BAS Review references no net loss in the context of wetland mitigation, consistent with state guidance, which requires the protection of critical area functions but does not prescribe a specific methodology for measuring no net loss. The City’s Comprehensive Plan Policy 8.6-1 affirms this objective. While the BAS does not include a formal tracking method for no net loss, it supports implementation through mitigation sequencing, buffer standards, and permit review.
How does off-site mitigation ensure there is no net loss to the habitat, if the mitigation actions are located elsewhere?
Federal and state guidance recognize mitigation banking as the preferred form of wetland mitigation when available, per 33 CFR Part 332.3(b)(2)–(6) and the 2022 Ecology Wetland Mitigation Guidance.
Mitigation banking is an ecological restoration and conservation practice that is intended to offset unavoidable impacts from development on critical areas. A wetland mitigation banking site is a specific site where restoration can occur, where wetlands can be created, and/or where wetlands can be enhanced. This is a certified, off-site location, where mitigation work is conducted at a banking site instead of the site where impacts and development occur.
King County currently has a total of two approved mitigation banks, which have gone through state certification and are available for mitigation use (Keller Farm, Springbrook). When a project cannot rectify or mitigate the impacts on site, a mitigation bank could be one way to provide applicants a pathway to mitigate for the unavoidable impacts. It is important to note that mitigation banking will not be appropriate for all projects, and any proposals wishing to use a mitigation bank will be required to provide a banking plan. More information on Mitigation Banking and projects that qualify for banking can be found on the Department of Ecology’s Website here.
Benefits:
Mitigation banking provides benefits as it typically involved incorporating multiple mitigation actions at a larger site. Providing multiple mitigation actions at a large site can encourage more diverse habitats and growth which aids in creating more sustainable systems, becoming an avenue to increase habitat functions. Additionally, since these sites are built prior to impacts occurring within other wetlands, the mitigation bank will have a higher chance at succeeding and will in turn support an increase to ecological function within the banking site.
The June 2025 BAS Review notes that the use of an in-lieu fee (ILF) program or mitigation bank is generally the preferred method of compensation when on-site mitigation is not feasible (p. 31). The 2025 Gap Analysis similarly highlights the City’s allowance for out-of-basin mitigation only when no feasible alternative exists, consistent with Ecology’s guidance.
Site-specific factors—such as ecological connectivity, watershed priorities, and habitat value—are evaluated during permit review.
How to stay connected and up to date:
Visit our Community Hub page for the most up to date information regarding the CAO.
- Attend an event. Periodically City staff will be out in the community for you to provide your feedback and ask questions. Events are listed on our Community Hub, project page.
- Attend a public meeting. You can follow the progress and provide feedback on the CAO update by attending upcoming Planning Commission and City Council meetings. Agendas and packet materials will be posted here ahead of the meeting.
- Email a planner at planning@burienwa.gov
