Washington State’s wetland and critical area regulations are among the most protective in the United States, a product of the state’s environmental tradition, its extensive network of wetlands and streams, and the Growth Management Act’s requirement that all GMA-planning counties adopt Critical Area Ordinances (CAOs) protecting wetlands, streams, wildlife habitat, geologically hazardous areas, and frequently flooded areas. For developers acquiring land in Washington, critical area constraints are a site selection filter as important as zoning, and far more expensive to discover after acquisition than before.
Understanding how Washington’s critical area framework works, what buffers require, and when federal wetland permits are required gives developers and lenders the tools to evaluate Washington sites without the expensive surprises that critical area issues regularly create for practitioners who encounter them for the first time in the middle of a development program.
What Critical Areas Are Regulated
Washington’s GMA requires that counties and cities adopt Critical Area Ordinances protecting five categories of critical areas:
Wetlands. Areas with hydric soils, wetland hydrology, and wetland vegetation, defined by the presence of all three indicators at the wetland boundary. Washington’s wetland protection regulations are more protective than federal wetland regulations; a wetland that is below the federal acreage threshold for Section 404 permit requirements may still require a local critical area buffer that significantly constrains the development of an adjacent site.
Streams and fish and wildlife habitat conservation areas. Streams supporting fish, including seasonal streams that carry salmon or trout at any time of year, and their riparian buffers are protected critical areas. Buffers from fish-bearing streams in Washington commonly run 100 to 200 feet from the ordinary high water mark, depending on the stream’s classification and the local jurisdiction’s CAO. Development within or adjacent to those buffers requires critical area review and, in many cases, mitigation.
Geologically hazardous areas. Landslide hazard areas, erosion hazard areas, seismic hazard areas, and mine hazard areas are designated critical areas in many Washington jurisdictions. Development in or near these areas requires geotechnical investigation and may require specific construction measures to protect the site and adjacent properties.
Frequently flooded areas. Areas in FEMA-designated Special Flood Hazard Areas are regulated critical areas under the GMA and under local flood damage prevention ordinances. Development in these areas requires flood hazard review and may require elevation of structures, floodproofing, and compensatory storage for any fill placed in the floodplain.
Aquifer recharge areas. Areas that contribute recharge to aquifers used for potable water supply are designated critical areas in jurisdictions where the aquifer is identified in the comprehensive plan.
Buffers: How Development Is Constrained
The practical impact of critical area designation on development is delivered primarily through buffer requirements, the undisturbed zones adjacent to the critical area feature within which development, grading, and vegetation clearing are prohibited or significantly limited. Buffer widths vary by jurisdiction and by the specific critical area category and classification.
In Seattle, wetland buffers run 25 to 225 feet depending on the wetland’s rating (Category I through IV under the Washington State rating system) and the proposed land use. A Category I wetland, the highest quality designation, carries a 225-foot standard buffer. A Category IV wetland carries a 25-foot minimum buffer, which can sometimes be reduced through buffer enhancement mitigation.
Stream buffers in the Puget Sound region commonly run 100 to 200 feet from fish-bearing streams under local CAOs, with some jurisdictions, particularly those with salmon recovery commitments, maintaining buffers at the upper end of that range regardless of stream classification.
The acreage that critical area buffers remove from a site’s developable area can be substantial. A site that contains or is adjacent to a Category I wetland or a fish-bearing stream may have more than half of its gross area consumed by critical area buffer, making the remaining net developable area, and the resulting development density, dramatically smaller than the gross site area suggests.
The Section 404 Permit: Federal Wetland Authority
Federal authority over wetland fill and alteration comes from Section 404 of the Clean Water Act, administered by the U.S. Army Corps of Engineers. Any discharge of dredged or fill material into waters of the United States, including wetlands, requires a Section 404 permit unless an exemption applies.
For development projects that require filling or grading within jurisdictional wetlands, the Section 404 permit is a pre-construction requirement. The Corps of Engineers evaluates permit applications under the Clean Water Act’s public interest review framework, which considers alternatives, impacts, and mitigation. Where practicable alternatives to the proposed wetland fill exist, the Corps may require the applicant to redesign the project to avoid or minimize wetland impacts.
The Section 404 individual permit process, required for significant wetland impacts, takes 12 to 18 months in most cases and often requires compensatory mitigation: the creation, restoration, or enhancement of wetland acreage elsewhere to offset the impacts of the permitted fill. Mitigation ratios of 2:1 to 3:1 (two to three acres of mitigation for each acre of wetland filled) are common for wetland fill permits in Washington.
Section 404 Nationwide Permits (NWPs), pre-approved general permits for categories of activities with minimal individual and cumulative impacts, can be used for smaller wetland impacts that meet the NWPs’ specific criteria. The most commonly used NWPs for development activities have acreage limits, and activities that exceed those limits require individual permits.
Pre-Acquisition Critical Area Assessment
The pre-acquisition critical area assessment is the most cost-effective investment a developer can make when evaluating a Washington site. A qualified wetland biologist and environmental consultant can review the site’s critical area status, reviewing National Wetland Inventory maps, site topography and soils data, and aerial photography, in advance of acquisition, and can conduct a rapid field reconnaissance to identify obvious critical area features that would affect site development.
This assessment does not replace the detailed critical area delineation and evaluation that permitting requires, but it identifies the sites where critical area constraints are material enough to change the acquisition decision or the development program before significant capital is committed.
Related: SEPA and Washington State Development · Washington Growth Management Act · Multifamily Development Seattle WA · Development Advisory Guide