Critical Area Requirements

Snohomish County regulations are designed to protect environmental resources. The following areas are regulated: 

  • Wetlands and Fish & Wildlife Conservation Areas, including wetlands, streams, lakes, marine waters, wildlife habitat conservation areas, frequently flooded areas, and buffers.
  • Geologically hazardous area (erosion/landslide hazard areas and seismic areas)
  • Channel Migration Zone
  • Critical Aquifer Recharge Area

Some properties contain only one type of critical area while others may have more than one. When a parcel contains multiple critical areas the project must comply with all applicable chapters of the critical area code.

Image of a mountain with pond

Land Use/Commercial

Land Use Site Plan Requirements: All development that occurs within 400 feet of geological hazard areas or within 500 feet of all other critical areas including buffers must be identified. Critical areas within the property boundaries will need to be depicted on the site development plan. In some instances, critical areas may be located off site but the buffer or required setback may extend onto the property being developed. These areas should be clearly shown on the subdivision, records of survey, official site plan, administrative site plan, or binding site plan recorded with the county auditor at final approval of a plat. 

Residential

Residential Site Plan Requirements: All residential development that occurs within 400 feet of geological hazard areas or within 500 feet of all other critical areas including buffers must be identified. Critical areas within the property boundaries will need to be depicted on the site development plan. In some instances critical areas may be located off site but the buffer or required setback may extend onto the property being developed. These areas should be clearly shown on the site plan.

Critical Area Site Plan Requirements (CASP): Regulations require critical areas to be permanently protected and recorded with the county auditor once approved by county staff. The document used for recording is a (CASP). The applicant will need to prepare a separate site plan on the CASP form showing critical areas and the proposed development.

Reports and Approvals

Based on the development proposal additional information may be required to ensure that the project complies with county code. This may include either a report or study and sometimes both. These items should be prepared by a qualified consultant and submitted at the time of application. 

Wetlands and Fish & Wildlife Habitat Conservation Areas - Reports that may be needed include a Wetland Delineation, Wetland Assessment, Ordinary High Water Mark Determination, Critical Area Study, Mitigation Plan, and/or Habitat Management Plant.  Refer to SCC 30.62A.140 for details.

Geologically Hazardous Areas - A Geological Report/Study may be needed.  Refer to SCC 30.62B.140 for details.
Channel Migration Zones - A Chanel Migration Zone study may be needed. Refer to SCC 30.62B.330 for details.

Critical Aquifer Recharge Areas - A Hydrogeological Report may be needed. Refer to SCC 30.62C.140 for details.

Please refer to the applicable code sections linked above for specific report or study requirements.  

For more general information, refer to Critical Area Regulations for Residential Projects (Assistance Bulletin #15).

Maps and GIS

Snohomish County offers a wide variety of Critical Area related data and maps, though the PDS GIS webpage. Pre-built printed maps and cartographic products, including the 2015 Critical Area Regulation Update, are available through the PDS iGallery which simplifies located PDF maps. In addition, the fully interactive PDS Map Portal provides quick access to Critical Area Regulations and recorded CASPs with links to the Snohomish County Auditor's Office public documents. You can build custom maps with full control of what information is presented and export your own map as a PDF.