King County Critical Area Determinations (CAD)

The first step towards development of a property in King County that will require an on-site septic system is going through the County’s Critical Areas Designation (CAD) process. Any wetland or stream near a proposed development activity must be flagged on-site and a report submitted to the County that depicts the location of the wetland as well as required buffer setbacks. This is the work that Aquatica Environmental Consulting performs.

Following receipt of Aquatica’s report, the County will visit the site and verify the delineation and wetland/stream classification. The County then writes a CAD letter, summarizing critical area restrictions. The review time is variable depending on work load and may take a couple weeks or a few months. After you receive the CAD letter from the County, you then can apply for an on-site septic permit from the health department.

Recommendations
Teresa, our wetland specialist, and her husband have built a home in unincorporated King County and have personal experience with the process. If you need a septic designer, surveyor, or engineer, referrals are available.