Septic companies in Seattle, WA

What the ground in Seattle is like

The USDA soil survey rates mapped ground in Seattle for septic drain-field suitability across roughly 84 square miles. About 100% of the rated ground is classed "Very limited", meaning the soil has one or more features unfavorable for a conventional drain field, and the limits generally cannot be overcome without major soil reclamation, special design or expensive installation.

In Seattle, the leading limit is depth to the saturated zone: the water table sits so close to the surface that a drain field has little dry soil left underneath it. Effluent needs unsaturated ground to treat and disperse; when that column is thin, the field has nowhere safe to go. The survey flags that limit on about 100% of the rated ground here.

The limiting features the survey records most often here:

• Depth to saturated zone100.0%
• Slope53.8%
• Filtering capacity23.3%

This is survey data for mapped areas, not a substitute for a site evaluation on your own lot. Conditions on a single parcel can differ from the map.

USDA NRCS SSURGO, ENG Septic Tank Absorption Fields · 100% Very limited · Depth to saturated zone · 17 map units · 84.02 sq mi · read 2026-08-30