Soil at the center of Seattle, WA
The USDA soil survey maps the point near 47.6062, -122.3321 in Seattle as Urban land, 5 to 20 percent slopes (map unit 989, City of Seattle, Washington). The dominant component is Alderwood, a moderately well drained soil.
| Component | Share of unit | Drainage class | Hydrologic group |
|---|---|---|---|
| Alderwood | 5% | Moderately well drained | A |
| Anthraltic Xerorthents | 5% | Moderately well drained | A/D |
Source: USDA NRCS SSURGO via Soil Data Access, City of Seattle, Washington (WA775), survey data version dated 9/10/2026.
NRCS septic tank absorption field rating for Alderwood: Very limited. Source: USDA NRCS SSURGO via Soil Data Access, City of Seattle, Washington (WA775), survey data version dated 9/10/2026.
This is the soil at one reference point, not your parcel. Soils change within a block. Enter a street address to get the map unit, layers, shrink-swell, water table and NRCS ratings for that exact point.