City of Seattle, Washington
The dominant drainage class is Moderately well drained and the dominant hydrologic group is A (high infiltration, low runoff). This report summarizes the major soil map units across the survey area to help you understand what to expect when buying, building, or gardening in City of Seattle, Washington.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Urban land-Alderwood complex, 5 to 12 percent slopes | 21K | Not rated | Not rated | ||
| Urban land-Alderwood complex, 0 to 5 percent slopes | 20K | Not rated | Not rated | ||
| Urban land, 0 to 5 percent slopes | 13K | Not rated | Not rated | ||
| Urban land-Alderwood complex, 12 to 35 percent slopes | 11K | Not rated | Not rated | ||
| Urban land, 5 to 20 percent slopes | 4K | Not rated | Not rated | ||
| Alderwood-Everett-Urban land complex, 12 to 35 percent slopes | 3K | Moderately well drained | A | Very limited | Very limited |
| Alderwood-Everett-Urban land complex, 35 to 60 percent slopes | 2K | Moderately well drained | A | Very limited | Very limited |
| Alderwood-Kitsap complex, 12 to 60 percent slopes | 2K | Moderately well drained | A | Very limited | Very limited |
| Alderwood-Everett-Urban land complex, 0 to 12 percent slopes | 1K | Moderately well drained | A | Very limited | Very limited |
| Alderwood-Everett complex, 0 to 12 percent slopes | 1K | Moderately well drained | A | Very limited | Very limited |
| Alderwood-Everett complex, 12 to 35 percent slopes | 1K | Moderately well drained | A | Very limited | Very limited |
| Anthraltic Xerorthents gravelly sandy loam, 0 to 12 percent slopes | 840 | Moderately well drained | A/D | Very limited | Very limited |
| Water, fresh | 633 | Not rated | Not rated | ||
| Alderwood-Everett complex, 35 to 60 percent slopes | 382 | Moderately well drained | A | Very limited | Very limited |
| Beaches-Endoaquents, tidal-Xerorthents association, 0 to 5 percent slopes | 164 | Very limited | Very limited | ||
| Mukilteo-Water complex, 0 to 2 percent slopes | 126 | Very poorly drained | A/D | Very limited | Very limited |
| Anthraltic Xerorthents gravelly sandy loam, 12 to 35 percent slopes | 118 | Moderately well drained | A/D | Very limited | Very limited |
| Urban land-Beausite complex, 12 to 35 percent slopes | 101 | Not rated | Not rated | ||
| Urban land-Beausite complex, 5 to 12 percent slopes | 48 | Not rated | Not rated | ||
| Beausite-Alderwood-Urban land complex, 12 to 35 percent slopes | 35 | Well drained | B | Very limited | Very limited |
What This Means
Building & Foundations
Most soils are generally favorable for residential construction. Standard foundations are usually viable, though site-specific evaluation is always recommended.
Septic Systems
Most soils are reasonably suitable for conventional septic systems, though site-specific conditions always matter. Get a perc test to confirm.
Gardening & Agriculture
Well-drained soils on sloped terrain — good for most plants but watch for erosion. Terracing, contour planting, and mulching help retain moisture and topsoil. Drip irrigation is more effective than sprinklers on slopes.