Snohomish County Area, Washington
The most common soil here is Tokul, on about 20% of the land: a gravelly medial loam, a balanced mix that crumbles in your hand. Alderwood and Elwell come next.
About 18% of the land drains well, and 13% stays wet for long stretches; groundwater comes within two feet of the surface under 8% of it.
USDA rates 96% of the land very limited for a standard septic drain field, and 83% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 2% of the land floods occasionally or more, and bedrock lies within 40 inches under 17% of it.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in Snohomish County Area, Washington, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Moderately well drained and the dominant hydrologic group is B (moderate infiltration). The most common soil order is Inceptisols — young soils with minimal horizon development but more than Entisols. 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 Snohomish County Area, Washington. Search your address to find the exact soil composition, drainage, and series details at your specific location.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Tokul gravelly medial loam, 0 to 8 percent slopes | 61K | Moderately well drained | B | Very limited | Very limited |
| Tokul gravelly medial loam, 8 to 15 percent slopes | 44K | Moderately well drained | B | Very limited | Very limited |
| Alderwood gravelly sandy loam, 0 to 8 percent slopes | 42K | Moderately well drained | B | Very limited | Very limited |
| Elwell-Olomount-Rock outcrop complex, 30 to 60 percent slopes | 34K | Moderately well drained | C | Very limited | Very limited |
| Alderwood-Urban land complex, 2 to 8 percent slopes | 27K | Moderately well drained | B | Very limited | Very limited |
| Puget silty clay loam | 24K | Poorly drained | C | Very limited | Very limited |
| Tokul-Winston gravelly loams, 25 to 65 percent slopes | 20K | Moderately well drained | C | Very limited | Very limited |
| Tokul-Ogarty-Rock outcrop complex, 25 to 65 percent slopes | 19K | Moderately well drained | C | Very limited | Very limited |
| Everett very gravelly sandy loam, 0 to 8 percent slopes | 18K | Somewhat excessively drained | A | Not limited | Very limited |
| Tokul gravelly medial loam, 15 to 30 percent slopes | 15K | Moderately well drained | B | Very limited | Very limited |
| Ragnar fine sandy loam, 0 to 8 percent slopes | 15K | Well drained | A | Not limited | Very limited |
| Sultan silt loam | 14K | Moderately well drained | C | Somewhat limited | Very limited |
| Alderwood gravelly sandy loam, 8 to 15 percent slopes | 14K | Moderately well drained | B | Very limited | Very limited |
| Norma loam | 14K | Poorly drained | B/D | Very limited | Very limited |
| Water | 12K | Not rated | Not rated | ||
| Mukilteo muck | 12K | Very poorly drained | B/D | Very limited | Very limited |
| Pastik silt loam, 0 to 8 percent slopes | 12K | Moderately well drained | C | Very limited | Very limited |
| Elwell silt loam, 3 to 30 percent slopes | 12K | Moderately well drained | C | Very limited | Very limited |
| Skykomish gravelly loam, 0 to 30 percent slopes | 11K | Somewhat excessively drained | A | Very limited | Very limited |
| Getchell-Oso-Rock outcrop complex, 30 to 65 percent slopes | 10K | Moderately well drained | C | Very limited | Very limited |
Soil Orders in This Area
The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.
What This Means
Building & Foundations
About 83% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 96% of soils are rated "very limited" for septic absorption fields. Despite good drainage overall, limitations may stem from shallow bedrock, steep slopes, or seasonal conditions. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
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.