Snohomish
silt loam

Mapping Symbol: So

The Snohomish series consists of poorly-drained soils that formed in alluvium in stream valleys. Slopes are 0 to 2%, annual precipitation is 35 to 50 inches, and the frost-free season ranges from 150 to 200 days.

Typical Profile:
Depth from Surface:
0 to 17 Inches: Dark grayish-brown silt loam and clay loam 
17 to 27 Inches: Black mucky peat
27 to 60 Inches: Dark gray loamy fine sand

Permeability: Moderate in upper part; moderately rapid in lower part

Rooting Depth: 60 inches + if drained

Depth to Seasonal High Water Table: 0 to 1 foot

Available Water Holding Capacity: High

Runoff Potential: Slow

Erosion and Slippage Hazard: Slight

Stream Overflow Hazard: Severe

Use and Management: Primary uses are for hay, pasture, and row crops. Pasture forage yields are 3.0 tons/acre/year if undrained and 6.0 tons/acre/year if drained. Douglas-fir, Western Red Cedar, Western Hemlock, Red Alder, Willow, and Sitka Spruce are important tree species. These soils have severe limitations on equipment use for site preparation and timber harvest, seedling mortality, plant competition, and windthrow hazard for forestry use. These soils have severe limitations on recreational and engineering uses due to their seasonal high water table, flood hazard, organic materials, and low shear strength.

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