Washington County, Oregon

Survey Area OR067• Oregon

The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil. 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 Washington County, Oregon. 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
Aloha silt loam	28K	Somewhat poorly drained	C/D	Very limited	Very limited
Woodburn silt loam, 0 to 3 percent slopes	21K	Moderately well drained	C	Very limited	Very limited
Melby silt loam, 2 to 30 percent slopes	20K	Well drained	C	Very limited	Very limited
Olyic silt loam, 30 to 60 percent slopes	20K	Well drained	B	Very limited	Very limited
Melby silt loam, 30 to 60 percent slopes	16K	Well drained	C	Very limited	Very limited
Tolke silt loam, 5 to 30 percent slopes	15K	Well drained	B	Very limited	Very limited
Olyic silt loam, 5 to 30 percent slopes	14K	Well drained	B	Very limited	Very limited
Wapato silty clay loam	12K	Poorly drained	C/D	Very limited	Very limited
Laurelwood silt loam, 12 to 20 percent slopes	12K	Well drained	B	Very limited	Very limited
Woodburn silt loam, 3 to 7 percent slopes	11K	Moderately well drained	C	Very limited	Very limited
McBee silty clay loam	10K	Moderately well drained	C	Very limited	Very limited
Cornelius and Kinton silt loams, 7 to 12 percent slopes	9K	Moderately well drained	C	Somewhat limited	Very limited
Cornelius and Kinton silt loams, 12 to 20 percent slopes	9K	Moderately well drained	C	Very limited	Very limited
Hembre silt loam, 30 to 60 percent slopes	8K	Well drained	B	Very limited	Very limited
Laurelwood silt loam, 7 to 12 percent slopes	8K	Well drained	B	Somewhat limited	Very limited
Murtip-Caterl-Laderly complex, 30 to 60 percent slopes	8K	Well drained	B	Very limited	Very limited
Cornelius and Kinton silt loams, 2 to 7 percent slopes	8K	Moderately well drained	C	Somewhat limited	Very limited
Helvetia silt loam, 2 to 7 percent slopes	8K	Moderately well drained	C	Somewhat limited	Very limited
Quatama loam, 0 to 3 percent slopes	7K	Moderately well drained	C	Very limited	Very limited
Verboort silty clay loam, 0 to 3 percent slopes	7K	Poorly drained	D	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.

Alfisols

Moderately weathered forest soils with clay-enriched subsoil. Productive for agriculture, generally good for building and septic.

Mollisols

Fertile grassland soils with thick, dark topsoil. Among the best for agriculture, building, and gardening.

Ultisols

Strongly weathered clay soils of the Southeast. Acidic and naturally low in nutrients. Clay subsoil can slow drainage.

Inceptisols

Young but developing soils found in mountains and river terraces. Variable properties — check drainage and bedrock depth.

Andisols

Volcanic ash soils — light, porous, and fertile. Excellent drainage, but low density can complicate foundations.

What This Means

Building & Foundations

About 86% 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 100% 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.