Thurston County Area, Washington

Survey Area WA667• Washington

The dominant drainage class is Somewhat excessively drained and the dominant hydrologic group is A (high infiltration, low runoff). 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 Thurston 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
Spanaway gravelly sandy loam, 0 to 3 percent slopes	26K	Somewhat excessively drained	A	Not limited	Very limited
Alderwood gravelly sandy loam, 8 to 15 percent slopes	25K	Moderately well drained	B	Very limited	Very limited
Everett very gravelly sandy loam, 8 to 15 percent slopes	14K	Somewhat excessively drained	A	Somewhat limited	Very limited
Olympic silt loam, 20 to 40 percent slopes	12K	Well drained	C	Very limited	Very limited
Everett very gravelly sandy loam, 0 to 8 percent slopes	11K	Somewhat excessively drained	A	Not limited	Very limited
Nisqually loamy fine sand, 0 to 3 percent slopes	9K	Somewhat excessively drained	A	Not limited	Very limited
Spanaway-Nisqually complex, 2 to 10 percent slopes	9K	Somewhat excessively drained	A	Not limited	Very limited
Melbourne silty clay loam, 20 to 40 percent slopes	9K	Well drained	C	Very limited	Very limited
Kapowsin silt loam, 3 to 15 percent slopes	9K	Moderately well drained	C/D	Very limited	Very limited
Kapowsin silt loam, 0 to 3 percent slopes	8K	Moderately well drained	C/D	Very limited	Very limited
Raught silt loam, 30 to 65 percent slopes	8K	Well drained	B	Very limited	Very limited
Yelm fine sandy loam, 0 to 3 percent slopes	8K	Moderately well drained	B	Very limited	Very limited
Water	7K			Not rated	Not rated
Baumgard loam, 40 to 65 percent slopes	7K	Well drained	B	Very limited	Very limited
Norma silt loam	7K	Poorly drained	B/D	Very limited	Very limited
Cathcart gravelly loam, 3 to 15 percent slopes	7K	Well drained	B	Somewhat limited	Somewhat limited
Baumgard loam, 10 to 40 percent slopes	7K	Well drained	B	Very limited	Very limited
Tenino gravelly loam, 3 to 15 percent slopes	7K	Well drained	C	Somewhat limited	Very limited
Skipopa silt loam, 3 to 15 percent slopes	6K	Somewhat poorly drained	D	Very limited	Very limited
Wilkeson silt loam, 20 to 40 percent slopes	6K	Well drained	B	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.

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.

Ultisols

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

Entisols

Young soils with little development — found on floodplains, dunes, and steep slopes. Properties vary widely by setting.

Alfisols

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

What This Means

Building & Foundations

About 55% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, poor drainage in some areas, sandy or gravelly soils with low bearing capacity. A geotechnical assessment is recommended before building.

Septic Systems

About 92% of soils are rated "very limited" for septic absorption fields. The well-drained soils may actually drain too fast for standard leach fields, allowing effluent to reach groundwater. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.

Gardening & Agriculture

Soils tend to drain very quickly, meaning nutrients and water don't stick around long. Raised beds with amended soil, drip irrigation, and heavy mulching will give the best results. Compost is your best friend here — it improves water retention dramatically.