Thurston County Area, Washington
The most common soil here is Spanaway, on about 8% of the land: a gravelly sandy loam, gritty and crumbly. Alderwood and Everett come next.
About 65% of the land drains well, and 12% stays wet for long stretches; groundwater comes within two feet of the surface under 19% of it.
USDA rates 93% of the land very limited for a standard septic drain field, and 66% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 5% of the land floods occasionally or more, and bedrock lies within 40 inches under 5% 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 Thurston 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 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.
What This Means
Building & Foundations
About 66% 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 93% 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.