Thurston County Area, Washington
The dominant drainage class is Somewhat excessively drained and the dominant hydrologic group is A (high infiltration, low runoff). 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.
| 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 |
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.