Soil series profile
Kapowsin soil series
Kapowsin is a moderately well drained soil with a gravelly ashy loam surface, mapped on 105,545 acres in 3 counties in WA. Hydrologic group B.
- Drainage class
- Moderately well drained 100% of mapped acres
- Hydrologic group
- B 79% of mapped acres
- Typical topsoil pH
- 5.6 moderately acidic · range 5.6–6.1
- Mapped area
- 106k acres in 3 counties, 1 state
Typical Kapowsin profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–7 in (Ap) | Gravelly ashy loam | 5.6 | 10% | 45% | 6% |
| 7–11 in (Bhs) | Gravelly ashy loam | 5.5 | 10% | 45% | 1.5% |
| 11–15 in (Bs1) | Gravelly ashy loam | 5.8 | 10% | 45% | 0.5% |
| 15–25 in (2Bs2) | Loam | 5.8 | 10% | 45% | 0.25% |
| 25–29 in (3Bstm) | Loam | 5.8 | 10% | 45% | 0.05% |
| 29–59 in (3Cd) | Gravelly loam | 5.8 | 10% | 45% | 0.02% |
What this means
What Kapowsin soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Kapowsin soils is moderately acidic: pH 5.6 (most land between 5.6 and 6.1). Many vegetables grow well here, and some gardens benefit from a little lime. Test before adding any.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Kapowsin acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is gravelly ashy loam (82% of mapped Kapowsin acres).
100% of mapped Kapowsin acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
Most land is in hydrologic groups B and C, where rain soaks in at a moderate pace.
For a septic system
For conventional septic absorption fields, NRCS rates 100% of the acres in mapped Kapowsin soils very limited, 0% somewhat limited and 0% not limited.
Where the soil is very limited (slow permeability, a high water table, flooding, shallow bedrock or steep slopes), alternative systems such as mound or sand-filter designs are common and cost more.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Kapowsin soil is found
Mapped acres
Kapowsin is mapped in Washington.
| County | Acres | Share of county land |
|---|---|---|
| Pierce County, WA | 71,222 | 6.5% |
| Thurston County, WA | 19,167 | 3.9% |
| Kitsap County, WA | 15,157 | 6.0% |
Septic absorption fields
NRCS rating, share of Kapowsin acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 100.0% |
Drainage, water table and flooding
Share of Kapowsin acres
- Depth to seasonal high water table
- About 1.7 feet (20 in) (median where reported); within 18 inches on 19% of acres.
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 2–10% (median 2%).
- Topsoil organic matter
- Median 6%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 0.0% |
| Moderately well drained | 100.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 79.0% |
| C: slow infiltration | 2.1% |
| D: very slow infiltration (clayey, shallow or wet) | 0.0% |
| A/D: D as is, A if drained | 0.0% |
| B/D: D as is, B if drained | 0.7% |
| C/D: D as is, C if drained | 18.2% |
Sources & data dates
- Source
- USDA NRCS Soil Survey Geographic Database (SSURGO), queried through Soil Data Access. Public domain.
- Data date
- SSURGO as published on November 3, 2026 (most recent survey area update October 26, 2026). NRCS refreshes SSURGO each October.
- Scope
- All map unit components named Kapowsin (component kind "Series") in SSURGO: 105,545 acres.
- Method
- Shares are by mapped acres of Kapowsin components. The profile comes from the single largest Kapowsin component. Full methodology.