County soil summary
Soil types in Kitsap County, Washington
The most widespread soils are Alderwood, Harstine and Shelton; the most common drainage class is moderately well drained (65% of the land), and typical topsoil pH is 5.6.
- Well or moderately well drained
- 87% of land · state 82%
- Typical topsoil pH
- 5.6 moderately acidic · state 6.5
- Septic fields very limited
- 92% of land · state 81%
- Subject to flooding
- <1% of land, any frequency · state 4%
Most common soils in Kitsap County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 72% of the mapped land; 24 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Alderwood | 18.9% | Moderately well drained | 5.8 |
| Harstine | 11.7% | Moderately well drained | 5.0 |
| Shelton | 9.7% | Moderately well drained | 5.3 |
| Poulsbo | 7.5% | Moderately well drained | 5.3 |
| Indianola | 6.7% | Somewhat excessively drained | 5.9 |
| Ragnar | 6.3% | Well drained | 6.1 |
| Kapowsin | 6.0% | Moderately well drained | 5.6 |
| Dystric XerorthentsGeneral soil group, not a named series | 5.0% | — | — |
What this means
What the soils in Kitsap County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Kitsap County is moderately acidic: pH 5.6 (most land between 5.0 and 5.8). 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 73% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is gravelly ashy sandy loam (19% of the land).
87% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
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 92% of the land in Kitsap County very limited, 5% somewhat limited and 0% not limited (3% not rated, such as urban land, pits or water).
Statewide, 81% of the land is very limited, so Kitsap County is more restrictive than typical.
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.
Drainage
How long the soil stays wet
The most common drainage class is moderately well drained (65%). 87% of the land is moderately well drained or better, compared with 82% across Washington.
Show as a table
| Category | Kitsap County | Washington |
|---|---|---|
| Excessively drained | 3.0% | 2.1% |
| Somewhat excessively drained | 9.0% | 5.7% |
| Well drained | 10.2% | 65.7% |
| Moderately well drained | 64.9% | 8.7% |
| Somewhat poorly drained | 0.4% | 2.4% |
| Poorly drained | 8.6% | 2.3% |
| Very poorly drained | 2.8% | 0.7% |
| Not rated | 1.1% | 12.4% |
Septic absorption fields
NRCS rating for conventional drain fields
The rating looks at the soil from 24 to 60 inches deep: permeability, depth to a seasonal water table or bedrock, flooding and slope. “Very limited” means at least one feature is unfavorable enough that a conventional field is hard to make work.
Show as a table
| Category | Kitsap County | Washington |
|---|---|---|
| Not limited | 0.0% | 0.6% |
| Somewhat limited | 5.4% | 9.4% |
| Very limited | 91.6% | 81.4% |
| Not rated | 3.0% | 8.6% |
Rain, runoff and water table
Hydrologic soil group, flooding, seasonal water table
Hydrologic soil group
How fast rain soaks in when the soil is already wet. Group A soaks in fastest, D slowest.
Show as a table
| Category | Kitsap County | Washington |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 23.9% | 15.6% |
| B: moderate infiltration | 23.4% | 37.1% |
| C: slow infiltration | 15.1% | 19.9% |
| D: very slow infiltration (clayey, shallow or wet) | 11.3% | 8.7% |
| A/D: D as is, A if drained | 4.9% | 0.8% |
| B/D: D as is, B if drained | 11.5% | 1.6% |
| C/D: D as is, C if drained | 0.8% | 2.2% |
| Not rated | 9.1% | 14.2% |
Flooding
Show as a table
| Category | Kitsap County | Washington |
|---|---|---|
| No flooding | 88.3% | 84.2% |
| Rare or very rare | 0.0% | 0.8% |
| Occasional | 0.2% | 2.3% |
| Frequent or very frequent | 0.4% | 1.1% |
| Not reported | 11.1% | 11.6% |
Seasonal high water table
Show as a table
| Category | Kitsap County | Washington |
|---|---|---|
| Within 18 inches at some time of year | 12.8% | 5.3% |
| 18 inches to 3.3 feet | 53.4% | 8.1% |
| Deeper than 3.3 feet or none reported | 22.6% | 75.1% |
| Not reported | 11.1% | 11.5% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 5.6 (moderately acidic); 80% of rated land falls between 5.0 and 5.8. Median topsoil organic matter is 7.5%.
Show as a table
| Category | Kitsap County | Washington |
|---|---|---|
| Strongly acidic (below 5.5) | 42.4% | 17.7% |
| Moderately to slightly acidic (5.5–6.4) | 52.2% | 22.4% |
| Near neutral (6.5–7.3) | 1.0% | 37.6% |
| Alkaline (7.4 and up) | 0.0% | 8.2% |
| Not reported | 4.5% | 14.1% |
Texture
Show as a table
| Category | Kitsap County | Washington |
|---|---|---|
| Sandy | 21.7% | 7.9% |
| Loamy (loam, silt loam and similar) | 73.1% | 77.9% |
| Clayey (40%+ clay) | 0.0% | 0.0% |
| Organic (muck or peat) | 2.2% | 0.6% |
| Not reported (rock, urban land, etc.) | 3.0% | 13.6% |
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
- Kitsap County, Washington (FIPS 53035): 252,011 acres of mapped land, 3,422 acres of open water excluded. State comparisons pool all mapped land in Washington.
- Method
- Shares are by mapped land area: each map unit’s acres in the county times each soil component’s percentage. Open water is excluded. Topsoil values use the first mineral horizon of each component. Full methodology.