County soil summary
Soil types in Linn County, Oregon
The most widespread soils are Dayton, Honeygrove and Kinney; the most common drainage class is well drained (63% of the land), and typical topsoil pH is 5.6.
- Well or moderately well drained
- 75% of land · state 82%
- Typical topsoil pH
- 5.6 moderately acidic · state 6.7
- Septic fields very limited
- 97% of land · state 85%
- Subject to flooding
- 13% of land, any frequency · state 3%
Most common soils in Linn County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 36% of the mapped land; 102 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Dayton | 6.5% | Poorly drained | 5.6 |
| Honeygrove | 6.1% | Well drained | 5.5 |
| Kinney | 5.6% | Well drained | 5.8 |
| Klickitat | 4.0% | Well drained | 5.3 |
| Harrington | 3.7% | Well drained | 6.1 |
| Nekia | 3.5% | Well drained | 5.6 |
| Blachly | 3.5% | Well drained | 5.3 |
| Keel | 3.5% | Well drained | 5.3 |
What this means
What the soils in Linn County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Linn County is moderately acidic: pH 5.6 (most land between 5.2 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 93% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silty clay loam (31% of the land).
75% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
On 71% of the land, rain soaks in slowly (hydrologic groups C and D, including dual groups that are D until drained). Expect runoff and puddles after heavy rain: core-aerate compacted lawns and keep ground sloping away from foundations.
A seasonal high water table comes within 18 inches of the surface on 25% of the land, often in spring. Basements, sump pumps and lawns in low spots feel it first.
For a septic system
For conventional septic absorption fields, NRCS rates 97% of the land in Linn County very limited, 3% somewhat limited and 0% not limited.
Statewide, 85% of the land is very limited, so Linn 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.
Flooding is mapped on 13% of the land (5% occasional, 5% frequent).
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 well drained (63%). 75% of the land is moderately well drained or better, compared with 82% across Oregon.
Show as a table
| Category | Linn County | Oregon |
|---|---|---|
| Excessively drained | 0.5% | 2.4% |
| Somewhat excessively drained | 1.3% | 4.8% |
| Well drained | 62.6% | 71.6% |
| Moderately well drained | 10.7% | 3.4% |
| Somewhat poorly drained | 7.2% | 2.4% |
| Poorly drained | 16.6% | 2.8% |
| Very poorly drained | 0.0% | 0.8% |
| Not rated | 1.1% | 11.8% |
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 | Linn County | Oregon |
|---|---|---|
| Not limited | 0.0% | 0.5% |
| Somewhat limited | 2.5% | 4.4% |
| Very limited | 97.4% | 85.3% |
| Not rated | 0.1% | 9.8% |
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 | Linn County | Oregon |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 2.6% | 10.0% |
| B: moderate infiltration | 24.1% | 16.7% |
| C: slow infiltration | 40.0% | 30.1% |
| D: very slow infiltration (clayey, shallow or wet) | 25.4% | 30.4% |
| A/D: D as is, A if drained | 0.0% | 0.3% |
| B/D: D as is, B if drained | 0.0% | 0.7% |
| C/D: D as is, C if drained | 6.0% | 2.4% |
| Not rated | 1.9% | 9.4% |
Flooding
Show as a table
| Category | Linn County | Oregon |
|---|---|---|
| No flooding | 87.2% | 80.8% |
| Rare or very rare | 2.5% | 1.4% |
| Occasional | 5.2% | 1.0% |
| Frequent or very frequent | 4.8% | 1.0% |
| Not reported | 0.2% | 15.9% |
Seasonal high water table
Show as a table
| Category | Linn County | Oregon |
|---|---|---|
| Within 18 inches at some time of year | 24.9% | 5.5% |
| 18 inches to 3.3 feet | 9.4% | 3.5% |
| Deeper than 3.3 feet or none reported | 65.5% | 75.5% |
| Not reported | 0.2% | 15.6% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 5.6 (moderately acidic); 80% of rated land falls between 5.2 and 6.1. Median topsoil organic matter is 4.5%.
Show as a table
| Category | Linn County | Oregon |
|---|---|---|
| Strongly acidic (below 5.5) | 23.2% | 10.4% |
| Moderately to slightly acidic (5.5–6.4) | 70.9% | 23.0% |
| Near neutral (6.5–7.3) | 2.9% | 40.4% |
| Alkaline (7.4 and up) | 0.0% | 13.8% |
| Not reported | 3.0% | 12.4% |
Texture
Show as a table
| Category | Linn County | Oregon |
|---|---|---|
| Sandy | 0.3% | 8.5% |
| Loamy (loam, silt loam and similar) | 92.8% | 77.3% |
| Clayey (40%+ clay) | 4.3% | 1.1% |
| Organic (muck or peat) | 0.0% | 0.4% |
| Not reported (rock, urban land, etc.) | 2.7% | 12.8% |
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
- Linn County, Oregon (FIPS 41043): 841,784 acres of mapped land, 13,662 acres of open water excluded. State comparisons pool all mapped land in Oregon.
- 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.