County soil summary
Soil types in Washington County, Pennsylvania
The most widespread soils are Dormont, Culleoka and Guernsey; the most common drainage class is moderately well drained (45% of the land), and typical topsoil pH is 6.2.
- Well or moderately well drained
- 91% of land · state 80%
- Typical topsoil pH
- 6.2 slightly acidic · state 5.3
- Septic fields very limited
- 98% of land · state 91%
- Subject to flooding
- 7% of land, any frequency · state 5%
Most common soils in Washington County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 89% of the mapped land; 28 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Dormont | 33.1% | Moderately well drained | 6.2 |
| Culleoka | 29.2% | Well drained | 6.3 |
| Guernsey | 9.5% | Moderately well drained | 5.1 |
| Lowell | 5.0% | Well drained | 6.1 |
| Weikert | 3.9% | Well drained | 5.0 |
| FluvaquentsGeneral soil group, not a named series | 3.2% | — | — |
| Fairpoint | 2.8% | Well drained | 6.5 |
| Newark | 2.7% | Somewhat poorly drained | 6.7 |
What this means
What the soils in Washington County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Washington County is slightly acidic: pH 6.2 (most land between 5.3 and 6.5), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 98% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (56% of the land).
91% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
On 66% 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.
For a septic system
For conventional septic absorption fields, NRCS rates 98% of the land in Washington County very limited, <1% somewhat limited and 0% not limited (2% not rated, such as urban land, pits or water).
Statewide, 91% of the land is very limited, so Washington 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 7% of the land (<1% occasional, 7% 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 moderately well drained (45%). 91% of the land is moderately well drained or better, compared with 80% across Pennsylvania.
Show as a table
| Category | Washington County | Pennsylvania |
|---|---|---|
| Excessively drained | 0.0% | 0.5% |
| Somewhat excessively drained | 3.9% | 4.7% |
| Well drained | 41.8% | 51.5% |
| Moderately well drained | 45.0% | 23.3% |
| Somewhat poorly drained | 3.2% | 9.3% |
| Poorly drained | 4.2% | 6.5% |
| Very poorly drained | 0.0% | 0.8% |
| Not rated | 1.9% | 3.4% |
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 | Washington County | Pennsylvania |
|---|---|---|
| Not limited | 0.0% | 0.4% |
| Somewhat limited | 0.3% | 6.4% |
| Very limited | 97.8% | 91.0% |
| Not rated | 1.9% | 2.3% |
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 | Washington County | Pennsylvania |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 1.0% | 15.8% |
| B: moderate infiltration | 30.9% | 20.3% |
| C: slow infiltration | 8.0% | 19.1% |
| D: very slow infiltration (clayey, shallow or wet) | 38.8% | 23.9% |
| A/D: D as is, A if drained | 0.0% | 0.4% |
| B/D: D as is, B if drained | 6.5% | 3.2% |
| C/D: D as is, C if drained | 12.8% | 13.6% |
| Not rated | 1.9% | 3.7% |
Flooding
Show as a table
| Category | Washington County | Pennsylvania |
|---|---|---|
| No flooding | 92.3% | 94.0% |
| Rare or very rare | 0.0% | 0.4% |
| Occasional | 0.7% | 2.0% |
| Frequent or very frequent | 6.6% | 2.7% |
| Not reported | 0.3% | 0.9% |
Seasonal high water table
Show as a table
| Category | Washington County | Pennsylvania |
|---|---|---|
| Within 18 inches at some time of year | 9.6% | 26.1% |
| 18 inches to 3.3 feet | 42.8% | 18.0% |
| Deeper than 3.3 feet or none reported | 47.2% | 55.6% |
| Not reported | 0.3% | 0.3% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 6.2 (slightly acidic); 80% of rated land falls between 5.3 and 6.5. Median topsoil organic matter is 2.5%.
Show as a table
| Category | Washington County | Pennsylvania |
|---|---|---|
| Strongly acidic (below 5.5) | 20.8% | 54.8% |
| Moderately to slightly acidic (5.5–6.4) | 65.6% | 35.8% |
| Near neutral (6.5–7.3) | 11.7% | 6.0% |
| Alkaline (7.4 and up) | 0.0% | 0.0% |
| Not reported | 1.9% | 3.5% |
Texture
Show as a table
| Category | Washington County | Pennsylvania |
|---|---|---|
| Sandy | 0.0% | 0.4% |
| Loamy (loam, silt loam and similar) | 98.1% | 95.8% |
| Clayey (40%+ clay) | 0.0% | 0.0% |
| Organic (muck or peat) | 0.0% | 0.2% |
| Not reported (rock, urban land, etc.) | 1.9% | 3.6% |
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
- Washington County, Pennsylvania (FIPS 42125): 547,128 acres of mapped land, 4,313 acres of open water excluded. State comparisons pool all mapped land in Pennsylvania.
- 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.