County soil summary
Soil types in Fairfax County, Virginia
The most widespread soils are Glenelg, Wheaton and Codorus; the most common drainage class is well drained (61% of the land), and typical topsoil pH is 5.0.
- Well or moderately well drained
- 70% of land · state 85%
- Typical topsoil pH
- 5.0 very strongly acidic · state 5.3
- Septic fields very limited
- 69% of land · state 77%
- Subject to flooding
- 9% of land, any frequency · state 10%
Most common soils in Fairfax County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 63% of the mapped land; 52 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Glenelg | 18.8% | Well drained | 5.4 |
| Wheaton | 13.1% | Well drained | 7.5 |
| Urban LandLand type, not a soil series | 11.6% | — | — |
| Codorus | 4.6% | Somewhat poorly drained | 5.3 |
| Urban landLand type, not a soil series | 4.1% | — | — |
| Chantilly | 3.6% | Well drained | 4.5 |
| Kingstowne | 3.5% | Well drained | 4.8 |
| Sassafras | 3.4% | Well drained | 6.0 |
What this means
What the soils in Fairfax County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Fairfax County is very strongly acidic: pH 5.0 (most land between 4.5 and 7.5). Most vegetables and lawn grasses do best around 6.0 to 7.0, so lime is often needed; blueberries, azaleas and rhododendrons like it as it is.
Loamy topsoil (loam, silt loam and similar) covers 80% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (40% of the land).
70% 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 69% of the land in Fairfax County very limited, 15% somewhat limited and 0% not limited (16% not rated, such as urban land, pits or water).
Statewide, 77% of the land is very limited, so Fairfax County is less 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 9% of the land (6% occasional, 3% 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 (61%). 70% of the land is moderately well drained or better, compared with 85% across Virginia.
Show as a table
| Category | Fairfax County | Virginia |
|---|---|---|
| Excessively drained | 0.0% | 2.1% |
| Somewhat excessively drained | 0.0% | 4.9% |
| Well drained | 60.8% | 67.8% |
| Moderately well drained | 9.5% | 10.1% |
| Somewhat poorly drained | 8.8% | 3.1% |
| Poorly drained | 4.4% | 7.0% |
| Very poorly drained | 0.5% | 2.0% |
| Not rated | 16.0% | 3.0% |
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 | Fairfax County | Virginia |
|---|---|---|
| Not limited | 0.0% | 0.1% |
| Somewhat limited | 14.7% | 20.6% |
| Very limited | 69.4% | 76.5% |
| Not rated | 16.0% | 2.8% |
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 | Fairfax County | Virginia |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 4.4% | 10.8% |
| B: moderate infiltration | 29.8% | 49.0% |
| C: slow infiltration | 32.9% | 15.0% |
| D: very slow infiltration (clayey, shallow or wet) | 3.9% | 10.1% |
| A/D: D as is, A if drained | 0.0% | 0.9% |
| B/D: D as is, B if drained | 7.1% | 6.7% |
| C/D: D as is, C if drained | 6.0% | 4.0% |
| Not rated | 16.0% | 3.5% |
Flooding
Show as a table
| Category | Fairfax County | Virginia |
|---|---|---|
| No flooding | 75.0% | 88.5% |
| Rare or very rare | 0.0% | 1.7% |
| Occasional | 6.4% | 2.1% |
| Frequent or very frequent | 2.6% | 6.5% |
| Not reported | 16.0% | 1.2% |
Seasonal high water table
Show as a table
| Category | Fairfax County | Virginia |
|---|---|---|
| Within 18 inches at some time of year | 14.7% | 13.0% |
| 18 inches to 3.3 feet | 8.4% | 9.8% |
| Deeper than 3.3 feet or none reported | 60.9% | 76.1% |
| Not reported | 16.0% | 1.1% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 5.0 (very strongly acidic); 80% of rated land falls between 4.5 and 7.5. Median topsoil organic matter is 1.5%.
Show as a table
| Category | Fairfax County | Virginia |
|---|---|---|
| Strongly acidic (below 5.5) | 61.1% | 64.8% |
| Moderately to slightly acidic (5.5–6.4) | 7.6% | 28.5% |
| Near neutral (6.5–7.3) | 1.7% | 3.4% |
| Alkaline (7.4 and up) | 13.1% | 0.4% |
| Not reported | 16.4% | 3.0% |
Texture
Show as a table
| Category | Fairfax County | Virginia |
|---|---|---|
| Sandy | 3.5% | 9.4% |
| Loamy (loam, silt loam and similar) | 80.1% | 86.6% |
| Clayey (40%+ clay) | 0.0% | 0.2% |
| Organic (muck or peat) | 0.5% | 0.8% |
| Not reported (rock, urban land, etc.) | 16.0% | 2.9% |
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
- Fairfax County, Virginia (FIPS 51059): 223,766 acres of mapped land, 7,712 acres of open water excluded. State comparisons pool all mapped land in Virginia.
- 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.