County soil summary
Soil types in Union County, North Carolina
The most widespread soils are Badin, Tarrus and Cid; the most common drainage class is well drained (71% of the land), and typical topsoil pH is 5.0.
- Well or moderately well drained
- 94% of land · state 68%
- Typical topsoil pH
- 5.0 very strongly acidic · state 5.2
- Septic fields very limited
- 72% of land · state 76%
- Subject to flooding
- 6% of land, any frequency · state 18%
Most common soils in Union County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 91% of the mapped land; 28 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Badin | 30.5% | Well drained | 5.0 |
| Tarrus | 19.3% | Well drained | 5.0 |
| Cid | 17.7% | Moderately well drained | 4.5 |
| Goldston | 10.8% | Well drained | 4.5 |
| Chewacla | 5.1% | Somewhat poorly drained | 5.5 |
| Cecil | 4.3% | Well drained | 5.5 |
| Secrest | 1.8% | Moderately well drained | 5.5 |
| Georgeville | 1.4% | Well drained | 5.5 |
What this means
What the soils in Union County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Union County is very strongly acidic: pH 5.0 (most land between 4.5 and 5.5). 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 99% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is channery silt loam (41% of the land).
94% 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.
For a septic system
For conventional septic absorption fields, NRCS rates 72% of the land in Union County very limited, 28% somewhat limited and 0% not limited (1% not rated, such as urban land, pits or water).
That is close to the state as a whole (76% very 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.
Flooding is mapped on 6% of the land (0% occasional, 6% 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 (71%). 94% of the land is moderately well drained or better, compared with 68% across North Carolina.
Show as a table
| Category | Union County | North Carolina |
|---|---|---|
| Excessively drained | 0.0% | 1.0% |
| Somewhat excessively drained | 0.0% | 2.8% |
| Well drained | 71.1% | 54.2% |
| Moderately well drained | 22.4% | 10.4% |
| Somewhat poorly drained | 5.2% | 5.4% |
| Poorly drained | 0.4% | 12.4% |
| Very poorly drained | 0.0% | 11.6% |
| Not rated | 0.9% | 2.3% |
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 | Union County | North Carolina |
|---|---|---|
| Not limited | 0.0% | 0.0% |
| Somewhat limited | 27.5% | 21.4% |
| Very limited | 71.5% | 76.4% |
| Not rated | 1.0% | 2.2% |
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 | Union County | North Carolina |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.4% | 11.8% |
| B: moderate infiltration | 27.9% | 35.7% |
| C: slow infiltration | 33.1% | 14.5% |
| D: very slow infiltration (clayey, shallow or wet) | 30.4% | 7.4% |
| A/D: D as is, A if drained | 0.0% | 10.6% |
| B/D: D as is, B if drained | 5.4% | 11.1% |
| C/D: D as is, C if drained | 1.8% | 7.1% |
| Not rated | 1.0% | 1.8% |
Flooding
Show as a table
| Category | Union County | North Carolina |
|---|---|---|
| No flooding | 94.1% | 81.9% |
| Rare or very rare | 0.0% | 7.5% |
| Occasional | 0.0% | 1.5% |
| Frequent or very frequent | 5.9% | 8.9% |
| Not reported | 0.0% | 0.2% |
Seasonal high water table
Show as a table
| Category | Union County | North Carolina |
|---|---|---|
| Within 18 inches at some time of year | 7.3% | 29.5% |
| 18 inches to 3.3 feet | 20.7% | 11.3% |
| Deeper than 3.3 feet or none reported | 72.0% | 59.0% |
| Not reported | 0.0% | 0.2% |
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 5.5. Median topsoil organic matter is 1.2%.
Show as a table
| Category | Union County | North Carolina |
|---|---|---|
| Strongly acidic (below 5.5) | 67.8% | 61.7% |
| Moderately to slightly acidic (5.5–6.4) | 31.1% | 33.5% |
| Near neutral (6.5–7.3) | 0.2% | 2.3% |
| Alkaline (7.4 and up) | 0.0% | 0.2% |
| Not reported | 1.0% | 2.3% |
Texture
Show as a table
| Category | Union County | North Carolina |
|---|---|---|
| Sandy | 0.6% | 24.0% |
| Loamy (loam, silt loam and similar) | 98.5% | 69.0% |
| Clayey (40%+ clay) | 0.0% | 0.0% |
| Organic (muck or peat) | 0.0% | 5.1% |
| Not reported (rock, urban land, etc.) | 1.0% | 1.8% |
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
- Union County, North Carolina (FIPS 37179): 359,849 acres of mapped land, 824 acres of open water excluded. State comparisons pool all mapped land in North Carolina.
- 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.