County soil summary
Soil types in Union County, New Jersey
The most widespread soils are Boonton, Haledon and Amwell; the most common drainage class is well drained (21% of the land), and typical topsoil pH is 5.3.
- Well or moderately well drained
- 37% of land · state 62%
- Typical topsoil pH
- 5.3 strongly acidic · state 5.0
- Septic fields very limited
- 64% of land · state 90%
- Subject to flooding
- 15% 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 86% of the mapped land; 32 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Urban landLand type, not a soil series | 34.3% | — | — |
| Boonton | 15.9% | Well drained | 3.9 |
| Haledon | 13.3% | Somewhat poorly drained | 5.3 |
| UdorthentsGeneral soil group, not a named series | 10.0% | — | — |
| Amwell | 3.5% | Somewhat poorly drained | 6.1 |
| Neshaminy | 3.5% | Well drained | 5.4 |
| Hasbrouck | 2.9% | Poorly drained | 5.5 |
| Birdsboro | 2.5% | Well drained | 5.4 |
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 strongly acidic: pH 5.3 (most land between 4.6 and 5.6). 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 61% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (35% of the land).
For your lawn and yard
On 55% 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 27% 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 64% of the land in Union County very limited, 5% somewhat limited and 14% not limited (18% not rated, such as urban land, pits or water).
Statewide, 90% of the land is very limited, so Union 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 15% 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 well drained (21%). 37% of the land is moderately well drained or better, compared with 62% across New Jersey.
Show as a table
| Category | Union County | New Jersey |
|---|---|---|
| Excessively drained | 0.0% | 5.3% |
| Somewhat excessively drained | 1.6% | 4.5% |
| Well drained | 21.2% | 36.6% |
| Moderately well drained | 14.1% | 15.4% |
| Somewhat poorly drained | 20.1% | 5.9% |
| Poorly drained | 7.1% | 9.5% |
| Very poorly drained | 1.9% | 13.6% |
| Not rated | 34.0% | 9.0% |
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 | Union County | New Jersey |
|---|---|---|
| Not limited | 13.7% | 1.2% |
| Somewhat limited | 4.6% | 2.9% |
| Very limited | 63.7% | 89.7% |
| Not rated | 18.0% | 6.1% |
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 | New Jersey |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 3.1% | 19.9% |
| B: moderate infiltration | 7.3% | 21.5% |
| C: slow infiltration | 37.0% | 17.8% |
| D: very slow infiltration (clayey, shallow or wet) | 12.0% | 10.6% |
| A/D: D as is, A if drained | 0.6% | 15.9% |
| B/D: D as is, B if drained | 2.6% | 4.7% |
| C/D: D as is, C if drained | 2.9% | 2.8% |
| Not rated | 34.5% | 6.8% |
Flooding
Show as a table
| Category | Union County | New Jersey |
|---|---|---|
| No flooding | 85.3% | 82.0% |
| Rare or very rare | 7.6% | 2.4% |
| Occasional | 0.7% | 2.1% |
| Frequent or very frequent | 6.5% | 13.4% |
| Not reported | 0.0% | 0.1% |
Seasonal high water table
Show as a table
| Category | Union County | New Jersey |
|---|---|---|
| Within 18 inches at some time of year | 26.8% | 32.1% |
| 18 inches to 3.3 feet | 16.3% | 15.8% |
| Deeper than 3.3 feet or none reported | 56.9% | 52.1% |
| Not reported | 0.0% | 0.1% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 5.3 (strongly acidic); 80% of rated land falls between 4.6 and 5.6. Median topsoil organic matter is 3%.
Show as a table
| Category | Union County | New Jersey |
|---|---|---|
| Strongly acidic (below 5.5) | 46.5% | 62.1% |
| Moderately to slightly acidic (5.5–6.4) | 17.3% | 22.5% |
| Near neutral (6.5–7.3) | 0.1% | 2.9% |
| Alkaline (7.4 and up) | 0.0% | 1.1% |
| Not reported | 36.2% | 11.4% |
Texture
Show as a table
| Category | Union County | New Jersey |
|---|---|---|
| Sandy | 3.3% | 24.8% |
| Loamy (loam, silt loam and similar) | 60.5% | 53.1% |
| Clayey (40%+ clay) | 0.0% | 0.1% |
| Organic (muck or peat) | 1.9% | 13.7% |
| Not reported (rock, urban land, etc.) | 34.3% | 8.2% |
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, New Jersey (FIPS 34039): 65,934 acres of mapped land, 1,566 acres of open water excluded. State comparisons pool all mapped land in New Jersey.
- 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.