County soil summary
Soil types in New Castle County, Delaware
The most widespread soils are Reybold, Glenelg and Fallsington; the most common drainage class is well drained (45% of the land), and typical topsoil pH is 5.9.
- Well or moderately well drained
- 62% of land · state 54%
- Typical topsoil pH
- 5.9 moderately acidic · state 6.0
- Septic fields very limited
- 73% of land · state 88%
- Subject to flooding
- 10% of land, any frequency · state 11%
Most common soils in New Castle County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 48% of the mapped land; 91 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Reybold | 10.8% | Well drained | 6.2 |
| Urban landLand type, not a soil series | 10.2% | — | — |
| Glenelg | 6.0% | Well drained | 5.4 |
| UdorthentsGeneral soil group, not a named series | 5.3% | — | — |
| Fallsington | 5.0% | Poorly drained | 5.2 |
| Sassafras | 4.1% | Well drained | 6.0 |
| Mattapex | 3.6% | Moderately well drained | 6.0 |
| Hammonton | 2.8% | Moderately well drained | 6.2 |
What this means
What the soils in New Castle County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in New Castle County is moderately acidic: pH 5.9 (most land between 5.2 and 6.3). 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 75% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (37% of the land).
62% 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 73% of the land in New Castle County very limited, 8% somewhat limited and 1% not limited (18% not rated, such as urban land, pits or water).
Statewide, 88% of the land is very limited, so New Castle 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 10% of the land (2% occasional, 9% 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 (45%). 62% of the land is moderately well drained or better, compared with 54% across Delaware.
Show as a table
| Category | New Castle County | Delaware |
|---|---|---|
| Excessively drained | 0.1% | 2.7% |
| Somewhat excessively drained | 0.2% | 2.4% |
| Well drained | 44.6% | 31.5% |
| Moderately well drained | 16.6% | 17.7% |
| Somewhat poorly drained | 0.8% | 4.1% |
| Poorly drained | 11.4% | 16.9% |
| Very poorly drained | 8.1% | 14.9% |
| Not rated | 18.2% | 9.7% |
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 | New Castle County | Delaware |
|---|---|---|
| Not limited | 1.3% | 0.3% |
| Somewhat limited | 7.8% | 1.8% |
| Very limited | 72.6% | 88.2% |
| Not rated | 18.2% | 9.7% |
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 | New Castle County | Delaware |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 6.4% | 24.2% |
| B: moderate infiltration | 33.7% | 17.9% |
| C: slow infiltration | 19.4% | 11.6% |
| D: very slow infiltration (clayey, shallow or wet) | 2.2% | 2.6% |
| A/D: D as is, A if drained | 1.1% | 14.2% |
| B/D: D as is, B if drained | 8.9% | 9.8% |
| C/D: D as is, C if drained | 10.2% | 11.6% |
| Not rated | 18.1% | 8.2% |
Flooding
Show as a table
| Category | New Castle County | Delaware |
|---|---|---|
| No flooding | 80.5% | 83.5% |
| Rare or very rare | 0.0% | 0.0% |
| Occasional | 1.6% | 1.2% |
| Frequent or very frequent | 8.6% | 9.8% |
| Not reported | 9.3% | 5.4% |
Seasonal high water table
Show as a table
| Category | New Castle County | Delaware |
|---|---|---|
| Within 18 inches at some time of year | 19.9% | 37.5% |
| 18 inches to 3.3 feet | 16.7% | 17.7% |
| Deeper than 3.3 feet or none reported | 54.1% | 39.4% |
| Not reported | 9.3% | 5.4% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 5.9 (moderately acidic); 80% of rated land falls between 5.2 and 6.3. Median topsoil organic matter is 1.9%.
Show as a table
| Category | New Castle County | Delaware |
|---|---|---|
| Strongly acidic (below 5.5) | 25.5% | 25.8% |
| Moderately to slightly acidic (5.5–6.4) | 48.9% | 59.0% |
| Near neutral (6.5–7.3) | 6.2% | 3.4% |
| Alkaline (7.4 and up) | 0.4% | 1.9% |
| Not reported | 18.9% | 9.9% |
Texture
Show as a table
| Category | New Castle County | Delaware |
|---|---|---|
| Sandy | 1.9% | 29.9% |
| Loamy (loam, silt loam and similar) | 75.3% | 51.9% |
| Clayey (40%+ clay) | 0.0% | 0.0% |
| Organic (muck or peat) | 4.7% | 10.1% |
| Not reported (rock, urban land, etc.) | 18.1% | 8.1% |
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
- New Castle County, Delaware (FIPS 10003): 253,198 acres of mapped land, 44,853 acres of open water excluded. State comparisons pool all mapped land in Delaware.
- 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.