County soil summary
Soil types in Adams County, Colorado
The most widespread soils are Weld, Ascalon and Adena; the most common drainage class is well drained (86% of the land), and typical topsoil pH is 7.2.
- Well or moderately well drained
- 90% of land · state 84%
- Typical topsoil pH
- 7.2 neutral · state 7.2
- Septic fields very limited
- 35% of land · state 68%
- Subject to flooding
- 7% of land, any frequency · state 5%
Most common soils in Adams County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 63% of the mapped land; 59 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Weld | 12.9% | Well drained | 7.0 |
| Ascalon | 11.3% | Well drained | 7.0 |
| Adena | 9.6% | Well drained | 7.2 |
| Colby | 6.7% | Well drained | 7.9 |
| Vona | 6.5% | Well drained | 7.2 |
| Platner | 5.5% | Well drained | 7.2 |
| Loamy alluvial landGeneral soil group, not a named series | 5.1% | — | — |
| Wiley | 4.9% | Well drained | 7.9 |
What this means
What the soils in Adams County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Adams County is neutral: pH 7.2 (most land between 7.0 and 7.9), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 78% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (56% of the land).
90% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
On 52% 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 35% of the land in Adams County very limited, 45% somewhat limited and 13% not limited (7% not rated, such as urban land, pits or water).
Statewide, 68% of the land is very limited, so Adams County is less restrictive than typical.
Flooding is mapped on 7% of the land (6% occasional, <1% 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 (86%). 90% of the land is moderately well drained or better, compared with 84% across Colorado.
Show as a table
| Category | Adams County | Colorado |
|---|---|---|
| Excessively drained | 1.0% | 5.1% |
| Somewhat excessively drained | 3.3% | 8.0% |
| Well drained | 86.1% | 70.2% |
| Moderately well drained | 0.0% | 0.9% |
| Somewhat poorly drained | 1.2% | 1.0% |
| Poorly drained | 0.4% | 1.5% |
| Very poorly drained | 0.0% | 0.5% |
| Not rated | 7.9% | 12.8% |
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 | Adams County | Colorado |
|---|---|---|
| Not limited | 13.1% | 6.3% |
| Somewhat limited | 44.8% | 15.4% |
| Very limited | 35.1% | 68.0% |
| Not rated | 7.1% | 10.4% |
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 | Adams County | Colorado |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 15.8% | 13.8% |
| B: moderate infiltration | 24.4% | 22.0% |
| C: slow infiltration | 47.2% | 32.3% |
| D: very slow infiltration (clayey, shallow or wet) | 4.8% | 23.2% |
| A/D: D as is, A if drained | 0.2% | 0.4% |
| B/D: D as is, B if drained | 0.0% | 0.6% |
| C/D: D as is, C if drained | 0.0% | 0.7% |
| Not rated | 7.7% | 7.0% |
Flooding
Show as a table
| Category | Adams County | Colorado |
|---|---|---|
| No flooding | 86.5% | 86.2% |
| Rare or very rare | 0.7% | 1.6% |
| Occasional | 6.0% | 1.8% |
| Frequent or very frequent | 0.4% | 1.1% |
| Not reported | 6.4% | 9.3% |
Seasonal high water table
Show as a table
| Category | Adams County | Colorado |
|---|---|---|
| Within 18 inches at some time of year | 0.6% | 1.8% |
| 18 inches to 3.3 feet | 1.0% | 1.4% |
| Deeper than 3.3 feet or none reported | 98.3% | 91.7% |
| Not reported | 0.0% | 5.0% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 7.2 (neutral); 80% of rated land falls between 7.0 and 7.9. Median topsoil organic matter is 1.2%.
Show as a table
| Category | Adams County | Colorado |
|---|---|---|
| Strongly acidic (below 5.5) | 0.0% | 3.7% |
| Moderately to slightly acidic (5.5–6.4) | 1.4% | 8.7% |
| Near neutral (6.5–7.3) | 68.3% | 42.6% |
| Alkaline (7.4 and up) | 22.4% | 30.7% |
| Not reported | 7.9% | 14.4% |
Texture
Show as a table
| Category | Adams County | Colorado |
|---|---|---|
| Sandy | 11.3% | 8.8% |
| Loamy (loam, silt loam and similar) | 77.5% | 75.0% |
| Clayey (40%+ clay) | 1.9% | 1.3% |
| Organic (muck or peat) | 0.0% | 0.2% |
| Not reported (rock, urban land, etc.) | 9.3% | 14.6% |
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
- Adams County, Colorado (FIPS 08001): 760,333 acres of mapped land, 4,706 acres of open water excluded. State comparisons pool all mapped land in Colorado.
- 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.