Soil series profile
Agassiz soil series
Agassiz is a somewhat excessively drained soil with a very stony loam surface, mapped on 119,544 acres in 13 counties across 2 states. Hydrologic group D.
- Drainage class
- Somewhat excessively drained 72% of mapped acres
- Hydrologic group
- D 94% of mapped acres
- Typical topsoil pH
- 7.3 neutral · range 6.3–8.2
- Mapped area
- 120k acres in 13 counties, 2 states
Typical Agassiz profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–4 in (A11) | Very stony loam | 7.0 | 23% | 40% | 3% |
| 4–9 in (A12) | Very stony loam | 7.0 | 23% | 40% | 2% |
| 9–14 in (A13) | Very stony loam | 7.0 | 23% | 40% | 2% |
| 14–19 in (C) | Extremely stony loam | 7.5 | 23% | 40% | 0.75% |
| 19–23 in (R) | Unweathered bedrock | Not reported | Not reported | Not reported | Not reported |
What this means
What Agassiz soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Agassiz soils is neutral: pH 7.3 (most land between 6.3 and 8.2), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 95% of mapped Agassiz acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is very cobbly silt loam (46% of mapped Agassiz acres).
72% of mapped Agassiz acres is excessively or somewhat excessively drained: water moves through fast, so gardens need more frequent watering in dry spells.
For lawns and yards
On 94% of mapped acres, 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 95% of the acres in mapped Agassiz soils very limited, 0% somewhat limited and 0% not limited (6% not rated, such as urban land, pits or water).
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.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Agassiz soil is found
Mapped acres
Agassiz is mapped in Utah and Nevada.
| County | Acres | Share of county land |
|---|---|---|
| Cache County, UT | 34,540 | 6.9% |
| Salt Lake County, UT | 10,678 | 2.2% |
| Rich County, UT | 8,131 | 1.2% |
| Weber County, UT | 7,551 | 2.2% |
| Utah County, UT | 7,511 | 0.7% |
| Juab County, UT | 6,553 | 0.7% |
| Summit County, UT | 4,751 | 0.7% |
| Morgan County, UT | 4,497 | 1.2% |
| Box Elder County, UT | 4,298 | 0.1% |
| Elko County, NV | 3,150 | 0.0% |
| Wasatch County, UT | 967 | 0.2% |
| Sanpete County, UT | 160 | 0.0% |
| Davis County, UT | 0 | 0.0% |
Septic absorption fields
NRCS rating, share of Agassiz acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 94.5% |
| Not rated | 5.5% |
Drainage, water table and flooding
Share of Agassiz acres
- Depth to seasonal high water table
- None reported within about 6.5 feet (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 18–55% (median 50%).
- Topsoil organic matter
- Median 3%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 72.0% |
| Well drained | 22.6% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
| Not rated | 5.5% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 0.1% |
| C: slow infiltration | 0.0% |
| D: very slow infiltration (clayey, shallow or wet) | 94.4% |
| A/D: D as is, A if drained | 0.0% |
| B/D: D as is, B if drained | 0.0% |
| C/D: D as is, C if drained | 0.0% |
| Not rated | 5.5% |
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
- All map unit components named Agassiz (component kind "Series") in SSURGO: 119,544 acres.
- Method
- Shares are by mapped acres of Agassiz components. The profile comes from the single largest Agassiz component. Full methodology.