Soil series profile
St. Marys soil series
St. Marys is a well drained soil with a cobbly loam surface, mapped on 51,655 acres in 6 counties in UT. Hydrologic group B.
- Drainage class
- Well drained 96% of mapped acres
- Hydrologic group
- B 83% of mapped acres
- Typical topsoil pH
- 7.0 neutral · range 7.0–7.0
- Mapped area
- 52k acres in 6 counties, 1 state
Typical St. Marys profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–7 in (A11) | Cobbly loam | 7.0 | 23% | 40% | 2% |
| 7–19 in (A12) | Very cobbly loam | 7.0 | 23% | 40% | 2% |
| 19–49 in (B2) | Very cobbly loam | 6.7 | 24% | 39% | 0.75% |
| 49–60 in (C1, C2, C3) | Extremely cobbly sandy loam | 6.7 | 13% | 67% | 0.75% |
What this means
What St. Marys soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in St. Marys soils is neutral: pH 7.0, the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 96% of mapped St. Marys acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is cobbly loam (53% of mapped St. Marys acres).
96% of mapped St. Marys acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
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 96% of the acres in mapped St. Marys soils very limited, 0% somewhat limited and 0% not limited (5% 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 St. Marys soil is found
Mapped acres
St. Marys is mapped in Utah.
| County | Acres | Share of county land |
|---|---|---|
| Morgan County, UT | 29,008 | 7.4% |
| Weber County, UT | 14,209 | 4.1% |
| Rich County, UT | 4,644 | 0.7% |
| Cache County, UT | 1,919 | 0.4% |
| Salt Lake County, UT | 1,862 | 0.4% |
| Davis County, UT | 4 | 0.0% |
Septic absorption fields
NRCS rating, share of St. Marys acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 95.5% |
| Not rated | 4.5% |
Drainage, water table and flooding
Share of St. Marys 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 38–45% (median 40%).
- Topsoil organic matter
- Median 2%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 95.5% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
| Not rated | 4.5% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 12.5% |
| B: moderate infiltration | 83.0% |
| C: slow infiltration | 0.0% |
| D: very slow infiltration (clayey, shallow or wet) | 0.0% |
| 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 | 4.5% |
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 St. Marys (component kind "Series") in SSURGO: 51,655 acres.
- Method
- Shares are by mapped acres of St. Marys components. The profile comes from the single largest St. Marys component. Full methodology.