Soil series profile
San Joaquin soil series
San Joaquin is a moderately well drained soil with a silt loam surface, mapped on 297,180 acres in 12 counties in CA. Hydrologic group D.
- Drainage class
- Moderately well drained 86% of mapped acres
- Hydrologic group
- D 48% of mapped acres
- Typical topsoil pH
- 6.1 slightly acidic · range 6.1–6.1
- Mapped area
- 297k acres in 12 counties, 1 state
Typical San Joaquin profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–23 in (H1) | Silt loam | 6.1 | 20% | 27% | 0.75% |
| 23–28 in (H2) | Clay loam | 7.0 | 43% | 28% | 0% |
| 28–54 in (H3) | Indurated | Not reported | 0% | Not reported | Not reported |
| 54–60 in (H4) | Stratified sandy loam to loam | 7.0 | 18% | 43% | 0% |
What this means
What San Joaquin soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in San Joaquin soils is slightly acidic: pH 6.1, the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 95% of mapped San Joaquin acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (36% of mapped San Joaquin acres).
95% of mapped San Joaquin acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 95% 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 San Joaquin 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.
Flooding is mapped on 16% of the acres (<1% occasional, 0% frequent).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where San Joaquin soil is found
Mapped acres
San Joaquin is mapped in California.
| County | Acres | Share of county land |
|---|---|---|
| Sacramento County, CA | 117,106 | 19.0% |
| Yuba County, CA | 52,420 | 13.0% |
| Fresno County, CA | 44,653 | 0.9% |
| San Joaquin County, CA | 31,405 | 3.5% |
| Placer County, CA | 18,614 | 3.4% |
| Merced County, CA | 12,854 | 1.0% |
| Sutter County, CA | 10,288 | 2.7% |
| Stanislaus County, CA | 8,788 | 0.9% |
| Madera County, CA | 888 | 0.1% |
| Mariposa County, CA | 109 | 0.0% |
| Butte County, CA | 29 | 0.0% |
| Amador County, CA | 27 | 0.0% |
Septic absorption fields
NRCS rating, share of San Joaquin acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 94.9% |
| Not rated | 5.1% |
Drainage, water table and flooding
Share of San Joaquin acres
- Depth to seasonal high water table
- About 6.6 feet (79 in) (median where reported).
- Flooding
- Mapped as flooding on 16% of acres (<1% occasional, 0% frequent).
- Slope
- Typically 1–4% (median 1%).
- Topsoil organic matter
- Median 0.8%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 8.8% |
| Moderately well drained | 86.2% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
| Not rated | 5.0% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 0.0% |
| C: slow infiltration | 46.8% |
| D: very slow infiltration (clayey, shallow or wet) | 48.0% |
| 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 | 5.1% |
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
- All map unit components named San Joaquin (component kind "Series") in SSURGO: 297,180 acres.
- Method
- Shares are by mapped acres of San Joaquin components. The profile comes from the single largest San Joaquin component. Full methodology.