San Joaquin County, California
The most common soil here is Capay, on about 4% of the land: a silty clay, smooth and very sticky when wet. Rindge and Tokay come next.
About 34% of the land drains well, and 36% stays wet for long stretches; groundwater comes within two feet of the surface under 12% of it.
USDA rates 91% of the land very limited for a standard septic drain field, and 71% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 2% of the land floods occasionally or more, and bedrock lies within 40 inches under 10% of it.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in San Joaquin County, California, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Moderately well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Mollisols — grassland soils with a thick, dark, fertile topsoil rich in organic matter. This report summarizes the major soil map units across the survey area to help you understand what to expect when buying, building, or gardening in San Joaquin County, California. Search your address to find the exact soil composition, drainage, and series details at your specific location.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Tokay fine sandy loam, 0 to 2 percent slopes | 32K | Well drained | A | Not limited | Very limited |
| Rindge muck, 0 to 2 percent slopes, partially drained, MLRA 16 | 31K | Very poorly drained | A/D | Very limited | Very limited |
| Merritt silty clay loam, partially drained, 0 to 2 percent slopes | 28K | Poorly drained | C | Very limited | Very limited |
| Hollenbeck silty clay, 0 to 2 percent slopes | 26K | Moderately well drained | C | Very limited | Very limited |
| Jacktone clay, 0 to 2 percent slopes | 24K | Somewhat poorly drained | D | Very limited | Very limited |
| Capay clay, 0 to 1 percent slopes, MLRA 17 | 24K | Moderately well drained | C | Very limited | Very limited |
| Veritas fine sandy loam, 0 to 2 percent slopes | 24K | Moderately well drained | A | Not limited | Somewhat limited |
| Redding gravelly loam, 0 to 8 percent slopes, dry | 24K | Moderately well drained | D | Very limited | Very limited |
| Water | 22K | D | Not rated | Not rated | |
| Archerdale clay loam, 0 to 2 percent slopes | 20K | Well drained | C | Very limited | Very limited |
| Delhi loamy sand, 0 to 2 percent slopes, MLRA 17 | 19K | Somewhat excessively drained | A | Not limited | Very limited |
| Kingile muck, partially drained, 0 to 2 percent slopes, MLRA 16 | 18K | Very poorly drained | C | Very limited | Very limited |
| Jacktone-Urban land complex, 0 to 2 percent slopes | 18K | Somewhat poorly drained | D | Very limited | Very limited |
| Stockton clay, 0 to 2 percent slopes | 17K | Somewhat poorly drained | C | Very limited | Very limited |
| Madera sandy loam, 0 to 2 percent slopes | 17K | Moderately well drained | C | Somewhat limited | Very limited |
| Tinnin loamy coarse sand, 0 to 2 percent slopes | 16K | Well drained | A | Not limited | Very limited |
| Peltier mucky clay loam, partially drained, 0 to 2 percent slopes, MLRA 16 | 16K | Poorly drained | C | Very limited | Very limited |
| Capay clay, wet, 0 percent slopes, MLRA 17 | 14K | Moderately well drained | C | Very limited | Very limited |
| Guard clay loam, drained, 0 to 2 percent slopes | 14K | Poorly drained | C | Very limited | Very limited |
| Cogna loam, 0 to 2 percent slopes | 13K | Well drained | B | Very limited | Somewhat limited |
Soil Orders in This Area
The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.
What This Means
Building & Foundations
About 71% of soils are rated "very limited" for dwellings with basements. Specific challenges include poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 91% of soils are rated "very limited" for septic absorption fields. Despite good drainage overall, limitations may stem from shallow bedrock, steep slopes, or seasonal conditions. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
Gardening & Agriculture
Drainage is generally favorable for gardening. Adding compost and mulch will improve fertility and water retention. Test your soil's pH before planting — most vegetables prefer 6.0-7.0.