San Diego County Area, California
The most common soil here is Cieneba, on about 7% of the land: a gravelly loam, a balanced mix that crumbles in your hand. Fallbrook and Tollhouse come next.
About 82% of the land drains well.
USDA rates 95% of the land very limited for a standard septic drain field, and 79% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 1% of the land floods occasionally or more, and bedrock lies within 40 inches under 60% 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 Diego County Area, 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 Somewhat excessively drained and the dominant hydrologic group is D (very slow infiltration, high runoff). The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil. 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 Diego County Area, 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 |
|---|---|---|---|---|---|
| Cieneba-Rock outcrop complex, 30 to 75 percent slopes, very stony | 128K | Somewhat excessively drained | D | Very limited | Very limited |
| Acid igneous rock land | 109K | Very limited | Very limited | ||
| Cieneba-Fallbrook rocky sandy loams, 30 to 65 percent slopes, eroded | 104K | Somewhat excessively drained | D | Very limited | Very limited |
| Sheephead sandy loam, 30 to 65 percent slopes, eroded, stony | 92K | Well drained | D | Very limited | Very limited |
| Tollhouse coarse sandy loam, 30 to 70 percent slopes, very stony | 90K | Somewhat excessively drained | D | Very limited | Very limited |
| Las Posas loam, 30 to 65 percent slopes, stony | 55K | Well drained | D | Very limited | Very limited |
| San Miguel-Exchequer rocky silt loams, 9 to 70 percent slopes | 45K | Well drained | D | Very limited | Very limited |
| Tollhouse coarse sandy loam, 5 to 35 percent slopes, eroded, very stony | 37K | Somewhat excessively drained | D | Very limited | Very limited |
| Fallbrook sandy loam, 9 to 15 percent slopes, eroded | 37K | Well drained | C | Somewhat limited | Very limited |
| Cieneba rocky coarse sandy loam, 9 to 30 percent slopes, eroded | 32K | Somewhat excessively drained | D | Very limited | Very limited |
| La Posta loamy coarse sand, 5 to 30 percent slopes, eroded | 30K | Somewhat excessively drained | A | Very limited | Very limited |
| La Posta rocky loamy coarse sand, 5 to 30 percent slopes, eroded | 30K | Somewhat excessively drained | A | Very limited | Very limited |
| Mottsville loamy coarse sand, 2 to 9 percent slopes | 30K | Excessively drained | A | Not limited | Very limited |
| Friant rocky fine sandy loam, 30 to 70 percent slopes | 30K | Well drained | D | Very limited | Very limited |
| Redding cobbly loam, dissected, 15 to 50 percent slopes | 28K | Well drained | D | Very limited | Very limited |
| Yaquipass-Rock Outcrop-Typic Torriorthents complex, 15 to 75 percent slopes, eroded | 27K | Somewhat excessively drained | D | Very limited | Very limited |
| Water | 25K | D | Not rated | Not rated | |
| Bancas stony loam, 30 to 65 percent slopes | 25K | Well drained | C | Very limited | Very limited |
| Fallbrook sandy loam, 15 to 30 percent slopes, eroded | 25K | Well drained | C | Very limited | Very limited |
| Carrizo very gravelly sand, 0 to 9 percent slopes | 23K | Excessively drained | A | Very limited | Very 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 79% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, flood-prone areas, sandy or gravelly soils with low bearing capacity. A geotechnical assessment is recommended before building.
Septic Systems
About 95% of soils are rated "very limited" for septic absorption fields. The well-drained soils may actually drain too fast for standard leach fields, allowing effluent to reach groundwater. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
Gardening & Agriculture
Soils tend to drain very quickly, meaning nutrients and water don't stick around long. Raised beds with amended soil, drip irrigation, and heavy mulching will give the best results. Compost is your best friend here — it improves water retention dramatically.