San Luis Obispo County, California, Paso Robles Area
The most common soil here is Nacimiento, on about 8% of the land: a silty clay loam, smooth and slightly sticky. Arbuckle and Dibble come next.
About 88% of the land drains well.
USDA rates 96% of the land very limited for a standard septic drain field, and 80% 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 71% 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 Luis Obispo County, California, Paso Robles Area, 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 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 Luis Obispo County, California, Paso Robles Area. 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 |
|---|---|---|---|---|---|
| Nacimiento-Los Osos complex, 9 to 30 percent slopes | 53K | Well drained | Very limited | Very limited | |
| Nacimiento-Los Osos complex, 30 to 50 percent slopes | 38K | Well drained | Very limited | Very limited | |
| Balcom-Calleguas complex, 50 to 75 percent slopes | 26K | Well drained | Very limited | Very limited | |
| Balcom-Nacimiento association, moderately steep | 24K | Well drained | C | Very limited | Very limited |
| Arbuckle-San Ysidro complex, 2 to 9 percent slopes | 24K | Well drained | C | Not limited | Very limited |
| Cieneba coarse sandy loam, 30 to 75 percent slopes, MLRA 15 | 22K | Somewhat excessively drained | D | Very limited | Very limited |
| Linne-Calodo complex, 9 to 30 percent slopes | 20K | Well drained | Very limited | Very limited | |
| Rock outcrop-Gaviota complex, 30 to 75 percent slopes, MLRA 15 | 19K | D | Not rated | Not rated | |
| Arbuckle-Positas complex, 9 to 15 percent slopes | 16K | Well drained | C | Somewhat limited | Very limited |
| Nacimiento-Ayar complex, 9 to 30 percent slopes | 16K | Well drained | C | Very limited | Very limited |
| Gaviota-Rock outcrop complex, 30 to 75 percent slopes | 15K | D | Very limited | Very limited | |
| Lompico-McMullin complex, 50 to 75 percent slopes | 14K | Well drained | C | Very limited | Very limited |
| Millsholm-Dibble complex, 30 to 50 percent slopes | 14K | Well drained | D | Very limited | Very limited |
| Balcom-Nacimiento association,steep | 14K | Well drained | C | Very limited | Very limited |
| Linne-Calodo complex, 50 to 75 percent lsopes | 14K | Well drained | Very limited | Very limited | |
| Arbuckle-Positas complex, 15 to 30 percent slopes | 13K | Well drained | C | Very limited | Very limited |
| Dibble clay loam, 9 to 46 percent slopes, dry, MLRA 15 | 13K | Well drained | C | Very limited | Very limited |
| Linne-Calodo complex, 30 to 50 percent slopes | 13K | Well drained | Very limited | Very limited | |
| Shimmon-Dibble association, very steep | 11K | Well drained | C | Very limited | Very limited |
| Los Osos-Lodo complex, 50 to 75 percent slopes | 11K | Well drained | D | 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 80% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes. A geotechnical assessment is recommended before building.
Septic Systems
About 96% 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
Well-drained soils on sloped terrain — good for most plants but watch for erosion. Terracing, contour planting, and mulching help retain moisture and topsoil. Drip irrigation is more effective than sprinklers on slopes.