San Mateo County, Eastern Part, and San Francisco County, California
The most common soil here is Orthents, on about 11% of the land. Alambique and Candlestick come next.
About 28% of the land drains well, and 3% stays wet for long stretches; groundwater comes within two feet of the surface under 9% of it.
USDA rates 41% of the land very limited for a standard septic drain field, and 35% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: bedrock lies within 40 inches under 16% 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 Mateo County, Eastern Part, and San Francisco 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 Well drained and the dominant hydrologic group is D (very slow infiltration, high 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 Mateo County, Eastern Part, and San Francisco 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 |
|---|---|---|---|---|---|
| Water | 105K | D | Not rated | Not rated | |
| Urban land-Orthents, reclaimed complex, 0 to 2 percent slopes | 18K | D | Not limited | Not limited | |
| Alambique-McGarvey complex, 30 to 75 percent slopes | 13K | Well drained | C | Very limited | Very limited |
| Urban land | 13K | D | Not limited | Not limited | |
| Orthents, cut and fill-Urban land complex, 5 to 75 percent slopes | 12K | Well drained | Very limited | Very limited | |
| Urban land-Orthents, cut and fill complex, 0 to 5 percent slopes | 10K | D | Not limited | Not limited | |
| Urban land-Orthents, cut and fill complex, 5 to 75 percent slopes | 9K | D | Very limited | Very limited | |
| Barnabe-Candlestick complex, 30 to 75 percent slopes | 8K | Well drained | D | Very limited | Very limited |
| Urban land-Orthents, smoothed complex, 5 to 50 percent slopes | 8K | D | Very limited | Very limited | |
| Urban land-Sirdrak complex, 2 to 50 percent slopes | 6K | D | Very limited | Very limited | |
| Botella-Urban land complex, 0 to 5 percent slopes | 6K | C | Somewhat limited | Very limited | |
| Los Gatos loam, 30 to 75 percent slopes, MLRA 15 | 6K | Well drained | C | Very limited | Very limited |
| Candlestick-Kron-Buriburi complex, 30 to 75 percent slo pes | 5K | Well drained | C | Very limited | Very limited |
| Orthents, cut and fill, 0 to 15 percent slopes | 5K | Well drained | Not limited | Not limited | |
| Fagan loam, 15 to 50 percent slopes | 4K | Well drained | C | Very limited | Very limited |
| Novato clay, 0 to 1 percent slopes ponded | 3K | Very poorly drained | C/D | Very limited | Very limited |
| Reyes clay, 0 to 1 percent slopes | 3K | Somewhat poorly drained | C | Very limited | Very limited |
| Scarper-Miramar complex, 30 to 75 percent slopes | 2K | Well drained | B | Very limited | Very limited |
| Accelerator-Fagan-Urban land complex, 5 to 15 percent s lopes | 2K | Well drained | C | Somewhat limited | Very limited |
| Sirdrak sand, 5 to 50 percent slopes | 2K | Somewhat 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 35% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 41% of soils have significant septic limitations, while others are more suitable. A perc test is essential — conditions vary across the area.
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.