San Luis Obispo County, California, Coastal Part

Survey Area CA664• California

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 Luis Obispo County, California, Coastal Part. 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
Rock outcrop-Lithic Haploxerolls complex, 30 to 75 percent slopes	29K		D	Very limited	Very limited
Santa Lucia channery clay loam, 50 to 75 percent slopes, MLRA 15	25K	Well drained	C	Very limited	Very limited
Lopez very shaly clay loam, 30 to 75 percent slopes	25K	Somewhat excessively drained	D	Very limited	Very limited
Lompico-McMullin loams, 30 to 75 percent slopes	20K	Well drained	C	Very limited	Very limited
Los Osos-Lodo complex, 30 to 75 percent slopes	20K	Well drained	D	Very limited	Very limited
Diablo-Lodo complex, 15 to 50 percent slopes	18K	Well drained	C	Very limited	Very limited
Gazos-Lodo clay loams, 30 to 50 percent slopes	15K	Well drained	C	Very limited	Very limited
Diablo and Cibo clays, 30 to 50 percent slopes	14K	Well drained	C	Very limited	Very limited
Oceano sand, 0 to 9 percent slopes	14K	Excessively drained	A	Not limited	Very limited
Diablo and Cibo clays, 15 to 30 percent slopes	13K	Well drained	C	Very limited	Very limited
Dune land	13K	Excessively drained		Very limited	Very limited
Los Osos-Diablo complex, 30 to 50 percent slopes	12K	Well drained	D	Very limited	Very limited
Obispo-Rock outcrop complex, 15 to 75 percent slopes	12K	Well drained	D	Very limited	Very limited
Henneke-Rock outcrop complex, 15 to 75 percent slopes	11K		D	Very limited	Very limited
Santa Lucia channery clay loam, 30 to 50 percent slopes, MLRA 15	10K	Well drained	D	Very limited	Very limited
Gaviota fine sandy loam, 15 to 50 percent slopes	10K	Well drained	D	Very limited	Very limited
Los Osos loam, 30 to 50 percent slopes	10K	Well drained	D	Very limited	Very limited
Cropley clay, 2 to 9 percent slopes, MLRA 14	10K	Moderately well drained	C	Very limited	Very limited
Lodo-Rock outcrop complex, 30 to 75 percent slopes	9K	Somewhat excessively drained	D	Very limited	Very limited
Corducci and Typic Xerofluvents, 0 to 5 percent slopes, occasionally flooded, MLRA 14	8K	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.

Mollisols

Fertile grassland soils with thick, dark topsoil. Among the best for agriculture, building, and gardening.

Vertisols

High-clay soils that shrink and swell dramatically. Fertile but challenging for foundations and septic systems.

Alfisols

Moderately weathered forest soils with clay-enriched subsoil. Productive for agriculture, generally good for building and septic.

What This Means

Building & Foundations

About 95% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, flood-prone areas. A geotechnical assessment is recommended before building.

Septic Systems

About 100% 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.