Santa Monica Mountains National Recreation Area

Survey Area CA692• 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 Santa Monica Mountains National Recreation 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
Mipolomol-Topanga association, 30 to 75 percent slopes	31K	Well drained	D	Very limited	Very limited
Chumash-Boades-Malibu association, 30 to 75 percent slopes	23K	Somewhat excessively drained	D	Very limited	Very limited
Topanga-Mipolomol-Sapwi association, 30 to 75 percent slopes	19K	Well drained	D	Very limited	Very limited
Cotharin clay loam, 30 to 75 percent slopes	13K	Well drained	D	Very limited	Very limited
Urban land-Xerorthents, landscaped complex, 0 to 5 percent slopes	12K		D	Not rated	Not rated
Cotharin-Talepop association, 15 to 50 percent slopes, MLRA 20	10K	Well drained	D	Very limited	Very limited
Linne-Los Osos, warm-Calcic Haploxerepts association, 15 to 65 percent slopes	7K	Well drained	C	Very limited	Very limited
Cotharin-Talepop association, 30 to 75 percent slopes	7K	Well drained	D	Very limited	Very limited
Rock outcrop-Sumiwawa-Hipuk complex, 30 to 75 percent slopes	7K		D	Not rated	Not rated
Zumaridge-Kawenga association, 30 to 75 percent slopes	5K	Well drained	D	Very limited	Very limited
Cotharin loam-Rock outcrop complex, very bouldery, 30 to 75 percent slopes	4K	Well drained	D	Very limited	Very limited
Gaviota-Rock outcrop association, 50 to 100 percent slopes	4K	Somewhat excessively drained	D	Very limited	Very limited
Xerorthents-Urban land-Balcom complex, 0 to 15 percent slopes	3K	Well drained	C	Somewhat limited	Very limited
Tongva-Cotharin-Rock outcrop complex, 30 to 75 percent slopes	2K	Well drained	D	Very limited	Very limited
Sumiwawa-Hipuk-Rock outcrop complex, 30 to 75 percent slopes	2K	Somewhat excessively drained	D	Very limited	Very limited
Balcom silty clay loam, 30 to 50 percent slopes, MLRA 20	2K	Well drained	C	Very limited	Very limited
Malibu-Chumash-Boades association, 15 to 50 percent slopes	2K	Moderately well drained	D	Very limited	Very limited
Calcic Haploxerepts-Mollic Haploxeralfs association, 30 to 75 percent slopes	2K	Well drained	C	Very limited	Very limited
Zumaridge-Sapwi-Kawenga association, bouldery, 30 to 75 percent slopes	2K	Well drained	D	Very limited	Very limited
Cotharin loam, 30 to 75 percent slopes, dry	1K	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.

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.

Entisols

Young soils with little development — found on floodplains, dunes, and steep slopes. Properties vary widely by setting.

Inceptisols

Young but developing soils found in mountains and river terraces. Variable properties — check drainage and bedrock depth.

What This Means

Building & Foundations

About 86% 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 87% 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.