Territory of Guam

Survey Area GU640• Guam

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 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 Territory of Guam. 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
Guam cobbly clay loam, 3 to 7 percent slopes	28K	Well drained	D	Very limited	Very limited
Guam-Urban land complex, 0 to 3 percent slopes	14K	Well drained	D	Very limited	Very limited
Agfayan-Akina-Rock outcrop association, extremely steep	9K	Well drained	D	Very limited	Very limited
Ritidian-Rock outcrop complex, 3 to 15 percent slopes	7K	Well drained	D	Very limited	Very limited
Ritidian-Rock outcrop complex, 15 to 60 percent slopes	6K	Well drained	D	Very limited	Very limited
Inarajan clay, 0 to 4 percent slopes	4K	Somewhat poorly drained	D	Very limited	Very limited
Agfayan-Akina association, 40 to 90 percent slopes	4K	Well drained	D	Very limited	Very limited
Pulantat clay, 30 to 60 percent slopes	4K	Well drained	D	Very limited	Very limited
Akina-Badland complex, 15 to 30 percent slopes, MLRA 192	4K	Well drained	C	Very limited	Very limited
Pulantat clay, 15 to 30 percent slopes	4K	Well drained	D	Very limited	Very limited
Akina-Agfayan association, 30 to 60 percent slopes	3K	Well drained	C	Very limited	Very limited
Akina-Badland association, steep	3K	Well drained	C	Very limited	Very limited
Rock outcrop-Ritidian complex, 60 to 99 percent slopes	3K	Well drained	D	Very limited	Very limited
Pulantat clay, 7 to 15 percent slopes	2K	Well drained	D	Very limited	Very limited
Guam cobbly clay loam, 7 to 15 percent slopes	2K	Well drained	D	Very limited	Very limited
Akina-Atate association, steep	2K	Well drained	C	Very limited	Very limited
Urban land-Ustorthents complex, nearly level	2K		D	Not limited	Not limited
Pulantat-Urban land complex, 0 to 7 percent slopes	2K	Well drained	D	Very limited	Very limited
Ylig clay, 3 to 7 percent slopes	2K	Somewhat poorly drained	C	Very limited	Very limited
Akina silty clay 7 to 15 percent slopes	2K	Well drained	C	Somewhat 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.

Alfisols

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

Oxisols

Deeply weathered tropical soils. Nutrient-poor despite appearing lush. Rare in the continental US.

Entisols

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

Mollisols

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

What This Means

Building & Foundations

About 96% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.

Septic Systems

About 98% 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.