Territory of Guam
The dominant drainage class is Well drained and the dominant hydrologic group is D (very slow infiltration, high runoff). 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.
| 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 |
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.