American Samoa, Islands of Aunuu, Ofu, Olosega, Tau, and Tutuila
The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate 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 American Samoa, Islands of Aunuu, Ofu, Olosega, Tau, and Tutuila.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Fagasa family-Lithic Hapludolls-Rock outcrop association, 70 to 99 percent slopes | 21K | Well drained | C | Very limited | Very limited |
| Olotania family, 15 to 40 percent slopes | 5K | Well drained | B | Very limited | Very limited |
| Rock outcrop-Hydrudands-Hapludands association, 70 to 99 percent slopes | 3K | Well drained | Very limited | Very limited | |
| Aua very stony silty clay loam, 30 to 60 percent slopes | 2K | Well drained | A | Very limited | Very limited |
| Iliili extremely stony highly organic clay loam, 3 to 15 percent slopes | 2K | Well drained | D | Very limited | Very limited |
| Fagasa-Ofu silty clays, 30 to 60 percent slopes | 1K | Well drained | B | Very limited | Very limited |
| Ofu taxadjunct-Pavaiai association, 15 to 50 percent slopes | 1K | Well drained | B | Very limited | Very limited |
| Ofu silty clay, 40 to 70 percent slopes | 1K | Well drained | A | Very limited | Very limited |
| Pavaiai stony clay loam, 25 to 40 percent slopes | 1K | Well drained | B | Very limited | Very limited |
| Tafuna extremely stony highly decomposed plant matter, 3 to 15 percent slopes | 990 | Well drained | A | Very limited | Very limited |
| Udorthents, 0 to 6 percent slopes | 948 | Well drained | D | Not limited | Very limited |
| Sogi-Puapua clay loams, 0 to 6 percent slopes | 914 | Well drained | B | Very limited | Very limited |
| Urban land-Aua-Leafu complex, 0 to 30 percent slopes, occasionally flooded | 901 | Not rated | Not rated | ||
| Sogi-Puapua clay loams, 6 to 20 percent slopes | 900 | Well drained | B | Very limited | Very limited |
| Oloava silty clay loam, 40 to 100 percent slopes | 895 | Well drained | A | Very limited | Very limited |
| Pavaiai stony clay loam, 6 to 12 percent slopes | 770 | Well drained | B | Very limited | Very limited |
| Pavaiai stony clay loam, 12 to 25 percent slopes | 633 | Well drained | B | Very limited | Very limited |
| Ofu silty clay, 15 to 40 percent slopes | 587 | Well drained | A | Very limited | Very limited |
| Leafu silty clay, 0 to 3 percent slopes, occasionally flooded | 530 | Somewhat poorly drained | A | Very limited | Very limited |
| Oloava silty clay loam, 12 to 25 percent slopes | 517 | Well drained | A | Very limited | Very limited |
What This Means
Building & Foundations
About 95% 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 97% 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.