Columbia County, Oregon
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 Columbia County, Oregon.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Bacona silt loam, 3 to 30 percent slopes | 62K | Moderately well drained | C | Very limited | Very limited |
| Scaponia-Braun silt loams, 30 to 60 percent south slopes | 36K | Well drained | B | Very limited | Very limited |
| Vernonia silt loam, 3 to 30 percent slopes | 29K | Well drained | B | Very limited | Very limited |
| Scaponia-Braun silt loams, 30 to 60 percent north slopes | 27K | Well drained | B | Very limited | Very limited |
| Goble silt loam, warm, 3 to 15 percent slopes | 24K | Moderately well drained | C | Somewhat limited | Very limited |
| Goble silt loam, warm, 15 to 30 percent slopes | 21K | Moderately well drained | C | Very limited | Very limited |
| Mayger silt loam, 3 to 30 percent slopes | 19K | Somewhat poorly drained | C | Very limited | Very limited |
| Tolany loam, 3 to 30 percent slopes | 11K | Well drained | B | Very limited | Very limited |
| Glohm silt loam, 3 to 30 percent slopes | 10K | Moderately well drained | C | Very limited | Very limited |
| Hapludalfs-Udifluvents complex | 9K | Moderately well drained | C | Somewhat limited | Very limited |
| Alstony gravelly loam, 30 to 60 percent south slopes | 8K | Well drained | A | Very limited | Very limited |
| Braun-Scaponia silt loams, 5 to 30 percent slopes | 8K | Well drained | C | Very limited | Very limited |
| Dowde silt loam, 30 to 60 percent south slopes | 7K | Well drained | B | Very limited | Very limited |
| Murnen silt loam, 3 to 30 percent slopes | 7K | Well drained | B | Very limited | Very limited |
| Anunde silt loam, 3 to 30 percent slopes | 6K | Well drained | B | Very limited | Very limited |
| Braun-Scaponia silt loams, 60 to 90 percent south slopes | 5K | Well drained | C | Very limited | Very limited |
| Alstony gravelly loam, 30 to 60 percent north slopes | 5K | Well drained | A | Very limited | Very limited |
| Rinearson silt loam, 3 to 30 percent slopes | 5K | Well drained | B | Very limited | Very limited |
| Wauna silt loam, protected | 4K | Poorly drained | C | Very limited | Very limited |
| Dowde silt loam, 30 to 60 percent north slopes | 4K | Well drained | B | Very limited | Very limited |
What This Means
Building & Foundations
About 89% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, poor drainage in some areas, 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.